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

Abstract

We 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.

Quaternary Environmental Changes Shaped Mitochondrial DNA Diversity in the Large Japanese Wood Mouse Apodemus speciosus in Hokkaido, Japan

“…The grassland-dwelling striped field mouse A. agrarius occurring in a broad area of northern Eurasia from Europe to Asia a rapid expansion signal during MIS 4-3 in mtDNA sequence data (Kozyra et al 2021). Interestingly, the forest-dwelling Asian house rat (Rattus rattus complex mitochondrial Lineage II, defined by Pagès et al 2010 andAplin et al 2011), which occurs in East and Southeast Asia including Myanmar, also showed rapid expansion signals in mtDNA analysis (Maung Maung Theint et al 2020), suggesting that the effects of climate change on small rodents associated with the early MIS 3 were widespread and numerous at the global level. In the Japanese archipelago, MIS 4 was characterized by more snowfall and greater glacial development due to the presence of high mountain ranges (e.g., Hidaka Mountains, Hokkaido; Fig.…”

The time-dependent evolutionary rate of mitochondrial DNA in small mammals inferred from biogeographic calibration points with reference to the late Quaternary environmental changes in the Japanese archipelago

“…The importance of the early MIS 3 period for demographic expansion has been noted in grassland voles in North America (Kohli et al, 2015), and in hares in Europe (Fickel et al, 2008). However, an early MIS 3 expansion event has also been posited in a forest-dwelling wood mouse (A. argenteus) from Japan (Hanazaki et al, 2017) and roof rats (Rattus rattus) in Myanmar (Maung Maung Theint et al, 2020).…”

“…Lipson et al, 2014;Deng et al, 2020) and this may have caused the dispersal of the house mouse to Indonesia. Recent work on the population dynamics of M. musculus from Myanmar showed evident population expansion in the Cytb sequence data that began about 5400 (95% CI: 2300-8000) years ago (Maung Maung Theint et al, 2020). In addition, the migration from southern China to the Japanese archipelago was deduced to have occurred 3500 years ago (Li et al, 2020b), which may be correlated with the introduction of cold-tolerant temperate japonica rice strains developed in response to the extreme environmental degradation 4200 years ago (Mao et al, 2019;Guo et al, 2020;Gutaker et al, 2020).…”

AsianMus musculus: Subspecies Divergence, Genetic Diversity, and Historical Biogeography

“…Based on these τ values, we applied three different evolutionary rates: 0.11, 0.047, and 0.028 substitutions per site per million years (substitutions/site/myr) for calculating the time since expansion. These rates were adapted from Honda et al (2019) and Maung Maung Theint et al (2021) to estimate the expansion parameters effectively.…”