Chaos of Wolbachia Sequences Inside the Compact Fig Syconia of Ficus benjamina (Ficus: Moraceae)

Abstract

Figs and fig wasps form a peculiar closed community in which the Ficus tree provides a compact syconium (inflorescence) habitat for the lives of a complex assemblage of Chalcidoid insects. These diverse fig wasp species have intimate ecological relationships within the closed world of the fig syconia. Previous surveys of Wolbachia, maternally inherited endosymbiotic bacteria that infect vast numbers of arthropod hosts, showed that fig wasps have some of the highest known incidences of Wolbachia amongst all insects. We ask whether the evolutionary patterns of Wolbachia sequences in this closed syconium community are different from those in the outside world. In the present study, we sampled all 17 fig wasp species living on Ficus benjamina, covering 4 families, 6 subfamilies, and 8 genera of wasps. We made a thorough survey of Wolbachia infection patterns and studied evolutionary patterns in wsp (Wolbachia Surface Protein) sequences. We find evidence for high infection incidences, frequent recombination between Wolbachia strains, and considerable horizontal transfer, suggesting rapid evolution of Wolbachia sequences within the syconium community. Though the fig wasps have relatively limited contact with outside world, Wolbachia may be introduced to the syconium community via horizontal transmission by fig wasps species that have winged males and visit the syconia earlier.

Wolbachia in guilds of Anastrepha fruit flies (Tephritidae) and parasitoid wasps (Braconidae)

“…The striking cases seem to be those of Wolbachia wsp-156 found in D. fluminensis derived from two species of fruit flies, and of Wolbachia wsp-23 that was found in Utetes anastrephae derived from four species of Anastrepha . These data indicate that horizontal transmission might have occurred in the communities of fruit flies and braconid wasps, similarly to what was assumed in guilds of other insects with their parasitoid wasps (Vavre et al , 1999; Yang et al , 2012; Yang et al , 2013; Morrow et al , 2014). …”

“…This is a very high infection rate even among tephritid flies since, for example, in Bactrocera from Thailand Wolbachia infection occurred in 28.3% of the species (Kittayapong et al , 2000) and in 37% of species of fruit flies, including Bactrocera from Australia (Morrow et al , 2015). Amongst the braconids, five out of six (83.3%) species were infected by the endosymbiont, a rate similar to the 84% (14 out of 17 species) found in fig wasps from China (Yang et al , 2012). Thus, the species infection rate found in Anastrepha and in the parasitoid wasps are among the highest found in insect species which span from 40 to 76% (Werren and Windsor, 2000; Jeyaprakash and Hoy, 2000; Hilgenboecker et al , 2008; Zug and Hammerstein, 2012).…”

“…The electropherograms were examined by the web tool Electropherogram Quality Analysis (Togawa and Brigido, 2003). Beside these analyses, sequences without signals of PCR artifacts were considered free of errors if they were found in more than two individuals in a given sample, and for unique sequences if their amino acid conceptual translation was achieved without interruptions (Yang et al , 2012). For sequences with evidence of two distinct nucleotides in any given peak in the electropherogram, the amplified fragments were cloned in Top 10 E. coli bacteria using the Topo Cloning kit (Invitrogen).…”

“…, 2013), or by contact of haemolymph through wounds in the host's bodies (Rigaud and Juchault, 1995). Horizontal transmission was also considered the route of infection by multiple Wolbachia strains, as is frequently observed in many species of Coleoptera, Diptera, Hymenoptera and Lepidoptera (Werren et al , 1995; Jamnongluk et al , 2002; Rokas et al , 2002; Reuter and Keller, 2003; Hiroki et al , 2004; Schuler et al , 2011; Yang et al , 2012, 2013; Augustinos et al , 2014). …”

“…Putative recombinant haplotypes involving distinct Wolbachia strains were found to be widespread among insect species (Jiggins et al , 2001; Werren and Bartos, 2001; Reuter and Keller, 2003; Baldo et al , 2005, 2006a; Arthofer et al , 2009; Yang et al , 2012, 2013). Intragenic recombination occurs frequently in the wsp gene of Wolbachia, infecting a large number of insect species (Baldo et al , 2005, 2006a).…”