MtDNA metagenomics reveals large-scale invasion of belowground arthropod communities by introduced species.

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 human-mediated species introductions, with minimum estimates for the proportion of introduced species 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.

A combined field survey and molecular identification protocol for comparing forest arthropod biodiversity across spatial scales.

Obtaining 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 Réunion (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.

Islands as model systems in ecology and evolution: prospects fifty years after MacArthur-Wilson.

The study of islands as model systems has played an important role in the development of evolutionary and ecological theory. The 50th anniversary of MacArthur and Wilson's (December 1963) article, 'An equilibrium theory of insular zoogeography', was a recent milestone for this theme. Since 1963, island systems have provided new insights into the formation of ecological communities. Here, building on such developments, we highlight prospects for research on islands to improve our understanding of the ecology and evolution of communities in general. Throughout, we emphasise how attributes of islands combine to provide unusual research opportunities, the implications of which stretch far beyond islands. Molecular tools and increasing data acquisition now permit re-assessment of some fundamental issues that interested MacArthur and Wilson. These include the formation of ecological networks, species abundance distributions, and the contribution of evolution to community assembly. We also extend our prospects to other fields of ecology and evolution - understanding ecosystem functioning, speciation and diversification - frequently employing assets of oceanic islands in inferring the geographic area within which evolution has occurred, and potential barriers to gene flow. Although island-based theory is continually being enriched, incorporating non-equilibrium dynamics is identified as a major challenge for the future.

Chelex without boiling, a rapid and easy technique to obtain stable amplifiable DNA from small amounts of ethanol-stored spiders.

DNA barcoding projects require high-throughput generation of sequence data to assemble the comprehensive reference databases that are required to perform large-scale biodiversity inventories and molecular ecology studies. With the advent of new sequencing technologies, the extraction step, which often requires a considerable amount of time and money, represents a significant bottleneck in many studies. Here, we present a one-step Chelex double-stranded DNA extraction protocol that is quick, cheap, easy and works with a small quantity of ethanol-stored tissue. We developed this protocol by removing the denaturation step appearing in classic methods. This modification reduces the number of handling steps to one, thus simplifying the extraction procedure and reducing the risk of sample contamination, and yields double-stranded DNA instead of the single-stranded form that classical Chelex extraction protocols usually release. DNA obtained through our method is then suitable for long-term conservation (over 1.5 years). We tested our protocol on a highly diverse genus of spiders comprised of mainly very small species. We also apply the method to two other genera of spiders, one with average size species, the other one with giant species, to test the efficacy of the method with varying amounts of input tissue. We also discuss the advantages and limitations of this DNA extraction technique when working with arthropods.