Geothermal activity helps life survive glacial cycles

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.dispersal | GIS | polar region | volcano | Last Glacial Maximum

Genetic signatures indicate widespread antibiotic resistance and phage infection in microbial communities of the McMurdo Dry Valleys, East Antarctica

“…While lichens and mosses are visible as patchily distributed surface biota, the biology of this region is dominated by cryptic microbial communities within soils and rocks (Fraser et al 2014;Pointing et al 2014). These sub-surface communities account for the majority of standing biomass in desert systems (Pointing and Belnap 2012) including polar deserts (Cary et al 2010;Wierzchos et al 2012).…”

Diverse cryptic refuges for life during glaciation

“…They are easily linked to a wide range of satellite, airborne, and other remote sensors and provide the ideal tool for visualizing and analyzing the spatial diversity gradient away from Antarctic hot spots. By analyzing spatial patterns using a range of models, Fraser et al (4) identify strong support for the role of geothermal heating in explaining contemporary patterns of biogeography. Some differences between higher taxonomic ranks were evident.…”

“…The work by Fraser et al (4) in PNAS concludes that, because species richness does not correlate with contemporary climate, the hot spots are refugia where taxa have survived previous glacial periods, thus providing an Antarctic parallel to the notion of the tropics as a "museum" rather than a "cradle" for diversity (14). The authors reject the metabolic theory of diversity (15) as an explanation for their results on the grounds that diversity is distance related rather than related to contemporary climate.…”

“…The nested diversity gradient away from the Antarctic hot spots is consistent with the "out of the tropics model" of global diversity (18), in which the tropics act as both cradles and museums of diversity; taxa preferentially originate in the tropics, or in this case, volcanic hot spots, and expand toward cooler regions without losing their warm climate component. The application of GIS used by Fraser et al (4) to explore spatial relationships in Antarctic systems opens up exciting new opportunities for further investigation of Antarctic hot spots as both cradles and museums of diversity.…”

Cross-disciplinarity in the advance of Antarctic ecosystem research

“…Most terrestrial habitats are extremely isolated. Potential refugia locations are poorly localised at anything less than regional scale, although in some areas there is evidence for refugia in volcanic and other geothermal areas (Fraser et al, 2014). Marine habitats seem to be more connected, although dispersal limitation between regions appears to be present for example of Southern Ocean octopods of tropic clown fish (Strugnell et al, 2012;Pinsky et al, 2017), but can vary even between closely related species (Strugnell et al, 2017).…”