Doctor of Philosophy, Stanford University, BIO-PHD (2017)
Bachelor of Arts, University of California Berkeley, Integrative Biology (2007)
Dmitri Petrov, Postdoctoral Faculty Sponsor
Evolution for extreme living: variation in mitochondrial cytochrome c oxidase genes correlated with elevation in pikas (genus Ochotona).
The genus Ochotona (pikas) is a clade of cold-tolerant lagomorphs that includes many high-elevation species. Pikas offer a unique opportunity to study adaptations and potential limitations of an ecologically important mammal to high-elevation hypoxia. We analyzed the evolution of three mitochondrial genes encoding the catalytic core of cytochrome c oxidase (COX) in 10 pika species occupying elevations from sea level to 5,000 meters. COX is an enzyme highly reliant on oxygen and essential for cell function. One amino acid property, the equilibrium constant (ionization of COOH), was found to be under selection in the overall protein complex. We observed a strong relationship between the net value change in this property and the elevation each species occupies, with higher-elevation species having potentially more efficient proteins. We also found evidence of selection in low-elevation species for potentially less efficient COX, perhaps trading efficiency for heat production in the absence of hypoxia. Our results suggest that different pika species may have evolved elevation-specific COX proteins, specialization that may indicate limitations in their ability to shift their elevational ranges in response to future climate change. This article is protected by copyright. All rights reserved.
View details for PubMedID 29851233
Gene expression is implicated in the ability of pikas to occupy Himalayan elevational gradient.
2018; 13 (12): e0207936
Species are shifting their ranges due to climate change, many moving to cooler and higher locations. However, with elevation increase comes oxygen decline, potentially limiting a species' ability to track its environment depending on what mechanisms it has available to compensate for hypoxic stress. Pikas (Family Ochotonidae), cold-specialist small mammal species, are already undergoing elevational range shifts. We collected RNA samples from one population of Ochotona roylei in the western Himalaya at three sites- 3,600, 4,000, and 5,000 meters-and found no evidence of significant population genetic structure nor positive selection among sites. However, out of over 10,000 expressed transcripts, 26 were significantly upregulated at the 5,000 m site and were significantly enriched for pathways consistent with physiological compensation for limited oxygen. These results suggest that differences in gene expression may play a key role in enabling hypoxia tolerance on this local scale, indicating elevational flexibility that may facilitate successful range shifts in response to climate change.
View details for PubMedID 30540800
Merging paleobiology with conservation biology to guide the future of terrestrial ecosystems
2017; 355 (6325): 594-?
Conservation of species and ecosystems is increasingly difficult because anthropogenic impacts are pervasive and accelerating. Under this rapid global change, maximizing conservation success requires a paradigm shift from maintaining ecosystems in idealized past states toward facilitating their adaptive and functional capacities, even as species ebb and flow individually. Developing effective strategies under this new paradigm will require deeper understanding of the long-term dynamics that govern ecosystem persistence and reconciliation of conflicts among approaches to conserving historical versus novel ecosystems. Integrating emerging information from conservation biology, paleobiology, and the Earth sciences is an important step forward on the path to success. Maintaining nature in all its aspects will also entail immediately addressing the overarching threats of growing human population, overconsumption, pollution, and climate change.
View details for DOI 10.1126/science.aah4787
View details for PubMedID 28183912
Genetics, morphology and ecology reveal a cryptic pika lineage in the Sikkim Himalaya.
Molecular phylogenetics and evolution
2017; 106: 55-60
Asian pika species are morphologically ∼similar and have overlapping ranges. This leads to uncertainty and species misidentification in the field. Phylogenetic analyses of such misidentified samples leads to taxonomic ambiguity. The ecology of many pika species remains understudied, particularly in the Himalaya, where sympatric species could be separated by elevation and/or substrate. We sampled, measured, and acquired genetic data from pikas in the Sikkim Himalaya. Our analyses revealed a cryptic lineage, Ochotona sikimaria, previously reported as a subspecies of O. thibetana. The results support the elevation of this lineage to the species level, as it is genetically divergent from O. thibetana, as well as sister species, O. cansus (endemic to central China) and O. curzoniae (endemic to the Tibetan plateau). The Sikkim lineage diverged from its sister species' about 1.7-0.8myrago, coincident with uplift events in the Himalaya. Our results add to the recent spate of cryptic diversity identified from the eastern Himalaya and highlight the need for further study within the Ochotonidae.
View details for DOI 10.1016/j.ympev.2016.09.015
View details for PubMedID 27640954
Opportunity for some, extinction for others: the fate of tetrapods in the Anthropocene
EVOLUTIONARY ECOLOGY RESEARCH
2016; 17 (6): 787-813
View details for Web of Science ID 000392724100006