Meeting Abstract
Morphological evolution proceeds unequally, leading some features to be highly diverse and others almost unchanged over millions of years. We capitalize on outstanding morphological, mechanical and phylogenetic datasets of several four-bar linkage systems in bony fishes and crustaceans to illustrate how mechanical relationships bias the tempo and mode of morphological evolution. Evolution is consistently faster in a subset of morphological traits exhibiting strong relationships with mechanical output. These systems vary in predatory behavior, body size, and locomotion, implying a generalizable phenomenon. Size-scaling differences in linkage geometry contribute to evolutionary rate disparity. Using the especially large wrasse dataset, we found that contingency and determinism underlie morphological evolution through many-to-one mapping. Whereas convergent mechanics evolved through different morphological pathways, shifts were nonetheless restricted to a subset of traits of high mechanical effect. Mechanical variation is predictably clustered around a few morphological traits, which could facilitate rapid ecological specialization through relatively small changes.
