Morphological Divergence of Native and Recently Established Populations of White Sands Pupfish (Cyprinodon tularosa) Author(s): Michael L. Collyer, James M. Novak, Craig A. Stockwell Source: Copeia, Vol. 2005, No. 1 (Feb. 24, 2005), pp. 1-11 Published by: American Society of Ichthyologists and Herpetologists Stable URL: http://www.jstor.org/stable/4098615 . Accessed: 13/01/2011 13:16 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. 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STOCKWELL 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 es- tablished 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 con- figurations. The significant shape divergence of introduced populations warrants consideration for the conservation of this rare species, as creation of refuge pop- ulations for native stocks is a current management strategy. UPFISHES the methods for the of Rohlf P of genus Cyprinodonrepre- analysis shape (e.g., sent a group of fishes known for their abil- and Slice, 1990). These techniques, inclusively ity to tolerate variable environmental conditions named geometric morphometrics (Rohlf and in desert aquatic habitats of North America. Marcus 1993; Adams et al., 2004), describe the Morphological diversification of inland species spatial arrangement of anatomical features of is thought to be associated with isolation of pop- organisms, providing statistical (Rohlf, 1999) ulations in ecologically disparate, remnant and visual (e.g., Caldecutt and Adams, 1998; Ad- aquatic habitats following desiccation of large ams and Rohlf, 2000; Rfiber and Adams, 2001) Pleistocene lakes (Miller, 1981). Early accounts advantages to traditional approaches based on of species descriptions were based chiefly on dif- linear distance measures. These techniques ferences in morphometric and meristic data have been used increasingly over the past de- (e.g., Hubbs, 1932; Miller, 1943, 1948). These cade with morphological data from fishes for early papers represent exhaustive studies of spe- studies of phylogenetics and species descrip- cies descriptions, where detailed morphometric tions (e.g., Corti and Crosetti, 1996; Cavalcanti and meristic measurements were compared, et al., 1999; Douglas et al., 2001), ontogenetic trait-by-trait. However, intraspecific ecological allometry (e.g., Walker, 1993; Hood and Heins, morphology comparisons have not been consid- 2000; Gallo-Da-Silva et al., 2002), trophic mor- ered in detail for this group of fishes, despite phology (e.g., Caldecutt and Adams, 1999; Rfib- their renowned ability to survive in a variety of er and Adams, 2001), ecological morphology aquatic desert habitats. (e.g., Corti et al., 1996; Walker, 1996, 1997), and Recent advances in morphometric analytical osteology (e.g., Loy et al., 1999, 2001). Geo- techniques have provided statistically powerful metric morphometric methods allow fine-scale C 2005 by the American Society of Ichthyologists and Herpetologists 2 COPEIA, 2005, NO. 1 assessment of shape differences and, therefore, among populations, shape covariation with pup- could be valuable for discerning patterns of in- fish size (shape allometry), and sexual dimor- traspecific morphological variation. phism in body shape, to gain an understanding In this study, we use landmark-based, geo- of pupfish ecological morphology. metric morphometric methods to describe pat- terns of body shape variation and covariation MATERIALSAND METHODS with fish size among populations of White Sands Pupfish (Cyprinodon tularosa), which occur in We examined 393 specimens of White Sands dissimilar environments in the Tularosa Basin Pupfish collected from the four populations (N in southern New Mexico. The White Sands Pup- = 49-50 females and N = 45-50 males from each fish is listed as threatened by New Mexico and population). Descriptions of collection sites are composed of two native and two recently intro- described in detail by Collyer (2003). Nonmet- duced populations (Pittenger and Springer, ric multidimensional scaling revealed that 1999). The native populations occur in brackish White Sands Pupfish habitats can be distinctly spring (Malpais Spring) and saline river (Salt described as brackish springs (BS = Malpais Creek) habitats and have been isolated presum- Spring and Mound Spring) or saline rivers (SR ably since the desiccation of the Pleistocene = Salt Creek and Lost River) based on abiotic Lake Otero (Miller and Echelle, 1975; Pittenger factors including temperature, salinity, and wa- and Springer, 1999). Miller and Echelle (1975) ter flow (Collyer, 2003). noted morphological and meristic differences between the two native populations. Salt Creek Fish collection and landmark acquisition.--Adult Pupfish had a more slender body and scales that pupfish were used in this study to reduce the were smaller and more numerous. In addition, amount of intrapopulation shape variation Salt Creek Pupfish had less scalation of the bel- based on ontogeny. Pupfish were collected from ly. These differences did not warrant subspecies 26 May to 8 June 2001, at the middle sections designation, however, according to the authors. of Lost River (26-27 May) and Salt Creek (30 Nevertheless, genetic distinction of the two na- May), the springhead and outflow marsh of Mal- tive populations has been reported (Stockwell pais Spring (4-5 June), and the upper pond of et al., 1998; Iyengar et al., 2004) based on fixed Mound Spring (8 June). Fish were live-captured or nearly fixed differences in allele frequencies with unbaited minnow traps placed at depths of allozymes and microsatellites. less than one meter at Lost River and Salt The two introduced populations also occur in Creek, with beach seines at Mound Spring, and a brackish spring (Mound Spring) and a saline with a combination of the two techniques at river (Lost River). These populations were es- Malpais Spring. Fish were transported live to a tablished circa 1970 (Pittenger and Springer, research laboratory at Holloman Air Force 1999) from translocation of Salt Creek fish Base, sacrificed in approximately 500 mg/L tri- (Stockwell et al., 1998). They are not genetically caine methanesulfonate (MS 222; Summerfelt differentiated fi-om the Salt Creek population and Smith, 1990), separated into female and based on genetic distances using allozyme and male groups, and placed into ice baths. Fish microsatellite data (Stockwell et al., 1998), but were patted dry, labeled, and photographed the introductions resulted in shifts in allele fre- within two hours of sacrifice. quency from the Salt Creek population and loss Digital photographs were captured with a of some alleles at various microsatellite markers Minolta RD-175(r) digital camera mounted on for both introduced populations (Stockwell and a photography table approximately 0.25 m di- Mulvey, 1998; Stockwell et al., 1998; Miller,