Meeting Abstract

45-2   13:45 - 14:00  Evolution of body elongation in fishes and its ecological consequences Holliday, G*; Alencar, LRV; Hodge, J; Price , S; Clemson University, Clemson, SC; Clemson University, Clemson, SC; Clemson University, Clemson, SC; Clemson University, Clemson, SC ghollid@g.clemson.edu

Elongation is one of the primary axes of body shape variation among fishes, however the drivers of variation and ecological consequences of elongation remain relatively unexplored. We investigated how size, clade age and richness influence variation and clade position on the elongation axis. We also visualized and compared the ecological diversity of elongated taxa. Our dataset comprised morphological measurements for 42 orders of teleosts taken from specimens in the Smithsonian collections. We defined elongation as fineness ratio (standard length/sqrt(max body depth x max fish width)) and quantified the axis of elongation across teleosts to identify taxa on the extremes. We used phylogenetic regressions to explore relationships across teleost species, between and within orders, and Multiple Correspondence Analysis to generate an ecospace using published datasets. Eels (Anguilliformes) and knifefish (Gymnotiformes) were the most elongated while spadefish (Ephippiformes), and anglerfish (Lophiiformes) were the least. Overall there was a trend for smaller species to be more elongated, although this pattern varied across orders. Older clades contain more elongation variation, implying time is an important source of body shape diversity. Variation in elongation increased with species richness when quantified by range, possibly due the increased likelihood of obtaining extreme values as species richness increases. As body size increased, range of elongation decreased, but this may be due to species richness decreasing with increasing body size. These findings reveal that the evolution of body elongation depends on body size, while variation in elongation is influenced by both time and species richness. Our results also suggest that being very elongated does not prevent lineages from occupying diverse ecological niches with exceptions of reef habitats and certain benthic lifestyles.