Differences in mating behavior lead to asymmetric mating interactions and consequential changes in sex ratio between...

The invasive B whitefly and the indigenous ZHJ2 whitefly in China of the Bemisia tabaci complex represent two previously allopatric cryptic species. Laboratory experiments have shown that the invasive B can displace the indigenous ZHJ2. Here, we observed the mating behavior and mating interactions between B and ZHJ2 to elucidate the behavioral mechanisms underlying their competition. The 2 species are able to mate with each other, although at a significantly lower frequency than that between males and females within the same species. Heterospecifically-mated females produce only male progeny, indicating reproductive isolation. Heterospecific mating had only a marginal effect on reproduction of females in either species. Detailed observations on mating interactions between the 2 species showed that B had higher sexual activity than ZHJ2. B males were more likely to interrupt courtships initiated by rival males than ZHJ2 males. Compared with ZHJ2 males, B males were also more likely to successfully interrupt courtships initiated by rival heterospecific males than by males of the same species. In addition, B males guarded B females post-copulation, whereas ZHJ2 males did not. When the 2 species co-occurred, the behavioral differences and interactions between them resulted in an increased proportion of females produced in the offspring of B but reduced proportion of females in the progeny of ZHJ2. These asymmetric mating interactions might be an important mechanism underlying the displacement of ZHJ2 by B. Our study shows that reproductive interference might contribute to the competitive exclusion between closely related species during biological invasions.