Our paper on the evolution of terrestrial breeding in frogs is out in Evolution! This was a fun one to write, and also the first chapter of Fabio de Sa’s PhD thesis.
Using comparative analyses and a multilocus phylogeny for the genera Cycloramphus and Zachaenus, our paper shows that terrestrial breeding has evolved three times in the clade, from a stream breeding (saxicolous) ancestor. Each time that happened, we see a correlated “shrinking” on the part of males, but not females, resulting in larger degree of sexual size dimorphism between the sexes.
Our conclusion is that by moving onto land, and breeding in concealed terrestrial chambers, or in leaf-litter, males are released from costly male-male competition that is typical for males defending territories and females in exposed stream breeding environments.