The frog symphony: comparing the evolutionary rates of dominant frequency and body size

The evolution of dominant frequency in frog calls is constrained by a conserved allometric relationship with body size, which has rarely been circumvented. However, four cases of allometric escape have been documented. Despite these deviations, no previous study has examined the evolutionary rates of dominant frequency and body size in Anura. If these traits have undergone evolutionary decoupling, their rates of evolution should vary independently across lineages. Here, we investigate this possibility using a dataset comprising 1641 species. We independently estimated branch-specific rates of dominant frequency and body size across the anuran phylogeny and identified shifts in rates. Our results reveal heterogeneous patterns of evolutionary rate variation in both traits, with accelerations and decelerations occurring either jointly or independently across clades. As predicted, decoupled evolutionary rates were found in clades where allometric escape had previously been reported: in these cases, one trait exhibited a rate shift while the other remained stable. However, the direction of rate change in the shifting trait varied across clades, involving either acceleration or deceleration, suggesting no consistent pattern of evolutionary response in these instances of decoupling. We discuss these rate shift patterns in relation to the call-associated morphological and ecological trait characteristics of each clade.