Limitations of beta diversity in conservation site selection

Abstract

Preservation of diversity is a key issue in many conservation efforts. It has recently been suggested that beta diversity should be considered in conservation planning and that sites with high local contribution to beta diversity (LCBD) may be valuable for conservation. Yet, such an approach has not been applied to freshwater mussels, a highly imperiled group of organisms. We used a dataset on freshwater mussel from the five largest rivers of southwestern Ontario, Canada to examine whether LCBD would be an efficient approach for assessing the conservation value of sites and compared it to more traditional conservation approaches (biomonitoring, high richness, high abundance). Sites with high LCBD value were associated with low mussel richness and were often characterized by mussels that are regionally widespread and usually abundant in lentic systems or smaller streams, limiting site selection based on beta diversity. Species at risk (including IUCN categories of Critically Endangered through Near Threatened) were more likely to occur in communities with high richness and abundance at sites chosen by the more traditional approaches. Thus, protecting sites with higher alpha diversity of mussels would also support higher gamma diversity of mussels. The provision of important ecosystem services by higher abundances of mussels which was also correlated with local richness should be considered as well. Our study suggests that there likely is an important link between high richness and abundance of mussels and the presence of species at risk which we argue is driven by facilitation (i.e., positive species interaction), an important, yet understudied, process that deserves more attention in conservation.