Prevalence and genetic diversity of three bacterial endosymbionts (Wolbachia, Arsenophonus, and Rhizobiales) associated with the invasive yellow crazy ant (Anoplolepis gracilipes)

Invasive species carry pathogens, parasites and mutualistic microorganisms into their new range. We examined the prevalence and genetic diversity of three bacterial endosymbionts (Wolbachia, Arsenophonus, and Rhizobiales) in four Anoplolepis gracilipes (Smith) populations in the Pacific region, four populations from mainland Australia and one population from Christmas Island in the Indian Ocean. Wolbachia was found in eight of the nine sampling sites, with between 31.8 and 100% of ants infected. These infection rates are substantially higher than those previously observed for other invasive ants such as Linepithema humile and Solenopsis invicta. All sequences of Wolbachia were genetically identical. Arsenophonus was observed in five of the nine sampling sites, with infection rates ranging between 4.5 and 50.8%. Like Wolbachia, Arsenophonus can modify the sex-ratio of its hosts via male-killing. Arsenophonus was found to co-occur with Wolbachia in the same ants in five of the nine sampling sites. Rhizobiales is a clade of symbiotic bacteria mostly found in herbivorous ants. These bacteria help provide nitrogen to their hosts and were found in only three of the nine sampling sites with an infection rate of 1.6–11.8%. It also co-occurred with the other bacteria. There was no genetic variation in Arsenophonus and Rhizobiales samples, with the exception of a sequence from one Arsenophonus sample in Samoa that differed by a single base pair. These bacterial endosymbionts may contribute to the population variability in A. gracilipes and may be manipulated for the purpose of pest management.