Form-function relationships within species are uncoupled from those across species in swimming and jumping performance in arboreal frogs.

Abstract

Variation of form-function relationships within populations is the substrate for adaptation at higher levels. Therefore, assessing similarity in form-function relationships within and between species may help reveal the processes shaping functional diversity. Here we test such similarity across three levels of anuran phenotypic divergence: within a population, among species in a single family (Hylidae; ~60 myr), and across a much broader sample of all anuran species using a single microhabitat (arboreal; ~120 myr). We expected less interspecific divergence to show higher similarity of form-function relationships with the intraspecific level. We analyzed the relationships between locomotor performance (in both swimming and jumping) and several hindlimb traits across these three evolutionary levels. While we found a positive correlation between swimming and jumping velocity at both intra- and interspecific levels, relationships between performance and body form did not match across levels. We suggest that different strengths of functional constraints or trade-offs may have produced more variation in form-function relationships across species, decoupling them from within-species patterns. We conclude that performance landscapes are likely qualitatively different across the different evolutionary scales, potentially reflecting changes in the relative importance of different behaviors across all arboreal species.