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Steven L. Chown & Laura Phillips, School of Biological Sciences, Monash University
Over the past several decades, much of our research and collaborations with colleagues has concerned the sub-Antarctic islands. These islands lie in the Southern Ocean, between about 40°S and 55°S, and are the only land in this region (with the exception of small parts of Australia, New Zealand and South America).
Australia is responsible for two of the sub-Antarctic island groups: the Heard and McDonald Islands (HIMI) in the Indian sector of the Southern Ocean, and Macquarie Island (MI) in the Pacific. We have been fortunate enough to work at both. Our research has spanned the mountainous, glaciated South Georgia in the west, to the more temperate Macquarie Island in the east. Our major aims have been to use sub-Antarctic island biotas to test ecological theories and provide answers to management questions relevant to the region and elsewhere.
Heard Island in the southern Indian Ocean in 2017, a rare clear day. Credit: Steven L. Chown.
Our work at Heard Island has been through a long-standing collaboration with the Australian Antarctic Division and a suite of collaborators both from the Division and elsewhere. Mostly our research has been focussed on two groups—weevils and springtails. Amazingly, HIMI has at least five species of weevils, most closely related to those of the Indian Ocean Province islands to the north and west (Kerguelen, Crozet and Prince Edwards). The fauna includes an extraordinary weevil which lives in the intertidal and feeds on algae and lichens. Weevils are the most diverse beetle family globally (tens of thousands of species) and are usually associated with flowering plants. The HIMI weevils are truly unusual because at least three of the species are specialists on algae, mosses and lichens.
Our work has tested the ecological idea that in seasonal climates, like that found on HIMI, body size in ectotherms decreases with declining temperatures. Low temperatures limit the growing season, thus insects cannot get very big. But in aseasonal climates (like the more northerly sub-Antarctic Prince Edward Islands), the opposite is true. By comparing HIMI and Prince Edward Islands weevils across the full elevational range of their distribution we were able to show how this happens.Our later work also showed that invasive house mice at one of the Prince Edward Islands completely alter these patterns, changing community structure and functioning.
Luckily, HIMI is one of the few sub-Antarctic islands with almost no invasive species. Australia has done a great job of biosecurity, but our research has also shown that as climates warm, more will have to be done. HIMI environments are becoming easier for the establishment of non-indigenous species.
At MI, our recent work has had one major goal—we use springtails (small soil invertebrates key for all terrestrial ecosystems) to test the idea that warming and drying will benefit alien over indigenous species. What we have found is that, largely, this is true. Alien springtails tend to be more tolerant of dry conditions, develop faster and prefer warmer temperatures. Our research has shown that this is true not only for MI, but also for springtails down the coast of Australia, from the tropics to the sub-Antarctic.
Laura Phillips and Ian Aitkenhead (Monash University) sampling springtails on Macquarie Island. Credit: Laura Phillips.
We often get asked what it’s like working on these islands. ‘Life-changing’ is the best response. Yes, it rains, snows and blows. And life in the field can be cold, wet and very uncomfortable. But it also glows; either from the Aurora Australis, from light reflected off glaciers, or from Big Ben on Heard Island showing that it is an active volcano.
A good lesson has also been to be careful about what you wish for. At Atlas Cove on HIMI, one of the small field camp teams wished for a white Christmas. Hey presto, it started snowing and sleeting on Christmas Eve, and did not let up until about the 18th of January!
Australians are in the fortunate position to be responsible for two sub-Antarctic island groups. That responsibility has been shown through the program at MI to remove alien vertebrates—a global success story. It has also been shown through the stringent biosecurity measures applied to visits to HIMI. As ecologists we have had the fortune to visit both places. Much further responsibility rests on us and all visitors to ensure that Australians are aware of these gifts to the world of knowledge and wonder.