Investigating biodiversity patterns across scales in freshwater mussels.

Hypotheses relating genomic diversity to community attributes such as abundance and species diversity attract attention from a wide and varied audience because their applications are twofold. First, testing such hypotheses can further a theoretical-and hopefully generalizable-understanding of the forces that assemble communities and create observed patterns of biodiversity. Second, relationships that hold true could ease the burden of data collection for conservation or other urgent applications; for example, a strong correlation between species diversity and genetic diversity could make it possible to use one as a proxy for the other, and focus limited resources on measuring the easier of the two without sacrificing information gained. In a From the Cover article in this issue of Molecular Ecology, Bucholz et al. (2023) explore the relationships between within-species genomic diversity, community relative abundance and community species richness, testing three types of ecological hypotheses in the freshwater mussel communities of the southeastern United States. They find positive relationships between mussel density and species richness, and between genomic diversity within a species and density of that species, but no robust support for the expectation of correlated genomic and species diversity. Their analyses highlight the among-species variability in relationships among these different levels of organization and also the complex ways in which interactions with the broader ecosystem (i.e. unionid mussels require fish hosts for maturation) affect these quantitative relationships, nonetheless pushing forward into the important frontier of community-wide genomic assessment for theoretical and conservation applications.