Widespread occurrence of the microorganism Wolbachia in ants

Abstract

For more than 20 years, sex allocation in hymenopteran societies has been a major topic in insect sociobiology. A recurring idea was that relatedness asymmetries arising from their haplodiploid sex determination system would lead to various parent^o¡spring con£icts over optimal reproduction. A possible weakness of existing theory is that only interests of nuclear genes are properly accounted for. Yet, a diversity of maternally transmitted elements manipulate the reproduction of their host in many solitary arthropod groups. The bacterium Wolbachia is a striking example of such a sel¢sh cytoplasmic element, with e¡ects ranging from reproductive incompatibility between host strains, induction of parthenogenesis and feminization of males. This paper reports on a ¢rst PCR-based Wolbachia screening in ants. Out of 50 Indo-Australian species, 50% screened positive for an A-group strain. One of these species also harboured a B-group strain in a double infection. Various factors that might explain the unusually high incidence of Wolbachia in ants are discussed. In general, Wolbachia may represent a widespread and previously unrecognized party active in the con£icts of interest within social insect colonies.

Cloning and sequencing of wsp encoding gene fragments reveals a diversity of co-infecting Wolbachia strains in Acromyrmex leafcutter ants

“…Previous work has documented the widespread occurrence of Wolbachia in ant species (Jeyaprakash and Hoy, 2000;Wenseleers et al, 1998) and has demonstrated a high prevalence of these symbionts in colonies of Atta and Acromyrmex leafcutter ants and Formica wood ants Wenseleers et al, 2001). In the present study we demonstrate a highly complex diversity of strains occurring in single individuals of three Acromyrmex leafcutter ant hosts.…”

“…Sequences generated in this study are indicated in bold. The bar represents a distance of 0.050 (about 25 MY if a wsp evolutionary rate of 0.2% per MY is assumed, Wenseleers et al, 2001). and Solignac, 1995;Wenseleers et al, 1998;Werren et al, 1995a, b;Werren and Windsor, 2000) or more rarely, triple infections (Kondo et al, 2002;Vavre et al, 1999). A stable triple Wolbachia infection has also been created artificially by microinjection of an additional strain in double infected Drosophila (Rousset et al, 1999).…”

“…Previous work on ants has shown that the majority of species screened so far carry Wolbachia infections: 25 out of 50 (50%) Indo-Australian ants (Wenseleers et al, 1998), 10 out of 10 (100%) Nearctic ants (Jeyaprakash and Hoy, 2000), and 7 out of 7 (100%) Panamanian leafcutter ants ) have now been shown to harbour Wolbachia. The high incidence of Wolbachia in ants might be due to the more favourable conditions for invasion and maintenance in haplodiploid social hosts compared to solitary hosts (Wenseleers et al, 1998).…”

“…The high incidence of Wolbachia in ants might be due to the more favourable conditions for invasion and maintenance in haplodiploid social hosts compared to solitary hosts (Wenseleers et al, 1998). For leafcutter and wood ants, Wolbachia has also been shown to be present at or near to fixation Wenseleers et al, 2001 (Jeyaprakash and Hoy, 2000;Shoemaker et al, 2000;Van Borm et al, 2001), but until now it has remained unclear how many distinct strains they represent.…”

Convergent incidences ofWolbachiainfection in fig wasp communities from two continents

“…For example, infection levels are significantly higher than 20% for Hymenoptera in the broad surveys. They are also generally high in studies focused on particular hymenopteran groups, with estimates of 50% (25/50) of Indo-Australian ant species (Wenseleers et al 1998), 59% (26/44) of Panamanian fig wasp species (Shoemaker et al 2002), 62% (13/ 21) of rose gall-inducing wasps (Rhoditini), 57% (4/7) of rose gall parasites (multiple tribes), 44% (4/9) of herb gallinducing wasps ('Aylacini') and 60% (6/10) of gall inquiline wasps (Synergini) (Schilthuizen & Stouthamer 1998;Plantard et al 1999;Rokas et al 2002). A curious exception is provided by oak-gall-inducing wasps (Cynipini), where only 9% (5/53) of species are infected (Rokas et al 2002).…”