Functional performance of turtle humerus shape across an ecological adaptive landscape

Abstract

The concept of the adaptive landscape has been invaluable to evolutionary biologists for visualizing the dynamics of selection and adaptation, and is increasingly being used to study morpho‐functional data. Here, we construct adaptive landscapes to explore functional trade‐offs associated with variation in humerus morphology among turtles adapted to three different locomotor environments: marine, semiaquatic, and terrestrial. Humerus shape from 40 species of cryptodire turtles was quantified using a pseudolandmark approach. Hypothetical shapes were extracted in a grid across morphospace and four functional traits (strength, stride length, mechanical advantage, and hydrodynamics) measured on those shapes. Quantitative trait modeling was used to construct adaptive landscapes that optimize the functional traits for each of the three locomotor ecologies. Our data show that turtles living in different environments have statistically different humeral shapes. The optimum adaptive landscape for each ecology is defined by a different combination of performance trade‐offs, with turtle species clustering around their respective adaptive peak. Further, species adhere to pareto fronts between marine–semiaquatic and semiaquatic–terrestrial optima, but not between marine–terrestrial. Our study demonstrates the utility of adaptive landscapes in informing the link between form, function, and ecological adaptation, and establishes a framework for reconstructing turtle ecological evolution using isolated humeri from the fossil record.

Paraphyletic species no more – genomic data resolve a Pleistocene radiation and validate morphological species of the Melanoplus scudderi complex (Insecta: Orthoptera)

“…Márquez & Knowles, ; Oneal & Knowles, ; Knowles & Cohn, ), as well as in other animal groups [e.g. catfish (Silva et al ., ) and turtles (Dickson & Pierce, )]. Shape analyses were performed on the outline coordinates using the r package momocs (Bonhemme et al ., ).…”

Rapid adaptive evolution of scale-eating kinematics to a novel ecological niche

“…Future work should estimate performance across multiple performance axes (e.g. Stayton, 2019;Keren et al, 2018 preprint, Dickson andPierce, 2019), ideally using F2 hybrids. F2 hybrids are a useful tool for this type of experiment, as they are the first generation of offspring in which recombination among parental alleles can produce new combinations of kinematic, morphological and behavioral traits not observed in the F0 or F1 generations.…”

Decoupling Functional and Morphological Convergence, the Study Case of Fossorial Mammalia

“…However, species can adapt to similar environmental pressures in different ways (Wainwright et al, 2005;Losos, 2011). One-to-many mapping, and functional trade-offs will drive the phenotypic evolution of a structure according to which traits affect fitness the most (Polly et al, 2016;Dickson and Pierce, 2019;Moen, 2019), and the evolution of a particular phenotype may result in the reduced fitness of other attributes (Alfaro et al, 2004;Moen, 2019). In addition, many different phenotypes can produce highly similar functional outputs, known as many-to-one mapping, and divergent morphologies may perform convergently in function (Alfaro et al, 2005;Wainwright et al, 2005;Losos, 2011;Renaud et al, 2018), meaning that functional convergence can be recognized even in the absence of morphological convergence.…”