Browsing by Author "Casquet, Juliane"
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- A combined field survey and molecular identification protocol for comparing forest arthropod biodiversity across spatial scalesPublication . Emerson, Brent C.; Casquet, Juliane; López, Heriberto; Cardoso, Pedro; Borges, Paulo A. V.; Mollaret, Noémy; Oromí, Pedro; Strasberg, Dominique; Thébaud, ChristopheObtaining fundamental biodiversity metrics such as alpha, beta and gamma diversity for arthropods is often complicated by a lack of prior taxonomic information and/or taxonomic expertise, which can result in unreliable morphologically based estimates. We provide a set of standardized ecological and molecular sampling protocols that can be employed by researchers whose taxonomic skills may be limited, and where there may be a lack of robust a priori information regarding the regional pool of species. These protocols combine mass sampling of arthropods, classification of samples into parataxonomic units (PUs) and selective sampling of individuals for mtDNA sequencing to infer biological species. We sampled ten lowland rainforest plots located on the volcanic oceanic island of R eunion (Mascarene archipelago) for spiders, a group with limited taxonomic and distributional data for this region. We classified adults and juveniles into PUs and then demonstrated the reconciliation of these units with presumed biological species using mtDNA sequence data, ecological data and distributional data. Because our species assignment protocol is not reliant upon prior taxonomic information, or taxonomic expertise, it minimizes the problem of the Linnean shortfall to yield diversity estimates that can be directly compared across independent studies. Field sampling can be extended to other arthropod groups and habitats by adapting our field sampling protocol accordingly.
- MtDNA metagenomics reveals large-scale invasion of belowground arthropod communities by introduced speciesPublication . Cicconardi, Francesco; Borges, Paulo A. V.; Strasberg, Dominique; Oromí, Pedro; López, Heriberto; Pérez-Delgado, Antonio J.; Casquet, Juliane; Caujapé-Castells, Juli; Fernández-Palacios, José María; Thébaud, Christophe; Emerson, Brent C.Using a series of standardized sampling plots within forest ecosystems in remote oceanic islands, we reveal fundamental differences between the structuring of aboveground and belowground arthropod biodiversity that are likely due to large-scale species introductions by humans. 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 species are genetically identical, or near identical, to individuals sampled from often very distant geographic regions of the world. Patterns of mtDNA relatedness among Collembola implicate humanmediated species introductions, with minimum estimates for the proportion of introducedspecies on the sampled islands ranging from 45% to 88%. Our results call for more attention to soil mesofauna to understand the global extent and ecological consequences of species introductions.