Data from: Performance in three shell functions predicts the phenotypic distribution of hard-shelled turtles

Adaptive landscapes have served as fruitful guides to evolutionary
research for nearly a century. Current methods guided by landscape
frameworks mostly utilize evolutionary modelling (for example, fitting
data to Ornstein-Uhlenbeck models) to make inferences about adaptive
peaks. Recent alternative methods utilize known relationships between
phenotypes and functional performance to derive information about adaptive
landscapes; this information can then help explain the distribution of
species in phenotypic space and help infer the relative importance of
various functions for guiding diversification. Here, data on performance
for three turtle shell functions – strength, hydrodynamic efficiency, and
self-righting ability – are used to develop a set of predicted performance
optima in shell shape space. The distribution of performance optima shows
significant similarity to the distribution of existing turtle species and
helps explain the absence of shells in otherwise anomalously-empty regions
of morphospace. The method outperforms modelling-based approaches in
inferring the location of reasonable adaptive peaks and in explaining the
shape of the phenotypic distributions of turtle shells. Performance
surface-based methods allow researchers to more directly connect
functional performance with macroevolutionary diversification, and to
explain the distribution of species (including presences and absences)
across phenotypic space.