Urban development explains reduced genetic diversity in a narrow range endemic freshwater fish

Whereas the negative impact of human caused habitat degradation on community species richness is well established, less is known about its effect on within species genetic diversity. Here we investigate how different aspects of habitat degradation affects genetic diversity of an Australian native freshwater fish, Rhadinocentrus ornatus, and what impacts this may have on this species' conservation status. We perform this investigation for R. ornatus across southeast Queensland. Based on mtDNA sequence data from 327 individuals and 20 populations, we identified three distinct genetic lineages that were allopatric at the stream level. Indicators of habitat degradation have large negative effects on measures of genetic diversity, with close proximity to urban development and alterations to waterways associated with drastically reduced measures of genetic diversity across three distinct mtDNA lineages (evolutionary significant units). Low effective population sizes and low standing genetic variation in degraded habitats may result in reduced adaptive potential in this already threatened narrow range endemic. The only surveyed populations with high genetic diversity are found in protected National Parks. Many historical populations of R. ornatus in the highly developed Greater Brisbane Region are already probably extinct, and without further study and management this may be the fate of presently genetically depauperate populations in urban areas