18.2 Friday, Jan. 4 Fractal radiation: repeated patterns of diversification along an axis of body elongation in fishes CLAVERIE, T*; WAINWRIGHT, P C; Univ. of California, Davis; Univ. of California, Davis email@example.com
We explored patterns of body shape diversification in the mega-diverse spiny-rayed fishes. Geometric morphometric tools were used with landmark data collected from lateral-view photographs to characterize body shape for more than 2000 species of spiny-rayed fishes belonging to more than 40 families. Across the entire data set the first principal component of morphological variation reflects the extent of body elongation or shortening. When we conducted a separate PCA on each fish family we found the most common first PC reflects body elongation. Using available time calibrated species-level phylogenies for several individual families we worked up from the base to the tip of each tree, calculating PCAs at each node. At most nodes variation in body elongation characterized the first PC, even at very shallow phylogenetic scales. This fractal pattern, where elongation is the dominant axis of body shape evolution, whether the scale is across spiny-rayed fishes or within much smaller clades that are less than 10 million years old, indicates that fish body shape evolution has been characterized by repeated, similar changes in elongation. The repeated nature of the pattern raises the question of whether the morphology and developmental genetics underlying this axis of shape change is consistent, and highlights the importance of understanding the morphological and genetic underpinnings of this axis of body shape as well as its performance and ecological consequences.