Genetic variation and differentiation of remnant natural populations of the desert pupfish, Cyprinodon macularius.

Abstract

Six remnant natural populations of Cyprinodon macularius, a formerly broadly distributed Colorado Basin species, were surveyed for allozyme variation at the products of 38-39 structural gene loci. The samples included 4 populations from the Salton Sea area (including one from an adjacent relatively pristine natural desert spring habitat), one from the Sonoyta (Quitobaquito Springs), and one ultimately from near the delta of the Colorado River. Mean heterozygosity values are within the range reported by others for ecologically comparable Aphanius populations, and are not strikingly low. Eight loci display statistically significant differences in gene frequency. Differences are detectable among Salton Sea populations, and among all 3 geographic areas. The general pattern of the differentiation is temporally (and geographically) hierarchical, and is consistent with previous perceptions of the relationships of the populations based on morphology. The overall level of differentiation is low. The effect of geographic isolation on the divergence of pupfish populations has almost certainly been overestimated.-from Author