Despite once existing throughout the Pecos River, C. pecosensis populations have become increasingly isolated due to significant portions of their native habitat being removed. [2][3] Following the introduction of Cyprinodon variegatus (sheepshead minnow), pure Pecos pupfish populations have been further isolated and largely exist in scattered sinkholes, man-made impoundments, and marshes.[3][4] Its natural habitat includes springs, sinkholes, and pools of streams.[5]
Introduction of Cyprinodon variegatus
Cyprinodon variegatus is thought to have been introduced during the early 1980s, presumably via bait-bucket dumping. Shortly after the introduction of C. variegatus, C. variegatus X C. pecosensis hybrids quickly became widespread, occupying an estimated 50% of the native Pecos pupfish range by 1985. [6][7] The widespread success of hybrids, and quick range expansion throughout native Pecos pupfish waters, has been hypothesized to be the result of selection mechanisms for hybrids during a period when the native C. pecosensis population had experienced a reduction.[8]
Additionally, hybrid populations have been reported to have increased growth-rates and vigor (
Heterosis), resulting in Pecos pupfish females to actively choose to mate with hybrids over pure male Pecos pupfish.[9][10] Given this, conservation efforts have been difficult and efforts are being made to prevent C. variegatus from entering into isolated C. pecosensis populations.
^
abC. Hoagstrom; J. Brooks (1999). "Distribution, Status, and Concervation of the Pecos pupfish, Cyprinodon pecosensis". Technical Report No. 2, Santa Fe, New Mexico.
^A. A. Echelle; P. J. Connor (1989). "Rapid, geographically extensive genetic introgression after secondary contact between two pupfish species (Cyprinodon, Cyprinodontidae)". Evolution. 43 (4): 717–727.
doi:
10.1111/j.1558-5646.1989.tb05171.x.
PMID28564193.
^A. A. Echelle; C. W. Hoagstrom; A. F. Echelle; E. James (1997). "Expanded occurrence of genetically introgressed pupfish ( Cyprinodontidae : Cyprinodon pecosensis X variegatus ) in New Mexico". Southwestern Naturalist. 42 (3): 336–339.
JSTOR30055287.
^J. A. Rosenfield; S. Nolasco; C. Sandoval; A. Kodric-Brown (2004). "The Role of Hybrid Vigor in the Replacement of Pecos Pupfish by Its Hybrids with Sheepshead Minnow". Conservation Biology. 18 (6): 1589–1598.
doi:
10.1111/j.1523-1739.2004.00356.x.
S2CID39553092.