Wolbachia within the Hawaiian Drosophilidae

Abstract

Wolbachia has attracted considerable interest in recent years due to its abundance, widespread distribution and the multifaceted impact that it can have on the reproductive functions of its host. The ability of Wolbachia to induce cytoplasmic incompatibility has led to its use as a biological control agent and its purported ability to be a potential driving force in speciation, as it can create reproductive isolation both between and within their host species. Comprised of up to 1000 species in 2 major genera the Hawaiian Drosophilidae are an impressive example of adaptive radiation. Although many mechanisms have been proposed to explain their rapid and extensive diversification, the relationship between Wolbachia and the Hawaiian Drosophilidae has yet to be fully explored. To date most of what is known about Wolbachia in naturally occurring populations Hawaiian Drosophilidae is based on a single gene, Wolbachia surface protein (wsp). However, recent studies have indicated that phylogenetic reconstructions for Wolbachia based solely on the wsp gene are unreliable. Overall, the aims of this study were to: (1) create a more accurate phylogenetic reconstruction for Wolbachia within the Hawaiian Drosophilidae based on a multi-locus sequencing typing (MLST) scheme and (2) investigate the patterns of Wolbachia transmission within the Hawaiian Drosophilidae. More specifically, this study sought to test if Wolbachia could be a potential driver of diversification and speciation in the Hawaiian Drosophilidae. Patterns of co-diversification between host and symbiont phylogenies were assessed through co-phylogenetic reconciliation analyses and comparative phylogenetic methods based on character traits of the host (i.e., island of collection, preferred ovipositional substrate, and host plant family). Overall, the results of this study indicate that the incidence of Wolbachia within the Hawaiian Drosophilidae (18.71% species-level; 11.03% individual-level) and the designation of most alleles to supergroup B (81.95%), were consistent with previous findings. Furthermore, Wolbachia strain diversity within the Hawaiian Drosophilidae was determined to be best explained by vertical (e.g., co-speciation) and horizontal (e.g., host switch) modes of transmission. Therefore, future research aimed at improving the understanding of how Wolbachia are transmitted horizontally in nature are of great importance, especially in Hawaiian ecosystems. Recently, strategies have been proposed that utilize Wolbachia to reduce mosquito populations and impede the transmission of mosquito-borne diseases, such as avian malaria. However, until it is understood how Wolbachia is horizontally transmitted in natural insect communities, its use may have unintended consequences that could negatively impact native Hawaiian arthropod taxa.