Variability, drivers, and utility of genetic diversity-area relationships in terrestrial vertebrates

Chloé Schmidt , Sean M. Hoban, Deborah M. Leigh, Walter Jetz, Colin Garroway

Maintaining genetic diversity within and among populations is critical for conservation and a prominent goal of the Kunming-Montreal Global Biodiversity Framework. However, direct estimates of genetic diversity are unavailable for most species, and time and resources are insufficient to fill these substantial data gaps and meet conservation target timelines. Robust, proxy-based predictions of genetic diversity loss would therefore be valuable for conserving genetic diversity for the many species lacking DNA-based data. We evaluated one such approach, the Genetic Diversity Area Relationship (GDAR), which describes the relationship between genetic diversity and the geographic area occupied by a species. We estimated differences in genetic diversity relative to the size of sample area using 55 previously published datasets from 51 species and found that GDARs were highly variable across species and strongly dependent on population structure. The mean change in allele count relative to area sampled across all species did not predict genetic diversity differences for individual species well. Traits correlated with population structure explained little variation in the GDAR. Our findings suggest that using a single GDAR is not appropriate to predict genetic diversity loss for individual species following area loss. Further work is needed to identify accurate methods to estimate species-specific levels of genetic diversity decline with area without genetic data. Although the GDAR remains valuable to highlight likely global patterns and scales of genetic diversity loss across many species, our results suggest it is currently too inaccurate for species-specific use.