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  • 1.
    Alm, Ulrika
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    The effect of food quality and relative abundance on food choice in fallow deer2002In: Animal Behaviour, Vol. 64, p. 439-445Article in journal (Refereed)
  • 2.
    Balogh, Alexandra C.V.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Learning and the mimicry spectrum: from quasi-Bates to super-Müller2008In: Animal Behaviour, ISSN 0003-3472, Vol. 76, no 5, p. 1591-1599Article in journal (Refereed)
    Abstract [en]

    Müllerian mimicry is the mutualistic resemblance between two defended species, while Batesian mimicry is the parasitic resemblance between a palatable species (the mimic) and an unpalatable one (the model). These two kinds of mimicry are traditionally seen as extreme ends of a mimicry spectrum. For the range in between, it has been suggested that mimetic relations between unequally defended species could be parasitic, and this phenomenon has been referred to as quasi-Batesian mimicry. Where a mimetic relation is placed along the mimicry spectrum depends on the assumptions made about predator learning. In this work, we use a variant of the Rescorla-Wagner learning model for virtual predators to analyse the different possible components of the mimicry spectrum. Our model entails that the rate of associative learning is influenced by variation in the stimuli to be learned. Variable stimuli, i.e. unequal defences, can increase the predator learning rate and thus lead to an increased level of mutualism in a mimetic relation. In our analysis, we make use of the concepts of super-Müllerian mimicry, where the benefit of mimicry is even greater than in traditional Müllerian mimicry, and quasi-Müllerian mimicry, where mimicry by a palatable mimic is mutualistic. We suggest that these types of mimicry should be included in the mimicry spectrum along with Müllerian, Batesian and quasi-Batesian mimicry.

  • 3.
    Balogh, Alexandra C.V.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Feature theory and the two-step hypothesis of Müllerian mimicry evolution2010In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 64, no 3, p. 810-822Article in journal (Refereed)
    Abstract [en]

    The two-step hypothesis of Müllerian mimicry evolution states that mimicry starts with a major mutational leap between adaptive peaks, followed by gradual fine-tuning. The hypothesis was suggested to solve the problem of apostatic selection producing a valley between adaptive peaks, and appears reasonable for a one-dimensional phenotype. Extending the hypothesis to the realistic scenario of multidimensional phenotypes controlled by multiple genetic loci can be problematic, because it is unlikely that major mutational leaps occur simultaneously in several traits. Here we consider the implications of predator psychology on the evolutionary process. According to feature theory, single prey traits may be used by predators as features to classify prey into discrete categories. A mutational leap in such a trait could initiate mimicry evolution. We conducted individual-based evolutionary simulations in which virtual predators both categorize prey according to features and generalize over total appearances. We found that an initial mutational leap towards feature similarity in one dimension facilitates mimicry evolution of multidimensional traits. We suggest that feature-based predator categorization together with predator generalization over total appearances solves the problem of applying the two-step hypothesis to complex phenotypes, and provides a basis for a theory of the evolution of mimicry rings.

  • 4.
    Balogh, Alexandra C.V.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Müllerian mimicry: an examination of Fisher's theory of gradual evolutionary change2005In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 272, p. 2269-2275Article in journal (Refereed)
    Abstract [en]

    In 1927, Fisher suggested that Müllerian mimicry evolution could be gradual and driven by predator generalization. A competing possibility is the so-called two-step hypothesis, entailing that Müllerian mimicry evolves through major mutational leaps of a less-protected species towards a better-protected, which sets the stage for coevolutionary fine-tuning of mimicry. At present, this hypothesis seems to be more widely accepted than Fisher’s suggestion. We conducted individual-based simulations of communities with predators and two prey types to assess the possibility of Fisher’s process leading to a common prey appearance. We found that Fisher’s process worked for initially relatively similar appearances. Moreover, by introducing a predator spectrum consisting of several predator types with different ranges of generalization, we found that gradual evolution towards mimicry occurred also for large initial differences in prey appearance. We suggest that Fisher’s process together with a predator spectrum is a realistic alternative to the two-step hypothesis and, furthermore, that it has fewer problems with purifying selection.  We also examined factors influencing gradual evolution towards mimicry and found that not only the relative benefits from mimicry but also the mutational schemes of the prey types matter.

  • 5.
    Bergvall, Ulrika A.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Directional associational plant defense from Red deer (Cervus elaphus) foraging decisions2017In: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 8, no 3, article id e01714Article in journal (Refereed)
    Abstract [en]

    The concept of associational plant defenses is widely accepted and implies that an unpalatable plant can protect its neighbors from grazing. We have investigated the new but similar question of whether a part of a plant, for example, the top or bottom, can protect other parts. At the same time, we investigated whether the previously observed selection of the apical shoot and upper leaves of plants is a direct consequence of food quality (the plant vigor hypothesis) or whether there is an innate or learnt foraging pattern behind the observation. In experiments, we used 1 m high artificial trees, made from aspen branches, and measured red deer browsing from the top (above 0.5 m) and bottom (below 0.5 m), with application of condensed tannin to the top or bottom as a proxy for plant part unpalatability. There were four treatments where either none, both, or one part (top or bottom) of the artificial trees had tannin applied. As expected, we found that red deer consumed less from parts with tannin. We also found that a defended top protected an undefended bottom, but we found no evidence for the opposite relationship, which could be explained by foraging behavior. When examining the behavior, we found that adult red deer prefer to start feeding from the top of a plant. We also found that they spent a shorter time feeding on a defended top. This behavior might cause a defended top to protect an undefended bottom. Such directional associational plant defense could be the result of selectivity with limited flexibility and might be more pronounced for mammalian herbivores than for insects, since mammals are bigger in size and more restricted in their head position. An important applied aspect of these results is that when saplings are protected by adding a repellent, for instance in forestry, it might be enough to apply repellent to the tops. On the other hand, according to this directional associational plant defense, protected bottoms will not protect tops, so newly grown apical shoots may need new protection.

  • 6.
    Bergvall, Ulrika A
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Rautio, Pasi
    Kesti, Kari
    Tuomi, Juha
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Associational effects of plant defences in relation to within- and between-patch food choice by a mammalian herbivore: neighbour contrast susceptibility and defence.2006In: Oecologia, ISSN 0029-8549, Vol. 147, no 2, p. 253-60Article in journal (Refereed)
  • 7.
    Bergvall, Ulrika A
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Rautio, Pasi
    Luotola, Tuomas
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    A test of simultaneous and successive negative contrast in fallow deer foraging behaviour2007In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 74, no 3, p. 395-402Article in journal (Refereed)
    Abstract [en]

    The study of contrast investigates how rewards influence behaviour when animals are exposed to two or more levels of rewards compared to when they experience only a single level. The appearance of an exaggerated response to a shift in reward is referred to as a contrast effect and is an empirically well-established phenomenon. Although contrast effects could be important in foraging behaviour, no direct experimental tests of contrast effects in foraging by mammalian herbivores exist. During foraging, mammalian herbivores can encounter a range of plants that vary in the amount of nutrients and toxins. They may thus compare food items by taste, which in turn can give rise to contrast effects. In feeding experiments with fallow deer, Dama dama, we investigated the presence of simultaneous negative contrast. We found that the deer consumed less from a bowl of pellets containing 1% tannin when they shifted to it from a bowl with pellets containing only 0.25% tannin than when they shifted from another bowl with pellets containing 1% tannin. We estimated a fourfold difference between treatments in test food consumption at the highest levels of preloading, but none at the lowest levels. We found no support for successive negative contrast in experiments where the deer approached food in a runway, comparing a current reward with the memory of a previous reward. We suggest that simultaneous negative contrast can influence foraging decisions in mammalian herbivores.

  • 8.
    Bergvall, Ulrika A
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Rautio, Pasi
    Siren, Hanna
    Tuomi, Juha
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    The effect of spatial scale on plant associational defences against mammalian herbivores2008In: Ecoscience, Vol. 15, p. 343-348Article in journal (Refereed)
    Abstract [en]

    Intraspecific variation in plant toxins at different spatial scales can influence foraging decisions by wild herbivores. In order to investigate plant associational defences in relation to spatial scale, we performed an experiment with fallow deer encountering 2 patches of low- and high-tannin hazel branches. One patch was good, consisting of 7 low- and I high-tannin branch, and the other bad, with low- and 7 high-tannin branches. We kept the between-patch spatial scale constant and varied the within-patch spatial scale: the branches in a patch were either spread out or close together in a bundle. When the low-tannin branches were spread out, the deer showed a clear preference for low_tannin branches both patches and consumed similar amounts from low-tannin branches in the good and the bad patch, which means that there was no associational defence. In contrast, when the branches instead were together in a bundle, within-patch selectivity decreased and between-patch selectivity increased, and the low-tannin branches in the bad patch were less eaten than the low-tannin branches in the good patch, which corresponds to associational defence. We conclude that small inter-plant distances can be crucial for the operation of plant associational defences

  • 9.
    Bergvall, Ulrika Alm
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Plant secondary compounds and the frequency of food types affect food choice by mammalian herbivores2005In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 86, no 9, p. 2450-2460Article in journal (Refereed)
    Abstract [en]

    We have investigated food choice in individual fallow deer (Dama dama) encountering different relative frequencies of food types in the form of bowls containing pellets with either high or low concentrations of hydrolyzable tannin. We performed two similar experiments, one with large and one with small differences in tannic acid concentration. With small differences in tannic acid concentration, the ratio of the consumption per low- and high-tannin bowl was independent of frequency of occurrence, but with large differences in tannic acid concentration, we found frequency-dependent food choice. The deer ate proportionally less from high-tannin bowls if these occurred at low relative frequency. Variation between frequency treatments in the average order of encounter of bowl types might have produced this effect, because we found that the deer left a high-tannin bowl more quickly if they had switched to it from a low-tannin bowl. We argue that the perceived contrast between the tastes of different food types can play a role for food choice by mammalian herbivores.

  • 10. Bshary, Redouan
    et al.
    Grutter, Alexandra S
    Willener, Astrid S T
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Pairs of cooperating cleaner fish provide better service quality than singletons.2008In: Nature, ISSN 1476-4687, Vol. 455, no 7215, p. 964-6Article in journal (Refereed)
    Abstract [en]

    Service providers may vary service quality depending on whether they work alone or provide the service simultaneously with a partner. The latter case resembles a prisoner's dilemma(1-4), in which one provider may try to reap the benefits of the interaction without providing the service. Here we present a game- theory model based on the marginal value theorem(5), which predicts that as long as the client determines the duration, and the providers cooperate towards mutual gain, service quality will increase in the pair situation. This prediction is consistent with field observations and with an experiment on cleaning mutualism, in which stable male - female pairs of the cleaner wrasse Labroides dimidiatus repeatedly inspect client fish jointly. Cleaners cooperate by eating ectoparasites(6) off clients but actually prefer to cheat and eat client mucus(7). Because clients often leave in response to such cheating, the benefits of cheating can be gained by only one cleaner during a pair inspection. In both data sets, the increased service quality during pair inspection was mainly due to the smaller females behaving significantly more cooperatively than their larger male partners. In contrast, during solitary inspections, cleaning behaviour was very similar between the sexes. Our study highlights the importance of incorporating interactions between service providers to make more quantitative predictions about cooperation between species.

  • 11. Dall, Sasha R. X.
    et al.
    McNamara, John M.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm Univ, Dept Zool, SE-10691 Stockholm, Sweden.
    Genes as cues: phenotypic integration of genetic and epigenetic information from a Darwinian perspective2015In: Trends in Ecology & Evolution, ISSN 0169-5347, E-ISSN 1872-8383, Vol. 30, no 6, p. 327-333Article in journal (Refereed)
    Abstract [en]

    The development of multicellular organisms involves a delicate interplay between genetic and environmental influences. It is often useful to think of developmental systems as integrating available sources of information about current conditions to produce organisms. Genes and inherited physiology provide cues, as does the state of the environment during development. The integration systems themselves are under genetic control and subject to Darwinian selection, so we expect them to evolve to produce organisms that fit well with current ecological (including social) conditions. We argue for the scientific value of this explicitly informational perspective by providing detailed examples of how it can elucidate taxonomically diverse phenomena. We also present a general framework for linking genetic and phenotypic variation from an informational perspective. This application of Darwinian logic at the organismal level can elucidate genetic influences on phenotypic variation in novel and counterintuitive ways.

  • 12. Doebeli, Michael
    et al.
    Blok, Hendrik J
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Dieckmann, Ulf
    Multimodal pattern formation in phenotype distributions of sexual populations.2007In: Proceedings of the Royal Society B - Biological Sciences, ISSN 0962-8452, Vol. 274, no 1608, p. 347-57Article in journal (Refereed)
    Abstract [en]

    During bouts of evolutionary diversification, such as adaptive radiations, the emerging species cluster around different locations in phenotype space. How such multimodal patterns in phenotype space can emerge from a single ancestral species is a fundamental question in biology. Frequency-dependent competition is one potential mechanism for such pattern formation, as has previously been shown in models based on the theory of adaptive dynamics. Here, we demonstrate that also in models similar to those used in quantitative genetics, phenotype distributions can split into multiple modes under the force of frequency-dependent competition. In sexual populations, this requires assortative mating, and we show that the multimodal splitting of initially unimodal distributions occurs over a range of assortment parameters. In addition, assortative mating can be favoured evolutionarily even if it incurs costs, because it provides a means of alleviating the effects of frequency dependence. Our results reveal that models at both ends of the spectrum between essentially monomorphic (adaptive dynamics) and fully polymorphic (quantitative genetics) yield similar results. This underscores that frequency-dependent selection is a strong agent of pattern formation in phenotype distributions, potentially resulting in adaptive speciation.

  • 13.
    Enfjäll, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    The evolution of dispersal - the importance of information about population density and habitat characteristics2009In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, p. 291-299Article in journal (Refereed)
    Abstract [en]

    The evolution of mobility patterns and dispersal strategies depend on different population, habitat and life history characteristics. The ability to perceive and make use of information about the surrounding environment for dispersal decisions will also differ between organisms. To investigate the evolutionary consequences of such differences, we have used a simulation model with nearest-neighbour dispersal in a metapopulation to study how variation in the ability to obtain and make use of information about habitat quality and conspecific density affects the evolution of dispersal strategies. We found a rather strong influence of variation in information on the overall rate of dispersal in a metapopulation. The highest emigration rate evolved in organisms with no information about either density or habitat quality and the lowest rate was found in organisms with information about both the natal and the neighbouring patches. For organisms that can make use of information about conspecific density, positively density-dependent dispersal evolved in the majority of cases, with the strongest density dependence occurring when an individual only has information about density in the natal patch. However, we also identified situations, involving strong local population fluctuations and frequent local extinctions, where negatively density-dependent dispersal evolved.

  • 14.
    Favati, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Løvlie, Hanne
    Personality predicts social dominance in male domestic fowl2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 7, article id e103535Article in journal (Refereed)
    Abstract [en]

    Individuals in social species commonly form dominance relationships, where dominant individuals enjoy greater access to resources compared to subordinates. A range of factors such as sex, age, body size and prior experiences has to varying degrees been observed to affect the social status an individual obtains. Recent work on animal personality (i.e. consistent variation in behavioural responses of individuals) demonstrates that personality can co-vary with social status, suggesting that also behavioural variation can play an important role in establishment of status. We investigated whether personality could predict the outcome of duels between pairs of morphologically matched male domestic fowl (Gallus gallus domesticus), a species where individuals readily form social hierarchies. We found that males that more quickly explored a novel arena, or remained vigilant for a longer period following the playback of a warning call were more likely to obtain a dominant position. These traits were uncorrelated to each other and were also uncorrelated to aggression during the initial part of the dominance-determining duel. Our results indicate that several behavioural traits independently play a role in the establishment of social status, which in turn can have implications for the reproductive success of different personality types.

  • 15.
    Favati, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Radesäter, Tommy
    Stockholm University, Faculty of Science, Department of Zoology.
    Løvlie, Hanne
    Stockholm University, Faculty of Science, Department of Zoology. Linköping University, Sweden.
    Social status and personality: stability in social state can promote consistency of behavioural responses2014In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, no 1774, article id 20132531Article in journal (Refereed)
    Abstract [en]

    Stability of 'state' has been suggested as an underlying factor explaining behavioural stability and animal personality (i.e. variation among, and consistency within individuals in behavioural responses), but the possibility that stable social relationships represent such states remains unexplored. Here, we investigated the influence of social status on the expression and consistency of behaviours by experimentally changing social status between repeated personality assays. We used male domestic fowl (Gallus gallus domesticus), a social species that forms relatively stable dominance hierarchies, and showed that behavioural responses were strongly affected by social status, but also by individual characteristics. The level of vigilance, activity and exploration changed with social status, whereas boldness appeared as a stable individual property, independent of status. Furthermore, variation in vocalization predicted future social status, indicating that individual behaviours can both be a predictor and a consequence of social status, depending on the aspect in focus. Our results illustrate that social states contribute to both variation and stability in behavioural responses, and should therefore be taken into account when investigating and interpreting variation in personality.

  • 16.
    Favati, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Løvlie, Hanne
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Effects of social experience during development on competitive ability and personality traits in male domestic fowlManuscript (preprint) (Other academic)
    Abstract [en]

    The ability to dominate conspecifics and thereby gain access to important resources depends on a number of traits and skills that may be both heritable and influenced by the environment. Experience of dominance relationships during development is a potential source of learning such skills. We here study the relative importance of social experience, personality, and morphological traits on competitive ability in male domestic fowl (Gallus gallus domesticus). By letting males grow up as either a single (dominant) male, as the dominant male of a pair, or as an intermediate ranked male in a group of males, we investigate if competitiveness in social interactions (winning duels) is mainly due to individual qualities or also influenced by social experience. We found that males were consistent over time in their competitive ability. Single raised males were inferior to pair dominant males and group-raised males in competitive ability, while pair dominant and group males did not differ significantly. This indicates that social training is important for future fighting success, but that the social position during development does not have a decisive influence on male fighting success in adulthood. Aggression and comb size, the latter possibly being a proxy for testosterone levels, had a marked effect on competitive ability. Together, our results indicate that certain behavioural and morphological traits are more important than experience of a social position in shaping competitive ability. These findings elucidate the relationship between social dominance and personality.

  • 17.
    Favati, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Løvlie, Hanne
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Individual aggression, but not winner–loser effects, predicts social rank in male domestic fowl2017In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 28, no 3, p. 874-882Article in journal (Refereed)
    Abstract [en]

    Many factors can affect the probability for an individual to obtain a high social rank, including size, weaponry, and behavioral attributes such as aggression. Recent experiences of winning or losing can also affect the chances of winning future contests, commonly referred to as “winner–loser effects”. Individuals often differ in behavior in a consistent way, including in aggression, thereby showing differences in personality. However, the relative importance of recent experience and aspects of personality in determining rank, as well as the extent to which winning or losing affects aggression, has rarely been studied. Here, we investigate these questions using male domestic fowl. We matched males for body size, comb size, and aggression in pair-wise duels to: 1) study the effect of contest outcome on aggression and 2) compare the effect of individual aggression and contest experience on future social status in small groups. We found that aggression was a highly repeatable personality trait and that aggression increased after winning and decreased after losing. Nevertheless, such winner–loser effects were not enough to increase the odds of becoming dominant in a small group. Instead, aggressiveness measured prior to a contest experience best predicted future rank. Boldness and exploration did not predict rank and of the 2, only boldness was positively correlated with aggressiveness. We conclude that for male domestic fowl in contests among phenotypically matched contestants, aggressiveness is more important for obtaining high rank than winner–loser effects, or other aspects of personality.

  • 18.
    Favati, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Udén, Eva
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Løvlie, Hanne
    Personality remains: no effect of 3-week social status experience on personality in male fowl2018In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 29, no 2, p. 312-320Article in journal (Refereed)
    Abstract [en]

    Behavioral responses of male fowl did not depend on social rank after 3 weeks in stable groups, but were consistent over time for an individual. Theory suggests that stable social states, for example, stable social hierarchies, may lead to consistent variation in behavior, that is, variation in personality. Our results suggest that variation in personality is not a consequence of variation in social status and that personality is more important than current social position in determining individual behavior in stable groups.Individuals often differ in behavior in a consistent way, that is, they show variation in personality. Understanding the processes explaining the emergence and maintenance of this variation is a current major topic in the field of animal behavioral research. Recent theoretical models predict that differences in various states can generate individual variation in behavior. Previous studies have mainly focused on endogenous states like metabolic rate or energy reserves, but theory also suggests that states based on social interactions could play important roles in shaping personality. We have earlier demonstrated short-term status-dependent variation in behavior in the domestic fowl (Gallus gallus domesticus), but whether such behavioral variation remains also after a longer period of time, is unknown. Therefore, we examine the influence of social status on variation in behavior, using experimental manipulation of social status in pairs of male domestic fowl. We scored males in 3 personality assays (novel arena test, novel object test, and aggression test) before and after 3 weeks in pairs as either dominant or subordinate. We observed individual consistency of behavior despite alteration of social status. We further found no support for social status acting as a state that generates variation in personality over the used time interval: social status had no significant effect on the change in behavioral responses between repeated personality tests. Our results suggest that personality is more important than current social situation for describing individual behavior in stable groups.

  • 19.
    Friberg, Magne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala universitet.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Heterospecific courtship, minority effects and niche separation between cryptic butterfly species2013In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 26, no 5, p. 971-979Article in journal (Refereed)
    Abstract [en]

    Species interacting in varied ecological conditions often evolve in different directions in different local populations. The butterflies of the cryptic Leptidea complex are sympatrically distributed in different combinations across their Eurasian range. Interestingly, the same species is a habitat generalist in some regions and a habitat specialist in others, where a sibling species has the habitat generalist role. Previous studies suggest that this geographically variable niche divergence is generated by local processes in different contact zones. By varying the absolute and relative densities of Leptidea sinapis and Leptidea juvernica in large outdoor cages, we show that female mating success is unaffected by conspecific density, but strongly negatively affected by the density of the other species. Whereas 80% of the females mated when a conspecific couple was alone in a cage, less than 10% mated when the single couple shared the cage with five pairs of the other species. The heterospecific courtships can thus affect the population fitness, and for the species in the local minority, the suitability of a habitat is likely to depend on the presence or absence of the locally interacting species. If the local relative abundance of the different species depends on the colonization order, priority effects might determine the ecological roles of interacting species in this system.

  • 20.
    Friberg, Magne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Heterospecific courtships, Allee-effects and niche separation between Leptidea sinapis and Leptidea realiManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    Increasing attention is given to coevolutionary studies and to the role of ecology in local adaptation. The coevolutionary process can act in parallel throughout the distribution of species that interact in similar ecologies, whereas species interacting in varied ecological conditions might coevolve in different directions in different local populations. The butterflies Leptidea sinapis and L. reali have partitioned their niches differently in different parts of their sympatric distribution, with one species being a local habitat generalist in several different regions, and a local specialist in other areas where the sister species has adopted the habitat generalist role. Niche separation is likely independent of resource competition in this phytophagous system, and we study the potential for heterospecific sexual interference competition to redefine the suitability of a habitat and select for niche separation. We used the average female mating success in large outdoor cage experiments that varied both the absolute and relative density of the two species to estimate potential fitness costs of being in local minority. The mating success was unaffected by absolute density (conspecifics/m2) but strongly affected by the proportion of con- and heterospecifics in each cage. The proportion of mated females was ten times higher when a conspecific couple spent the day alone in the cage compared to when the single couple shared the cage with five heterospecific pairs. Being in the minority thus resulted in strong sexual interference from the locally more common competitor. We propose that these Allee effects select for habitat specialisation in the locally rare species as individuals leaving the core population likely suffer decreased fitness from spending time in heterospecific courtship. Hence, habitat suitability might depend less on local resource availability and more on the presence or absence of a local sexual competitor in this system.

  • 21.
    Gamberale-Stille, Gabriella
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Balogh, Alexandra C. V.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    FEATURE SALTATION AND THE EVOLUTION OF MIMICRY2012In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 66, no 3, p. 807-817Article in journal (Refereed)
    Abstract [en]

    In Batesian mimicry, a harmless prey species imitates the warning coloration of an unpalatable model species. A traditional suggestion is that mimicry evolves in a two-step process, in which a large mutation first achieves approximate similarity to the model, after which smaller changes improve the likeness. However, it is not known which aspects of predator psychology cause the initial mutant to be perceived by predators as being similar to the model, leaving open the question of how the crucial first step of mimicry evolution occurs. Using theoretical evolutionary simulations and reconstruction of examples of mimicry evolution, we show that the evolution of Batesian mimicry can be initiated by a mutation that causes prey to acquire a trait that is used by predators as a feature to categorize potential prey as unsuitable. The theory that species gain entry to mimicry through feature saltation allows us to formulate scenarios of the sequence of events during mimicry evolution and to reconstruct an initial mimetic appearance for important examples of Batesian mimicry. Because feature-based categorization by predators entails a qualitative distinction between nonmimics and passable mimics, the theory can explain the occurrence of imperfect mimicry.

  • 22.
    Gamberale-Stille, Gabriella
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kazemi, Baharan
    Stockholm University, Faculty of Science, Department of Zoology.
    Balogh, Alexandra
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Biased generalization of salient traits drives the evolution of warning signals2018In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 285, no 1877, article id 20180283Article in journal (Refereed)
    Abstract [en]

    The importance of receiver biases in shaping the evolution of many signalling systems is widely acknowledged. Here, we show that receiver bias can explain which traits evolve to become warning signals. For warning coloration, a generalization bias for a signalling trait can result from predators learning to discriminate unprofitable from profitable prey. However, because the colour patterns of prey are complex traits with multiple components, it is crucial to understand which of the many aspects of prey appearance evolve into signals. We provide experimental evidence that the more salient differences in prey traits give rise to greater generalization bias, corresponding to stronger selection towards trait exaggeration. Our results are based on experiments with domestic chickens as predators in a Skinner-box-like setting, and imply that the difference in appearance between profitable and unprofitable prey that is most rapidly learnt produces the greatest generalization bias. As a consequence, certain salient traits of unprofitable prey are selected towards exaggeration to even higher salience, driving the evolution of warning coloration. This general idea may also help to explain the evolution of many other striking signalling traits found in nature.

  • 23.
    Kazemi, Baharan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Stimulus Salience as an Explanation for Imperfect Mimicry2014In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 24, no 9, p. 965-969Article in journal (Refereed)
    Abstract [en]

    The theory of mimicry explains how a mimic species gains advantage by resembling a model species [1-3]. Selection for increased mimic-model similarity should then result in accurate mimicry, yet there are many surprising examples of poor mimicry in the natural world [4-8]. The existence of imperfect mimics remains a major unsolved conundrum. We propose and experimentally test a novel explanation of the phenomenon. We argue that predators perceive prey as having several traits, but that the traits differ in their importance for learning. When predators learn to discriminate prey, high-salience traits overshadow other traits, leaving them under little or no selection for similarity, and allow imperfect mimicry to succeed. We tested this idea experimentally, using blue tits as predators and artificial prey with three prominent traits: color, pattern, and shape. We found that otherwise imperfect color mimics were avoided about as much as perfect mimics, whereas pattern and shape mimics did not gain from their similarity to the model. All traits could separately be perceived and learned by the predators, but the color trait was learned at a higher rate, implying that it had higher salience. We conclude that difference in salience between components of prey appearance is of major importance in explaining imperfect mimicry.

  • 24.
    Kazemi, Baharan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Multi-trait mimicry and the relative salience of individual traits2015In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1818, article id 20152127Article in journal (Refereed)
    Abstract [en]

    Mimicry occurs when one species gains protection from predators by resembling an unprofitable model species. The degree of mimic-model similarity is variable in nature and is closely related to the number of traits that the mimic shares with its model. Here, we experimentally test the hypothesis that the relative salience of traits, as perceived by a predator, is an important determinant of the degree of mimic-model similarity required for successful mimicry. We manipulated the relative salience of the traits of a two-trait artificial model prey, and subsequently tested the survival of mimics of the different traits. The unrewarded model prey had two colour traits, black and blue, and the rewarded prey had two combinations of green, brown and grey shades. Blue tits were used as predators. We found that the birds perceived the black and blue traits similarly salient in one treatment, and mimic-model similarity in both traits was then required for high mimic success. In a second treatment, the blue trait was the most salient trait, and mimic-model similarity in this trait alone achieved high success. Our results thus support the idea that similar salience of model traits can explain the occurrence of multi-trait mimicry.

  • 25.
    Kazemi, Baharan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gamberale-Stille, Gabriella
    Stockholm University, Faculty of Science, Department of Zoology.
    Wåtz, Therese
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Learning of salient prey traits explains Batesian mimicry evolution2018In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 72, no 3, p. 531-539Article in journal (Refereed)
    Abstract [en]

    Batesian mimicry evolution involves an initial major mutation that produces a rough resemblance to the model, followed by smaller improving changes. To examine the learning psychology of this process, we applied established ideas about mimicry in Papilio polyxenes asterius of the model Battus philenor. We performed experiments with wild birds as predators and butterfly wings as semiartificial prey. Wings of hybrids of P. p. asterius and Papilio machaon were used to approximate the first mutant, with melanism as the hypothesized first mimetic trait. Based on previous results about learning psychology and imperfect mimicry, we predicted that: melanism should have high salience (i.e., being noticeable and prominent), meaning that predators readily discriminate a melanistic mutant from appearances similar to P. machaon; the difference between the first mutant and the model should have intermediate salience to allow further improvement of mimicry; and the final difference in appearance between P. p. asterius and B. philenor should have very low salience, causing improvement to level off. Our results supported both the traditional hypothesis and all our predictions about relative salience. We conclude that there is good agreement between long-held ideas about how Batesian mimicry evolves and recent insights from learning psychology about the role of salience in mimicry evolution.

  • 26.
    Kivelä, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Towards a mechanistic understanding of insect life history evolution: oxygen-dependent induction of moulting explains moulting sizes2016In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 117, no 3, p. 586-600Article in journal (Refereed)
    Abstract [en]

    Moults characterise insect growth trajectories, typically following a consistent pattern known as Dyar's rule; proportional size increments remain constant across inter-instar moults. Empirical work suggests that oxygen limitation triggers moulting. The insect respiratory system, and its oxygen supply capacity, grows primarily at moults. It is hypothesized that the oxygen demand increases with increasing body mass, eventually meeting the oxygen supply capacity at an instar-specific critical mass where moulting is triggered. Deriving from this hypothesis, we develop a novel mathematical model for moulting and growth in insect larvae. Our mechanistic model has great success in predicting moulting sizes in four butterfly species, indirectly supporting a size-dependent mechanism underlying moulting. The results demonstrate that an oxygen-dependent induction of moulting mechanism would be sufficient to explain moulting sizes in the study species. Model predictions deviated slightly from Dyar's rule, the deviations being typically negligible within the present data range. The developmental decisions (e.g. moulting) made by growing larvae significantly affect age and size at maturity, which has important life history implications. The successful modelling of moulting presented here provides a novel framework for the development of realistic insect growth models, which are required for a better understanding of life history evolution.

  • 27.
    Kubrak, Olga I.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Flatt, Thomas
    Nässel, Dick R.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Adaptation to fluctuating environments in a selection experiment with Drosophila melanogaster2017In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 7, no 11, p. 3796-3807Article in journal (Refereed)
    Abstract [en]

    A fundamental question in life-history evolution is how organisms cope with fluctuating environments, including variation between stressful and benign conditions. For short-lived organisms, environments commonly vary between generations. Using a novel experimental design, we exposed wild-derived Drosophila melanogaster to three different selection regimes: one where generations alternated between starvation and benign conditions, and starvation was always preceded by early exposure to cold; another where starvation and benign conditions alternated in the same way, but cold shock sometimes preceded starvation and sometimes benign conditions; and a third where conditions were always benign. Using six replicate populations per selection regime, we found that selected flies increased their starvation resistance, most strongly for the regime where cold and starvation were reliably combined, and this occurred without decreased fecundity or extended developmental time. The selected flies became stress resistant, displayed a pronounced increase in early life food intake and resource storage. In contrast to previous experiments selecting for increased starvation resistance in D. melanogaster, we did not find increased storage of lipids as the main response, but instead that, in particular for females, storage of carbohydrates was more pronounced. We argue that faster mobilization of carbohydrates is advantageous in fluctuating environments and conclude that the phenotype that evolved in our experiment corresponds to a compromise between the requirements of stressful and benign environments.

  • 28.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Environmental and genetic cues in the evolution of phenotypic polymorphism2009In: Evolutionary Ecology, ISSN 0269-7653, E-ISSN 1573-8477, Vol. 23, p. 125-135Article in journal (Refereed)
    Abstract [en]

    Phenotypic polymorphism is a consequence of developmental plasticity, in which the trajectories of developing organisms diverge under the influence of cues. Environmental and genetic phenotype determination are the two main categories of polymorphic development. Even though both may evolve as a response to varied environments, they are traditionally regarded as fundamentally distinct phenomena. They can however be joined into a single framework that emphasizes the parallel roles of environmental and genetic cues in phenotype determination. First, from the point of view of immediate causation, it is common that phenotypic variants can be induced either by environmental or by allelic variation, and this is referred to as gene-environment interchangeability. Second, from the point of view of adaptation, genetic cues in the form of allelic variation at polymorphic loci can play similar roles as environmental cues in providing information to the developmental system about coming selective conditions. Both types of cues can help a developing organism to fit its phenotype to selective circumstances. This perspective of information in environmental and genetic cues can produce testable hypotheses about phenotype determination, and can thus increase our understanding of the evolution of phenotypic polymorphism.

  • 29.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Game theory and biology2008In: The New Palgrave Dictionary of Economics, 2nd Edition, Palgrave Macmillan , 2008Chapter in book (Refereed)
    Abstract [en]

    Darwinian evolutionary dynamics and learning dynamics provide the foundation for game theory in biology. The theory is used to analyse interactions between individuals. Animal fighting behaviour, cooperative interactions and signalling interactions are examples of important areas of application. The payoffs to strategies in biological games represent Darwinian fitness, viz. survival and reproductive success. The strategies can be behaviour patterns, but also choices of phenotypic properties such as becoming a male or a female. The evolutionary analysis of allocation to male and female function is one of the most successful applications of game theory in biology.

  • 30.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Multidimensional convergence stability2009In: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 11, p. 191-208Article in journal (Refereed)
    Abstract [en]

    Questions: Are there general stability conditions for the evolution Of Multidimensional traits, regardless of genetic correlations between traits? Can genetic correlations influence whether evolution converges to a stable trait vector?

    Mathematical methods: Adaptive dynamics theory and the weak selection limit of quantitative genetics.

    Key assumptions: Evolutionary change is represented as either (i) any gradualistic adaptive path in trait space, consisting of a sequence of small-effect mutant invasions, allowing for pleiotropic mutants, or (ii) a solution to the 'canonical equation' of adaptive dynamics with a gradually varying mutational covariance matrix. Assumption (ii) is a special case of (i).

    Conclusions: It is possible to formulate robust stability conditions for multidimensional traits, but most evolutionary equilibria will not satisfy these conditions. Under the liberal assumption (i), there will in general be no 'absolutely convergence stable' equilibria in multidimensional trait spaces (except for simplified models). Under the more restrictive assumption (ii), a Much larger proportion of evolutionary equilibria is 'strongly convergence stable', i.e. are stable irrespective of genetic correlations.

  • 31.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dall, Sasha R. X.
    Hammerstein, Peter
    McNamara, John M.
    Genes as Cues of Relatedness and Social Evolution in Heterogeneous Environments2016In: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 12, no 6, article id e1005006Article in journal (Refereed)
    Abstract [en]

    There are many situations where relatives interact while at the same time there is genetic polymorphism in traits influencing survival and reproduction. Examples include cheater-cooperator polymorphism and polymorphic microbial pathogens. Environmental heterogeneity, favoring different traits in nearby habitats, with dispersal between them, is one general reason to expect polymorphism. Currently, there is no formal framework of social evolution that encompasses genetic polymorphism. We develop such a framework, thus integrating theories of social evolution into the evolutionary ecology of heterogeneous environments. We allow for adaptively maintained genetic polymorphism by applying the concept of genetic cues. We analyze a model of social evolution in a two-habitat situation with limited dispersal between habitats, in which the average relatedness at the time of helping and other benefits of helping can differ between habitats. An important result from the analysis is that alleles at a polymorphic locus play the role of genetic cues, in the sense that the presence of a cue allele contains statistical information for an organism about its current environment, including information about relatedness. We show that epistatic modifiers of the cue polymorphism can evolve to make optimal use of the information in the genetic cue, in analogy with a Bayesian decision maker. Another important result is that the genetic linkage between a cue locus and modifier loci influences the evolutionary interest of modifiers, with tighter linkage leading to greater divergence between social traits induced by different cue alleles, and this can be understood in terms of genetic conflict.

  • 32.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dall, Sasha R. X.
    McNamara, John M.
    Kuijper, Bram
    Hammerstein, Peter
    Ecological Genetic Conflict: Genetic Architecture Can Shift the Balance between Local Adaptation and Plasticity2019In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 193, no 1, p. 70-80Article in journal (Refereed)
    Abstract [en]

    Genetic polymorphism can contribute to local adaptation in heterogeneous habitats, for instance, as a single locus with alleles adapted to different habitats. Phenotypic plasticity can also contribute to trait variation across habitats, through developmental responses to habitat-specific cues. We show that the genetic architecture of genetically polymorphic and plasticity loci may influence the balance between local adaptation and phenotypic plasticity. These effects of genetic architecture are instances of ecological genetic conflict. A reduced effective migration rate for genes tightly linked to a genetic polymorphism provides an explanation for the effects, and they can occur both for a single trait and for a syndrome of coadapted traits. Using individual-based simulations and numerical analysis, we investigate how among-habitat genetic polymorphism and phenotypic plasticity depend on genetic architecture. We also study the evolution of genetic architecture itself, in the form of rates of recombination between genetically polymorphic loci and plasticity loci. Our main result is that for plasticity genes that are unlinked to loci with between-habitat genetic polymorphism, the slope of a reaction norm is steeper in comparison with the slope favored by plasticity genes that are tightly linked to genes for local adaptation.

  • 33.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Doebeli, Michael
    Dieckmann, Ulf
    Evolution of phenotypic clusters through competition and local adaptation along an environmental gradient.2008In: Evolution, ISSN 0014-3820, Vol. 62, no 4, p. 807-22Article in journal (Refereed)
    Abstract [en]

    We have analyzed the evolution of a quantitative trait in populations that are spatially extended along an environmental gradient, with gene flow between nearby locations. In the absence of competition, there is stabilizing selection toward a locally best-adapted trait that changes gradually along the gradient. According to traditional ideas, gradual spatial variation in environmental conditions is expected to lead to gradual variation in the evolved trait. A contrasting possibility is that the trait distribution instead breaks up into discrete clusters. Doebeli and Dieckmann (2003) argued that competition acting locally in trait space and geographical space can promote such clustering. We have investigated this possibility using deterministic population dynamics for asexual populations, analyzing our model numerically and through an analytical approximation. We examined how the evolution of clusters is affected by the shape of competition kernels, by the presence of Allee effects, and by the strength of gene flow along the gradient. For certain parameter ranges clustering was a robust outcome, and for other ranges there was no clustering. Our analysis shows that the shape of competition kernels is important for clustering: the sign structure of the Fourier transform of a competition kernel determines whether the kernel promotes clustering. Also, we found that Allee effects promote clustering, whereas gene flow can have a counteracting influence. In line with earlier findings, we could demonstrate that phenotypic clustering was favored by gradients of intermediate slope.

  • 34.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hammerstein, Peter
    Cooperation for direct fitness benefits2010In: Philosophical transactions of the Royal Society of London. Series B, Biological sciences, ISSN 1471-2970, Vol. 365, no 1553, p. 2619-2626Article in journal (Refereed)
    Abstract [en]

    Studies of the evolution of helping have traditionally used the explanatory frameworks of reciprocity and altruism towards relatives, but recently there has been an increasing interest in other kinds of explanations. We review the success or otherwise of work investigating alternative processes and mechanisms, most of which fall under the heading of cooperation for direct benefits. We evaluate to what extent concepts such as by-product benefits, pseudo-reciprocity, sanctions and partner choice, markets and the build-up of cross-species spatial trait correlations have contributed to the study of the evolution of cooperation. We conclude that these alternative ideas are successful and show potential to further increase our understanding of cooperation. We also bring up the origin and role of common interest in the evolution of cooperation, including the appearance of organisms. We note that there are still unresolved questions about the main processes contributing to the evolution of common interest. Commenting on the broader significance of the recent developments, we argue that they represent a justified balancing of the importance given to different major hypotheses for the evolution of cooperation. This balancing is beneficial because it widens considerably the range of phenomena addressed and, crucially, encourages empirical testing of important theoretical alternatives.

  • 35.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hartfelder, Klaus
    Laubichler, Manfred D.
    Page, Robert E., Jr.
    Development and evolution of caste dimorphism in honeybees: a modeling approach2012In: Ecology and Evolution, ISSN 2045-7758, Vol. 2, no 12, p. 3098-3109Article in journal (Refereed)
    Abstract [en]

    The difference in phenotypes of queens and workers is a hallmark of the highly eusocial insects. The caste dimorphism is often described as a switch-controlled polyphenism, in which environmental conditions decide an individual's caste. Using theoretical modeling and empirical data from honeybees, we show that there is no discrete larval developmental switch. Instead, a combination of larval developmental plasticity and nurse worker feeding behavior make up a colony-level social and physiological system that regulates development and produces the caste dimorphism. Discrete queen and worker phenotypes are the result of discrete feeding regimes imposed by nurses, whereas a range of experimental feeding regimes produces a continuous range of phenotypes. Worker ovariole numbers are reduced through feeding-regime-mediated reduction in juvenile hormone titers, involving reduced sugar in the larval food. Based on the mechanisms identified in our analysis, we propose a scenario of the evolutionary history of honeybee development and feeding regimes.

  • 36.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    McNamara, John M.
    Learning leads to bounded rationality and the evolution of cognitive bias in public goods games2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 16319Article in journal (Refereed)
    Abstract [en]

    In social interactions, including cooperation and conflict, individuals can adjust their behaviour over the shorter term through learning within a generation, and natural selection can change behaviour over the longer term of many generations. Here we investigate the evolution of cognitive bias by individuals investing into a project that delivers joint benefits. For members of a group that learn how much to invest using the costs and benefits they experience in repeated interactions, we show that overestimation of the cost of investing can evolve. The bias causes individuals to invest less into the project. Our explanation is that learning responds to immediate rather than longer-term rewards. There are thus cognitive limitations in learning, which can be seen as bounded rationality. Over a time horizon of several rounds of interaction, individuals respond to each other's investments, for instance by partially compensating for another's shortfall. However, learning individuals fail to strategically take into account that social partners respond in this way. Learning instead converges to a one-shot Nash equilibrium of a game with perceived rewards as payoffs. Evolution of bias can then compensate for the cognitive limitations of learning.

  • 37.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    McNamara, John M.
    The Evolution of Transgenerational Integration of Information in Heterogeneous Environments2015In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 185, no 3, p. E55-E69Article in journal (Refereed)
    Abstract [en]

    An organism's phenotype can be influenced by maternal cues and directly perceived environmental cues, as well as by its genotype at polymorphic loci, which can be interpreted as a genetic cue. In fluctuating environments, natural selection favors organisms that efficiently integrate different sources of information about the likely success of phenotypic alternatives. In such situations, it can be beneficial to pass on maternal cues that offspring can respond to. A maternal cue could be based on environmental cues directly perceived by the mother but also partly on cues that were passed on by the grandmother. We have used a mathematical model to investigate how the passing of maternal cues and the integration of different sources of information evolve in response to qualitatively different kinds of temporal and spatial environmental fluctuations. The model shows that the passing of maternal cues and the transgenerational integration of sources of information readily evolve. Factors such as the degree of temporal autocorrelation, the predictive accuracy of different environmental cues, and the level of gene flow strongly influence the expression of adaptive maternal cues and the relative weights given to different sources of information. We outline the main features of the relation between the characteristics of environmental fluctuations and the adaptive systems of phenotype determination and compare these predictions with empirical studies on cue integration.

  • 38.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Norberg, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Metapopulation extinction and genetic variation in dispersal-related traits1997In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 80, p. 448-458Article in journal (Refereed)
  • 39.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Norberg, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Habitat preference and habitat exploration in two species of satyrine butterflies2003In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 26, p. 474-480Article in journal (Refereed)
  • 40.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sasaki, Akira
    Doebeli, Michael
    Dieckmann, Ulf
    Limiting similarity, species packing, and the shape of competition kernels2013In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 339, p. 3-13Article in journal (Refereed)
    Abstract [en]

    A traditional question in community ecology is whether species' traits are distributed as more-or-less regularly spaced clusters. Interspecific competition has been suggested to play a role in such structuring of communities. The seminal theoretical work on limiting similarity and species packing, presented four decades ago by Robert MacArthur, Richard Levins and Robert May, has recently been extended. There is now a deeper understanding of how competitive interactions influence community structure, for instance, how the shape of competition kernels can determine the clustering of species' traits. Competition is typically weaker for greater phenotypic difference, and the shape of the dependence defines a competition kernel. The clustering tendencies of kernels interact with other effects, such as variation in resource availability along a niche axis, but the kernel shape can have a decisive influence on community structure. Here we review and further extend the recent developments and evaluate their importance.

  • 41.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Tullberg, Birgitta S.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mallet, James
    Mimicry, saltational evolution, and the crossing of fitness valleys2012In: The adaptive landscape in evolutionary biology / [ed] Erik I. Svensson, Ryan Calsbeek, New York: Oxford University Press, 2012, p. 259-270Chapter in book (Refereed)
  • 42. McNamara, John M.
    et al.
    Dall, Sasha R. X.
    Hammerstein, Peter
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Detection vs. selection: integration of genetic, epigenetic and environmental cues in fluctuating environments2016In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 19, no 10, p. 1267-1276Article in journal (Refereed)
    Abstract [en]

    There are many inputs during development that influence an organism's fit to current or upcoming environments. These include genetic effects, transgenerational epigenetic influences, environmental cues and developmental noise, which are rarely investigated in the same formal framework. We study an analytically tractable evolutionary model, in which cues are integrated to determine mature phenotypes in fluctuating environments. Environmental cues received during development and by the mother as an adult act as detection-based (individually observed) cues. The mother's phenotype and a quantitative genetic effect act as selection-based cues (they correlate with environmental states after selection). We specify when such cues are complementary and tend to be used together, and when using the most informative cue will predominate. Thus, we extend recent analyses of the evolutionary implications of subsets of these effects by providing a general diagnosis of the conditions under which detection and selection-based influences on development are likely to evolve and coexist.

  • 43.
    McNamara, John M
    et al.
    Department of Mathematics, University of Bristol, University Walk, Bristol .
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Variation and the response to variation as a basis for successful cooperation.2010In: Philosophical transactions of the Royal Society of London. Series B, Biological sciences, ISSN 1471-2970, Vol. 365, no 1553, p. 2627-33Article in journal (Refereed)
    Abstract [en]

    In applying game theory to problems in biology, differences between individuals are often ignored. In particular, when analysing the evolution of cooperation it is often implicitly assumed that ignoring variation will produce predictions that approximate the solution when differences are included. This need not be true. As we demonstrate, differences are not innocuous noise, but can fundamentally change the nature of a game. Even small amounts of variability can stabilize cooperation by, for example, maintaining the need to deal with cheaters. Differences promote the need to learn about others in an interaction, leading to contingent behaviour that can reduce conflict, and to negotiated outcomes that may or may not be more cooperative than unconditional actions. Once there are mechanisms such as mutation and environmental influences that maintain variation within populations, whether cooperation evolves may depend on the variation in the cooperativeness trait. Variation means that it may be worth taking a chance that a partner is cooperative by being cooperative. When there are markets, so that individuals can break off interactions to seek a better partner, variation promotes choosiness and hence penalizes those uncooperative individuals, who are rejected. Variation promotes the need to monitor the previous behaviour of others, and once this social sensitivity exists, the need to maintain a good reputation can promote cooperation.

  • 44.
    Metz, Hans
    et al.
    Leiden University.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    A simple fitness proxy for structured populations with continuous traits, with case studies on the evolution of haplo-diploids and genetic dimorphisms2011In: Journal of Biological Dynamics, ISSN 1751-3758, E-ISSN 1751-3766, Vol. 5, no 2, p. 163-190Article in journal (Refereed)
    Abstract [en]

    For structured populations in equilibrium with everybody born equal ln(R0) is a useful fitness proxy for ESS and most adaptive dynamics calculations, with R0 the average lifetime number of offspring in the clonal and haploid cases, and half the average lifetime number of offspring fathered or mothered for Mendelian diploids. When individuals have variable birth states, as is e.g. the case in spatial models, R0 is itself an eigenvalue, which usually cannot be expressed explicitly in the trait vectors under consideration. In that case Q(Y | X ) := - det (I - L(Y | X )) can often be used as fitness proxy, with L the next-generation matrix for a potential mutant characterised by the trait vector Y in the (constant) environment engendered by a resident characterised by X . If the trait space is connected, global univadability can be determined from it. Moreover it can be used in all the usual local calculations like the determination of evolutionarily singular trait vectors and their local invadability and attractivity.

    We conclude with three extended case studies demonstrating the usefulness of Q: the calculation of ESSes under haplo-diploid genetics (I), of Evolutionarily Steady genetic Dimorphisms with a priori proportionality of macro- and micro-gametic outputs (an assumption that is generally made but the fulfilment of which is a priori highly exceptional) (II), and of ESDs without such proportionality (III). These case studies should also have some interest in their own right for the spelled out calculation recipes and their underlying modelling methodology. 

  • 45.
    Norberg, Ulf
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Enfjäll, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Habitat exploration in butterflies - an outdoor cage experiment2002In: Evolutionary ecology, Vol. 16, p. 1-14Article in journal (Refereed)
  • 46.
    Norberg, Ulf
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Spatial and temporal variation in flight morphology in the butterfly Melitaea cixia (Lepidoptera: Nymphalidae)2002In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 77, p. 445-453Article in journal (Refereed)
  • 47.
    Rautio, Pasi
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bergvall, Ulrika A.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish University of Agricultural Sciences, Sweden.
    Tuomi, Juha
    Kesti, Kari
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Food selection by herbivores and neighbourhood effects in the evolution of plant defences2012In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 49, no 1-2, p. 45-57Article in journal (Refereed)
    Abstract [en]

    A number of studies have reported how neighbouring plants may influence herbivory on palatable or unpalatable plants. Such neighbourhood effects can have important evolutionary consequences as they may either promote the evolutionary stability of plant defences or, alternatively, select against the fixation of plant defences and instead promote a stable polymorphism of palatable and unpalatable plants. These consequences depend on whether the difference in herbivore damage between unpalatable and palatable plants is smaller or, alternatively, greater when the neighbours are unpalatable instead of palatable. Such relations can arise when the neighbourhood effects are non-parallel among palatable and unpalatable plants. We outline two basic situations of non-parallel neighbourhood effects and illustrate how they can come about. A detailed dissection of these interactions reveals that there are several qualitatively distinct mechanisms that promote either evolutionary stability of plant defences or alternatively polymorphism. Our classification of mechanisms can be used to clarify and explain observations obtained in the field of plant herbivore interactions and predator prey interactions, both at the population and the community level.

  • 48. Rautio, Pasi
    et al.
    Kesti, Kari
    Alm Bergvall, Ulrika
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Tuomi, Juha
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Spatial scales of foraging in fallow deer: Implications for associational effects in plant defences2008In: Acta Oecologica, Vol. 34Article in journal (Refereed)
    Abstract [en]

    Large herbivores select food at several spatial scales: plant communities are chosen at a landscape scale, plant patches are chosen within a plant community, and individual plants within a patch. Foraging decision at the patch level can result in associational effects in plant communities and populations. Several studies have shown that herbivore attack and consumption rates may not only depend on a plant's own defence traits, but also on the defence traits of its neighbours. In the present experiment we investigated whether the spatial scale of the food distribution affects food selection by fallow deer and whether the foraging behaviour gives rise to associational effects in plant defences. In a population of captured wild fallow deer we simulated a natural situation where two separate plant patches are exposed to intense herbivory pressure. We presented different spatial arrangements of low- and high-tannin food to the deer, varying the frequency of the feeder types within and between patches. We found that the deer consumed palatable food among the unpalatable food on average as much as they consumed palatable food among other palatable feeders. However, when unpalatable food occurred among the palatable food it was more consumed than among other unpalatable feeders. Hence, we did not find support for associational defence, but our results supported associational susceptibility. At the between patch level a patch of mainly high-tannin feeders was consumed less when presented near to a patch of mainly low-tannin feeders, suggesting that for well-defended plants having palatable neighbours in a nearby patch might accentuate the effectiveness of their defence.

  • 49. Ruxton, Graeme D.
    et al.
    Franks, Dan W.
    Balogh, Alexandra C.V.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Evolutionary implications of the form of predator generalisation for aposematic signals and mimicry in prey2008In: Evolution: International Journal of Organic Evolution, ISSN 1558-5646, Vol. 62, no 11, p. 2913-2921Article in journal (Refereed)
    Abstract [en]

    Generalization is at the heart of many aspects of behavioral ecology; for foragers it can be seen as an essential feature of learning about potential prey, because natural populations of prey are unlikely to be perfectly homogenous. Aposematic signals are considered to aid predators in learning to avoid a class of defended prey. Predators do this by generalizing between the appearance of prey they have previously sampled and the appearance of prey they subsequently encounter. Mimicry arises when such generalization occurs between individuals of different species. Our aim here is to explore whether the specific shape of the generalization curve can be expected to be important for theoretical predictions relating to the evolution of aposematism and mimicry. We do this by a reanalysis and development of the models provided in two recent papers. We argue that the shape of the generalization curve, in combination with the nature of genetic and phenotypic variation in prey traits, can have evolutionary significance under certain delineated circumstances. We also demonstrate that the process of gradual evolution of Müllerian mimicry proposed by Fisher is particularly efficient in populations with a rich supply of standing genetic variation in mimetic traits.

  • 50.
    Ryman, Nils
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Populationsgenetik.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Etologi.
    Effect of mutation on genetic differentiation among nonequilibrium populations.2008In: Evolution, ISSN 0014-3820, Vol. 62, no 9, p. 2250-9Article in journal (Refereed)
    Abstract [en]

    The usefulness of G(ST) and similar measures of genetic differentiation has been questioned repeatedly because of their dependence on the amount of heterozygosity within populations, creating problems when comparing degrees of divergence at loci with different mutation rates. Although the effect of mutation on G(ST) is expected to be small in the early phases of divergence, it is unclear for how long after separation from a common ancestral population that G(ST) is largely unaffected by mutation and by the resulting effect on heterozygosity. We address this question through analysis of the recursion equations for gene identity under the infinite allele model of mutation, and derive conditions describing when the effect of mutation on G(ST) can be ignored under mutation-migration-drift equilibrium conditions and during the preceding transition phase. An important result is that during the transition phase G(ST) is not only affected by mutation, but also by the heterozygosity in the base population from which the subpopulations diverged. The effect of mutation on G(ST) is significant from the very start of the divergence process when initial heterozygosity is low, whereas G(ST) is only weakly affected by mutation in the early phases of differentiation when initial heterozygosity is high. Thus, differentiation following a severe bottleneck is strongly dependent on mutation. The standardized measure of differentiation, G'(ST), suggested by Hedrick (2005), may be helpful when comparing amounts of divergence at loci with different mutation rates under steady-state conditions, provided that migration is very low. In many other situations the use of G'(ST) might be misleading, however, and its application should be exercised with caution.

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