Patterns of evolutionary diversification through lineages, morphology, and mechanics

A fundamental challenge in evolutionary biology lies in explaining why some groups are more diverse than others. This dissertation focuses on three components of diversity: lineages, morphology, and mechanical property. The first chapter examines the relationship between morphology and mechanical property. Although morphological change is frequently interpreted as an indication of mechanical diversification it is not known whether the evolution of mechanical properties in complex traits corresponds with similar diversification patterns in underlying morphology. I focus on the feeding system of fishes that display many-to-one mapping (or functional convergence) and test whether historical patterns of mechanical and morphological evolution fit concordant models of diversification. I find that despite a tight link between the morphology and emergent mechanical properties of a trait, the diversification pattern between them can be significantly different. The second chapter focuses on ancestral state reconstruction. Many times the feature being reconstructed is not itself of interest, but rather serves as a proxy for other important (but unmeasured) characters. In this chapter, I explored the accuracy of inferring ancestral mechanical properties using simulation models and two empirical traits. I found that precision is linked to the complexity of the mathematical model and accuracy was affected by both mathematical complexity and the number of interacting parts in the system. My results suggest caution when extrapolating mechanical property from ancestral morphology, and I argue that the same principle should be applied to many differing levels of design with hierarchical traits. Chapter three focuses on the relationship between lineage accumulation and morphological diversification in a group of "primitive" frogs (superfamily Pelobatoidea) and their most species-rich family (Megphryidae). Here, I present the first time-calibrated phylogenetic analysis of Pelobatoidea, including 52 megophryid species, using molecular data combined with fossil constraints. I also test the hypothesis that megophryids underwent an adaptive radiation using several comparative methods, including lineage-through-time plots, Monte Carlo constant rates test, disparity-through-time plots, and evolutionary likelihood model fitting. Despite their large clade size and high degree of morphological variation, we do not find the classic signature of adaptive radiation in the family Megophryidae. v...