Does ecology or phylogeny explain fish morphological diversity in a mosaic of desert aquatic
habitats?
Meghan E. Hall, Carol Martin Gatton Academy of Mathematics and Science in Kentucky;
Western Kentucky University
Michael L. Collyer, Department of Biology, Western Kentucky University
North American pupfishes in the genus, Cyprinodon, are renowned for their euryhalinity – an
ability to survive large salinity changes. Euryhaline fish that occur in diverse habitats typically
display morphological variation associated with greater streamlining in saline environments.
This pattern has been observed in recent studies of pupfishes (Cyprinodon) that occur in
environments of different salinities. These studies focused on the ecological morphology of
specific taxa in few environments, but no studies have compared intraspecific morphological
variation to interspecific variation, especially over large ecological gradients. In the current
study, we performed a broad-scale morphological survey from museum collections of several
species of Cyrinodon, focusing primarily on one species, the Pecos pupfish (Cypirnodon
pecosensis), which has a large distribution comprised of populations in a diverse array of
habitats. We considered whether (1) species differences or ecological variation was more
important for explaining body 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. Regardless of ecological reason,
intraspecific body shape variation in Pecos pupfish was much more pronounced than the overall
interspecific variation of Cyprinodon in this study, indicating that local environments rather than
phylogeny predominantly influence body shape. These results suggest that divergent ecological
conditions may have been important for the rapid diversification of Cyprinodon in North
American deserts.