Oscar E. Gaggiotti | Search bioRxiv

bioRxiv2016

Population dynamics of Arabis alpina in the French Alps: evidence for demographic compensation?

O_LIDue to its genetic proximity with Arabidopsis thaliana, Arabis alpina (Brassicaceae) is increasingly used as a perennial model species in studies of molecular evolution and adaptation.\nC_LIO_LIWe studied the demography of A. alpina in six natural sites widely differing in their degree of disturbance, slope and vegetation, and encompassing the full altitudinal range of the species.\nC_LIO_LIWe estimated three vital rates (growth, reproductive effort and survival) for individually-marked plants, studied for six years (2008-2014). We characterized the thermic conditions of each site with different thermal variables obtained using in situ continuous-time data loggers.\nC_LIO_LIAlthough A. alpina is described as a perennial species, the average life expectancy was only 1.82 years and most plants died before setting seeds. Plant size was a strong predictor of all three vital rates.\nC_LIO_LIMean daily temperature showed a positive effect on growth and a negative effect on survival. Furthermore, reproductive effort covaried negatively with survival, suggesting a mechanism of demographic compensation acting on an elevational gradient.\nC_LIO_LISynthesis. These results are informative of the selective pressures experienced by A. alpina in natural conditions and will help design experimental and molecular studies of local adaptation in this species.\nC_LI

Ecology↗

bioRxiv2014

Widespread signals of convergent adaptation to high altitude in Asia and America

Living at high-altitude is one of the most difficult challenges that humans had to cope with during their evolution. Whereas several genomic studies have revealed some of the genetic bases of adaptations in Tibetan, Andean and Ethiopian populations, relatively little evidence of convergent evolution to altitude in different continents has accumulated. This lack of evidence can be due to truly different evolutionary responses, but it can be also due to the low power of former studies that have mainly focused on populations from a single geographical region or performed separate analyses on multiple pairs of populations to avoid problems linked to shared histories between some populations. We introduce here a hierarchical Bayesian method to detect local adaptation that can deal with complex demographic histories. Our method can identify selection occurring at different scales, as well as convergent adaptation in different regions. We apply our approach to the analysis of a large SNP dataset from low- and high-altitude human populations from America and Asia. The simultaneous analysis of these two geographic areas allows us to identify several candidate genome regions for altitudinal selection, and we show that convergent evolution among continents has been quite common. In addition to identifying several genes and biological processes involved in high altitude adaptation, we identify two specific biological pathways that could have evolved in both continents to counter toxic effects induced by hypoxia.

Genetics↗