Impact of Pleistocene geoclimatic events on the genetic structure in mid-latitude South American plants: Insights from the phylogeography of Turnera sidoides complex (Passifloraceae, Turneroideae)

Abstract

Aiming to shed light on the influence of Pleistocene geoclimatic events on the current genetic patterns in the flora of the South American Chaqueño Phytogeograpic Domain, we performed phylogeographic and Bayesian ancestral area reconstruction analyses based on plastid DNA sequences of Turnera sidoides. Lineages started to diversify 2.02 Mya, forming two major clades, one comprising extant populations from the western boundary and the other including populations from the eastern boundary of the distribution of T. sidoides. Major divergences within clades occurred at two years 1.44 and 1.72 Mya. Ancestral area reconstruction analyses suggest a western origin of T. sidoides in the Peripampasic Arc. Our results support the hypothesis that Pleistocene geoclimatic events in the Chaqueño Domain played an important role in shaping genetic variation. The establishment of the Arid Diagonal acted as a barrier to gene flow between the western and eastern populations during the Pleistocene Patagonian Glaciations. After this period, the orogeny of the region and Pleistocene climatic oscillations played a role in the divergence of isolated ancestral populations followed by migrations to the Chaco-Pampa plain.