Horizontal transmission and recombination of Wolbachia in the butterfly tribe Aeromachini Tutt, 1906 (Lepidoptera: Hesperiidae).

Zimiao Zhao,Qunxiu Liu,Jianqing Zhu,Ary A Hoffmann,Liying Tang,Shuojia Ma,Lijun Cao,Jie Fang,Li Shen,Weidong Yu,Weibin Jiang,Yongqiang Wang

doi:10.1093/g3journal/jkab221

Abstract

Wolbachia is arguably one of the most ubiquitous heritable symbionts among insects and understanding its transmission dynamics is crucial for understanding why it is so common. While previous research has studied the transmission pathways of Wolbachia in several insect lineages including Lepidoptera, this study takes advantage of data collected from the lepidopteran tribe Aeromachini in an effort to assess patterns of transmission. Twenty-one of the 46 species of Aeromachini species were infected with Wolbachia. Overall, 25% (31/125) of Aeromachini specimens tested were Wolbachia positive. All Wolbachia strains were species-specific except for the wJho strain which appeared to be shared by three host species with a sympatric distribution based on a cophylogenetic comparison between Wolbachia and the Aeromachini species. Two tests of phylogenetic congruence did not find any evidence for cospeciation between Wolbachia strains and their butterfly hosts. The cophylogenetic comparison, divergence time estimation, and Wolbachia recombination analysis revealed that Wolbachia acquisition in Aeromachini appears to have mainly occurred mainly through horizontal transmission rather than codivergence.

Highlights

Wolbachia is the most widespread endosymbiotic bacterium that infects a large variety of arthropods and filarial nematodes (Bandi et al 1998; Weinert et al 2015)
25% (31/125) of samples were Wolbachia positive and 46% (21/46) of Aeromachini species in this study were considered infected with Wolbachia, with some of these shown to be polymorphic for the infection despite limited sampling
The Mantel test analysis indicated a nonsignificant correlation between Wolbachia frequency and geographic location of their corresponding Aeromachini hosts when pooled across species and samples (r 1⁄4 0.1714, P 1⁄4 0.060), suggesting a weak spatial structure in the incidence of Wolbachia

Summary

Introduction

Wolbachia is the most widespread endosymbiotic bacterium that infects a large variety of arthropods and filarial nematodes (Bandi et al 1998; Weinert et al 2015). While Wolbachia has been investigated in detail in some infected butterfly species (Hornett et al 2006; Charlat et al 2007; Narita et al 2007; Gompert et al 2008; Duplouy et al 2010; Jiang et al 2014, 2016), there are few systematic studies of Wolbachia at the molecular level across a group of related species even though such an analysis can be useful in assessing horizontal transmission patterns in other insects such as Drosophila (Turelli et al 2018), Agelenopsis (Baldo et al 2008), Trichogramma (Huigens et al 2004), Rhagoletis (Schuler et al 2013), and Altica (Jackel et al 2013). We tackle this issue by evaluating the molecular phylogeny of the tribe Aeromachini and associating it with phylogenetic patterns for Wolbachia infections to assess patterns of transmission

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Conclusion