Phylogeny and speciation in Saxifraga sect. Ciliatae (Saxifragaceae): Evidence from psbA‐trnH, trnL‐F and ITS sequences

Abstract

Nearly half of the species in the large genus Saxifraga belong to Saxifraga sect. Ciliatae, a largely Sino‐Himalayan taxon. We report here that evidence from chloroplast DNA sequences (psbA‐trnH, trnL‐F) and from nuclear sequences (ITS) indicates that this section is monophyletic and composed of at least three main lineages, corresponding to (1) a clade made up of species from S. subsect. Gemmiparae, subsect. Cinerascentes, subsect. Flagellares and subsect. Hemisphaericae, in which the last three subsections are nested in the first; (2) a clade of species belonging to S. subsect. Rosulares (including S. subsect. Serpyllifoliae); and (3) a clade of species belonging to S. subsect. Hirculoideae. Species relationships in S. subsect. Rosulares and subsect. Hirculoideae are not well resolved. A molecular clock analysis indicates that the diversification of S. sect. Ciliatae into its three lineages dates from ca. 9.48 Ma, coinciding with orogenic events associated with one of the most important phases of uplift of the Qinghai‐Tibet Plateau. Extensive diversifications within S. subsect. Rosulares and subsect. Hirculoideae have been more recent (ca. 4.51 Ma and 2.12 Ma, respectively), again correlated with Qinghai‐Tibet Plateau uplift events and, in the case of S. subsect. Hirculoideae, have occurred at a rate comparable to that seen in the radiation of Hawaiian fruit flies.

Evolutionary radiations in the species-rich mountain genus Saxifraga L.

“…Two of these rate shifts led to substantially increased diversification rates within Saxifraga sections Ciliatae and Porphyrion which had previously been suggested as having experienced rapid radiations [31, 32]. Therefore, diversification rate shifts at least partially explain clade size differences in Saxifraga .…”

“…In addition, three taxa ( S. haplophylloides , S. diffusicallosa and S. maxionggouensis ) from the dataset of Gao et al [32] were added to all trees using the bind.tip function of the phytools package [64] in R [65]. This function allows to add tips to a phylogeny while rescaling the tree to conserve its ultrametric properties.…”

“…This function allows to add tips to a phylogeny while rescaling the tree to conserve its ultrametric properties. According to Gao et al [32] these three taxa are all part of subsect. Hirculoideae which form a well-defined subclade of Saxifraga section Ciliatae , but their exact position is unclear due to low resolution.…”

“…For example, species of section Porphyrion (90–112 species) are mostly cushion plants not taller than a few centimetres, whereas Irregulares Haworth species (10–20 species) are erect, with large, petiolate basal leaves, and reaching up to 40 cm in height [26, 30]. Several sections within Saxifraga have radiated within relatively short geological time-frames [31, 32], but the underlying factors behind these radiations have not been studied in detail. For these reasons, Saxifraga is an ideally suited study system to investigate patterns and processes connected to alpine radiations.…”

Development of EST‐SSR markers in Saxifraga sinomontana (Saxifragaceae) and cross‐amplification in three related species

“…The genus Saxifraga L. (Saxifragaceae) consists of approximately 500 species that are mainly distributed in the mountainous regions of Europe and Asia (Pan et al., ; Gao et al., ; Tkach et al., ), including the Qinghai–Tibetan Plateau (QTP) and Hengduan Mountains region (HDM), which is a biodiversity hotspot of Saxifraga (Pan et al., ). Saxifraga sinomontana J. T. Pan & Gornall is a widespread perennial herb in the QTP and its peripheral regions.…”