Geothermal activity helps life survive glacial cycles
- aFenner School of Environment and Society, Australian National University, Canberra, ACT 0200, Australia;
- bTerrestrial and Nearshore Ecosystems, Australian Antarctic Division, Department of the Environment, Kingston, TAS 7050, Australia;
- cDepartment of Geology, University of Leicester, Leicester LE1 7RH, United Kingdom;
- dBritish Antarctic Survey, Cambridge CB3 0ET, United Kingdom;
- eGateway Antarctica, University of Canterbury, Christchurch 8140, New Zealand; and
- fSchool of Biological Sciences, Monash University, Melbourne, VIC 3800, Australia
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Edited by James P. Kennett, University of California, Santa Barbara, CA, and approved February 19, 2014 (received for review November 14, 2013)

Significance
The evolution and maintenance of diversity through cycles of past climate change have hinged largely on the availability of refugia. Geothermal refugia may have been particularly important for survival through past glaciations. Our spatial modeling of Antarctic biodiversity indicates that some terrestrial groups likely survived throughout intense glacial cycles on ice-free land or in sub-ice caves associated with areas of geothermal activity, from which recolonization of the rest of the continent took place. These results provide unexpected insights into the responses of various species to past climate change and the importance of geothermal regions in promoting biodiversity. Furthermore, they indicate the likely locations of biodiversity “hotspots” in Antarctica, suggesting a critical focus for future conservation efforts.
Abstract
Climate change has played a critical role in the evolution and structure of Earth’s biodiversity. Geothermal activity, which can maintain ice-free terrain in glaciated regions, provides a tantalizing solution to the question of how diverse life can survive glaciations. No comprehensive assessment of this “geothermal glacial refugia” hypothesis has yet been undertaken, but Antarctica provides a unique setting for doing so. The continent has experienced repeated glaciations that most models indicate blanketed the continent in ice, yet many Antarctic species appear to have evolved in almost total isolation for millions of years, and hence must have persisted in situ throughout. How could terrestrial species have survived extreme glaciation events on the continent? Under a hypothesis of geothermal glacial refugia and subsequent recolonization of nongeothermal regions, we would expect to find greater contemporary diversity close to geothermal sites than in nongeothermal regions, and significant nestedness by distance of this diversity. We used spatial modeling approaches and the most comprehensive, validated terrestrial biodiversity dataset yet created for Antarctica to assess spatial patterns of diversity on the continent. Models clearly support our hypothesis, indicating that geothermally active regions have played a key role in structuring biodiversity patterns in Antarctica. These results provide critical insights into the evolutionary importance of geothermal refugia and the history of Antarctic species.
Footnotes
↵1C.I.F. and A.T. contributed equally to this work.
- ↵2To whom correspondence should be addressed. E-mail: ceridwen.fraser{at}gmail.com.
Author contributions: C.I.F. designed research; C.I.F., A.T., J.S., P.C., and S.L.C. performed research; A.T. analyzed data; and C.I.F., A.T., J.S., P.C., and S.L.C. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
See Commentary on page 5452.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1321437111/-/DCSupplemental.
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