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Dryad

Molecular delimitation of evolutionary significant units reveals hidden geographic drivers of extinction risk within island arthropods

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Dec 24, 2024 version files 3.12 MB

Abstract

Aim: Globally, arthropod biodiversity is under threat, with increased risk of species-level extinctions, and this threat is particularly acute on oceanic islands. A fundamental first step toward understanding extinction risk is to understand genetic connectivity among the constituent populations of a species. Our aim is to develop and implement a protocol to characterise genetic connectivity among island populations within arthropod species to reveal otherwise hidden range size drivers of extinction.

Location: Canary Islands, Spain.

Methods: We implement a protocol based on mtDNA sequence data for the delimitation of evolutionary significant units (ESUs) to evaluate extinction risk among species of beetle and spider distributed across multiple islands.

Results: Our results reveal that more than half of the species analysed are comprised of two or more ESUs. We also find that low dispersal ability was a significant predictor of ESUs within species of Coleoptera, but with no significant difference for Araneae.

Main conclusions: Most ESUs are consistent with early stage differentiation, or incipient speciation, with some exceeding a conservative interspecific threshold, thus indicative of cryptic species. We suggest that extending our approach with the integration of other species-level traits may provide for a more refined predictive framework for understanding extinction risks across island arthropod species.