AustralianBryobiamites (Trombidiformes: Tetranychidae) form a complex of cryptic taxa with unique climatic niches and insecticide responses

Abstract

BACKGROUND: Bryobia (Koch) mites belong to the economically important spider mite family, the Tetranychidae, with >130 species described worldwide. Due to taxonomic difficulties and most species being asexual, species identification relies heavily on genetic markers. Multiple putative Bryobia mite species have been identified attacking pastures and grain crops in Australia. In this study, we collected 79 field populations of Bryobia mites and combined these with 134 populations that were collected previously. We characterised taxonomic variation of mites using 28S rDNA amplicon-based DNA metabarcoding using nextgeneration sequencing approaches and direct Sanger sequencing. We then undertook species distribution modelling of the main genetic lineages and examined the chemical responses of multiple field populations.RESULTS: We identified 47 unique haplotypes across all mites sampled that grouped into four distinct genetic lineages. These lineages have different distributions, with three of the four putative lineages showing different climatic envelopes, as inferred from species distribution modelling. Bryobia mite populations also showed different responses to a widely used insecticide (the organophosphate, omethoate), but not to another chemical (the pyrethroid, bifenthrin) when examined using laboratory bioassays.CONCLUSION: Our findings indicate that cryptic diversity is likely to complicate the formulation of management strategies for Bryobia mites. Although focussed on Australia, this study demonstrates the challenges of studying Bryobia and highlights the importance of further research into this complex group of mites across the world.