Research on the fascinating Neotropical poison frogs has focused mainly on two separate tracks, with limited integration: either on the evolution of toxicity, warning coloration (aposematism) and mimicry, or on reproductive strategies and parental care. Carvajal-Castro et al. (2021) attempt to unify these research areas in an updated phylogenetic framework. In reconstructing ancestral states, they found that male parental care is most likely to be the ancestral condition, and that aposematism likely evolved before the use of small leaf axil pools for breeding (phytotelmata). The authors found the complexity of parental care (i.e., intensive care of small numbers of offspring that are transported separately to phytotelmata) correlated with aposematism. The authors also asked whether tadpole deposition sites (phytotelmata versus non-phytotelmata) and components of aposematism (conspicuousness and toxicity) were evolutionarily correlated. They found that transitions from crypticity to conspicuousness, and from non-toxic to toxic, were significantly more common in phytotelm-breeding lineages with complex care. They hypothesize that aposematism may provide a kind of "umbrella trait" which allows the evolution of complex breeding behaviors, but also that these complex reproductive strategies may have favored the evolution of aposematism. Hence, these two suites of traits may have coevolved, each promoting the evolution of the other. They also found a negative correlation between aposematism and clutch size and the number of tadpoles transported at one time, which is consistent with changing life-history strategies associated with increased complexity and intensity of parental care. They argue increased aposematism and decreasing clutch-size may arise from the need to display warning coloration during long-range tadpole transport.
