Mitochondrial and nuclear DNA diversity in the Chocó and Chibcha Amerinds of Panamá

Abstract

Mitochondrial and nuclear DNA diversities weredetermined for two Choc6speaking Amerind populations, the Embed and Wounan, sampled widely across their geographic range in eastern PanamP. These data were compared with mitochondrial and nuclear diversities determined here and previously for neighboring Chibcha-speaking Ng6b& and Kuna populations. Chocoangroups exhibited mitochondrial diversity levels typicalfor Amerind populations while Chibchan groups revealed reduced mitochondrial diversity. A slightreduction in autosomal levels of heterozygosity was determined for the Chibcha while X and Y variation appeared equivalent in all populations. Genetic distinctiveness of the two linguistic groups contradicts the anthropological theory that Paleoindians migrated repeatedly through the isthmian region and, instead, supports the idea of cultural adaptation by endogenous populations. Reduced genetic diversity in Chibchan populations has been proposed to represent a population bottleneck dating to Chibchan ethnogenesis. The relative sensitivitiesof haplotype pairwise difference distributions and Tajima’s D to detect demographic events such as population bottlenecks are examined. Also, the potential impact of substitution rate heterogeneity, population subdivision, and genetic selection on painvise difference distributions are discussed. Evidence is presented suggesting that a larger effective population size mayobscure the historical signalobtained from nuclear genes whilethe single mitochondrial locus may provide a moderately strong signal.