Amargosa River Research Articles

Genetic Differences in Physiological Tolerances of Amargosa Pupfish ( Cyprinodon nevadensis ) Populations

Amargosa pupfish from a constant-temperature spring have a narrower range of temperature and oxygen tolerances than pupfish from the much more variable Amargosa River, indicating that the two populations have diverged genetically since their isolation. The reduced tolerances of the fish inhabiting a constant environment support the predictions of evolution theory.

Genetic variation of mitochondrial aspartate aminotransferase in the teleost Cyprinodon nevadensis.

Abstract 1. 1. An apparent genetic polymorphism of mitochondrial aspartate aminotransferase was discovered in a population of the Nevada pupfish, Cyprinodon nevadensis, from the Amargosa River in Death Valley, California. 2. 2. Three phenotypes were noted. Presumptive homozygotes display single bands of activity; presumptive heterozygotes display the characteristic triplet pattern expected from the random combination of two different (allelomorphic) monomers into dimers. 3. 3. The phenotypic frequency distribution is in agreement with that predicted by a Hardy-Weinberg equilibrium for a one-locus di-allelic polymorphism with allelic frequencies of 0·8 and 0·2.

Cyprinodon salinus, a New Species of Fish from Death Valley, California

DEATH Valley once formed the terminus of an extensive Pleistocene drainage herein referred to as the Death Valley System. This system, lying in eastern California and southwestern Nevada, comprises a number of now isolated valleys and basins of interior drainage, including Owens Valley, the Indian Wells-Searles basin, Panamint Valley, Death Valley, the Amargosa River basin, Pahrump Valley,' and the Mohave River basin. Though now much disrupted, most of the complex was integrated into a hydrographic unit during the latter part of Pleistocene time (Gale, 1914; Waring, 1920; Noble, 1926, 1931; Blackwelder, 1933; and others). Lake Manly, the body of water then existing in Death Valley, formed the sump for all the waters of the system. Its two main tributaries, Owens River and the stream formed by the confluence of the Amargosa and Mohave rivers, entered the valley at the southern end. The Amargosa still pours its flood waters onto the salt flat remnant of Lake Manly, but the other tributaries have long since ceased to flow into Death Valley. The distribution of the fishes of the Death Valley System substantiates the physiographic evidence for the former hydrographic continuity of these basins. The occurrence of the minnow genus Siphateles in the Owens and Mohave rivers, of Cyprinodon in the Amargosa-Death Valley region and Owens Valley, and of the cyprinodont, Empetrichthys, in Pahrump Valley and in Ash Meadows of the Amargosa drainage, testifies to a former connection of the waters of these basins. Local differentiation in each of the three genera suggests that the basins have been isolated since the Pleistocene. One of the most strongly marked of the isolates is described in this paper.