Local not vocal: assortative female choice in divergent populations of red-eyed treefrogs,<i>Agalychnis callidryas</i>(Hylidae: Phyllomedusinae)

Abstract

Premating behavioural isolation can facilitate divergence among natural populations. The red-eyed treefrog (Agalychnis callidryas) exhibits a strong population genetic structure that coincides with geographical differentiation in colour pattern and body size. We examined assortative mating for local males in two geographically isolated populations that exhibit high levels of phenotypic and genetic differentiation in Costa Rica. At each site, we placed a gravid female in an enclosure that contained one local and one nonlocal male (N = 79 trials total). We used log-linear modelling to analyze the parameters that best predicted female choice. We found that females in each population preferred local mates. Furthermore, 73% of females chose a male in the absence of any male advertisement call, highlighting the importance of non-acoustic cues in mate choice. Our mate-choice trials provide evidence that population divergence in phenotype could be partly mediated by behavioural interactions. We found no significant effect of male body size on female choice; however, because body size, colour pattern, and behaviour are all important sexual signals for anuran species, we discuss the potential roles of these divergent phenotypes in mate recognition and female choice in the red-eyed treefrog.