Cryptic female Strawberry poison frogs experience elevated predation risk when associating with an aposematic partner

Abstract

Population divergence in sexual signals may lead to speciation through prezygotic isolation. Sexual signals can change solely due to variation in the level of natural selection acting against conspicuousness. However, directional mate choice (i.e., favoring conspicuousness) across different environments may lead to gene flow between populations, thereby delaying or even preventing the evolution of reproductive barriers and speciation. In this study, we test whether natural selection through predation upon mate‐choosing females can favor corresponding changes in mate preferences. Our study system, Oophaga pumilio, is an extremely color polymorphic neotropical frog with two distinctive antipredator strategies: aposematism and crypsis. The conspicuous coloration and calling behavior of aposematic males may attract both cryptic and aposematic females, but predation may select against cryptic females choosing aposematic males. We used an experimental approach where domestic fowl were encouraged to find digitized images of cryptic frogs at different distances from aposematic partners. We found that the estimated survival time of a cryptic frog was reduced when associating with an aposematic partner. Hence, predation may act as a direct selective force on female choice, favoring evolution of color assortative mating that, in turn, may strengthen the divergence in coloration that natural selection has generated.

Dangerous love? Predation risk does not affect female mate choice in blue‐black grassquits

“…Our final scenario predicted that females would select more conspicuous male stimuli only in situations of low risk, and under high predation risk, they would choose male stimuli at random or even prefer more muted stimuli. This latter outcome assumed that association with vigorously displaying males might impose a great survival cost on females or their potential offspring (Dias et al, 2010;Marzal et al, 2016). Our results confirmed the first predicted scenario, given that females were non-responsive to male song stimuli, whether at low or high rates, across all experimental treatments.…”

“…A different scenario predicts that females may suffer a high survival cost by associating with conspicuous males (Marzal et al, 2016).…”

“…The third outcome assumes that females do not benefit from choosing conspicuous males in high predation risk environments. The greater reproductive costs endured by females with the increased predation risk to themselves (Marzal et al, 2016), and their offspring (Dias et al, 2010) cancel the benefits of pairing with a conspicuous male.…”

“…Within each experimental treatment context, females would be expected to favor males strongly (++), moderately (+) or not at all (−), as assessed by time spent in close proximity with the specific male stimulus (high or low song rate). Based onDias et al (2010) andMarzal et al (2016). Summary of possible female mate preference outcomes resulting from the experiments in this study.…”

Mating status correlates with dorsal brightness in some but not all poison frog populations

“…In case several females arrive at the territories of the males these might court the brightest females most intensely, while the other females leave the territory without entering courtship. On the other hand, it might be possible that less bright females avoid brighter males because of the enhanced probability to be detected by a predator (Marzal et al, 2016). Whether an extremely bright and conspicuous coloration as observed in Sarapiquí and Solarte can evolve might depend on resource availability and the heritability of coloration traits.…”