Richness and resilience in the Pacific: DNA metabarcoding enables parallelized evaluation of biogeographic patterns

Abstract

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 modelling 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 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.

Towards understanding insect species introduction and establishment: A community‐level barcoding approach using island beetles

“…Distinguishing between introduced and native not endemic species status within natural communities is often difficult, particularly among invertebrates. This has prompted efforts to use relatedness information from DNA sequence data to infer probable status, both for traditional specimen‐based sampling of invertebrate communities (Andersen et al, 2019; Smith & Fisher, 2009) and metabarcode sequencing (Kennedy et al, 2022). Here, we were able to address this limitation, and make species‐level taxonomic assignments for 268 of the 360 species sampled, providing a direct association with their recorded native or introduced species status.…”

“…While our level of taxonomic assignment addresses the limitations faced by Andersen et al (2019) and Kennedy et al (2022), we considered an additional source of error. For any given native not endemic species, it remains possible that historical inferences of native or introduced status may be incorrect.…”

Towards exhaustive community ecology via DNA metabarcoding

“…An alternative approach is combining multiple metabarcoding primers in the same PCR mix, to simultaneously amplify and sequence multiple taxonomic groups. So far, primer cocktails have been rarely used, but might provide extremely comprehensive information on biodiversity (Govender et al, 2022; Kennedy et al, 2022). For instance, Govender et al (2022) used six primer cocktails, each amplifying a different fragment of the COI‐5P gene region, to explore the diversity of marine zooplankton.…”

“…used, but might provide extremely comprehensive information on biodiversity (Govender et al, 2022;Kennedy et al, 2022). requires the identification of primers with similar annealing temperatures, but amplifying complementary groups.…”

Insights into Ecological & Evolutionary Processes via community metabarcoding

“…Results from metabarcoding of entire arthropod communities demonstrate that, where species diversity is lowest (on the youngest island), infiltration of non-native species is highest. Likewise, Kennedy et al (2022) used DNA metabarcoding and statistical modelling 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. Focusing on one island from each of the three archipelagos that differ with respect to age, area, and proportion of native habitat, there were three alternative hypotheses defined by fundamental eco-evolutionary processes with associated predictions that were detectable from the high-throughput metabarcoding surveys.…”