Combining phylogeography and landscape genetics reveals genetic variation and distribution patterns of Stipa breviflora populations

Abstract

• Stipa. breviflora originated on the northeastern QTP and the eastern Helan mountains. • S. breviflora originated in the late Miocene. • The genetic differentiation of S. breviflora was mainly caused by IBD. Historical and contemporary microevolutionary processes influence the extent and structure of genetic variation. Combining phylogeography and landscape genetics is an important approach for delineating the formation mechanisms about the patterns of genetic structures. Grassland ecosystems comprise approximately one-third of Earth's vegetative cover. The spatial distribution of genetic variations derived from dominant plant species in steppes is helpful to understand the origin and evolution of this kind of vegetation. In this paper, we took Stipa breviflora , a dominant species of desert steppe, as an example, and conducted the research on both chloroplast DNA sequences and microsatellite loci of populations. The results of analyzing haplotype and microsatellite diversity revealed that S. breviflora most probably originated from the region in eastern Helan Mountains and northeast of Qinghai-Tibet Plateau (QTP) during the late Miocene. The genetic variation distribution of the species was in accordance with the core-periphery hypothesis (CPH), i.e., populations located at the periphery of a species’ range should have lower levels of genetic variation than those at the center of the range. Paleoclimatic fluctuations contributed to haplotype evolution, while geographical distance played an important role in driving contemporary genetic differentiation. Our findings highlight the complexity of intraspecific evolution and clarify the biogeographical history of desert steppes based on molecular signals.