Abstracts (first author)


Being complex can be safe: testing predator avoidance of varying aposematic signals in a novel environment

Author(s): Rojas B, Rautiala P, Mappes J


Conspicuous colour patterns may function as interspecific signals in the context of predation by warning predators about prey unprofitability (aposematism). This strategy relies on the ability of predators to learn the association between colouration and unprofitability, and the subsequent avoidance of the unprofitable prey. Frequency-dependent selection is expected to favour uniformity and act against variability in aposematic signals. However, variation in aposematic species occurs in many taxa suggesting that signal variation may serve other purposes or be under variable selective pressures. Although the fundamental assumptions of aposematism have been well supported by mathematical models and experiments in controlled laboratory setups, their implications in the natural environment of both predators and prey have been until recently greatly overlooked. Predators are supposed to learn simpler patterns easier. Because variation in aposematic signals may imply morph-specific attack rates, aposematism as an anti-predator strategy could be overall less effective for individuals with complex colour patterns, especially when exposed to naïve predators or when invading novel environments, unless there were associated differences in detectability. We tested that hypothesis using wax models of the polymorphic, aposematic poison frog Dendrobates tinctorius placed in the wild, in a site where the actual frogs do not occur. We found that over time aposematic prey get less attacks than cryptic prey, but there were no differences in the attack rate between simple and complex morphs. However, complex morphs seemed to be more difficult to detect than simple ones. We suggest that wild predators are able to generalise aposematic colour patterns. Complex patterns may compensate being difficult to learn by being less detectable, which may contribute to the maintenance of the great intra-populational variation in colour patterns in this species.

Abstracts (coauthor)


The maintenance of trait polymorphisms in aposematic organisms is an evolutionary puzzle. The advantage of predator learning should drive warning signals of prey towards monomorphism, yet there are several examples of polymorphic aposematic species. Solving the riddle of polymorphism in such challenging cases would therefore represent an important contribution to our understanding of polymorphism maintenance in nature. Here, we examine the role of frequency dependent selection (FDS) on the maintenance of color polymorphism in an aposematic species. While models of frequency dependent selection are common, empirical evaluations are rare. The aposematic wood tiger moth (Parasemia plantaginis) presents two distinct male color morphs (yellow and white). Some populations have an admixture of both morphs whereas a few populations present only one of them. Research has previously shown that the more conspicuous yellow morph has a survival advantage under predation, which increases with morph frequency (i.e. positive FDS). This advantage and positive FDS should lead the yellow morph to fixation, yet this is not the case. We hypothesized that counteracting reproductive FDS (negative or positive) could maintain the polymorphism. First, we tested for reproductive FDS in the species using semi-natural enclosures set with three different frequencies of male color morphs (control, white-biased, and yellow-biased) to examine if the rare or common morph has a mating advantage. The experiment showed positive FDS in mating success for both morphs. Second, we formulated a theoretical model to test whether these results, and previous results on survival, can explain the maintenance of the observed polymorphism. The model showed that our patterns of positive frequency dependence can lead to polymorphism if considered in a spatial context, where variation in interacting ecological factors (e.g. predation), combined with a very small amount of gene flow can maintain the polymorphism.


Chairman: Octávio S. Paulo
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XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon


Computational Biology & Population Genomics Group