Abstract
BackgroundAposematic species advertise their unpalatability using warning signals such as striking coloration. Given that predators need to sample aposematic prey to learn that they are unprofitable, prey with similar warning signals share the cost of predator learning. This reduction in predation risk drives evolutionary convergence of warning signals among chemically defended prey (Müllerian mimicry). Whether such warning signal convergence is associated to similar defence levels among co-mimics is still an open question that has rarely been tested in wild populations. We quantified variation in cyanide-based (CN) chemical protection in wild caught individuals of eight aposematic Heliconius butterfly species belonging to four sympatric mimicry rings. We then tested for correlations between chemical protection and ecological species-specific traits.ResultsWe report significant differences in CN concentrations both within and between sympatric species, even when accounting for the phylogeny, and within and between mimicry rings, even after considering inter-specific variation. We found significant correlations between CN concentration and both hostplant specialization and gregarious behaviour in adults and larvae. However, differences in CN concentrations were not significantly linked to mimicry ring abundance, although the two most toxic species did belong to the rarest mimicry ring.ConclusionsOur results suggest that mimicry can explain the variation in the levels of chemical defence to a certain extent, although other ecological factors are also relevant to the evolution of such variability.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0843-5) contains supplementary material, which is available to authorized users.
Highlights
Aposematic species advertise their unpalatability using warning signals such as striking coloration
The association between warning coloration and distastefulness can rely on predators’ innate biases [3], they usually need several sampling events to learn it [4,5,6,7]. This predation pressure promotes evolutionary convergence in colour patterns between chemically protected species living in sympatry, because species that share a common warning signal share the cost of predator learning
Our sample included 8 Heliconius species belonging to 4 different mimicry rings, encompassing all the local Heliconius mimicry rings: H. numata (n = 28, 7 females, 20 males, 1 not registered sex (NRS)) and H. ethilla (n = 5, 2 females, 3 males), H. erato (n = 23, 5 females, 17 males, 1 NRS) and H. melpomene (n = 20, 6 females, 13 males, 1 NRSS), H. aoede (n = 9, 4 females, 5 males) and H. burneyi (n = 8, 1 female, 7 males), H. sara (n = 12, 2 females, 10 males) and H. doris (n = 15, 9 females, 6 males)
Summary
Aposematic species advertise their unpalatability using warning signals such as striking coloration. Given that predators need to sample aposematic prey to learn that they are unprofitable, prey with similar warning signals share the cost of predator learning This reduction in predation risk drives evolutionary convergence of warning signals among chemically defended prey (Müllerian mimicry). The association between warning coloration and distastefulness can rely on predators’ innate biases [3], they usually need several sampling events to learn it [4,5,6,7] This predation pressure promotes evolutionary convergence in colour patterns between chemically protected species living in sympatry, because species that share a common warning signal share the cost of predator learning.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
