Peer Review #2 of "Current state of knowledge on Wolbachia infection among Coleoptera: a systematic review (v0.2)"

Abstract

Background. Despite great progress in studies on Wolbachia infection in insects, the knowledge about its relations with beetle species, populations and individuals, and the effects of bacteria on these hosts is still unsatisfactory. In this review we summarize the current state of knowledge about Wolbachia occurrence and interactions with Coleopteran hosts. Methods. An intensive search of the available literature resulted in the selection of 86 publications that describe the relevant details about Wolbachia presence among beetles. These publications were then examined with respect to the distribution and taxonomy of infected hosts and diversity of Wolbachia found in beetles. Sequences of Wolbachia genes (16S rDNA, ftsZ) were used for the phylogenetic analyses. Results. The collected publications revealed that Wolbachia has been confirmed in 204 beetle species and that the estimated average prevalence of this bacteria across beetle species is 38.3% and varies greatly across families and genera (0-88% infected members) and is much lower (c. 13%) in geographic studies. The majority of the examined and infected beetles were from Europe and East Asia. The most intensively studied have been two groups of herbivorous beetles: Curculionidae and Chrysomelidae. Coleoptera harbor Wolbachia belonging to three supergroups: F found in only 3 species, and A and B found in similar numbers of beetles (including some doubly infected); however the latter two were most prevalent in different families. 59% of species with precise data were found to be totally infected. Single infections were found in 69% of species and others were doubly-or multiply-infected. Wolbachia caused numerous effects on its beetle hosts, including selective sweep with host mtDNA (found in 3% of species), cytoplasmic incompatibility (detected in c. 6% of beetles) and other effects related to reproduction or development (like male-killing, possible parthenogenesis or haplodiploidy induction, and egg development). Phylogenetic reconstructions for Wolbachia genes rejected cospeciation between these bacteria and Coleoptera, with minor exceptions found in some Hydraenidae, Curculionidae and Chrysomelidae. In contrast, horizontal transmission of