Jaatha: a fast composite-likelihood approach to estimate demographic parameters

Abstract

While information about a species' demography is interesting in its own right, it is an absolute necessity for certain types of population genetic analyses. The most widely used methods to infer a species' demographic history do not take intralocus recombination or recent divergence into account, and some methods take several weeks to converge. Here, we present Jaatha, a new composite-likelihood method that does incorporate recent divergence and is also applicable when intralocus recombination rates are high. This new method estimates four demographic parameters. The accuracy of Jaatha is comparable to that of other currently available methods, although it is superior under certain conditions, especially when divergence is very recent. As a proof of concept, we apply this new method to estimate demographic parameters for two closely related wild tomato species, Solanum chilense and S.peruvianum. Our results indicate that these species likely diverged 1.44·N generations ago, where N is the effective population size of S.chilense, and that some introgression between these species continued after the divergence process initiated. Furthermore, S.peruvianum likely experienced a population expansion following speciation.