Demography Predicts Genetic Effective Size in a Desert Stream Fish Community

Patterns of genetic diversity and effective size should be predicted by life history traits (intrinsic), landscape properties (extrinsic), and population dynamics. Theoretical models portray complicated relationships among population subdivision, rates of extirpation and recolonization, and metapopulation genetic effective size (metaN(e)) but make simplifying assumptions about effects of intrinsic and extrinsic factors. Using previously published data sets, we compared estimates of genetic effective size to demographic time-series data gathered for nine dominant species in a desert stream fish community. These species occupy a common desert stream network and experience the same disturbance regime but differ in abundance, distribution, and life history traits that should affect reproduction, dispersal, local persistence, and genetic diversity patterns. Measures of genetic effective size were positively related to network-wide abundance and mean adult density across species and were negatively related to extirpation probability. Comparative data supported the theoretical prediction that population subdivision decreases metapopulation genetic effective size relative to panmictic populations of the same size. Estimates of metaN(e) reflected differences in intrinsic traits and population dynamics across species measured over ecological timescales. This comparative study exemplifies why ecological differences are important considerations when seeking to preserve genetic diversity.