Host phylogeny and ecological associations best explain Wolbachia host shifts in scale insects

Abstract

Wolbachia are among the most prevalent and widespread endosymbiotic bacteria on earth. Wolbachia's success in infecting an enormous number of arthropod species is attributed to two features: the range of phenotypes they induce in their hosts, and their ability to switch to new host species. Whilst much progress has been made in elucidating the phenotypes induced by Wolbachia, our understanding of Wolbachia host shifting is still very limited: we lack answers to even fundamental questions concerning Wolbachia`s routes of transfer and the importance of factors influencing host shifts. Here, we investigate the diversity and host-shift patterns of Wolbachia in scale insects, a group of arthropods with intimate associations with other insects that make them well-suited to studying host shifts. Using Illumina pooled amplicon sequencing of Wolbachia-infected scale insects and their direct associates we determined the identity of all Wolbachia strains, revealing that 32% of samples were multiply infected (with up to five distinct strains per species). We then fitted a Generalised Additive Mixed Model (GAMM) to our data to estimate the influence of factors such as the host phylogeny and the geographic distribution of each species on Wolbachia strain sharing among scale insect species. The model predicts no significant contribution of host geography but strong effects of host phylogeny, with high rates of Wolbachia sharing among closely related species and a sudden drop-off in sharing with increasing phylogenetic distance. We also detected the same Wolbachia strain in scale insects and several intimately associated species (ants, wasps, beetles, and flies). This indicates putative host shifts and potential routes of transfers via these associates and highlights the importance of ecological connectivity in Wolbachia host-shifting.

Wolbachia in scale insects: a distinct pattern of infection frequencies and potential transfer routes via ant associates

“…As a positive control, we used extracted DNA of Drosophila melanogaster with a confirmed Wolbachia infection by w Mel strain (Monsanto‐Hearne and Johnson, 2018) for all PCRs. As part of a separate study, the amplicons generated by this study, including 16S, gatB, coxA and fbpA from 75 Wolbachia positive samples, were sent for Illumina pooled amplicon sequencing with 10–30 K coverage (Sanaei et al ., 2021a). The output of this high‐throughput sequencing approach yielded Wolbachia strains belonging to supergroups A, B and F for all samples (Sanaei et al ., 2021a), which is an indication of the specificity of our screening methodology.…”

“…As part of a separate study, the amplicons generated by this study, including 16S, gatB, coxA and fbpA from 75 Wolbachia positive samples, were sent for Illumina pooled amplicon sequencing with 10–30 K coverage (Sanaei et al ., 2021a). The output of this high‐throughput sequencing approach yielded Wolbachia strains belonging to supergroups A, B and F for all samples (Sanaei et al ., 2021a), which is an indication of the specificity of our screening methodology. Therefore, by using our suggested screening methodology, the probability of false‐positive samples seems to be very low.…”

Using Wolbachia to control rice planthopper populations: progress and challenges

“…MLST analysis of Wolbachia and successful horizontal transfer of Wolbachia by microinjection have also provided evidence for horizontal transmission (Xi et al, 2005(Xi et al, , 2006Li et al, 2017;Zheng et al, 2019). As recorded, horizontal transmission of Wolbachia could occur by many pathways, such as feeding on common plants (Sintupachee et al, 2006;Le Clec'h et al, 2013;Li et al, 2017;Sanaei et al, 2023), parasitic wasps (Ahmed et al, 2015;Brown and Lloyd, 2015;Goya et al, 2022), parasitic mites (Houck et al, 1991;Jaenike et al, 2007;Gehrer and Vorburger, 2012), hybridization (Jiang et al, 2018;Su et al, 2019), and predation (Goodacre et al, 2006;Wang et al, 2010;Su et al, 2019). Although interspecific horizontal transmission inefficiently occurs, Wolbachia horizontal transmission is found in many insects, including rice planthoppers (Zhang et al, 2013), wasps (Huigens et al, 2004;Goya et al, 2022;Zhou et al, 2022), fruit flies (Turelli et al, 2018), trypetids (Schuler et al, 2013(Schuler et al, ), psyllids 10.3389/fmicb.2023 Frontiers in Microbiology 03 frontiersin.org (Serbina et al, 2022), moths (Ahmed et al, 2016), ladybirds (Shaikevich and Romanov, 2023), mosquitoes (Shaikevich et al, 2019), mites (Su et al, 2019), butterflies (Ahmed et al, 2016;Zhao et al, 2021) and so forth.…”