A preliminary species‐level phylogeny of the alpine ginger Roscoea: Implications for speciation

Abstract

Speciation, the evolutionary process forming new species, is a key mode generating biodiversity on the Earth. In this study, we produced a species‐level phylogeny of Roscoea using one nuclear ribosomal and two chloroplast DNA fragments based on Bayesian inference and maximum likelihood. We then explored the possible speciation processes using the species‐level phylogeny and the heterozygous sites in the nuclear DNA. The incongruence between nuclear and chloroplast phylogenies, and several heterozygous sites in the nuclear DNA, suggested that R. auriculata might have a hybrid origin with R. purpurea and R. alpina being two possible parental progenitors; however, one alternative possibility through incomplete lineage sorting cannot be ruled out. In addition, R. kunmingensis likely originated from R. tibetica Batalin through the process of “budding speciation”. These results provided a valuable framework to draw testable hypotheses for future in‐depth comparative studies to further our understanding of the underpinning speciation and adaptation mechanisms that contribute to ultrahigh biodiversity in the Himalayas and the Hengduan Mountains.

Responses of an endemic species (Roscoea humeana) in the Hengduan Mountains to climate change

“…These results suggest that Roscoea species are sensitive to climate change, providing an interesting case for integrative studies of climate drivers of genetic diversity. R. humeana is an herb endemic to the Hengduan Mountains (Cowley, 2007;Zhao, Gugger, et al, 2016;Zhao et al, 2017). Despite having a long floral tube, this species is pollinated by bees (Zhang et al, 2011).…”

Genomic data reveal two distinct species from the widespread alpine ginger Roscoea tibetica Batalin (Zingiberaceae)

“…The distribution range of R. tibetica has been considered to extend into the Himalayas, albeit obscured by the Himalayan species R. alpina Royle and R. bhutanica Ngamriab Cowley et al, 2007). However, phylogenetic reconstruction suggested that R. tibetica was not present in the Himalayas and that R. alpina and R. bhutanica were not present in the Hengduan Mountains Zhao et al, 2016bZhao et al, , 2017. Moreover, R. tibetica with typical taxonomic traits was separated from other Roscoea species, such as distant clades R. scillifolia (Gagnepain) Cowley and R. schneideriana (Loesener) Cowley (Zhao et al, 2017).…”

“…However, phylogenetic reconstruction suggested that R. tibetica was not present in the Himalayas and that R. alpina and R. bhutanica were not present in the Hengduan Mountains Zhao et al, 2016bZhao et al, , 2017. Moreover, R. tibetica with typical taxonomic traits was separated from other Roscoea species, such as distant clades R. scillifolia (Gagnepain) Cowley and R. schneideriana (Loesener) Cowley (Zhao et al, 2017). Floras proposed that current R. tibetica plants contains three synonyms, namely R. intermedia Gagnepain var.…”

An ecological barrier between the Himalayas and the Hengduan Mountains maintains the disjunct distribution of Roscoea

“…Roscoea is a perennial deciduous genus that contains approximately 20 species, which are divided into ~8 species in the Himalayas and ~12 species in the Hengduan Mountains/Yun‐Gui Plateau, with some partially distributed in the north of Indochina, by an ~500‐km wide gap (Figure ), which is simply referred to as ‘Gap’ in this paper. These two groups of Roscoea are reciprocal monophyly (Ngamriabsakul et al, ; Zhao, Xia, et al, ; Zhao et al, ). Biogeographical reconstruction has suggested that the formation of the disjunction of Roscoea is likely caused by a rapid lateral extrusion of Indochina with the rapid uplift of the Himalayas during the early Miocene (approximately 23 Ma) and limited seed dispersal by ants (Ding et al, ; Zhao, Xia, et al, ).…”

“…Roscoea is the only genus in the ginger family (Zingiberaceae) that has a regional disjunction in alpine regions (Cowley, 2007;Ngamriabsakul, Newman, & Cronk, 2000;Zhao, Xia, Cannon, Kress, & Li, 2016;Zhao, Zhong, Fan, Xia, & Li, 2017). Roscoea is a perennial deciduous genus that contains approximately 20 species, which are divided into ~8 species in the Himalayas and ~12 species in the Hengduan Mountains/Yun-Gui Plateau, with some partially distributed in the north of Indochina, by an ~500-km wide gap (Figure 1), which is simply referred to as 'Gap' in this paper.…”