Co-speciation in bedbug Wolbachia parallel the pattern in nematode hosts

Ondřej Balvín,Benoit Talbot,Steffen Roth,Klaus Reinhardt

doi:10.1038/s41598-018-25545-y

Abstract

Wolbachia bacteria, vertically transmitted intracellular endosymbionts, are associated with two major host taxa in which they show strikingly different symbiotic modes. In some taxa of filarial nematodes, where Wolbachia are strictly obligately beneficial to the host, they show complete within- and among-species prevalence as well as co-phylogeny with their hosts. In arthropods, Wolbachia usually are parasitic; if beneficial effects occurs, they can be facultative or obligate, related to host reproduction. In arthropods, the prevalence of Wolbachia varies within and among taxa, and no co-speciation events are known. However, one arthropod species, the common bedbug Cimex lectularius was recently found to be dependent on the provision of biotin and riboflavin by Wolbachia, representing a unique case of Wolbachia providing nutritional and obligate benefits to an arthropod host, perhaps even in a mutualistic manner. Using the presence of presumably functional biotin gene copies, our study demonstrates that the obligate relationship is maintained at least in 10 out of 15 species of the genera Cimex and Paracimex. The remaining five species harboured Wolbachia as well, demonstrating the first known case of 100% prevalence of Wolbachia among higher arthropod taxa. Moreover, we show the predicted co-cladogenesis between Wolbachia and their bedbug hosts, also as the first described case of Wolbachia co-speciation in arthropods.

Highlights

Interspecific interactions that provide fitness benefits to all partners involved characterizes a large part of the world’s biodiversity[1,2]
The dominant signal belonged to the same Wolbachia strain that was found in other bedbug species
The low diversity of Wolbachia loci: the surface protein gene (WSP) among the bedbug species allowed for visual inspection of alignment and let us conclude that no codon mismatch or recombination across the WSP sequence had occurred

Summary

Introduction

Interspecific interactions that provide fitness benefits to all partners involved characterizes a large part of the world’s biodiversity[1,2]. Secondary symbioses are characterized by more generic, not necessarily host-specific benefits and bacteria vary in prevalence across cells, tissues and populations of the host Their effects on a given host may range from pathogenic to mutualistic, and they can be transmitted either vertically, horizontally, or both[3]. Nematode-associated Wolbachia are usually found in all individuals of a species[16,17] and in all species within larger clades[9] In these associations, Wolbachia seems to be exclusively vertically transmitted, which is regarded as a sign of host-provided benefits. Other RPs involve the killing or feminization of genetic males[22] or the induction of parthenogenesis[23] These RPs directly or indirectly increase the proportion of infected females and Wolbachia are, able to thrive without providing a fitness benefit to the host, despite vertical transmission and dependence on host fecundity

Methods

Results

Discussion

Conclusion