Wolbachia infection and host shifts in scale insects

AbstractWolbachia 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.

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Wolbachia infection in wild mosquitoes (Diptera: Culicidae): implications for transmission modes and host-endosymbiont associations in Singapore

Parasites & Vectors ◽

10.1186/s13071-020-04466-8 ◽

2020 ◽

Vol 13 (1) ◽

Author(s):

Huicong Ding ◽

Huiqing Yeo ◽

Nalini Puniamoorthy

Keyword(s):

Vertical Transmission ◽

Surface Protein ◽

Wolbachia Infection ◽

Host Shift ◽

Control Technique ◽

Host Shifts ◽

Reproductive Tissues ◽

Transmission Modes ◽

Bacterial Endosymbionts ◽

Event Based

Abstract Background Wolbachia are intracellular bacterial endosymbionts found in most insect lineages. In mosquitoes, the influence of these endosymbionts on host reproduction and arboviral transmission has spurred numerous studies aimed at using Wolbachia infection as a vector control technique. However, there are several knowledge gaps in the literature and little is known about natural Wolbachia infection across species, their transmission modes, or associations between various Wolbachia lineages and their hosts. This study aims to address these gaps by exploring mosquito-Wolbachia associations and their evolutionary implications. Methods We conducted tissue-specific polymerase chain reaction screening for Wolbachia infection in the leg, gut and reproductive tissues of wild mosquitoes from Singapore using the Wolbachia surface protein gene (wsp) molecular marker. Mosquito-Wolbachia associations were explored using three methods—tanglegram, distance-based, and event-based methods—and by inferred instances of vertical transmission and host shifts. Results Adult mosquitoes (271 specimens) representing 14 genera and 40 species were screened for Wolbachia. Overall, 21 species (51.2%) were found positive for Wolbachia, including five in the genus Aedes and five in the genus Culex. To our knowledge, Wolbachia infections have not been previously reported in seven of these 21 species: Aedes nr. fumidus, Aedes annandalei, Uranotaenia obscura, Uranotaenia trilineata, Verrallina butleri, Verrallina sp. and Zeugnomyia gracilis. Wolbachia were predominantly detected in the reproductive tissues, which is an indication of vertical transmission. However, Wolbachia infection rates varied widely within a mosquito host species. There was no clear signal of cophylogeny between the mosquito hosts and the 12 putative Wolbachia strains observed in this study. Host shift events were also observed. Conclusions Our results suggest that the mosquito-Wolbachia relationship is complex and that combinations of transmission modes and multiple evolutionary events likely explain the observed distribution of Wolbachia diversity across mosquito hosts. These findings have implications for a better understanding of the diversity and ecology of Wolbachia and for their utility as biocontrol agents.

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

10.1101/2021.08.23.457441 ◽

2021 ◽

Author(s):

Ehsan Sanaei ◽

Yen-Po Lin ◽

Lyn G Cook ◽

Jan Engelstaedter

Keyword(s):

Wolbachia Infection ◽

Scale Insect ◽

Distinct Pattern ◽

Scale Insects ◽

Infection Frequency ◽

Exponential Decline ◽

Wide Range ◽

Distribution Parameters ◽

Low Prevalence ◽

Evolutionary Consequences

Wolbachia is one of the most successful endosymbiotic bacteria of arthropods. Known as the master of manipulation, Wolbachia can induce a wide range of phenotypes in its host that can have far-reaching ecological and evolutionary consequences and may be exploited for disease and pest control. However, our knowledge of Wolbachia's distribution and infection rate is unevenly distributed across arthropod groups such as scale insects. We fitted a distribution of within-species prevalence of Wolbachia to our data and compared it to distributions fitted to an up-to-date dataset compiled from surveys across all arthropods. The estimated distribution parameters indicate a Wolbachia infection frequency of 43.6% (at a 10% prevalence threshold) in scale insects. Prevalence of Wolbachia in scale insects follows a distribution similar to exponential decline (most species are predicted to have low prevalence infections), in contrast to the U-shaped distribution estimated for other taxa (most species have a very low or very high prevalence). We observed no significant associations between Wolbachia infection and scale insect traits. Finally, we screened for Wolbachia in scale insect's ecological associates. We found a positive correlation between Wolbachia infection in scale insects and their ant associates, pointing to a possible route of horizontal transfer of Wolbachia.

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