Category Archives: published paper

Detecting range expansions from genetic data

Co-Author: Monty Slatkin

Populations are often structured, in the sense that individuals living next to each other are often related. This paper, we develop a statistic to test for equilibrium isolation-by-distance. Equilibrium isolation-by-distance implies a constant and symmetric population structure, and deviations can be useful in many contexts. In this paper, we look at range expansions, the process where a species expands its range from a small origin. We show that we can detect these expansions, as well as estimate the most likely origin.

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Evolution

Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA

Co-Authors: Emilia Huerta-Sanchez (first author), Rasmus Nielsen and 23 others.

Many Tibetans have a variant of the EPAS1 gene that facilitates survival in very high altitudes. In this paper, we show that the Tibetan variant of EPAS1 is the same as that of the Denisovans, an extinct hominid from which we only know the morphology and a tooth and its genome sequence. This supports our hypothesis that Denisovans have interbred with an ancestor of the modern Tibetans, and that the high-altitude allele increased in frequency due to natural selection.

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Distinguishing between population bottleneck and population subdivision by a Bayesian model choice procedure

Co-Authors: Daniel Wegmann, Laurent Excoffier

This is my first paper, published in Molecular Ecology in 2010. Using simulations and an inference procedure called Approximate Bayesian Computation (ABC), we showed that some methods to estimate population size changes may be biased if population structure is present.

We also showed that it is in principle possible to distinguish these two models, as we showed using two explicit models. For application purposes we demonstrated that the inbreeding coefficient FIS can be used to detect structure. The basic idea is that FIS will be non-zero if the population size is structured, as the two copies in a diplid individuals are from the same deme, and therefore more closely related than expected by chance.

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