Biogeography of Chilean Bees in the Atacama Desert: With a Focus on the Boundary Between Summer and Winter Rainfall Regions

There are two rainfall regimes in northern Chile where the majority of rain in the northeast occurs during the austral summer while the southwest receives rain mainly during the austral winter. The transition zone between these two rainfall regimes may have influenced speciation events in northern Chile by serving as a barrier to dispersal. This study tests for disjunct sister groups in the bee genera Neofidelia (Megachilidae), Callonychium (Andrenidae), and Caenohalictus (Halictidae) using the Spatial Analysis Vicariance method. Phylogenetic trees were constructed with mtDNA CO1 sequences for Callonychium and Caenohalictus and a combination of morphological and molecular data for Neofidelia. The Vicariance Inference Program returned a total of 4 disjunct nodes among the three genera with sister taxa residing on either side of the summer/winter rainfall transition zone in each of them. I conclude that the transition zone between summer/winter rainfall acts as a barrier to dispersal in northern Chile.