Horizon scanning for potential invasive non‐native species across the United Kingdom Overseas Territories

Abstract

Invasive non-native species (INNS) are recognized as a major threat to island biodiversity, ecosystems, and economies globally. Preventing high-risk INNS from being introduced is the most cost-effective way to avoid their adverse impacts. We applied a horizon scanning approach to identify potentially INNS in the United Kingdom Overseas Territories (OTs), ranging from Antarctica to the Caribbean, and from the Pacific to the Atlantic. High-risk species were identified according to their potential for arrival, establishment, and likely impacts on biodiversity and ecosystem function, economies, and human health. Across OTs, 231 taxa were included on high-risk lists. The highest ranking species were the Asian green mussel (Perna viridis), little fire ant (Wasmannia auropunctata), brown rat (Rattus norvegicus), and mesquite tree (Prosopis juliflora). Shipping containers were identified as the introduction pathway associated with the most species. The shared high-risk species and pathways identified provide a guide for other remote islands and archipelagos to focus ongoing biosecurity and surveillance aimed at preventing future incursions.

The first record of a non-native seaweed from South Georgia and confirmation of its establishment in the Falkland Islands: Ulva fenestrata Postels & Ruprecht

“…There is only one previous record of a non-native marine species in South Georgia, the mussel Mytilus edulis, a live individual of which was found at King Edward Point in 1974 (Ralph et al 1976). Although this species appears not to have become established, it is still considered a high-risk potential invader (Dawson et al 2022).…”

“…Heesch et al 2009;Krupnik et al 2018;Steinhagen et al 2019;Wei et al 2022), including regions such as China where their rapid spread is causing severe ecological and economic impacts (Xie et al 2020). For South Georgia, a recent horizon scanning study (Dawson et al 2022) listed five seaweed species (none of which were Ulva species) as potential invasive non-natives in South Georgia, of which two were identified as "highrisk". In addition to these other seaweeds, our findings provide a baseline for monitoring U. fenestrata in South Georgia and emphasise the need for strict biosecurity measures to minimise the risk of introducing non-native species into potentially fragile ecosystems.…”

“…In addition, the family Ulvaceae, to which this genus belongs, includes a disproportionately high number of known non-native species, and is regarded as a group with a great proclivity for invasion (Williams and Smith 2007). The use of a robust taxonomic approach for enhancing our knowledge of seaweed biodiversity is particularly important in remote areas where invasive species pose a significant threat to marine ecosystems comprising a relatively high proportion of rare and/or endemic species (Clubbe et al 2020;Dawson et al 2022), especially given the greater tendency for non-native seaweeds to exert negative effects on native biota in relatively pristine environments (Thomsen et al 2016a).…”

“…Existing seaweed species lists for South Georgia are based on morphological identification and outdated species concepts, making it difficult to make biogeographical comparisons; however, given the dominance of endemic and range-edge species in South Georgia's benthic invertebrate fauna (Hogg et al 2011), its seaweed flora may be expected to have similar characteristics. The unique inshore marine biodiversity of South Georgia faces threats predominantly from climate change and invasive species (Hogg et al 2011;Rogers et al 2015), including seaweeds, which could be introduced to the island via international shipping (Dawson et al 2022) involving tourist, research and fishing vessels. Many of these vessels arrive from the Falkland Islands, located approximately 1450 km west of South Georgia, which, therefore, represent a potential source of marine non-natives.…”

“…Many of these vessels arrive from the Falkland Islands, located approximately 1450 km west of South Georgia, which, therefore, represent a potential source of marine non-natives. While it is estimated that non-native species account for 70% of the island's terrestrial flora (Clubbe et al 2020), there have been no confirmed reports of non-native seaweeds in South Georgia, despite a number of species having been identified as high risk in terms of their likely arrival, establishment and ecological impact (Dawson et al 2022). Here, we provide the first record of a non-native seaweed in South Georgia, Ulva fenestrata, and evidence of its establishment in the Falkland Islands, supported by molecular-assisted taxonomy.…”