干旱区生态环境知识资源中心

Conservation genetic studies are challenged by the fact that populations of many imperiled species have experienced declines and fragmentation to the degree they no longer exhibit natural, self-sustaining metapopulation processes; characteristics of great importance to managers charged with their protection. Genetic patterns of species from minimally impacted systems can inform management practices for populations in more modified and fragmented systems. We assessed spatial and temporal patterns of intraspecific genetic diversity and differentiation using microsatellites for three imperiled fishes of the unfragmented upper Gila River, New Mexico, USA. Estimates of contemporary effective size were low for these species, but we observed little genetic evidence of inbreeding. Overall genetic structure was low (all species F-ST < 0.025) suggesting moderate to high gene flow for all species, but each exhibited different patterns of spatial structuring. Gila nigra (a candidate for listing under the Endangered Species Act) appears most at risk of short-term loss of genetic variation and local extinction relative to Meda fulgida or Rhinichthys (Tiaroga) cobitis (both federally endangered) because G. nigra exhibited the lowest diversity, smallest effective size (N-e similar to 100) and temporally unstable population structure. Meda fulgida and R. cobitis exhibited temporally stable spatial structure related to riverscape features but connectivity among occupied habitats is threatened by a proposed diversion structure. Data from this comparatively pristine system can inform management of these species in fragmented portions of their ranges.