Late Quaternary Environmental and Human Impacts on the Mitochondrial DNA Diversity of Four Commensal Rodents in Myanmar

Abstract

AbstractWe addressed the spatiotemporal characteristics of four commensal rodent species occurring in Myanmar in comparison with other areas of the Indo-Malayan region. We examined sequence variations of the mitochondrial cytochrome b gene (Cytb) in the Pacific rat (Rattus exulans), roof rat (Rattus rattus complex, RrC), lesser bandicoot rat (Bandicota bengalensis), and house mouse (Mus musculus) using the recently developed time-dependent evolutionary rates of mtDNA. The Cytb sequences of RrC from Myanmar were shown to belong to RrC Lineage II, and their level of genetic diversity was relatively high compared to those of the other three species. RrC was found to have experienced bottleneck and rapid expansion events at least twice in the late Pleistocene period in Myanmar and a nearby region. Accordingly, paleoclimatic environmental fluctuations were shown to be an important factor affecting rodents in the subtropics of the Indo-Malayan region. Our results show that human activities during the last 10,000 years of the Holocene period affected the population dynamics of the rodent species examined, including introducing them to Myanmar from neighboring countries. Further study of these four commensal rodents in other geographic areas of the Indo-Malayan region would allow us to better understand the factors that drove their evolution and their ecological trends.