Cicconardi, F., Borges, P.A.V., Strasberg, D., Oromí, P., López, H., Perez-Delgado, A.J., Casquet, J., Caujape-Castells, J, Fernandez-Palacios, J.M., Thebaud, C. & Emerson, B.C. (2017) MtDNA metagenomics reveals large-scale invasion of belowground arthropod communities by introduced species.Molecular Ecology, 26, 3104-3115. DOI:10.1111/mec.14037 (IF2017 6.131; Q1 Ecology)
Using a series of standardised sampling plots within forest ecosystems in remote oceanic islands, and mitochondrial metagenomics for the analysis of the Collembola component of the soil mesofauna, we reveal fundamental differences between the structuring of aboveground and belowground arthropod biodiversity that are likely due to large-scale species introductions by humans. Individual species of beetle and spider were sampled almost exclusively from single islands, while soil dwelling Collembola exhibited more than tenfold higher species sharing among islands. Comparison of Collembola mitochondrial metagenomic data to a database of more than 80,000 Collembola barcode sequences revealed almost 30% of sampled island taxa are genetically identical, or near identical, to individuals sampled from often very distant geographic regions of the world. The patterns of species sharing over vast geographical distances is in contrast with recent molecular studies that indicate often limited natural dispersal of Collembola over evolutionary timescales. Patterns of mtDNA relatedness of among Collembola implicate human-mediated species introductions, with minimum estimates for the proportion of introduced species on the sampled islands ranging from 43-84%. Our results call for more attention on soil mesofauna to understand the global extent and ecological consequences of species introductions.
Significance statement: Soil mesofauna, comprising invertebrates typically less than 2mm in size, is recognised as a species rich and ecologically important component of animal biodiversity. However, logistical challenges for species identification mean that the vast majority of mesofauna is uncatalogued, complicating both the measurement of soil invertebrate biodiversity, and the investigation of spatial patterns. We apply a novel genetic approach to identify species within the Collembola component of soil mesofauna. Our results reveal high levels of species sharing between geographically distant remote oceanic islands, greatly in excess of that seen for aboveground arthropod species. Comparison to a global database of Collembola DNA sequences reveals that minimum estimates for introduced species can reach as high as 84% within a community.