Population and conservation genetics of a habitat-specific riverine fish species, the eastern sand darter (Ammocrypta pellucida).

The eastern sand darter (Ammocrypta pellucida) is dependent on fine sandy substrates that are naturally fragmented at depositional areas in freshwater lakes and rivers. Loss of suitable habitat is the leading cause of population declines across the entire species distribution. I identified genetic connectivity among drainages, rivers, and populations to determine how eastern sand darter genetic structure is shaped by historic drainage and contemporary river connectivity. Using microsatellite markers, I found that low gene flow among rivers resulted in persistent influences of historic drainage connectivity on current range-wide genetic structure. High within-river genetic connectivity, especially in range-edge rivers, is attributed to extinction/re-colonization events resulting from temporally unstable sand bar habitats, although genetic diversity is preserved through stratified dispersals. Fine-scale and temporal genetic analysis revealed that the Grand River likely represents recent colonization of populations, while the Thames River represents a potentially valuable source for future reintroduction recovery actions