Global determinants of insect mitochondrial genetic diversity

Understanding global patterns of genetic diversity (GD) is essential for describing, monitoring, and preserving life on Earth. To date, efforts to map macrogenetic patterns have been restricted to vertebrates, which comprise only a small fraction of Earths biodiversity. Here, we construct the first global map of predicted insect mitochondrial (COI) GD, derived from publicly available data. We calculate the mitochondrial GD mean (GDM) and evenness (GDE) of insect assemblages across the globe, identify their environmental correlates, and make predictions of mitochondrial GD levels in unsampled areas based on environmental data. Using the largest single-locus genetic dataset yet assembled, we find that mitochondrial GDE follows a quadratic latitudinal gradient peaking in the subtropics. Both mitochondrial GDM and GDE positively correlate with seasonally hot temperatures, as well as climate stability since the last glacial maximum. Our models explain 27.9% and 24.0% of the observed variation in mitochondrial GDM and GDE in insects, respectively, making an important step towards understanding global biodiversity patterns in the most diverse animal taxon.