Meeting Abstract

P3.112  Tuesday, Jan. 6  Is the Weberian apparatus a key innovation: causal versus permissive evolutionary factors? BIRD, Nathan C.*; HERNANDEZ, L. Patricia; George Washington University; George Washington University nbird@gwmail.gwu.edu

Key innovations are structures, behaviors, or functions intimately linked with the evolutionary success of one or more groups of organisms. Over the past several decades, numerous potential key innovations have been proposed to explain the disparity of species diversity between closely related groups. Proposed key innovations include such examples as flight, phytophagy in insects, the labroid pharyngeal jaw apparatus, and floral nectar spurs. However, key innovations have been plagued with criticisms regarding their testability and their specific role in the evolutionary process. This confusion is readily apparent in the numerous competing definitions and tests proposed in the literature. A large segment of these tests focus on historical testing (causal factors), requiring at least two independent origins of the innovation. More recently, functional testing as well as the addition of developmental and genetic influences (permissive factors) into key innovation testing have become alternative means to address unique key innovations previously considered untestable using historical methods. We evaluate the utility of these competing methods of key innovation testing with respect to the Weberian apparatus, a hearing adaptation that includes a set of novel vertebral modifications diagnostic of the Otophysi, a large clade of freshwater fishes. We test the hypothesis that these hearing modifications are critical to the success of the clade using modified traditional criteria, as well as using more recent functional and developmental tests within an ecological context. We conclude that sufficient support exists for the role of the Weberian apparatus as a key innovation in the evolutionary history of otophysan fishes.