Body Shape Diversification of Pecos Pupfish (Cyprinodon Pecosensis) on Varying Habitats as Evaluated by Geometric Morphometrics

During the 19th and 20th centuries, alterations to the Pecos River in New Mexico and Texas, USA due to anthropogenic activities, including damning and river channelization, vast water extraction for irrigation, as well as pollution of associated habitats, have greatly impacted the fish fauna within the drainage. One of the endemic fish species, the Pecos pupfish (Cyprinodon pecosensis), might be the most affected. Historically abundant and widespread large populations have been disrupted and became a series of small isolated subpopulations that persist at a few highly fragmented habitats restricted to a small area in southern New Mexico. The connectivity among these habitats is extremely low, and can potentially prevent any gene flow among subpopulations, which might eventually result in morphological divergence among subpopulations in face of different ecological conditions. Here I utilized landmark-based Geometric Morphometrics to evaluate body shape variation of the Pecos pupfish at 26 different localities categorized into four general habitat types that each differ greatly in ecological properties. Results from this study suggest that, despite significant sexual dimorphism, body shape morphology of Pecos pupfish varied in response to spatial heterogeneity and it was most intensely influenced by specific localities within habitat types. There were overlaps of the convex hull regions of morphospace among the four habitat types, implying that ecomorphological dynamics of the Pecos pupfish were rather site-specific. Moreover, temporal variation of body morphology was statistically significant but not comparable to body shape variation among different localities. The empirical data collected from this study provides preliminary evidence for phenotypic diversity of Pecos pupfish in varied ecological conditions, which has important implications for the future conservation management of Pecos pupfish diversity and viability. Such implications could be extended to other endemic desert fishes in disrupted habitats