Meeting Abstract
The relationship between structure and function impacts the evolutionary dynamics of phenotypic diversification. Biophysical relationships are thus expected to influence rates of morphological evolution, but this has rarely been tested. Here we test the hypothesis that mechanical sensitivity – the sensitivity of mechanical output to variation in its underlying components – correlates with rates of morphological evolution in the four-bar linkage system of mantis shrimp. Mantis shrimp (Order: Stomatopoda) are crustaceans that possess a specialized raptorial appendage used to harpoon elusive prey or bludgeon hard-shelled prey. The four-bar linkage system in the raptorial appendage transmits stored elastic energy to the kinetic energy of the appendage. We compared evolutionary rates among the morphological components (links) of the four-bar linkage system and their mechanical output (kinematic transmission, KT). Using a likelihood-based phylogenetic approach, we found that rates of morphological evolution correlate positively with mechanical sensitivity, suggesting a connection between biophysical relationships and evolutionary dynamics. We then examined the connection between mechanical sensitivity and trait-dependent diversification between two types of mantis shrimp (“spearers” and “smashers”). Although the rate of evolution and strength of selection varied between smashers and spearers, mechanical sensitivity did not appear to impact these patterns. The connection between mechanical sensitivity and evolution provides a window into the interaction between physical rules and evolutionary diversification. We discuss how our results influence our understanding of evolutionary patterns of diversity, such as many-to-one mapping.
