Meeting Abstract
Understanding the diversity of body shapes across the tree of life is one of the central challenges in evolutionary biology. One potential mechanism of generating morphological diversity is the strongly conserved allometric relationship between size and shape. By altering body size, species undergo predictable changes in morphology, promoting phenotypic differentiation. Evolutionary changes in size have been shown to account for a large fraction of variation in facial morphology across small mammals (40% in squirrels, 38% in bats, 33% in mongooses) and almost 80% of shape variation in raptor beaks. Here, we quantify the amount of shape evolution attributable to changes in body size across nearly 800 species of teleost fishes. Using a phylogenetic framework, we analyze 17 geometric morphometric landmarks positioned to capture general body shape and functionally-significant features. In marked contrast to the vertebrate lineages noted above, we find that changes in body size only explain 11% of the morphological variation seen in teleost fishes. These findings suggest that morphological diversification in fishes is largely independent of body size. Furthermore, the role of body size in accounting for the evolution of body shape varies considerably among fish families, ranging from 6-50% of shape variation explained by size. Complexity in the relationship between size and shape across families may, in part, explain the immense morphological diversity seen in teleost fishes.
