For the last 20 years, Parque Nacional Nahuel Huapi in Argentina has been the site of a comparative study of ecology and genetics of two species of tuco-tuco, a type of burrowing rodent. The June 2011 ongoing eruption of the Puyehue-Cordon Caulle volcanic chain in southern Chile has created a time-sensitive opportunity to assess the impacts of a major geological event on patterns and processes of genetic diversification in natural populations of vertebrates. With extensive pre-eruption data, the proposed post-eruption monitoring will capitalize upon an unprecedented opportunity to explore the effects of a catastrophic environmental event on the population genetics of free-living organisms. Therefore, this study should lead to important new insights into the impacts, including long-term impacts, of volcanic activity, or other catastrophic events, on genetic diversity.

The proposed research supports student training, conservation, and local outreach and education efforts. It will involve undergraduate volunteers from Berkeley, Stanford, and the Universidad Nacional del Comahue in Bariloche, Argentina, thereby providing significant student training. With regard to public outreach, the PIs will maintain web and blog sites on the project, providing quick public access to research methods and results. For the past 20 years, the PIs have worked closely with Administracion de Parques Nacionales Argentinas and other conservation organizations in Patagonia to develop sound, data-based strategies for protecting one of the species of tuco-tuco, including development of the current monitoring and management program. Data generated by the proposed research will contribute to these ongoing efforts.

Project Report

A recent (June 2011) of the Puyehue-Cordón Caulle volcanic chain in southern Chile created a unique, time-sensitive opportunity to assess the impacts of a major environmental event on the demographic and evolutionary processes of two congeneric mammals occupying the same environment: the colonial tuco-tuco (Ctenomys sociabilis) and the Patagonian tuco-tuco (C. haigi) (Rodentia: Ctenomyidae). The initial event blanketed the region with over 30 cm of ash, sand, and golf-ball-sized pumice; the continuous eruption has left ash over thousands of square kilometers in Patagonia, where it was visible from space ( Impact to livestock was immediate, threatening hundreds of thousands of sheep and cattle with starvation. Eruptions are well-known to influence animal survival. An Icelandic eruption in 1783 lead to the subsequent demise of most of the island’s livestock and 20% of the human population due to fluorine poisoning (Stone 2004). Volcanic ash from a 1988 eruption in the Chilean Andes caused a 91.3% reduction in population size of C. maulinus brunneus, with a profound influence on heterozogosity (Gallardo et al. 1995). However, no comprehensive data set documents the before-and-after impacts of such an event: we proposed to use RAPID funds to do so. The colonial tuco-tuco is endemic to the region of Patagonia that was most severely impacted by the ash fall from the Puyehue eruption, with its entire species range affected. Due to its unusual social system, this species has been the focus of intensive study for the past 20 years, resulting in extensive pre-eruption data regarding their demography (Lacey et al. 2000a, 200b, Wieczorek & Lacey 2004, Izquierdo & Lacey 2008), current genetic structure (Lacey et al. 1999, 2001), and paleogenetic history (Hadly et al. 2003, Chan et al. 2005, 2006, in press). Comparable data have also been collected for the syntopic but behaviorally and demographically distinct Patagonian tuco-tuco. Our research capitalized upon the unprecedented opportunity provided by these detailed, comparative data sets to explore the effects of the current volcanic eruption on the evolutionary genetics of these animals. In particular, we sought to (1) identify the specific demographic parameters by which volcanic activity impacts processes of genetic change (i.e., How does ash fall affect survival?), (2) contrast the present impacts on this species with the known eruptions ~3000 ybp, which are implicated as the cause of a severe genetic bottleneck in the social tuco-tuco, and (3) predict the impacts of the ongoing eruption on the persistence of C. sociabilis, currently listed as critically endangered by the IUCN (IUCN 2009). Thus, we are studying this species before, during, and after a catastrophic volcanic eruption to assess how the demography and genetic diversity of species govern their evolution in real-time. Advances in our laboratory and in molecular techniques allowed us to use genomic assays to determine early Holocene (>10,000 ybp), mid-late Holocene (~3000 ybp), pre-2011 eruption, and post 2011 eruption specimens to ascertain genomic variation through time. These results and analyses are currently underway in the Hadly lab. We observed a decrease in wildlife and fauna in northern Patagonia following the June 2011 eruption of Volcan Puyehue, including mortality in the tuco-tuco populations. We observerd signs of physiological stress in tuco-tucos (loss of fur; changes in coloration to fur pattern). We found evidence for possible demographic shifts in tuco-tuco population, and surprisingly we noted an increase in the observed variation in quickly evolving markers after the eruption. We are presently investigating the putative genes we identified that appear to be under selection over the past 10,000 in this species.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Samuel Scheiner
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Stanford University
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