Prioritizing aquatic conservation areas using spatial patterns and partitioning of fish community diversity in a near-natural temperate basin

This study investigated spatial patterns and partitioning of fish community diversity in the Emory River basin, Tennessee, USA, which represents the best available biotic condition in a region characterized with high diversity and endemism. Fish community analyses were intended as one criterion for identifying aquatic conservation areas in a Habitat Conservation Plan (HCP) currently developed in the study region under the authority of the US Endangered Species Act. Spatial patterns of fish community diversity were examined at 57 stream sites located in the mainstem (13 sites) and four sub-basins (a total of 44 sites) by partitioning γ diversity (total diversity) into α (within-community) and β (among-community) components in a multiplicative manner at two spatial scales. Additional analyses were conducted to assess evidence of dispersal in structuring local communities. Mainstem sites were characterized with higher α diversity values relative to sub-basin sites, and γ diversity of 13 mainstem sites was comparable with that of 44 sub-basin sites. Site-level β diversity differed among sub-basins. Among-sub-basin β diversity was only modest, and one sub-basin harboured the majority of total species richness found among all sub-basins. Many species had high indicator values for mainstem sites, but sub-basin sites were associated with few indicator species. Spatial autcorrelation of fish community similarity was significant within mainstem sites and sites located within two sub-basins. Catchment area explained among-site variation in species richness better than stream order, link magnitude, confluence link or downstream link. Overall, there was a lack of evidence that dispersal played an important role in shaping local fish communities in either mainstem or sub-basin sites. Aquatic conservation in the study basin should focus on protecting aquatic diversity in the mainstem habitat, while a network of stream sites in the most diverse sub-basin may also be considered as aquatic conservation areas.