Ocean currents as a potential dispersal pathway for Antarctica\u2019s most persistent non-native terrestrial insect

Jesamine C Bartlett,S A L Hayward,K A Hughes,S E Thorpe,P Convey

doi:10.1007/s00300-020-02792-2

Abstract

The non-native midge Eretmoptera murphyi is Antarctica’s most persistent non-native insect and is known to impact the terrestrial ecosystems. It inhabits by considerably increasing litter turnover and availability of soil nutrients. The midge was introduced to Signy Island, South Orkney Islands, from its native South Georgia, and routes of dispersal to date have been aided by human activities, with little known about non-human-assisted methods of dispersal. This study is the first to determine the potential for dispersal of a terrestrial invertebrate species in Antarctica by combining physiological sea water tolerance data with quantitative assessments of ocean current journey times. Fourth instar larvae tolerated sea water submergence for up to 21 days, but submerged egg sacs had significantly reduced hatching success. Using near-surface drifter data, we conclude that ocean current dispersal from Signy Island would not present a risk of species transfer beyond the South Orkney Islands on the tested timescales. However, if E. murphyi were to be introduced to the South Shetlands Islands or Adelaide Island, which are located offshore of the Antarctic Peninsula, there would be a risk of successful oceanic dispersal to neighbouring islands and the Antarctic Peninsula mainland. This study emphasises the need for effective biosecurity measures and demonstrates the role that currently undocumented pathways may have in dispersing non-native species.

Highlights

Non-native species are one of the largest threats to global biodiversity (Pyšek et al 2020)
The survival of mature (L4) E. murphyi larvae in 100% seawater for as long as 21 days indicates that seawater exposure alone would not necessarily be a barrier to this species’ dispersal
E. murphyi L4 larvae showed considerable tolerance to seawater immersion, with no difference in survival between 100% seawater, freshwater or soil treatments over 21 days (Fig. 1). This is consistent with the findings of a recent, related study of the possibility of using seawater as a biosecurity measure, where E. murphyi larvae survived all seawater dilution treatments trialled over a 7 days period (Bartlett et al 2020a)

Summary

Introduction

Non-native species are one of the largest threats to global biodiversity (Pyšek et al 2020). Understanding their pathways for dispersal is crucial to ensuring that adequate management and biosecurity measures can be put in place. Invasive species can be impactful in the simple terrestrial ecosystems of the polar regions (e.g. Ernsting et al 1995; Hänel and Chown 1998), and the risk of their

Materials and methods

Results

Discussion

Compliance with ethical standards