Substrate-specific locomotor performance is associated with habitat use in six-lined racerunners (Aspidoscelis sexlineata)

Abstract

Natural selection is thought to act on performance capacities and to shape morphology in a population, but which capacities are most ecologically relevant remains unclear. In nature, organisms encounter various substrates that incite changes in locomotor performance and thus natural selection may favour different morphological traits on different substrates, and may also shape substrate choice based on performance ability on each. We explored the relationships among morphology, performance and habitat use by examining maximal sprint performance and sprint sensitivity of six-lined racerunner (Aspidoscelis sexlineata) lizards on four substrates: rock, pebbles, sand and grass. We also identified morphological predictors of performance on each substrate. We found performance on grass, the most common microhabitat at the field site, to be suboptimal. Lizards tended to use substrates that optimized performance. Performance on different substrates was predicted by different morphological traits. Heterogeneity in available substrates on which individuals accomplish tasks important to fitness may result in selection on different morphological traits or selection to avoid suboptimal substrates compared to if only optimal substrates are used.