Tertiary montane origin of the Central Asian flora, evidence inferred from cpDNA sequences of Atraphaxis (Polygonaceae)

Abstract

Atraphaxis has approximately 25 species and a distribution center in Central Asia. It has been previously used to hypothesize an origin from montane forest. We sampled 18 species covering three sections within the genus and sequenced five cpDNA spacers, atpB-rbcL, psbK-psbI, psbA-trnH, rbcL, and trnL-trnF. BEAST was used to reconstruct phylogenetic relationship and time divergences, and S-DIVA and Lagrange were used, based on distribution area and ecotype data, for reconstruction of ancestral areas and events. Our results appear compatible with designation of three taxonomic sections within the genus. The generic stem and crown ages were Eocene, approximately 47 Ma, and Oligocene 27 Ma, respectively. The origin of Atraphaxis is confirmed as montane, with an ancestral area consisting of the Junggar Basin and uplands of the Pamir-Tianshan-Alatau-Altai mountain chains, and ancestral ecotype of montane forest. Two remarkable paleogeographic events, shrinkage of the inland Paratethys Sea at the boundary of the late Oligocene and early Miocene, and the time intervals of cooling and drying of global climate from 24 (22) Ma onward likely facilitated early diversification of Atraphaxis, while rapid uplift of the Tianshan Mountains during the late Miocene may have promoted later diversification.

Young dispersal of xerophil Nitraria lineages in intercontinental disjunctions of the Old World

“…10-8 Ma, which drove by QTP rapid uplift. These geological and climate factors most likely drove rapid diversification of arid lineages, as has been evidenced by many plant cases, such as Caragana 40 , Artemisia 41 , Myricaria 42 , Atraphaxis 43 , and Reaumuria 44 . On the other hand, our inferred dispersal events within Central Asia during 8.96-5.95 Ma ( Figs 2 and 3 ), are also responses to these events; the union of arid climate and vegetation in eastern and western Central Asia during this period generated the possibility of spatiotemporal dispersals 23 41 45 .…”

Phylogeny of the Eurasian genus Jurinea (Asteraceae: Cardueae): Support for a monophyletic genus concept and a first hypothesis on overall species relationships

“…(2013) who found a high probability for a C Asian origin of the clade of Jurinea , Saussurea , Cousinia and Arctium . Central Asia and the Tian Shan region, in particular, have been shown to be the ancestral area for several plant genera, e.g., for Atraphaxis L. (Zhang & al., ), and Lagochilus Benth. (Zhang & al., ), which possibly migrated from there in eastern and western directions.…”

A broadly sampled 3-loci plastid phylogeny of Atraphaxis (Polygoneae, Polygonoideae, Polygonaceae) reveals new taxa: I. Atraphaxis kamelinii spec. nov. from Mongolia

“…We confirmed the monophyly of A. teretifolia (monotypic A. sect. Physopyrum) (Zhang et al 2014), which is a sister to the clade of morphologically distinct A. caucasica, A. badghysi, and A. rodinii, though there is no support for this relationship. As shown by Zhang et al (2014), we confirm that A. sect.…”

“…The latest yet preliminary circumscription of Atraphaxis (Schuster et al 2011a, b;Tavakkoli et al 2015;Yurtseva et al 2016) The phylogenetic analyses of Atraphaxis (21 species) (Zhang et al 2014) argue for the division of the genus into two major clades, with A. teretifolia (monotypic A. section Physopyrum) nested in one subclade, and A. section Atraphaxis, which includes the generic type A. spinosa, as part of the second subclade. Dual or ambiguous positions of some accessions in the plastid phylogeny of Zhang et al (2014) were possibly caused by erroneous determination of the voucher specimens or reciprocal hybridization of parental species both served as maternal plants for the hybrids.…”