Morphological Divergence of Native and Recently Established Populations of White Sands Pupfish (Cyprinodon tularosa)
We used landmark-based geometric morphometric methods to describe patterns of body shape variation and shape covariation with size among populations of the threatened White Sands Pupfish (Cyprinodon tularosa), a species that occurs in dissimilar aquatic habitats. White Sands Pupfish populations include two genetically distinct, native populations that have been historically isolated in Salt Creek, a saline river, and Malpais Spring, a brackish spring. In addition, two populations were established approximately 30 years before this study by translocation of fish from Salt Creek to Lost River (a saline river) and Mound Spring (a brackish spring). We found significant body shape variation among populations and between males and females. Body shapes were more slender for females than for males and more slender for saline river populations than brackish spring populations. Introductions of pupfish to new habitats resulted in significant departures in body shape and shape allometry from the native Salt Creek population. Shape divergence was more pronounced for the Mound Spring population, which is consistent with a greater change in abiotic conditions. Although Mound Spring pupfish, like Malpais Spring pupfish, were more deep-bodied than saline river pupfish, differences in body shape and the level of sexual dimorphism were significant between the two brackish spring populations, indicating that deep-bodied shapes may be achieved from different anatomical configurations. The significant shape divergence of introduced populations warrants consideration for the conservation of this rare species, as creation of refuge populations for native stocks is a current management strategy.Abstract

Landmark definition for morphometric analyses of White Sands Pupfish. A male pupfish from Mound Spring is shown

First three principal components (PC) of shape variation for White Sands Pupfish. The three PCs shown represent approximately 69% of the total shape variation. Values in the plot correspond to group means for females (circles) and males (squares). Populations are indicated with the following abbreviations: Lost River (LR), Malpais Spring (MA), Mound Spring (MO), and Salt Creek (SC). Deformation grids (with a scale factor of 2×) are shown to facilitate a visual understanding of the shape corresponding to group means

Shape allometry of male White Sands Pupfish. Shape allometries are shown for each population (abbreviations the same as in Fig. 1) with saline river (SR) populations above and brackish spring (BS) populations below. Box plots show the range, 25th percentile, median, and 75th percentiles of centroid size data. Deformation grids are shown for the extents of the centroid size range to demonstrate the regression of shape on size. Deformation grids at large sizes are scaled 3× to facilitate a visual understanding of shape change associated with size

Shape allometry of female White Sands Pupfish. Descriptions are the same as in Figure 3
Contributor Notes
(MLC, CAS) Department of Biological Sciences, North Dakota State University, Stevens Hall, Fargo, North Dakota 58102; and (JMN) Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, South Carolina 29802. Present Addresses: (MLC) Department of Ecology, Evolution, and Organismal Biology, Department of Statistics, Iowa State University, 315F Snedecor Hall, Ames, Iowa 50011; and (JMN) Department of Biology, University of South Dakota, 189 Churchill Haines, Vermilion, South Dakota 57069. E-mail: (MLC) collyer@iastate.edu; (JMN) jnovak@usd.edu; and (CAS) craig.stockwell@ndsu.nodak.edu Send reprint requests to MLC.