Ephemeral metapopulations show high genetic diversity at regional scales

One of the primary questions concerning the long-term preservation of nature and its diversity is the maintenance of genetic diversity. However, despite numerous theoretical investigations, comparative empirical information on how local extinctions influence regional genetic variation does not exist. To our knowledge, this is the first report of an empirical study comparing the genetic variation of permanent vs. ephemeral species at two scales (local variation, regional variation). This approach, utilizing a microsatellite analysis of six midge species of the genus Chaoborus generated intriguing scale-dependent results. Species that experienced repeated local extinctions had reduced genetic variation at the local level, yet the regional genetic variation was greater than in species with permanent populations. Our findings call into question the assumption that species with repeated local extinctions generally contain lower genetic diversity, especially if they experience a "nomadic" pattern of dispersal. We encourage comparative analyses of empirical genetic data at dual scales as molecular tools become more available in ecological studies.