干旱区生态环境知识资源中心

Variation in mitochondrial DNA (mtDNA) was assessed in a captive stock and 11 wild populations (n = 259) from throughout the native range of Desert Pupfish Cyprinodon macularius as traditionally understood. Using PCR-SSCP, 18 composite haplotypes were identified from a 333-bp segment of the mitochondrial D-loop and two segments of the ND2 gene (333 and 325 bp). Representatives of each haplotype were sequenced for the entire ND2 gene and the 337-bp segment of the D-loop. Phylogenetic analyses revealed that haplotypes form two monophyletic groups, one in the Rio Sonoyta/Qllitobaquito Springs area and one in the Salton Sea/Colorado River Delta. This, with previous observations on morphology, color pattern, and geological history, supports recognition of the Rio Sonoyta/Quitobaquito populations as a separate species, the Quitobaquito Pupfish C. eremus Miller and Fuiman, from the more widespread desert pupfish C. macularius Baird and Chard. More than 70% of mtDNA diversity across all populations was attributable to differences between the two species. Within species, the average local population contains 94% and 97% of the diversity in, respectively, C. eremus and C. macularius. Differences between the Salton Sea and Colorado River Delta populations of C. macularius ex plain a small (3.7%), but statistically significant, portion of mtDNA diversity in this species. This and the history of connections between Salton Sea and the delta suggest that the two regions should be managed separately with no intermixing of pupfish other than what occurs when the present, human-regulated hydrology is overcome by natural flooding. Haplotype frequencies in C. eremus from Quitobaquito Springs and Rio Sonoyta were not significantly different. However, the potentially long history of isolation between these two populations and evidence of some degree of morphological divergence indicate a need for conservative management with no intermixing The captive stock exhibited reduced mtDNA variation relative to its wild parent population from a locality on the delta.