The Qinghai-Tibetan Plateau (QTP) is the highest and one of the most extensive plateaus in the world. Phylogenetic, phylogeographic and ecological studies support plant diversifications on the QTP through multiple mechanisms such as allopatric speciation via geographic isolation, climatic oscillations and divergences, pollinator-mediated isolation, diploid hybridization and introgression, and allopolyploidy. These mechanisms have driven spectacular radiations and/or species diversifications in various groups of plants such as Pedicularis L., Saussurea DC., Rhododendron L., Primula L., Meconopsis Vig., Rhodiola L., and many lineages of gymnosperms. Nevertheless, much work is needed toward understanding the evolutionary mechanisms of plant diversifications on the QTP. Well-sampled biogeographic analyses of the QTP plants in the broad framework of the Northern Hemisphere as well as the Southern Hemisphere are still relatively few and should be encouraged in the next decade. This paper reviews recent evidence from phylogenetic and biogeographic studies in plants, in the context of rapid radiations, mechanisms of species diversifications on the QTP, and the biogeographic significance of the QTP in the broader context of both the Northern and Southern Hemisphere biogeography. Integrative multidimensional analyses of phylogeny, morphological innovations, geography, ecology, development, species interactions and diversifications, and geology are needed and should shed insights into the patterns of evolutionary assembly and radiations in this fascinating region.

The present work represents the first comprehensive taxonomic revision of Acacia sens. lat. (Leguminosae: Mimosoideae) in China, focusing on the indigenous species. Critical reassessments of specimens and re-definition of previously recorded species have resulted in recognising 21 indigenous species under Senegalia, a segregate of the former Acacia sens. lat. Detailed botanical profiles are provided for these species, together with a diagnostic line drawing and distribution map; photographs of living plants are provided for more than half the species. Terser treatments are also provided for the 15 species from four genera that are regarded as major introductions of Acacia sens. lat. to the country: Acacia Mill. (12 spp.), Acaciella Britton & Rose (1 sp.), Senegalia Raf. (1 sp.) and Vachellia Wight & Arn. (1 sp.). An identification key to all Acacia sens. lat. species in China is provided. The indigenous species of Senegalia in China belong to sect. Monacanthea (Vassal) Maslin, comb. nov., and the introduced ones to sect. Senegalia. As a consequence of this study, the number of Senegalia species now recognised for China has almost doubled. Six new species are described: Senegalia clandestina Maslin, B.C.Ho, H.Sun & L.Bai, sp. nov.; Senegalia guangdongensis Maslin, B.C.Ho, H.Sun & L.Bai, sp. nov.; Senegalia obliqua Maslin, B.C.Ho, H.Sun & L.Bai, sp. nov.; Senegalia orientalis Maslin, B.C.Ho, H.Sun & L.Bai, sp. nov.; Senegalia prominens Maslin, B.C.Ho, H.Sun & L.Bai, sp. nov.; Senegalia stipitata Maslin, B.C.Ho, H.Sun & L.Bai, sp. nov. Four new combinations are established: Senegalia garrettii (I.C.Nielsen) Maslin, B.C.Ho, H.Sun & L.Bai, comb. & stat. nov.; Senegalia kerrii (I.C.Nielsen) Maslin, B.C.Ho, H.Sun & L.Bai, comb. & stat. nov.; Senegalia kunmingensis (C.Chen & H.Sun) Maslin, B.C.Ho, H.Sun & L.Bai, comb. & stat. nov.; Senegalia macrocephala (Lace) Maslin, B.C.Ho, H.Sun & L.Bai, comb. nov. Senegalia andamanica (I.C.Nielsen) Maslin, Seigler & Ebinger and S. macrocephala are new records for China. A lectotype is designated for Acacia teniana Harms and 2nd step lectotypifications effected for Acacia delavayi Franch., Acacia insuavis Lace, Acacia pruinescens Kurz and Acacia yunnanensis Franch. Former holotype citations are corrected to lectotype for Acacia hainanensis Hayata, Acacia macrocephala Lace, Acacia oxyphylla Graham ex Benth. and Acacia philippinarum Benth. A neotype is designated for Acacia arrophula D.Don. China is a principal area of species-richness for Senegalia in Asia. Senegalia displays a high degree of endemism within China and almost half the species are endemic or near-endemic, with Yunnan the most species-rich and species-diverse Province.

The East Asian flora (EAF) is a key biodiversity hotspot for understanding the origin and evolution of Northern Hemisphere floras, but there is an ongoing debate on whether it is a museum or a cradle for seed plants. Within the EAF, two main floras, the Sino-Himalayan Flora (mainly the Rhododendron Flora) and the Sino-Japanese Flora (mainly the Metasequoia Flora), have been recognized. Previous studies suggested that the EAF is ancient and the Metasequoia Flora is older than the Rhododendron Flora. To test this hypothesis, we synthesized molecular as well as fossil data on seed plants, focusing on the biogeographical origins and historical evolution of the EAF. We compared the ages of its two constituent floras, and examined the impact of the Asian monsoon and other environmental changes on the development of EAF through meta-analysis. Our results suggest that the EAF might be relatively young, with most of its clades originating since the Miocene. The Rhododendron Flora and the Metasequoia Flora are probably of a similar age. The formation and development of the Asian monsoon might have been the main factors that have driven the evolution of EAF. In the Rhododendron Flora, the north-south mountain chains increased the concentration of species and reduced extinction, and the barriers between the east and west have resulted in species differentiation, which triggered it to become a diversity center. The EAF appears to have multiple biogeographical origins, having closely affiliated not only with other floras in the Northern Hemisphere, but also with Gondwanan floras.

The Hengduan Mountains (HDM) biodiversity hotspot exhibits exceptional alpine plant diversity. Here, we investigate factors driving intraspecific divergence within a HDM alpine species Salix brachista (Cushion willow), a common component of subnival assemblages. We produce a high-quality genome assembly for this species and characterize its genetic diversity, population structure and pattern of evolution by resequencing individuals collected across its distribution. We detect population divergence that has been shaped by a landscape of isolated sky island-like habitats displaying strong environmental heterogeneity across elevational gradients, combined with population size fluctuations that have occurred since approximately the late Miocene. These factors are likely important drivers of intraspecific divergence within Cushion willow and possibly other alpine plants with a similar distribution. Since intraspecific divergence is often the first step toward speciation, the same factors can be important contributors to the high alpine species diversity in the HDM.