Effects of Habitat Fragmentation on Effective Population Size in the Endangered Rio Grande Silvery Minnow

• Published in: Conservation biology Vol. 19; no. 4; pp. 1138 - 1148
• Main Authors: ALÒ, DOMINIQUE, TURNER, THOMAS F.
• Format: Journal Article
• Language: English
• Published: 350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK Blackwell Publishing, Inc 01.08.2005; Blackwell Science; Blackwell; Blackwell Publishing Ltd
• Subjects: adults; analytical methods; Animal and plant ecology; Animal populations; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation biology; Conservation, protection and management of environment and wildlife; Demography; Deoxyribonucleic acid; diversidad genética; Diversion dams; DNA; downstream transport; Ecological genetics; eggs; Emigration; Endangered & extinct species; Evolutionary genetics; Fish; fragmentación del río; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; gene flow; Genetic diversity; Genetic structure; genetic variation; Habitat fragmentation; Habitats; Hybognathus amarus; Larvae; Life history; microsatellite repeats; Minnows; Mitochondrial DNA; mortality; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Population estimates; Population genetics; Population number; Population size; Reproduction; river fragmentation; Rivers; río abajo transporte; Spawning; Synecology; variance; Rio Grande; USA, New Mexico; Brazil, Rio Grande do Sul, Rio Grande; Endangered species; downstream transport; Population number; Hybognathus amarus; Genetic diversity; Rivers; Biodiversity; Fragmentation; Freshwater environment; Vertebrata; Pisces; river fragmentation; Phoxinus phoxinus; Habitat; Transport; Downstream; Environmental protection
• ISSN: 0888-8892; 1523-1739
• DOI: 10.1111/j.1523-1739.2005.00081.x

We assessed spatial and temporal patterns of genetic diversity to evaluate effects of river fragmentation on remnant populations of the federally endangered Rio Grande silvery minnow (Hybognathus amarus). Analysis of microsatellite and mitochondrial DNA detected little spatial genetic structure over the current geographic range, consistent with high gene flow despite fragmentation by dams. Maximum-likelihood analysis of temporal genetic data indicated, however, that present-day effective population size (NeV) of the largest extant population of this species was 78 and the ratio of effective size to adult numbers$(N_{eV}/N)$was$\sim 0.001$during the study period (1999 to 2001). Coalescent-based analytical methods provided an estimate of historical (river fragmentation was completed in 1975) effective size (NeI) that ranged between 105and 106. We propose that disparity between contemporary and historical estimates of Neand low contemporary Ne/N result from recent changes in demography related to river fragmentation. Rio Grande silvery minnows produce pelagic eggs and larvae subject to downstream transport through diversion dams. This life-history feature results in heavy losses of yearly reproductive effort to emigration and mortality, and extremely large variance in reproductive success among individuals and spawning localities. Interaction of pelagic early life history and river fragmentation has altered demographic and genetic dynamics of remnant populations and reduced Neto critically low values over ecological time.