Evolutionary radiations of cushion plants on the Qinghai‐Tibet Plateau: Insights from molecular phylogenetic analysis of two subgenera of Arenaria and Thylacospermum (Caryophyllaceae)

Abstract

Cushion plants exhibiting adaptive convergence in cold and dry environments are keystone and foundation species in the alpine/subnival habitat on the Qinghai‐Tibet Plateau (QTP). To date, little attention has been paid to the molecular phylogeny, origin, and biogeography of cushion plants on the QTP. We investigated the molecular phylogeny of classic cushion Arenaria subg. Dolophragma, A. subg. Eremogoneastrum, and Thylacospermum on the QTP, within the framework of the Caryophyllaceae. A new Thylacospermum‐Dolophragma clade was identified using combined plastid markers (rps16, matK, trnL‐trnF, trnS‐trnfM) and nuclear ribosomal DNA. Molecular divergence dating suggested that Thylacospermum and A. subg. Dolophragma originated in the middle to late Miocene (11.68 Ma). Combined with ancestral range reconstruction, there is an indication that all species of cushion Arenaria (A. subg. Dolophragma, A. subg. Eremogoneastrum) originated during/after the late Pliocene, and the QTP was their ancestral area. Furthermore, ecological niche modeling showed that the areas occupied by the three studied cushion plants during the last glacial maximum (LGM) was broader than that of their present distribution, implying a reduction in their range after the LGM. This evidence clearly illustrates that multistage uplift of the QTP and bordering mountains since the Miocene associated with climatic change (worldwide cooling, aridification in Central Asia, Quaternary glaciation) played a role in triggering and facilitating the speciation and/or evolutionary radiations of the species studied.

Phylogenomics and rapid diversification of the genus Eutrema on the Qinghai–Tibet Plateau and adjacent regions

“…Therefore, it is likely that the progressive extension of the QTP region and drier climate in central Asia together triggered the early diversification of major clade (Clade A, subclade B1 and subclade B2) in Eutrema. This type of diversification scenario could also been found in other species-rich alpine or subalpine genera, such as cushion Arenaria and Thylacospermum (Xu et al, 2019a), Saussurea (Xu et al, 2019b) and Rhodiola (Zhang et al, 2014). For the QTP-related clade (mainly in Hengduan Mountains; Fig.…”

Phylogenetic estimation and morphological evolution of Alsineae (Caryophyllaceae) shed new insight into the taxonomic status of the genus Pseudocerastium

“…(2017) . However, a recent study based on ITS sequences provided strong support for the close relationship between P. jamesiana and the genus Cerastium ( Xu et al., 2019 ). Although the two North American species have three styles, similar to other members of the core Pseudostellaria and Stellaria , S. americana has three lobes at the apex of the capsule, which is very different from that of the core Stellaria (six lobes).…”

Pleistocene glaciation advances the cryptic speciation of Stellera chamaejasme L. in a major biodiversity hotspot

“…While Miocene events are acknowledged, we contend that more recent glaciations and biological factors, such as pollinator interactions, have driven diversification in the region. We spotlight the Pleistocene glaciation's underrated influence on recent species evolution (Table 1), notably through cryptic speciation, offering fresh perspectives on iconic speciation events that likely occurred prior to Pleistocene glaciation (Tu et al, 2010; Zhang et al, 2011a; Xu et al, 2019; Zhang et al, 2021b).…”