Macroevolutionary dynamics and comparative methods of morphological diversification

ABSTRACT

Among the comparative approaches that have been used to understand the patterns of morphologicaldiversification, those related to the detection and evaluation of large-scale evolutionary trends have recentlybeen highlighted. A new method known as the analysis of skewness (ANSKEW) allows partitioning betweenthe passive and driven trends associated with the random occupation of a bounded morphological spaceand a single morphological attractor, respectively. This partitioning provides a better understanding of therelative role of processes that occur at distinct hierarchical levels associated with the macroevolutionarytrends of morphological diversification. In this paper, we used this new approach to understand the patternsof morphological diversification in Erodiscini (Coleoptera, Curculionidae, Otidocephalinae) beetles. Whengenera were used as subclades, ANSKEW revealed that 19.9% of the body size variation in the Erodiscini wasattributable to driven trends, i.e., a morphological attractor, whereas 80.1% of the variation was attributableto the occupation of different adaptive zones by distinct subclades (a passive process), with the passivecomponents being significant (based on 5,000 bootstrap samples). This simple approach to partitioningprovided insights into the intrinsic dynamics of body size evolution in this group without the need to considerexplicit phylogenetic structures. Such analyses could provide a starting point for further evaluation of adaptivevariation at multiple hierarchical levels and of the processes underlying the relationship between variationin body size and other ecological, physiological and behavioral aspects.