How phenotypic variation in the polymorphic frog Oophaga pumilio influences agonistic behaviors mediating the strength of species interactions?

Background/Question/Methods

Intraspecific phenotypic variation associates with behaviors that can mediate the strength of species interactions, and may ultimately affect species distributions and abundances. Polymorphic species provide an effective tool to help us better understand the potential effects of intraspecific phenotypic variation in species interactions. The highly territorial and polymorphic frog Oophaga pumilio exhibits impressive coloration and body size variation among islands in the Bocas del Toro Archipelago, Panama, with frogs from different islands exhibiting either bright (red, orange) or dull colorations (green, brown).  We examined how intraspecific trait variation in O. pumilio (coloration and body size) influences its agonistic interactions with conspecifics and two sympatric heterospecifics in terms of dominance/subordinance. We hypothesized that: 1) coloration in males of bright and dull populations of O. pumilio influences their aggressive behavior affecting the outcome of intraspecific and interespecific interactions; and 2) Differences in body size asymmetry between O. pumilio and heterospecifics influences their aggressive behavior and the outcome of species interactions, independent of coloration. To address our hypothesis, we conducted resident-intruder encounter experiments in which we assessed the intensity of territorial aggressive behaviors, measuring latency to first aggression and estimating an aggressive index. We completed 157 trials of 15 minutes length each.

Results/Conclusions

Preliminary results show brightness as a trait that mediates the strength of intraspecific interactions, and body size as a trait that mediates the strength of interspecific interactions. Males from bright O. pumilio populations tend to exhibit shorter and less variable latency times than males from dull populations, when paired with males of their same population. Males of O. pumilio from large bodied populations tend to exhibit less variable latency times than males from small bodied populations, when paired with other species. Our results suggest that intraspecific variation in brightness and size in O. pumilio differ in their relative influence on male-male interactions, which might ultimately influence species’ relative distributions and abundances in the Archipelago.