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Islands make up a large proportion of Earth’s biodiversity, yet are also
some of the most sensitive systems to environmental perturbation.
Biogeographic theory predicts that geologic age, area, and isolation
typically drive islands’ diversity patterns, and thus potentially impact
non-native spread and community homogenization across island systems. One
limitation in testing such predictions has been the difficulty of
performing comprehensive inventories of island biotas and distinguishing
native from introduced taxa. Here, we use DNA metabarcoding and
statistical modeling as a high throughput method to survey community-wide
arthropod richness, the proportion of native and non-native species, and
the incursion of non-natives into primary habitats on three archipelagos
in the Pacific - the Ryukyus, the Marianas and Hawaii - which vary in age,
isolation and area. Diversity patterns largely match expectations based on
island biogeography theory, with the oldest and most geographically
connected archipelago, the Ryukyus, showing the highest taxonomic richness
and the lowest proportion of introduced species. Moreover, we find
evidence that forest habitats are more resilient to incursions of
non-natives in the Ryukyus than in the less taxonomically rich
archipelagos. Surprisingly, we do not find evidence for biotic
homogenization across these three archipelagos: the assemblage of
non-native species on each island is highly distinct. Our study
demonstrates the potential of DNA metabarcoding to facilitate rapid
estimation of biogeographic patterns, the spread of non-native species,
and the resilience of ecosystems.
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