Microbiome composition within a sympatric species complex of intertidal isopods (Jaera albifrons)

Marius A Wenzel* (Corresponding Author), Alexander Douglas, Stuart Brannon Piertney

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)
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Abstract

The increasingly recognised effects of microbiomes on the eco-evolutionary dynamics of their hosts are promoting a view of the “hologenome” as an integral host-symbiont evolutionary entity. For example, sex-ratio distorting reproductive parasites such as Wolbachia are well-studied pivotal drivers of invertebrate reproductive processes, and more recent work is highlighting novel effects of microbiome assemblages on host mating behaviour and developmental incompatibilities that underpin or reinforce reproductive isolation processes. However, examining the hologenome and its eco-evolutionary effects in natural populations is challenging because microbiome composition is considerably influenced by environmental factors. Here we illustrate these challenges in a sympatric species complex of intertidal isopods (Jaera albifrons spp.) with pervasive sex-ratio distortion and ecological and behavioural reproductive isolation mechanisms. We deep-sequence the bacterial 16S rRNA gene among males and females collected in spring and summer from two coasts in north-east Scotland, and examine microbiome composition with a particular focus on reproductive parasites. Microbiomes of all species were diverse (overall 3,317 unique sequences among 3.8 million reads) and comprised mainly Proteobacteria and Bacteroidetes taxa typical of the marine intertidal zone, in particular Vibrio spp. However, we found little evidence of the reproductive parasites Wolbachia, Rickettsia, Spiroplasma and Cardinium, suggesting alternative causes of sex-ratio distortion. Notwithstanding, a significant proportion of the variance in microbiome composition among samples was explained by sex (14.1 %), nested within geographic (26.9 %) and seasonal (39.6 %) variance components. The functional relevance of this sex signal was difficult to ascertain given the absence of reproductive parasites, the ephemeral nature of the species assemblages and substantial environmental variability. These results establish the Jaera albifrons species complex as an intriguing system for examining the effects of microbiomes on reproductive processes and speciation, and highlight the difficulties associated with snapshot assays of microbiome composition in dynamic and complex environments.

Original languageEnglish
Article numbere0202212
JournalPloS ONE
Volume13
Issue number8
DOIs
Publication statusPublished - 29 Aug 2018

Bibliographical note

Data Availability: Raw sequence data alongside all relevant metadata are deposited in the NCBI short-read archive (SRA) at accession SRP132549.

Funding: This work was funded by the UK Natural Environment Research Council (NERC), grant NE/M015661/1, awarded to SBP and AD. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Acknowledgments: We are grateful to Heather Ritchie and Laura Howell for fieldwork assistance. We acknowledge the computational support of the Maxwell HPC cluster funded by the University of Aberdeen.

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