Abstract
Wolbachia are endosymbionts found in more than half of all insect species. Previous research describes how Wolbachia often manipulate insect reproduction to spread. However, little is known about the impact Wolbachia have on insect diversification. Post-zygotic barriers created from cytoplasmic incompatibility between mismatched Wolbachia strains could cause insect populations to diverge and eventually speciate. To address the potential role Wolbachia have in the speciation of insects, we tested for Wolbachia-driven post-zygotic isolation between allopatric populations of Rhagoletis indifferens and Rhagoletis cingulata. These are closely related sister Rhagoletis species that can breed and produce viable offspring. Previous work shows that R. cingulata and R. indifferens contain four distinct Wolbachia infections in the United States: 1) wCin2 in eastern USA R. cingulata, 2) wCin2 and wCin3 concurrently in southwestern USA R. cingulata, 3) wCin2 in OR/WA R. indifferens, and 4) wCin2 and wCin4 concurrently in central Washington R. indifferens. To identify Wolbachia induced cytoplasmic incompatibility, we crossed adults between all populations and determined the hatch rate of F1 eggs. We find that crosses containing male southwestern R. cingulata with wCin2&3 follow a pattern that is consistent with one-way cytoplasmic incompatibility. In crosses with female wCin2&3 X other populations, we measured egg hatch rates from 50- 70% Crosses with female wCin2&3 X male wCin2&3 had a 51% egg hatch rate. Crosses with male wCin2&3 X other populations produced eggs with hatch rates at 20% Our results show that Wolbachia can create post-zygotic barriers, potentially isolating and leading to insect diversification.