Meeting Abstract
Many complex phenotypes such as the locomotor system perform multiple, and sometimes conflicting functions. The evolution of traits underlying such phenotypes may therefore be shaped by different selective pressures, compromises between functions, or be limited by constraints. Studies of complex phenotypes, however, often examine underlying traits individually or with respect to a single selective pressure. Here, we use a morphological “meta-analysis” to evaluate whether locomotor traits from the cellular to the whole-organism level show similar patterns of evolution in lizards. We tested evolutionary models based on habitat use, predator escape, foraging behavior, and Brownian motion to assess whether selection acts across all levels of the locomotor system. We find that selection related to both predator escape and foraging behavior influences the evolution of traits spanning the cellular to whole-organism level. However, a global optimum model best explains the evolution of several muscular traits, indicating selection on musculature is similar across lizards, or may be a consequence of functional constraints in the muscular system. Interestingly, a Brownian motion model best explained the evolution of some leg segments. While this finding suggests portions of the limb may not be subject to selection, it may also result from compromises between competing functions. Overall, we find that traits show distinct patterns of evolution within a complex phenotype; some reflecting selection related to performance, while others are more limited in their evolution.
