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Aposematism, Crypsis and Population Differentiation in the Strawberry Poison Frog
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Evolutionary transitions between the two major predator avoidance strategies aposematism and crypsis are expected to be associated with changes in many important traits of animals. However, empirical studies on populations experiencing ongoing or recent transitions between these strategies are rare. This thesis investigates the co-evolution of traits among populations of the Strawberry poison frog D.pumilio in Bocas del Toro, Panama. I found that all investigated populations were genetically distinct but that colour and pattern did not correlate with genetic or geographic distance, which suggests that selection needs to be invoked to explain the observed variation. Based on the chromatic contrast between frog dorsal colour and the natural habitat substrates used by the frogs, the populations were defined as bright or dull coloured. I found that frogs from bright coloured populations were larger. This is expected if aposematism is enhanced by large signals while crypsis is enhanced by small size. Further, individuals from bright coloured populations had a coarser black dorsal pattern, which is expected if crypsis is impaired by a bold pattern. The importance of pattern coarseness was confirmed by an avian detection experiment showing that coarse patterned dark green prey were more easily detected than dark green prey without pattern or with fine pattern. I put forward the hypothesis that enhanced protection, gained by aposematism, may affect behaviours that influence dispersal and pairing patterns. Indeed, males from bright coloured populations displayed at more exposed sites and showed a tendency to be more explorative and aggressive. In summary, my results show that the bright and dull coloured populations most likely represent an aposematic and a cryptic strategy, respectively. Furthermore, I show that evolutionary changes between aposematism and crypsis can be associated with coevolution of both morphology and behaviour. I argue that this coevolution may increase the likelihood of both pre- and post-zygotic reproductive isolation. This is because greater phenotypic differences between populations increase the likelihood of selection against badly adapted migrants and hybrids with intermediate traits.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , p. 43
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 956
Keywords [en]
co-evolution, population divergence, natural selection, sexual selection, warning colouration, Oophaga pumilio, Dendrobates pumilio, aggression, explorative behaviour, colour patterns
National Category
Evolutionary Biology Zoology Ecology
Research subject
Biology with specialization in Animal Ecology
Identifiers
URN: urn:nbn:se:uu:diva-175240ISBN: 978-91-554-8432-3 (print)OAI: oai:DiVA.org:uu-175240DiVA, id: diva2:544577
Public defence
2012-09-28, Zootissalen, Villavägen 9, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-09-06 Created: 2012-06-04 Last updated: 2013-01-22
List of papers
1. Non-gradual variation in colour morphs of the strawberry poison frog Dendrobates pumilio: genetic and geographical isolation suggest a role for selection in maintaining polymorphism
Open this publication in new window or tab >>Non-gradual variation in colour morphs of the strawberry poison frog Dendrobates pumilio: genetic and geographical isolation suggest a role for selection in maintaining polymorphism
2007 (English)In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 16, no 20, p. 4284-4294Article in journal (Refereed) Published
Abstract [en]

The relative roles that geographical isolation and selection play in driving population divergence remain one of the central questions in evolutionary biology. We approached this question by investigating genetic and morphological variation among populations of the strawberry poison frog, Dendrobates pumilio, in the Bocas del Toro archipelago, Panama. We found significant population genetic structure and isolation by distance based on amplified fragment length polymorphism markers. Snout vent length (SVL), coloration and the extent and size of dorsal black spots showed large variation among the studied populations. Differences in SVL correlated with genetic distance, whereas black spot patterns and other coloration parameters did not. Indeed, the latter characters were observed to be dramatically different between contiguous populations located on the same island. These results imply that neutral divergence among populations may account for the genetic patterns based on amplified fragment length polymorphism markers and SVL. However, selective pressures need to be invoked in order to explain the extraordinary variation in spot size and coverage, and coloration. We discuss the possibility that the observed variation in colour morphs is a consequence of a combination of local variation in both natural selection on an aposematic signal towards visual predators and sexual selection generated by colour morph-specific mate preferences.

Keywords
genetic diversity, morphological variation, neutral divergence, Poison dart frogs, selection, speciation
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-14742 (URN)10.1111/j.1365-294X.2007.03479.x (DOI)000249829700007 ()
Available from: 2008-01-31 Created: 2008-01-31 Last updated: 2017-12-11Bibliographically approved
2. Loss of conspicuous colouration has co-evolved with decreasing body size in populations of a poison dart frog
Open this publication in new window or tab >>Loss of conspicuous colouration has co-evolved with decreasing body size in populations of a poison dart frog
(English)Manuscript (preprint) (Other academic)
National Category
Zoology Evolutionary Biology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-179390 (URN)
Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2012-09-07
3. Pattern coarseness affects detectability of dull but not of conspicuously coloured poison frogs by an avian predator - implications for evolutionary transitions between aposematism and crypsis
Open this publication in new window or tab >>Pattern coarseness affects detectability of dull but not of conspicuously coloured poison frogs by an avian predator - implications for evolutionary transitions between aposematism and crypsis
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Zoology Evolutionary Biology Behavioral Sciences Biology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-179391 (URN)
Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2012-09-07
4. Rapid population divergence linked with co-variation between coloration and sexual display in strawberry poison frogs
Open this publication in new window or tab >>Rapid population divergence linked with co-variation between coloration and sexual display in strawberry poison frogs
2011 (English)In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 65, no 5, p. 1271-1282Article in journal (Refereed) Published
Abstract [en]

The likelihood of speciation is assumed to increase when sexually selected traits diverge together with ecologically important traits. According to sexual selection theory, the evolution of exaggerated display behavior is driven by increased mating success, but limited by natural selection, for example, through predation. However, the evolution of aposematic coloration (i.e., an ecologically important trait) could relieve the evolution of exaggerated display behavior from the bound of predation, resulting in joint divergence in aposematic coloration and sexual display behavior between populations. We tested this idea by examining conspicuousness, using color contrasts between individuals and their native backgrounds, and sexual display of 118 males from genetically diverged populations of the Strawberry poison frog, Dendrobates pumilio. Our results show that the level of conspicuousness of the population predicts the sexual display behavior of males. Males from conspicuous populations used more exposed calling sites. We argue that changes in aposematic coloration may rapidly cause not only postmating isolation due to poorly adapted hybrids, but also premating isolation through shifts in mating behaviors.

Keywords
Aposematism, natural selection, Oophaga pumilio, population differentiation, sexual selection, speciation
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-153586 (URN)10.1111/j.1558-5646.2010.01210.x (DOI)000289893000005 ()21166789 (PubMedID)
Available from: 2011-05-16 Created: 2011-05-16 Last updated: 2017-12-11Bibliographically approved
5. Does aggression and explorative behaviour decrease with lost warning colouration?
Open this publication in new window or tab >>Does aggression and explorative behaviour decrease with lost warning colouration?
2013 (English)In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 108, no 1, p. 116-126Article in journal (Refereed) Published
Abstract [en]

For prey, many behavioural traits are constrained by the risk of predation. Therefore, shifts between warning and cryptic coloration have been suggested to result in parallel changes in several behaviours. In the present study, we tested whether changes in chromatic contrast among eight populations of the strawberry poison-dart frog, Dendrobates pumilio, co-vary with behaviour, as expected if selection is imposed by predators relying on visual detection of prey. These eight populations are geographically isolated on different island in the Bocas del Toro region of Panama and have recently diverged morphologically and genetically. We found that aggression and explorative behaviour were strongly correlated and also that males tended to be more aggressive and explorative if they belonged to populations with conspicuously coloured individuals. We discuss how evolutionary switches between predator avoidance strategies and associated behavioural divergence between populations may affect reproductive isolation.

Keywords
Anura, Amphibia, aposematism, co-evolution, evolutionary innovation, Oophaga pumilio, population divergence
National Category
Zoology Evolutionary Biology
Research subject
Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-179389 (URN)10.1111/j.1095-8312.2012.02006.x (DOI)000312543100011 ()
Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2017-12-07Bibliographically approved

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