Petunia altiplana Raw sequence reads. Petunia altiplana

Phylogeographic history refers to how species evolve and diversify in response to historical, ecological, and demographic factors. The climate fluctuation during the Pleistocene period marked a crucial time to shape many species distribution and genetic structure, particularly those from southern South American grasslands. In this work, we investigated the phylogeographic history of a highland grassland Petunia Juss. species (Solanaceae), its diversity, and geographic distribution using a population genomic approach based on RAD-seq data. Our results indicated that, during the Pleistocene glacial periods, when the grasslands expanded to highlands, the lowland populations of P. altiplana reached the higher open fields, enlarging their geographic distribution. We found that the P. altiplana T. Ando & Hashim. genetic diversity followed the geographic division into eastern (E) and western (WE) population groups, with a subtle division in the E group regarding the Pelotas River headwater. The results also showed that isolation by distance was the main divergence pattern, with elevation playing a pivotal role in shaping WE and E groups. Our findings indicated that lowland-adapted populations quickly colonized highlands during the late Pleistocene.