Strong decreases in genetic diversity despite high gene flow for a solitary bee

Abstract

AbstractMany organisms live in landscapes that include fragments of natural habitat interspersed with agricultural or urban areas. In such areas, dispersal across human-dominated landscapes may be important for the maintenance of genetic diversity within habitat fragments. Understanding the extent to which dispersal occurs across fragmented habitat and how genetic diversity changes over time is particularly important for bee populations. Population sizes of many bee species are declining, which can have profound negative impacts on both agricultural pollination and the fitness of wild plants. We quantified dispersal across 100 km of mixed landscapes in southern Costa Rica for the solitary bee species Euglossa championi, and we quantified changes in genetic diversity over an eleven-year period. Our SNP-based analysis revealed high dispersal across the geographic area and no evidence that deforestation restricted dispersal. However, we found strong decreases in genetic diversity over time. Expected heterozygosity decreased by 28% over eleven years, regardless of the amount of forest that surrounded sites. Our results suggest that while high dispersal over deforested landscapes may render E. championi less susceptible to land use change than species that show restricted dispersal, the strong decrease in genetic diversity within sites over time suggests this species may warrant conservation monitoring.