Adaptive radiations in Cyprinodon body shape explained by salinity and other ecological factors

Authors: Michael L. Collyer

Year: 2008 (xl)

Abstract

Morphological variation of euryhaline fish species occurring in diverse habitats is typically associated with greater streamlining in saline environments. Past studies of Cyprinodon morphology have identified body shape divergence associated with salinity variation among environments where different populations of the same species occur. In the current study, I performed a broad-scale morphological survey from museum collections of six species of Cyprinodon occurring in diverse habitats. Body shape was quantified with geometric morphometric methods and model comparisons were performed to elucidate the ecological variables that are most important in explaining Cyprinodon body shape variation. Additionally, I considered whether (1) species differences or ecological variation was more important for explaining shape variation and (2) how recent morphological divergence compares to deeper phylogenetic variation in body shape. Results indicated that salinity is an important factor for explaining shape variation associated with streamlining both within and among species, but other ecological factors are also important. Further, ecological variation in body shape within species was much more pronounced than species differences in body shape. These results suggest that adaptive radiations of Cyprinodon in ecologically disparate environments were substantial.