Distribution and prevalence of Wolbachia in introduced populations of the fire ant Solenopsis invicta

Abstract

Wolbachia are intracellular bacteria that induce phenotypic effects in many arthropod hosts to enhance their own transmission within host populations. Wolbachia commonly infect the Red Imported Fire Ant, Solenopsis invicta, in native South American populations. A previous study failed to detect Wolbachia in fire ants from the introduced range in the USA. We conducted an extensive study of individuals collected from 1157 nests from 10 widespread geographical populations in the USA. Wolbachia were detected in ants from two nearby populations in southern Mississippi, with different variants (wsp gene sequences) infecting ants from colonies of the multiple-queen (polygyne) vs. single-queen (monogyne) social forms. The parsimonious explanation for the presence of Wolbachia in introduced S. invicta is that there have been one or more recent introductions of Wolbachia-infected fire ants into the southern USA.

Loss of microbial (pathogen) infections associated with recent invasions of the red imported fire ant Solenopsis invicta

“…This scenario is obviously the most parsimonious explanation for the absence of Wolbachia and V. invictae in these areas since the prevalence of these two microbes is quite low (perhaps even zero in the case of V. invictae, Oi and Valles, unpublished data) throughout the US, which appears to be most likely the source for these recent invasions (Shoemaker et al 2000(Shoemaker et al , 2003Bouwma et al 2006;Oi and Valles 2008). Thus, the absence of these two microbes, and perhaps others, in these areas may simply result from chance due to the sampling of relatively few numbers of individuals to serve as new founders from a source population where most individuals lack these infections.…”

“…We surveyed for the presence of Wolbachia using oligonucleotide primers Wsp81F and Wsp691R (Zhou et al 1998;Shoemaker et al 2000) following the methods described in Bouwma et al (2006). We also included two primers that amplify a portion of the nuclear EF1a gene (EF1a-532F and EF1a-610R) to serve as internal controls for DNA quality (described in Shoemaker et al 2000).…”

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

“…Wolbachia in Argentine ants (L. humile) has been observed only at one site within their introduced range, while infections were substantially more common in their native range (Tsutsui et al, 2003). Similarly Solenopsis invicta Buren and S. richteri Forel populations have low infection rates in their introduced compared to their native range (Bouwma et al, 2006;Shoemaker et al, 2000Shoemaker et al, , 2003Yang et al, 2010). The absence of pathogens such as Wolbachia in nearly all the introduced populations of these three invasive ants (L. humile, S. invicta and S. richteri) has been proposed as consistent with predictions of the enemy-release hypothesis, and as a potential reason for the ants' high abundance in the introduced range (Tsutsui et al, 2003;Yang et al, 2010).…”

Analysis of the Hypervariable Regions (HVRs) of the wsp Gene of Wolbachia from Solenopsis invicta Ants in Southeastern Brazil

“…We estimated 50% infection rate in the sampled S. invicta mounds which is probably due to Wolbachia-infected and uninfected S. invicta queens invading new areas, generating infected and uninfected nests [7] [8] [24] [25]. A previous study [24], found 10% to 90% prevalence of Wolbachia infection in native populations of S. invicta.…”