Dogs, Chickens and Ants: Investigating the reliability of modern maternal genetic data in retracing early dispersals

Abstract

Mitochondrial DNA (mtDNA) has been used extensively in the past few decades to investigate the phylogeny and phylogeography of domesticates but numerous episodes of homogenisation between populations caused by human agency have no doubt obscured past genetic signals. This research statistically tests for mtDNA genetic structure and variation within modern dog, ancient dog and modern chicken populations on a global scale using Wright's F-statistics and analysis of molecular variance (AMOVA). It also investigates the potential of the tramp ant Tapinoma melanocephalum (ghost ant) to be used as a new proxy for human dispersals in Oceania. Based on extensive datasets combining primary analyses and secondary sources, the statistical analyses reveal differing results according to species. A distinct lack of maternal genetic structure and variation between global populations of modern indigenous dogs is observed. The analyses conducted on 88 ancient dog specimens dating prior to the 15th century, however, reveal mtDNA structure and variation between continents. Thus, it is concluded that the genetic homogenisation observed within modern
dogs but absent in ancient populations most likely results from the European colonial expansion and the development of transoceanic travel. In contrast, modern maternal genetic structure was observed between chicken populations from across the world, and allowed for hypotheses to be formulated regarding the early dispersals of chickens. These studies support the fact that mtDNA fragments from modern dog populations cannot reliably infer their origin and early dispersals while analyses conducted on mtDNA fragments of modern chicken populations allow for the investigation of the origin and past migrations of chickens. Looking at the ghost ant which has been widely but unintentionally dispersed, its phylogenetic and phylogeographic analyses reveal two potential introductions of this tramp species into Oceania. While the timing of their introduction cannot yet be deciphered due to the lack of working samples, the correlation between the results and historical records infer potential trading routes, revealing Tapinoma melanocephalum as a potential proxy to trace past human migrations.