Summary Despite the role of polyploidy in multiple evolutionary processes, its impact on plant diversification remains controversial. An increased polyploid frequency may facilitate speciation through shifts in ecology, morphology or both. Here we used Allium to evaluate: (1) the relationship between intraspecific polyploid frequency and species diversification rate; and (2) whether this process is associated with habitat and/or trait shifts. Using eight plastid and nuclear ribosomal markers, we built a phylogeny of 448 Allium species, representing 46% of the total. We quantified intraspecific ploidy diversity, heterogeneity in diversification rates and their relationship along the phylogeny using trait‐dependent diversification models. Finally, we evaluated the association between polyploidisation and habitat or trait shifts. We detected high ploidy diversity in Allium and a polyploidy‐related diversification rate shift with a probability of 95% in East Asia. Allium lineages with high polyploid frequencies had higher species diversification rates than those of diploids or lineages with lower polyploid frequencies. Shifts in speciation rates were strongly correlated with habitat shifts linked to particular soil conditions; 81.7% of edaphic variation could be explained by polyploidisation. Our study emphasises the role of intraspecific polyploid frequency combined with ecological drivers on Allium diversification, which may explain plant radiations more generally.

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A new species of genus Rorippa, R. hengduanshanensis, from the Hengduan Mountains, is described herein. Comparing the floral structure and overall fruit morphology of R. hengduanshanensis with similar taxa (e.g., R. benghalensis, R. dubia, and R. indica) revealed a series of morphological differences, both qualitative and quantitative. R. hengduanshanensis differs from R. benghalensis in the ebracteate racemes; from R. dubia in the flattened silique, the presence of four petals and the ploidy level (2n=6x=48); and from R. indica in the uniseriate seeds. Phylogenetic analyses using three plastid markers (psbC-trnS, trnG-trnM, and trnL) further revealed clear interspecific divergences that can distinguish R. hengduanshanensis from its morphologically related taxa.

Aim: The strategies of reproductive adaptation for alpine plants have long been a hot topic in evolutionary ecology, but there is still a lack of quantitative measures for reproductive traits under natural conditions. Here, we investigated reproductive adaptation of Rorippa elata, an endemic Brassicaceae species in one of the world's temperate biodiversity hotspots, the Hengduan Mountains (HDM). Methods: We established a field-based common garden experiment at Shangri-La Alpine Botanical Garden in Yunnan. During 2019-2020, we transplanted a total of 633 R. elata plants for 150 accessions across latitudes and performed manipulative field experiments. First, we collected several life history-related traits of R. elata, including germination rate, flowering time, over-winter survival rate, and pollination-relevant characteristics. We then carried out a set of four experimental treatments to characterize natural variation of the mating system in R. elata, including (1) strict selfing rate by bagging inflorescences before flowering; (2) common outcrossing rate by emasculation and open pollination; (3) strict outcrossing rate by emasculation and artificial pollination among accessions; and (4) natural reproductive rate under open pollination. For each treatment, we counted seed setting rate per fruit per accession and used this information to assign a mating system type for each R. elata accession. Furthermore, we also quantified the extents of pollen limitation and reproductive assurance.

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