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  • 1.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The Evolution of Body Size in Mammals on Islands - Some Comments1985In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 125, no 2, p. 304-309Article in journal (Refereed)
  • 2.
    Arnqvist, Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Kirkpatrick, M.
    The Evolution of Infidelity in Socially Monogamous Passerines Revisited: A Reply to Griffith2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 169, no 2, p. 282-283Article in journal (Refereed)
  • 3.
    Arnqvist, Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Kirkpatrick, M
    The evolution of infidelity in socially monogamous passerines: The strength of direct and indirect selection on extrapair copulation behavior in females2005In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 165, no 5, p. S26-S37Article in journal (Refereed)
  • 4.
    Aunapuu, Maano
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dahlgren, Jonas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Oksanen, Tarja
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Grellmann, Doris
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Oksanen, Lauri
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rammul, Ullar
    Schneider, Michael
    Johansen, Bernt
    Hygen, Hans Olav
    Spatial patterns and dynamic responses of arctic food webs corroborate the exploitation ecosystems hypothesis (EEH)2008In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 171, no 2, p. 249-262Article in journal (Refereed)
    Abstract [en]

    According to the exploitation ecosystems hypothesis (EEH), productive terrestrial ecosystems are characterized by community‐level trophic cascades, whereas unproductive ecosystems harbor food‐limited grazers, which regulate community‐level plant biomass. We tested this hypothesis along arctic‐alpine productivity gradients at the Joatka field base, Finnmark, Norway. In unproductive habitats, mammalian predators were absent and plant biomass was constant, whereas herbivore biomass varied, reflecting the productivity of the habitat. In productive habitats, predatory mammals were persistently present and plant biomass varied in space, but herbivore biomass did not. Plant biomass of productive tundra scrublands declined by 40% when vegetation blocks were transferred to predation‐free islands. Corresponding transfer to herbivore‐free islands triggered an increase in plant biomass. Fertilization of an unproductive tundra heath resulted in a fourfold increase in rodent density and a corresponding increase in winter grazing activity, whereas the total aboveground plant biomass remained unchanged. These results corroborate the predictions of the EEH, implying that the endotherm community and the vegetation of the North European tundra behaves dynamically as if each trophic level consisted of a single population, in spite of local co‐occurrence of >20 plant species representing different major taxonomic groups, growth forms, and defensive strategies.

  • 5.
    Berger, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Martinossi-Allibert, Ivain
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Grieshop, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Lind, Martin I.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Maklakov, Alexei A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Arnqvist, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Intralocus Sexual Conflict and the Tragedy of the Commons in Seed Beetles2016In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 188, no 4, p. E98-E112Article in journal (Refereed)
    Abstract [en]

    The evolution of male traits that inflict direct harm on females during mating interactions can result in a so-called tragedy of the commons, where selfish male strategies depress population viability. This tragedy of the commons can be magnified by intralocus sexual conflict (IaSC) whenever alleles that reduce fecundity when expressed in females spread in the population because of their benefits in males. We evaluated this prediction by detailed phenotyping of 73 isofemale lines of the seed beetle Callosobruchus maculatus. We quantified genetic variation in life history andmorphology, as well as associated covariance in male and female adult reproductive success. In parallel, we created replicated artificial populations of each line and measured their productivity. Genetic constraints limited independent trait expression in the sexes, and we identified several instances of sexually antagonistic covariance between traits and fitness, signifying IaSC. Population productivity was strongly positively correlated to female adult reproductive success but uncorrelated with male reproductive success. Moreover, male (female) phenotypic optima for several traits under sexually antagonistic selection were exhibited by the genotypes with the lowest (highest) population productivity. Our study forms a direct link between individuallevel sex-specific selection and population demography and places lifehistory traits at the epicenter of these dynamics.

  • 6.
    Berger, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Olofsson, Martin
    Gotthard, Karl
    Wiklund, Christer
    Friberg, Magne
    Ecological Constraints on Female Fitness in a Phytophagous Insect2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 4, p. 464-480Article in journal (Refereed)
    Abstract [en]

    Although understanding female reproduction is crucial for population demography, determining how and to what relative extent it is constrained by different ecological factors is complicated by difficulties in studying the links between individual behavior, life history, and fitness in nature. We present data on females in a natural population of the butterfly Leptidea sinapis. These data were combined with climate records and laboratory estimates of life-history parameters to predict the relative impact of different ecological constraints on female fitness in the wild. Using simulation models, we partitioned effects of male courtship, host plant availability, and temperature on female fitness. Results of these models indicate that temperature is the most constraining factor on female fitness, followed by host plant availability; the short-term negative effects of male courtship that were detected in the field study were less important in models predicting female reproductive success over the entire life span. In the simulations, females with more reproductive reserves were more limited by the ecological variables. Reproductive physiology and egg-laying behavior were therefore predicted to be co-optimized but reach different optima for females of different body sizes; this prediction is supported by the empirical data. This study thus highlights the need for studying behavioral and life-history variation in orchestration to achieve a more complete picture of both demographic and evolutionary processes in naturally variable and unpredictable environments.

  • 7.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Olofsson, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Stockholm University, Faculty of Science, Department of Zoology.
    Ecological Constraints on Female Fitness in a Phytophagous Insect2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 4, p. 464-480Article in journal (Refereed)
    Abstract [en]

    Although understanding female reproduction is crucial for population demography, determining how and to what relative extent it is constrained by different ecological factors is complicated by difficulties in studying the links between individual behavior, life history, and fitness in nature. We present data on females in a natural population of the butterfly Leptidea sinapis. These data were combined with climate records and laboratory estimates of life-history parameters to predict the relative impact of different ecological constraints on female fitness in the wild. Using simulation models, we partitioned effects of male courtship, host plant availability, and temperature on female fitness. Results of these models indicate that temperature is the most constraining factor on female fitness, followed by host plant availability; the short-term negative effects of male courtship that were detected in the field study were less important in models predicting female reproductive success over the entire life span. In the simulations, females with more reproductive reserves were more limited by the ecological variables. Reproductive physiology and egg-laying behavior were therefore predicted to be co-optimized but reach different optima for females of different body sizes; this prediction is supported by the empirical data. This study thus highlights the need for studying behavioral and life-history variation in orchestration to achieve a more complete picture of both demographic and evolutionary processes in naturally variable and unpredictable environments.

  • 8.
    Berglund, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Rosenqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Svensson, Ingrid
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Reproductive success of females limited by males in two pipefish species1989In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 133, no 4, p. 506-516Article in journal (Refereed)
    Abstract [en]

    We investigate whether males limit the reproductive success of females in the two pipefish species Syngnathus typhle and Nerophis ophidion. Syngnathus typhle is sexually monomorphic, and courtship behavior does not differ between the sexes. In N. ophidion, on the contrary, females are larger, more colorful, and more active during courtship, possessing appearance-enlarging skin folds. In both species, males brood the offspring on their bodies, one internally and one externally. Males do not invest more energy in reproduction than do females, and in the sexually dimorphic species, males invest even less than females do. Natural sex ratios are equal in both species. Experimentally, we provided each female with an excess of males (i.e., three), in order to measure a female's maximal reproductive rate, and found that females of both species produced more eggs, or produced them at a faster rate, than naturally available males could care for. Within the time span of one male pregnancy, S. typhle females filled an average of 1.9 males and N. ophidion an average of 1.8 males; both numbers are significantly more than one (which is the average mate availability in natural populations). Measured in another way, during one male pregnancy, S. typhle and N. ophidion females both produced 41% more eggs than needed to fill a male, significantly more than no egg surplus in both species. Therefore, brood space and the rate of embryonic development limit female reproduction in these species. There was no significant difference between the species, however. Syngnathus typhle males might be expected to be less limiting than N. ophidion males, but sexual size dimorphism may be absent in S. typhle because, by contrast with N. ophidion, larger males enjoy greater reproductive success. Directional selection for increased male size may decrease sexual size dimorphism in S. typhle. At any rate, the limitation of the reproductive success of one sex by the other seems to be a necessary but not sufficient prerequisite for the evolution of sexual dimorphism and "sex roles."

  • 9.
    Brengdahl, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Kimber, Christopher
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Maguire-Baxter, Jack
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Malacrinò, Antonino
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Friberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Genetic Quality Affects the Rate of Male and Female Reproductive Aging Differently in Drosophila melanogaster2018In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 192, no 6, p. 761-772Article in journal (Refereed)
    Abstract [en]

    Males and females often maximize fitness by pursuing different reproductive strategies, with males commonly assumed to benefit more from increased resource allocation into current reproduction. Such investment should trade off with somatic maintenance and may explain why males frequently live shorter than females. It also predicts that males should experience faster reproductive aging. Here we investigate whether reproductive aging and life span respond to condition differently in male and female Drosophila melanogaster, as predicted if sexual selection has shaped male and female resource-allocation patterns. We manipulate condition through genetic quality by comparing individuals inbred or outbred for a major autosome. While genetic quality had a similar effect on condition in both sexes, condition had a much larger general effect on male reproductive output than on female reproductive output, as expected when sexual selection on vigor acts more strongly on males. We find no differences in reproductive aging between the sexes in low condition, but in high condition reproductive aging is relatively faster in males. No corresponding sex-specific change was found for life span. The sex difference in reproductive aging appearing in high condition was specifically due to a decreased aging rate in females rather than any change in males. Our results suggest that females age slower than males in high condition primarily because sexual selection has favored sex differences in resource allocation under high condition, with females allocating relatively more toward somatic maintenance than males.

  • 10. Brommer, J.E.
    et al.
    Wilson, A.J.
    Gustafsson, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Exploring the genetics of aging in a wild passerine bird2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 170, no 4, p. 643-650Article in journal (Refereed)
    Abstract [en]

    Senescence is the decline in survival and reproduction as an organism ages and is known to occur in collared flycatchers Ficedula albicollis. We consider annual fitness (the estimated genetic contribution that an individual makes to next year’s gene pool) as a measure of age‐specific fitness. We apply a restricted maximum likelihood linear mixed‐model approach on 25 years of data on 3,844 male and 4,992 female collared flycatchers. Annual fitness had a significant additive genetic component (h2 of about 4%). Annual fitness declined at later ages in both sexes. Using a random regression animal model, we show that the observed age‐related phenotypic changes in annual fitness were not present on the additive genetic level, contrary to predictions of genetic hypotheses of senescence. Our study suggests that patterns of aging in the wild need to be interpreted with caution in terms of underlying genetics because they may be largely determined by environmental processes.

  • 11. Brommer, Jon E.
    et al.
    Alho, Jussi S.
    Biard, Clotilde
    Chapman, Joanne R.
    Charmantier, Anne
    Dreiss, Amelie
    Hartley, Ian R.
    Hjernquist, Mårten B.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Kempenaers, Bart
    Komdeur, Jan
    Laaksonen, Toni
    Lehtonen, Paula K.
    Lubjuhn, Thomas
    Patrick, Samantha C.
    Rosivall, Balazs
    Tinbergen, Joost M.
    van der Velde, Marco
    van Oers, Kees
    Wilk, Tomasz
    Winkel, Wolfgang
    Passerine Extrapair Mating Dynamics: A Bayesian Modeling Approach Comparing Four Species2010In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 176, no 2, p. 178-187Article in journal (Refereed)
    Abstract [en]

    In many socially monogamous animals, females engage in extrapair copulation (EPC), causing some broods to contain both within-pair and extrapair young (EPY). The proportion of all young that are EPY varies across populations and species. Because an EPC that does not result in EPY leaves no forensic trace, this variation in the proportion of EPY reflects both variation in the tendency to engage in EPC and variation in the extrapair fertilization (EPF) process across populations and species. We analyzed data on the distribution of EPY in broods of four passerines (blue tit, great tit, collared flycatcher, and pied flycatcher), with 18,564 genotyped nestlings from 2,346 broods in two to nine populations per species. Our Bayesian modeling approach estimated the underlying probability function of EPC (assumed to be a Poisson function) and conditional binomial EPF probability. We used an information theoretical approach to show that the expected distribution of EPC per female varies across populations but that EPF probabilities vary on the above-species level (tits vs. flycatchers). Hence, for these four passerines, our model suggests that the probability of an EPC mainly is determined by ecological (population-specific) conditions, whereas EPF probabilities reflect processes that are fixed above the species level.

  • 12.
    Caruso, Christina M.
    et al.
    Univ Guelph, Dept Integrat Biol..
    Martin, Ryan A.
    Case Western Reserve Univ, Dept Biol..
    Sletvold, Nina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Morrissey, Michael B.
    Univ St Andrews, Sch Biol..
    Wade, Michael J.
    Indiana Univ, Dept Biol..
    Augustine, Kate E.
    Univ N Carolina, Dept Biol..
    Carlson, Stephanie M.
    Univ Calif Berkeley, Dept Environm Sci Policy & Management..
    MacColl, Andrew D. C.
    Univ Nottingham, Sch Life Sci..
    Siepielski, Adam M.
    Univ Arkansas, Dept Biol Sci..
    Kingsolver, Joel G.
    Univ N Carolina, Dept Biol..
    What Are the Environmental Determinants of Phenotypic Selection?: A Meta-analysis of Experimental Studies2017In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 190, no 3, p. 363-376Article in journal (Refereed)
    Abstract [en]

    Although many selection estimates have been published, the environmental factors that cause selection to vary in space and time have rarely been identified. One way to identify these factors is by experimentally manipulating the environment and measuring selection in each treatment. We compiled and analyzed selection estimates from experimental studies. First, we tested whether the effect of manipulating the environment on selection gradients depends on taxon, trait type, or fitness component. We found that the effect of manipulating the environment was larger when selection was measured on life-history traits or via survival. Second, we tested two predictions about the environmental factors that cause variation in selection. We found support for the prediction that variation in selection is more likely to be caused by environmental factors that have a large effect on mean fitness but not for the prediction that variation is more likely to be caused by biotic factors. Third, we compared selection gradients from experimental and observational studies. We found that selection varied more among treatments in experimental studies than among spatial and temporal replicates in observational studies, suggesting that experimental studies can detect relationships between environmental factors and selection that would not be apparent in observational studies.

  • 13.
    Cherif, Mehdi
    et al.
    Biogéochimie et Ecologie des Milieux Continentaux Laboratory, Unité Mixte de Recherche 7618, Ecole Normale Supérieure.
    Loreau, Michel
    Department of Biology, McGill University.
    Stoichiometric constraints on resource use, competitive interactions, and elemental cycling in microbial decomposers2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 169, no 6, p. 709-724Article in journal (Refereed)
    Abstract [en]

    Heterotrophic microbial decomposers, such as bacteria and fungi, immobilize or mineralize inorganic elements, depending on their elemental composition and that of their organic resource. This fact has major implications for their interactions with other consumers of inorganic elements. We combine the stoichiometric and resource-ratio approaches in a model describing the use by decomposers of an organic and an inorganic resource containing the same essential element, to study its consequences on decomposer interactions and their role in elemental cycling. Our model considers the elemental composition of organic matter and the principle of its homeostasis explicitly. New predictions emerge, in particular, ( 1) stoichiometric constraints generate a trade-off between the R* values of decomposers for the two resources; ( 2) they create favorable conditions for the coexistence of decomposers limited by different resources and with different elemental demands; ( 3) however, combined with conditions on species-specific equilibrium limitation, they draw decomposers toward colimitation by the organic and inorganic resources on an evolutionary time scale. Moreover, we derive the conditions under which decomposers switch from consumption to excretion of the inorganic resource. We expect our predictions to be useful in explaining the community structure of decomposers and their interactions with other consumers of inorganic resources, particularly primary producers.

  • 14. Claessen, David
    et al.
    Andersson, Jens
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, André M
    The effect of population size and recombination on delayed evolution of polymorphism and speciation in sexual populations2008In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 172, no 1, p. E18-34Article in journal (Refereed)
    Abstract [en]

    Recent theory suggests that absolute population size may qualitatively influence the outcome of evolution under disruptive selection in asexual populations. Large populations are predicted to undergo rapid evolutionary branching; however, in small populations, the waiting time to branching increases steeply with decreasing abundance, and below a critical size, the population remains monomorphic indefinitely. Here, we (1) extend the theory to sexual populations and (2) confront its predictions with empirical data, testing statistically whether lake size affects the level of resource polymorphism in arctic char (Salvelinus alpinus) in 22 lakes of different sizes. For a given level of recombination, our model predicts qualitatively similar relations between population size and time to evolutionary branching (either speciation or evolution of genetic polymorphism) as the asexual model, while recombination further increases the delay to branching. The loss of polymorphism at certain loci, an inherent aspect of multilocus-trait evolution, may increase the delay to speciation, resulting in stable genetic polymorphism without speciation. The empirical analysis demonstrates that the occurrence of resource polymorphism depends on both lake size and the number of coexisting fish species. For a given number of coexisting species, the level of polymorphism increases significantly with lake size, thus confirming our model prediction.

  • 15. Cornforth, Daniel M.
    et al.
    Sumpter, David J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics, Analysis and Applied Mathematics.
    Brown, Sam P.
    Brannstrom, Ake
    Synergy and Group Size in Microbial Cooperation2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 3, p. 296-305Article in journal (Refereed)
    Abstract [en]

    Microbes produce many molecules that are important for their growth and development, and the exploitation of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Although the production of these public-goods molecules has been studied intensely, little is known of how the benefits accrued and the costs incurred depend on the quantity of public-goods molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density, using a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating and then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an "evolutionary trap" that can stymie the establishment and maintenance of cooperation. By allowing density-dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results on experimental design.

  • 16. Cornforth, Daniel M
    et al.
    Sumpter, David J T
    Brown, Sam P
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Synergy and group size in microbial cooperation2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 3, p. 296-305Article in journal (Refereed)
    Abstract [en]

    Abstract Microbes produce many molecules that are important for their growth and development, and the exploitation of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Although the production of these public-goods molecules has been studied intensely, little is known of how the benefits accrued and the costs incurred depend on the quantity of public-goods molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density, using a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating and then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an "evolutionary trap" that can stymie the establishment and maintenance of cooperation. By allowing density-dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results on experimental design.

  • 17.
    Dahlgren, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Oksanen, Lauri
    Oksanen, Tarja
    Olofsson, Johan
    Trophic cascades and direct herbivore impacts in a low arctic scrublandIn: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323Article in journal (Other academic)
  • 18.
    de Roos, André M
    et al.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Schellekens, Tim
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    van Kooten, Tobias
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    van de Wolfshaar, Karen
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Claessen, David
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Food-dependent growth leads to overcompensation in stage-specific biomass when mortality increases: the influence of maturation versus reproduction regulation2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 170, no 3, p. E59-E76Article in journal (Refereed)
  • 19.
    Dean, Rebecca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nakagawa, Shinichi
    Pizzari, Tommaso
    The Risk and Intensity of Sperm Ejection in Female Birds2011In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 178, no 3, p. 343-354Article in journal (Refereed)
    Abstract [en]

    The way females utilize the gametes of different males has important consequences for sexual selection, sexual conflict, and intersexual coevolution in natural populations. However, patterns of sperm utilization by females are difficult to demonstrate, and their functional significance remains unclear. Here, we experimentally study sperm ejection in the fowl Gallus gallus domesticus, where females eject preferentially the sperm of socially subordinate males. We study two measures of sperm ejection, (i) the probability that an ejaculate is ejected ("risk") and (ii) the proportion of semen ejected ("intensity"), and show that both measures are strongly non-random with respect to characteristics of the ejaculate, the male, and the female. Sperm ejection neutralized on average 80% of an ejaculate, and while larger ejaculates suffered a higher ejection risk, smaller ejaculates suffered more intense ejection. After controlling for ejaculate volume, we found socially subdominant males suffered higher ejection intensity. After controlling for male and ejaculate effects, we found ejection risk increased and intensity declined as females mated with successive males. Collectively, these results reveal that sperm ejection risk and intensity are at least partly actively caused by female behavior and generate independent selective pressures on male and ejaculate phenotypes.

  • 20. DeAngelis, Donald L.
    et al.
    Wolkowicz, Gail S. K.
    Lou, Yuan
    Jiang, Yuexin
    Novak, Mark
    Svanbäck, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Araujo, Marcio S.
    Jo, YoungSeung
    Cleary, Erin A.
    The Effect of Travel Loss on Evolutionarily Stable Distributions of Populations in Space2011In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 178, no 1, p. 15-29Article in journal (Refereed)
    Abstract [en]

    A key assumption of the ideal free distribution (IFD) is that there are no costs in moving between habitat patches. However, because many populations exhibit more or less continuous population movement between patches and traveling cost is a frequent factor, it is important to determine the effects of costs on expected population movement patterns and spatial distributions. We consider a food chain (tritrophic or bitrophic) in which one species moves between patches, with energy cost or mortality risk in movement. In the two-patch case, assuming forced movement in one direction, an evolutionarily stable strategy requires bidirectional movement, even if costs during movement are high. In the N-patch case, assuming that at least one patch is linked bidirectionally to all other patches, optimal movement rates can lead to source-sink dynamics where patches with negative growth rates are maintained by other patches with positive growth rates. As well, dispersal between patches is not balanced (even in the two-patch case), leading to a deviation from the IFD. Our results indicate that cost-associated forced movement can have important consequences for spatial metapopulation dynamics. Relevance to marine reserve design and the study of stream communities subject to drift is discussed.

  • 21.
    Diehl, Sebastian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lundberg, Peter A
    Gardfjell, Hans
    Oksanen, Lauri
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Daphnia-phytoplankton interactions in lakes: is there a need for ratio-dependent consumer-resource models?1993In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 142, no 6, p. 1052-1061Article in journal (Refereed)
  • 22. Dowling, Damian K.
    et al.
    Meerupati, Tejashwari
    Arnqvist, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Cytonuclear Interactions and the Economics of Mating in Seed Beetles2010In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 176, no 2, p. 131-140Article in journal (Refereed)
    Abstract [en]

    Recent studies have uncovered an abundance of non-neutral cytoplasmic genetic variation within species, which suggests that we should no longer consider the cytoplasm an idle intermediary of evolutionary change. Nonneutrality of cytoplasmic genomes is particularly intriguing, given that these genomes are maternally transmitted. This means that the fate of any given cytoplasmic genetic mutation is directly tied to its performance when expressed in females. For this reason, it has been hypothesized that cytoplasmic genes will coevolve via a sexually antagonistic arms race with the biparentally transmitted nuclear genes with which they interact. We assess this prediction, examining the intergenomic contributions to the costs and benefits of mating in Callosobruchus maculatus females subjected to a mating treatment with three classes (kept virgin, mated once, or forced to cohabit with a male). We find no evidence that the economics of mating are determined by interactions between cytoplasmic genes expressed in females and nuclear genes expressed in males and, therefore, no support for a sexually antagonistic intergenomic arms race. The cost of mating to females was, however, shaped by an interaction between the cytoplasmic and nuclear genes expressed within females. Thus, cytonuclear interactions are embroiled in the economics of mating.

  • 23.
    Ehrlén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Münzbergova, Zuzana
    Timing of flowering - opposed selection on different fitness components and trait covariation2009In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 173, p. 819-830Article in journal (Refereed)
  • 24.
    Eklöv, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Svanbäck, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Predation risk influences adaptive morphological variation in fish populations2006In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 167, no 3, p. 440-452Article in journal (Refereed)
    Abstract [en]

    Predators can cause a shift in both density and frequency of a prey phenotype that may lead to phenotypic divergence through natural selection. What is less investigated is that predators have a variety of indirect effects on prey that could potentially have large evolutionary responses. We conducted a pond experiment to test whether differences in predation risk in different habitats caused shifts in behavior of prey that, in turn, would affect their morphology. We also tested whether the experimental data could explain the morphological variation of perch in the natural environment. In the experiment, predators caused the prey fish to shift to the habitat with the lower predation risk. The prey specialized on habitat-specific resources, and there was a strong correlation between diet of the prey fish and morphological variation, suggesting that resource specialization ultimately affected the morphology. The lack of differences in competition and mortality suggest that the morphological variation among prey was induced by differences in predation risk among habitats. The field study demonstrated that there are differences in growth related to morphology of perch in two different habitats. Thus, a trade-off between foraging and predator avoidance could be responsible for adaptive morphological variation of young perch.

  • 25.
    Evans, Simon R.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Schielzeth, Holger
    Forstmeier, Wolfgang
    Sheldon, Ben C.
    Husby, Arild
    Nonautosomal Genetic Variation in Carotenoid Coloration2014In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 184, no 3, p. 374-383Article in journal (Refereed)
    Abstract [en]

    Carotenoid-based coloration plays an important role in signaling, is often sexually dimorphic, and is potentially subject to directional and/or sex-specific selection. To understand the evolutionary dynamics of such color traits, it is essential to quantify patterns of inheritance, yet nonautosomal sources of genetic variation are easily overlooked by classical heritability analyses. Carotenoid metabolism has recently been linked to mitochondria, highlighting the potential for color variation to be explained by cytoplasmically inherited factors. In this study, we used quantitative genetic animal models to estimate the importance of mitochondrial and sex chromosome-linked sources of genetic variation in coloration in two songbird populations in which dietary carotenoids are either unmodified (great tit plumage) or metabolized into alternative color forms (zebra finch beak). We found no significant Z-linked genetic variance in great tit plumage coloration, while zebra finch beak coloration exhibited significant W linkage and cytoplasmic inheritance. Our results support cytoplasmic inheritance of color in the zebra finch, a trait based on endogenously metabolized carotenoids, and demonstrate the potential for nonautosomal sources to account for a considerable share of genetic variation in coloration. Although often overlooked, such nonautosomal genetic variation exhibits sex-dependent patterns of inheritance and potentially influences the evolution of sexual dichromatism.

  • 26.
    Evans, Simon R.
    et al.
    Univ Oxford, Dept Zool, Edward Grey Inst, Oxford OX1 3PS, England..
    Sheldon, Ben C.
    Univ Oxford, Dept Zool, Edward Grey Inst, Oxford OX1 3PS, England..
    Quantitative Genetics of a Carotenoid-Based Color: Heritability and Persistent Natal Environmental Effects in the Great Tit2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 179, no 1, p. 79-94Article in journal (Refereed)
    Abstract [en]

    The information content of signals such as animal coloration depends on the extent to which variation reflects underlying biological processes. Although animal coloration has received considerable attention, little work has addressed the quantitative genetics of color variation in natural populations. We investigated the quantitative genetics of a carotenoid-based color patch, the ventral plumage of mature great tits (Parus major), in a wild population. Carotenoid-based colors are often suggested to reflect environmental variation in carotenoid availability, but numerous mechanisms could also lead to genetic variation in coloration. Analyses of individuals of known origin showed that, although plumage chromaticity (i.e., color) was moderately heritable, there was no significant heritability to achromaticity (i.e., brightness). We detected multiple long-lasting effects of natal environment, with hatching date and brood size both negatively related to plumage chromaticity at maturity. Our reflectance measures contrasted in their spatiotemporal sensitivity, with plumage chromaticity exhibiting significant spatial variation and achromatic variation exhibiting marked annual variation. Hence, color variation in this species reflects both genetic and environmental influences on different scales. Our analyses demonstrate the context dependence of components of color variation and suggest that color patches may convey multiple aspects of individual state.

  • 27.
    Faulks, Leanne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Svanbäck, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Ragnarsson-Stabo, Henrik
    Eklöv, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Östman, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Intraspecific Niche Variation Drives Abundance-Occupancy Relationships in Freshwater Fish Communities2015In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 186, no 2, p. 272-283Article in journal (Refereed)
    Abstract [en]

    A positive relationship between occupancy and average local abundance of species is found in a variety of taxa, yet the mechanisms driving this association between abundance and occupancy are still enigmatic. Here we show that freshwater fishes exhibit a positive abundance-occupancy relationship across 125 Swedish lakes. For a subset of 9 species from 11 lakes, we estimated species-specific diet breadth from stable isotopes, within-lake habitat breadth from catch data for littoral and pelagic nets, adaptive potential from genetic diversity, abiotic niche position, and dispersal capacity. Average local abundance was mainly positively associated with both within-lake habitat and diet breadth, that is, species with larger intraspecific variation in niche space had higher abundances. No measure was a good predictor of occupancy, indicating that occupancy may be more directly related to abundance or abiotic conditions than to niche breadth per se. This study suggests a link between intraspecific niche variation and a positive abundance-occupancy relationship and implies that management of freshwater fish communities, whether to conserve threatened or control invasive species, should initially be aimed at niche processes.

  • 28. Fischer, Stefan
    et al.
    Bessert-Nettelbeck, Mathilde
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Taborsky, Barbara
    Rearing-Group Size Determines Social Competence and Brain Structure in a Cooperatively Breeding Cichlid2015In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 186, no 1, p. 123-140Article in journal (Refereed)
    Abstract [en]

    Social animals can greatly benefit from well-developed social skills. Because the frequency and diversity of social interactions often increase with the size of social groups, the benefits of advanced social skills can be expected to increase with group size. Variation in social skills often arises during ontogeny, depending on early social experience. Whether variation of social-group sizes affects development of social skills and related changes in brain structures remains unexplored. We investigated whether, in a cooperatively breeding cichlid, early group size (1) shapes social behavior and social skills and (2) induces lasting plastic changes in gross brain structures and (3) whether the development of social skills is confined to a sensitive ontogenetic period. Rearing-group size and the time juveniles spent in these groups interactively influenced the development of social skills and the relative sizes of four main brain regions. We did not detect a sensitive developmental period for the shaping of social behavior within the 2-month experience phase. Instead, our results suggest continuous plastic behavioral changes over time. We discuss how developmental effects on social behavior and brain architecture may adaptively tune phenotypes to their current or future environments.

  • 29. Gossner, Martin M.
    et al.
    Chao, Anne
    Bailey, Richard I.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Prinzing, Andreas
    Native Fauna on Exotic Trees: Phylogenetic Conservatism and Geographic Contingency in Two Lineages of Phytophages on Two Lineages of Trees2009In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 173, no 5, p. 599-614Article in journal (Refereed)
    Abstract [en]

    The relative roles of evolutionary history and geographical and ecological contingency for community assembly remain unknown. Plant species, for instance, share more phytophages with closer relatives (phylogenetic conservatism), but for exotic plants introduced to another continent, this may be overlaid by geographically contingent evolution or immigration from locally abundant plant species (mass effects). We assessed within local forests to what extent exotic trees (Douglas-fir, red oak) recruit phytophages (Coleoptera, Heteroptera) from more closely or more distantly related native plants. We found that exotics shared more phytophages with natives from the same major plant lineage (angiosperms vs. gymnosperms) than with natives from the other lineage. This was particularly true for Heteroptera, and it emphasizes the role of host specialization in phylogenetic conservatism of host use. However, for Coleoptera on Douglas-fir, mass effects were important: immigration from beech increased with increasing beech abundance. Within a plant phylum, phylogenetic proximity of exotics and natives increased phytophage similarity, primarily in younger Coleoptera clades on angiosperms, emphasizing a role of past codiversification of hosts and phytophages. Overall, phylogenetic conservatism can shape the assembly of local phytophage communities on exotic trees. Whether it outweighs geographic contingency and mass effects depends on the interplay of phylogenetic scale, local abundance of native tree species, and the biology and evolutionary history of the phytophage taxon.

  • 30.
    Gustafsson, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Terminal investment’ and a sexual conflict in the collared flycatcher (Ficedula albicollis)1992In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 140, no 5, p. 868-882Article in journal (Refereed)
  • 31.
    Göransson, Görgen
    et al.
    Lunds Universitet.
    Erlinge, S
    Högstedt, G
    Jansson, G
    Liberg, O
    Loman, J
    Nilsson, I N
    Schantz, T von
    Sylvén, M
    More thoughts on vertebrate predator regulation of prey.1988In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 132, no 1, p. 148-154Article in journal (Refereed)
  • 32.
    Hagman, Mattias
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of New South Wales, Australia.
    Ord, Terry J.
    Many Paths to a Common Destination: Morphological Differentiation of a Functionally Convergent Visual Signal2016In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 188, no 3, p. 306-318Article in journal (Refereed)
    Abstract [en]

    Understanding the interacting outcomes of selection and historical contingency in shaping adaptive evolution remains a challenge in evolutionary biology. While selection can produce convergent outcomes when species occupy similar environments, the unique history of each species can also influence evolutionary trajectories and result in different phenotypic end points. The question is to what extent historical contingency places species on different adaptive pathways and, in turn, the extent to which we can predict evolutionary outcomes. Among lizards there are several distantly related genera that have independently evolved an elaborate extendible dewlap for territorial communication. We conducted a detailed morphological study and employed new phylogenetic comparative methods to investigate the evolution of the underlying hyoid that powers the extension of the dewlap. This analysis showed that there appear to have been multiple phenotypic pathways for evolving a functionally convergent dewlap. The biomechanical complexity that underlies this morphological structure implies that adaptation should have been constrained to a narrow phenotypic pathway. However, multiple adaptive solutions have been possible in apparent response to a common selection pressure. Thus, the phenotypic outcome that subsequently evolved in different genera seems to have been contingent on the history of the group in question. This blurs the distinction between convergent and historically contingent adaptation and suggests that adaptive phenotypic diversity can evolve without the need for divergent natural selection.

  • 33. Hastad, Olle
    et al.
    Odeen, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Different ranking of avian colors predicted by modeling of retinal function in humans and birds2008In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 171, no 6, p. 831-838Article in journal (Refereed)
    Abstract [en]

    Only during the past decade have vision-system-neutral methods become common practice in studies of animal color signals. Consequently, much of the current knowledge on sexual selection is based directly or indirectly on human vision, which may or may not emphasize spectral information in a signal differently from the intended receiver. In an attempt to quantify this discrepancy, we used retinal models to test whether human and bird vision rank plumage colors similarly. Of 67 species, human and bird models disagreed in 26 as to which pair of patches in the plumage provides the strongest color contrast or which male in a random pair is the more colorful. These results were only partly attributable to human UV blindness. Despite confirming a strong correlation between avian and human color discrimination, we conclude that a significant proportion of the information in avian visual signals may be lost in translation.

  • 34.
    Hellström, Lars
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Umea Univ, Dept Math & Math Stat, SE-90187 Umeå, Sweden.
    Carlsson, Linus
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Umea Univ, Dept Math & Math Stat, SE-90187 Umea, Sweden.
    Falster, Daniel S.
    Univ New South Wales, Evolut & Ecol Res Ctr, Sydney, NSW 2052, Australia.;Univ New South Wales, Sch Biol Earth & Environm Sci, Sydney, NSW 2052, Australia.;Macquarie Univ, Dept Biol Sci, Sydney, NSW 2109, Australia..
    Westoby, Mark
    Macquarie Univ, Dept Biol Sci, Sydney, NSW 2109, Australia..
    Brannstrom, Ake
    Umea Univ, Dept Math & Math Stat, SE-90187 Umea, Sweden.;Int Inst Appl Syst Anal, Evolut & Ecol Program, A-2361 Laxenburg, Austria..
    Branch Thinning and the Large-Scale, Self-Similar Structure of Trees2018In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 192, no 1, p. E37-E47Article in journal (Refereed)
    Abstract [en]

    Branch formation in trees has an inherent tendency toward exponential growth, but exponential growth in the number of branches cannot continue indefinitely. It has been suggested that trees balance this tendency toward expansion by also losing branches grown in previous growth cycles. Here, we present a model for branch formation and branch loss during ontogeny that builds on the phenomenological assumption of a branch carrying capacity. The model allows us to derive approximate analytical expressions for the number of tips on a branch, the distribution of growth modules within a branch, and the rate and size distribution of tree wood litter produced. Although limited availability of data makes empirical corroboration challenging, we show that our model can fit field observations of red maple (Acer rubrum) and note that the age distribution of discarded branches predicted by our model is qualitatively similar to an empirically observed distribution of dead and abscised branches of balsam poplar (Populus balsamifera). By showing how a simple phenomenological assumptionthat the number of branches a tree can maintain is limitedleads directly to predictions on branching structure and the rate and size distribution of branch loss, these results potentially enable more explicit modeling of woody tissues in ecosystems worldwide, with implications for the buildup of flammable fuel, nutrient cycling, and understanding of plant growth.

  • 35.
    Hellström, Lars
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. School of Education, Culture and Communication, Mälardalen University, Västerås, Sweden.
    Carlsson, Linus
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. School of Education, Culture and Communication, Mälardalen University, Västerås, Sweden.
    Falster, Daniel S.
    Westoby, Mark
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg, Austria.
    Branch Thinning and the Large-Scale, Self-Similar Structure of Trees2018In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 192, no 1, p. E37-E47Article in journal (Refereed)
    Abstract [en]

    Branch formation in trees has an inherent tendency toward exponential growth, but exponential growth in the number of branches cannot continue indefinitely. It has been suggested that trees balance this tendency toward expansion by also losing branches grown in previous growth cycles. Here, we present a model for branch formation and branch loss during ontogeny that builds on the phenomenological assumption of a branch carrying capacity. The model allows us to derive approximate analytical expressions for the number of tips on a branch, the distribution of growth modules within a branch, and the rate and size distribution of tree wood litter produced. Although limited availability of data makes empirical corroboration challenging, we show that our model can fit field observations of red maple (Acer rubrum) and note that the age distribution of discarded branches predicted by our model is qualitatively similar to an empirically observed distribution of dead and abscised branches of balsam poplar (Populus balsamifera). By showing how a simple phenomenological assumptionthat the number of branches a tree can maintain is limitedleads directly to predictions on branching structure and the rate and size distribution of branch loss, these results potentially enable more explicit modeling of woody tissues in ecosystems worldwide, with implications for the buildup of flammable fuel, nutrient cycling, and understanding of plant growth.

  • 36. Hin, Vincent
    et al.
    Schellekens, Tim
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, Andre M.
    Coexistence of Predator and Prey in Intraguild Predation Systems with Ontogenetic Niche Shifts2011In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 178, no 6, p. 701-714Article in journal (Refereed)
    Abstract [en]

    In basic intraguild predation (IGP) systems, predators and prey also compete for a shared resource. Theory predicts that persistence of these systems is possible when intraguild prey is superior in competition and productivity is not too high. IGP often results from ontogenetic niche shifts, in which the diet of intraguild predators changes as a result of growth in body size (life-history omnivory). As a juvenile, a life-history omnivore competes with the species that becomes its prey later in life. Competition can hence limit growth of young predators, while adult predators can suppress consumers and therewith neutralize negative effects of competition. We formulate and analyze a stage-structured model that captures both basic IGP and life-history omnivory. The model predicts increasing coexistence of predators and consumers when resource use of stage-structured predators becomes more stage specific. This coexistence depends on adult predators requiring consumer biomass for reproduction and is less likely when consumers outcompete juvenile predators, in contrast to basic IGP. Therefore, coexistence occurs when predation structures the community and competition is negligible. Consequently, equilibrium patterns over productivity resemble those of three-species food chains. Life-history omnivory thus provides a mechanism that allows intraguild predators and prey to coexist over a wide range of resource productivity.

  • 37. HOGLUND, J
    SIZE AND PLUMAGE DIMORPHISM IN LEK-BREEDING BIRDS - A COMPARATIVE-ANALYSIS1989In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 134, no 1, p. 72-87Article in journal (Refereed)
  • 38. HOGLUND, J
    et al.
    SILLENTULLBERG, B
    DOES LEKKING PROMOTE THE EVOLUTION OF MALE-BIASED SIZE DIMORPHISM IN BIRDS - ON THE USE OF COMPARATIVE APPROACHES1994In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 144, no 6, p. 881-889Article in journal (Refereed)
  • 39.
    Husby, Arild
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Gustafsson, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Qvarnström, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Low Genetic Variance in the Duration of the Incubation Period in a Collared Flycatcher (Ficedula albicollis) Population2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 179, no 1, p. 132-136Article in journal (Refereed)
    Abstract [en]

    The avian incubation period is associated with high energetic costs and mortality risks suggesting that there should be strong selection to reduce the duration to the minimum required for normal offspring development. Although there is much variation in the duration of the incubation period across species, there is also variation within species. It is necessary to estimate to what extent this variation is genetically determined if we want to predict the evolutionary potential of this trait. Here we use a long-term study of collared flycatchers to examine the genetic basis of variation in incubation duration. We demonstrate limited genetic variance as reflected in the low and nonsignificant additive genetic variance, with a corresponding heritability of 0.04 and coefficient of additive genetic variance of 2.16. Any selection acting on incubation duration will therefore be inefficient. To our knowledge, this is the first time heritability of incubation duration has been estimated in a natural bird population.

  • 40.
    Husby, Arild
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
    Hille, Sabine M.
    Visser, Marcel E.
    Testing Mechanisms of Bergmann's Rule: Phenotypic Decline but No Genetic Change in Body Size in Three Passerine Bird Populations2011In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 178, no 2, p. 202-213Article in journal (Refereed)
    Abstract [en]

    Bergmann's rule predicts a decrease in body size with increasing temperature and has much empirical support. Surprisingly, we know very little about whether "Bergmann size clines" are due to a genetic response or are a consequence of phenotypic plasticity. Here, we use data on body size (mass and tarsus length) from three long-term (1979-2008) study populations of great tits (Parus major) that experienced a temperature increase to examine mechanisms behind Bergmann's rule. We show that adult body mass decreased over the study period in all populations and that tarsus length increased in one population. Both body mass and tarsus length were heritable and under weak positive directional selection, predicting an increase, rather than a decrease, in body mass. There was no support for microevolutionary change, and thus the observed declines in body mass were likely a result of phenotypic plasticity. Interestingly, this plasticity was not in direct response to temperature changes but seemed to be due to changes in prey dynamics. Our results caution against interpreting recent phenotypic body size declines as adaptive evolutionary responses to temperature changes and highlight the importance of considering alternative environmental factors when testing size clines.

  • 41. Härdling, Roger
    et al.
    Bergsten, Johannes
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Nonrandom Mating Preserves Intrasexual Polymorphism and Stops Population Differentiation in Sexual Conflict2006In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 167, p. 401-409Article in journal (Refereed)
    Abstract [en]

    Evolutionary conflict between the sexes is predicted to lead to sexual arms races in which male adaptations for acquiring mates (“offense” traits) are met by female counteradaptations—for example, to reduce mating rate (“defense” traits). Such coevolutionary chases may be perpetual. However, we show here that the coevolutionary process may also lead to a stable state in which multiple offense‐defense trait pairs are maintained. This type of polymorphism below the species level is a result of sexual conflict in combination with nonrandom mating. Our results show that if nonrandom mating occurs with respect to male and female conflict traits, genetic correlations will act to stabilize the trait frequencies so that all morphs are maintained. We discuss the results in special relation to the evolution of female polymorphism in diving beetles and argue that the process we describe may be a general force that maintains polymorphism in other taxa as well.

  • 42.
    Immler, Simone
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Otto, Sarah Perin
    Univ British Columbia, Dept Zool, Vancouver, BC V6T 1Z4, Canada.
    Driven Apart: The Evolution of Ploidy Differences between the Sexes under Antagonistic Selection2014In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 183, no 1, p. 96-107Article in journal (Refereed)
    Abstract [en]

    Sexual reproduction in eukaryotes implies a biphasic life cycle with alternating haploid and diploid phases. The nature of the biphasic life cycle varies markedly across taxa, and often either the diploid or the haploid phase is predominant. Why some taxa spend a major part of their life cycle as diploids and others as haploids remains a conundrum. Furthermore, ploidy levels may not only vary across life cycle phases but may also differ between males and females. The existence of two life cycle phases and two sexes bears a high potential for antagonistic selection, which in turn may influence the evolution of ploidy levels. We explored the evolution of ploidy levels when selection depends on both ploidy and sex. Our analyses show that antagonistic selection may drive the ploidy levels between males and females apart. In a subsequent step, we explicitly explored the evolution of arrhenotoky (i.e., haploid males and diploid females) in the context of antagonistic selection. Our model shows that selection on arrhenotoky depends on male fitness but evolves regardless of the fitness consequences to females. Overall we provide a plausible explanation for the evolution of sex differences in ploidy levels, a principle that can be extended to any system with asymmetric inheritance.

  • 43.
    Lehtovaara, Anne
    et al.
    Ageing Research Group, Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden.
    Schielzeth, Holger
    Ageing Research Group, Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden, Department of Evolutionary Biology, Bielefeld University, Bielefeld, Germany.
    Flis, Ilona
    Ageing Research Group, Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden.
    Friberg, Urban
    Ageing Research Group, Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden.
    Heritability of life span is largely sex limited in Drosophila.2013In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 182, no 5, p. 653-65Article in journal (Refereed)
    Abstract [en]

    Males and females differ with respect to life span and rate of aging in most animal species. Such sexual dimorphism can be associated with a complex genetic architecture, where only part of the genetic variation is shared between the sexes. However, the extent to which this is true for life span and aging is not known, because studies of life span have given contradictory results and aging has not been studied from this perspective. Here we investigate the additive genetic architecture of life span and aging in Drosophila melanogaster. We find substantial amounts of additive genetic variation for both traits, with more than three-quarters of this variation available for sex-specific evolutionary change. This result shows that the sexes have a profoundly different additive genetic basis for these traits, which has several implications. First, it translates into an, on average, three-times-higher heritability of life span within, compared to between, the sexes. Second, it implies that the sexes are relatively free to evolve with respect to these traits. And third, as life span and aging are traits that integrate over all genetic factors that contribute to mortal disease, it also implies that the genetics of heritable disease differs vastly between the sexes.

  • 44.
    Lehtovaara, Anne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Schielzeth, Holger
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Flis, Ilona
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Friberg, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Heritability of Life Span Is Largely Sex Limited in Drosophila2013In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 182, no 5, p. 653-665Article in journal (Refereed)
    Abstract [en]

    Males and females differ with respect to life span and rate of aging in most animal species. Such sexual dimorphism can be associated with a complex genetic architecture, where only part of the genetic variation is shared between the sexes. However, the extent to which this is true for life span and aging is not known, because studies of life span have given contradictory results and aging has not been studied from this perspective. Here we investigate the additive genetic architecture of life span and aging in Drosophila melanogaster. We find substantial amounts of additive genetic variation for both traits, with more than three-quarters of this variation available for sex-specific evolutionary change. This result shows that the sexes have a profoundly different additive genetic basis for these traits, which has several implications. First, it translates into an, on average, three-times-higher heritability of life span within, compared to between, the sexes. Second, it implies that the sexes are relatively free to evolve with respect to these traits. And third, as life span and aging are traits that integrate over all genetic factors that contribute to mortal disease, it also implies that the genetics of heritable disease differs vastly between the sexes.

  • 45.
    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.

  • 46.
    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.

  • 47. Liao, Wen Bo
    et al.
    Lou, Shang Ling
    Zeng, Yu
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Large Brains, Small Guts: The Expensive Tissue Hypothesis Supported within Anurans2016In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 188, no 6, p. 693-700Article in journal (Refereed)
    Abstract [en]

    Brain size differs substantially among species, and several hypotheses have been proposed to explain the evolution of brain size. Because the brain is among the most energetically expensive organs in the vertebrate body, trade-offs have been hypothesized to exert constraints on brain size evolution. Prominently, the expensive tissue hypothesis (ETH) proposes that reducing the size of another expensive organ, such as the gut, should compensate for the cost of a large brain. But energetic constraints may also drive covariation between the brain and other costly traitssuch as body maintenance, locomotion, or reproductionas formulated in the energy trade-off hypothesis. To date, these hypotheses have mainly been tested in homeothermic animals and within the ectothermic animals, primarily in fishes. Here, we undertake a comparative test of the interplay between energetic limitations and brain size evolution within amphibians. After controlling for phylogenetic relationships and body size, we find a negative correlation between brain mass and the length of the digestive tract within 30 species of anurans. We further find that the evolution of large brain size is accompanied by an increase in female reproductive investment into egg size. Our results suggest that the evolution of brain size follows general patterns across vertebrate clades.

  • 48.
    Libby, Eric
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Santa Fe Institute, Santa Fe, New Mexico.
    Ratcliff, William C.
    Shortsighted Evolution Constrains the Efficacy of Long-Term Bet Hedging2019In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 193, no 3, p. 409-423Article in journal (Refereed)
    Abstract [en]

    To survive unpredictable environmental change, many organisms adopt bet-hedging strategies that are initially costly but provide a long-term fitness benefit. The temporal extent of these deferred fitness benefits determines whether bet-hedging organisms can survive long enough to realize them. In this article, we examine a model of microbial bet hedging in which there are two paths to extinction: unpredictable environmental change and demographic stochasticity. In temporally correlated environments, these drivers of extinction select for different switching strategies. Rapid phenotype switching ensures survival in the face of unpredictable environmental change, while slower-switching organisms become extinct. However, when both switching strategies are present in the same population, then demographic stochasticity-enforced by a limited population size-leads to extinction of the faster-switching organism. As a result, we find a novel form of evolutionary suicide whereby selection in a fluctuating environment can favor bet-hedging strategies that ultimately increase the risk of extinction. Population structures with multiple subpopulations and dispersal can reduce the risk of extinction from unpredictable environmental change and shift the balance so as to facilitate the evolution of slower-switching organisms.

  • 49.
    Lovlie, Hanne
    et al.
    Stockholm University.
    Pizzari, Tom
    Sex in the Morning or in the Evening? Females Adjust Daily Mating Patterns to the Intensity of Sexual Harassment2007In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 170, no 1, p. E1-E13Article in journal (Refereed)
    Abstract [en]

    Selection on males to mate at a higher rate than females often results in male harassment of females and counteracting female responses. When the reproductive value of copulation changes over time, these mating strategies are expected to be time dependent. Here, we demonstrate that variation in the intensity of male harassment leads to drastic changes in female daily mating patterns. In feral populations of fowl Gallus gallus domesticus, male harassment is intense, particularly in the evening when inseminations are most likely to result in fertilization. We experimentally manipulated the intensity of male harassment through similar‐sized groups of different sex ratios. Male mating propensity was always higher than females’, particularly in male‐biased groups and in the evening, when males were closer to and more likely to approach females. Females counteracted male harassment by escalating resistance to mating and—crucially—by shifting their daily mating pattern: in strongly female‐biased groups with relaxed sexual harassment, females solicited sex in the evening, while in male‐biased groups, they solicited sex in the morning, thus avoiding harassment in the evening. Together, these results indicate that intersexual conflict may occur not only over mating rates but also over when in the day to copulate.

  • 50.
    Lundström, Niklas L. P.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Loeuille, Nicolas
    Meng, Xinzhu
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. College of Mathematics and System Science, Shandong University of Science and Technology, Qingdao, China.
    Bodin, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg, Austria.
    Meeting yield and conservation objectives by harvesting both juveniles and adults2019In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 193, no 3, p. 373-390Article in journal (Refereed)
    Abstract [en]

    Sustainable yields that are at least 80% of the maximum sustainable yield are sometimes referred to as "pretty good yields" (PGY). The range of PGY harvesting strategies is generally broad and thus leaves room to account for additional objectives besides high yield. Here, we analyze stage-dependent harvesting strategies that realize PGY with conservation as a second objective. We show that (1) PGY harvesting strategies can give large conservation benefits and (2) equal harvesting rates of juveniles and adults is often a good strategy. These conclusions are based on trade-off curves between yield and four measures of conservation that form in two established population models, one age-structured model and one stage-structured model, when considering different harvesting rates of juveniles and adults. These conclusions hold for a broad range of parameter settings, although our investigation of robustness also reveals that (3) predictions of the age-structured model are more sensitive to variations in parameter values than those of the stage-structured model. Finally, we find that (4) measures of stability that are often quite difficult to assess in the field (e.g., basic reproduction ratio and resilience) are systematically negatively correlated with impacts on biomass and size structure, so that these later quantities can provide integrative signals to detect possible collapses.

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