Ecophysiology and ecological impacts of an Antarctic invader: the chironomid, Eretmoptera murphyi.

Bartlett, Jesamine C. ORCID: 0000-0001-7464-5440 (2019). Ecophysiology and ecological impacts of an Antarctic invader: the chironomid, Eretmoptera murphyi. University of Birmingham. Ph.D.

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Abstract

Antarctica has entered a period of rapid, and potentially drastic, change. The combined pressures of anthropogenic climate change, which disproportionately affects the polar regions, and an increase in human activity and connectivity in and around the Antarctic, is opening the least invaded continent on the planet to new species. As ice retreats, terrestrial habitats ripe for colonisation by both humans and non native species are increasing, and so must our knowledge of the biology, ecology and impact of invading species. This thesis explores these issues through the model invasive species, the chironomid, Eretmoptera murphyi Schaeffer (Diptera: Chironomidae), which has successfully colonised Signy Island in the maritime Antarctic, following introduction by humans in the 1960s. Through whole organism experiments and field observations, we confirm parthenogenesis and adult emergence throughout summer on Signy. Physiological studies are employed to assess the midge’s potential to establish further south, and/or cope with climate change. Differing responses to temperature are identified in different life stages, which at various points in the life cycle must endure microclimate temperatures from +30 ºC to -20 ºC, on Signy Island. The impact of microhabitat temperature and moisture conditions on development and overwintering survival is examined, with oviposition sites found to be an important factor in determining reproductive success, especially considering a warming climate. The extent of E. murphyi’s distribution on Signy is updated, doubling previous estimates of its range, and finding that it is on the brink of moving into new valley systems. Where it occurs, the midge is capable of increasing soil nitrates by as much as five times the background levels, bringing nitrogen levels up to that seen in association with seal colonies. As the only true insect on the island, and a significant detritivore, E. murphyi has the potential to affect change to local vegetation and is arguably a new keystone species in this nutrient-poor ecosystem. Existing biosecurity measures in place seem unlikely to limit its spread which appears to be tracking footpaths used by researchers on the island. Larval stages are also able to survive several weeks in sea water, suggesting there is little impediment to its eventual colonisation of other islands and the Antarctic Peninsula, where it would likely flourish. This body of work encompasses a range of disciplines from whole organism biology through to ecosystem function, and highlights the impact that a single, and seemingly innocuous invasive species can have on an Antarctic terrestrial ecosystem.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):