Large carpenter bees show high dispersal in a tropical semi-arid region susceptible to desertification

Desertification is a major threat to biodiversity in arid areas of the world, partly because many organisms in these regions already exist at or near the limits of their movement and physiology. Here, we used molecular data to investigate patterns of persistence and dispersal in an ecologically and economically important carpenter bee (Xylocopa grisescens Lepeletier) found throughout the semiarid Caatinga region of Brazil. We used a genome-wide approach (double digest restriction-site associated DNA, ddRAD) to gather genetic data from bees sampled from eight sites within a semiarid region subject to desertification in Northeastern Brazil. Across all populations, we observed a consistent heterozygosity and effective population size deficit along with low genetic differentiation. We did not find strong evidence of dispersal limitations caused by desertification in this study system despite data collection from sites up to 300 km distant. Thus, our data suggest that human-mediated changes in the Caatinga, such as habitat loss, have impacted the population genetic patterns of X. grisescens. However, these impacts have also been softened by the species' biological characteristics, such as its relatively high capacity for movement. This study provides insights into how habitat changes might impact the long-term survival of large solitary bees.