Aims: It has been assumed that montane species will undergo upslope shifts in response to climate warming and their range sizes are therefore predicted to decrease. However, this view has been challenged because a recent study (Elsen & Tingley, 2015) indicated that land surface area increases with increasing altitude in some mountains. To test this prediction, we used one of the world's biodiversity hotspots as a study system to examine overall patterns of plant distribution shift in response to climate warming. Location: The Hengduan Mountains and adjacent regions.Methods: Based on distribution data for 151 species at a resolution of 2.5 arc minutes, we employed ecological niche modelling to model their distributions under the climatic conditions of the Last Glacial Maximum, Current (2017), and 2050 separately.We examined the distributional shifts of these species, especially with respect to altitude and range size, in response to two periods of stepwise climate warming. Results: All the montane plants sampled shifted upward during the two warming stages, but not only northward, some shifted westward or in other directions. In contrast with the expected consistent loss of range when shifting upward, 63.6% of the plants expanded their range size continuously since the LGM. Only 11.9% of the plants contracted their range size continuously from the LGM to 2050. Estimates of species richness in the regions studied changed greatly, but in an unbalanced manner, from the LGM to the Current and from the Current to 2050. Main conclusions: Numerous montane plants in the Hengduan Mountains are predicted to expand their range sizes as they shift upslope in response to climate warming. Our results highlight the possibility that more available land surface area due to the heterogeneous topography along altitudinal gradients and the adjacent large Qinghai-Tibet Plateau sensu stricto can mediate the range loss of the montane plants under climate warming. These findings are crucial for estimating the future range sizes of plants and planning biodiversity protection formountain ecosystems under the anticipated warming of the world'sclimate. K E Y W O R D S climate warming, ecological niche modelling, montane plants, range shift, the Hengduan Mountains, the Qinghai-Tibet Plateau *These authors contribute equally to this work.

Soil-plant-atmosphere interactions regulate the impact of climate on forest ecosystems.

No abstract

No abstract

Bupleurum commelynoideum H. Boissieu is a perennial herb occurring throughout the Hengduan Mountains region. This species was found to have more than one chromosome number in our previous chromosomal study. For a better understanding of its intraspecific genetic differentiation and interspecific relationships with other Bupleurum members, phylogenetic relationships among 15 populations of B. commelynoideum and 22 other Bupleurum members were investigated using the nuclear ribosomal DNA internal transcribed spacer (ITS) region and three chloroplast DNA (cpDNA) fragments (trnL‐F, rps16, and rpl32‐trnL). Both phylogenetic analyses of the ITS region and combined cpDNA data indicated that B. commelynoideum has more than one geographically delimited lineage. Among them, accessions from Shangri‐La and other regions were considered as different cryptic species according to the unified species concept. Our analyses also revealed that a complex pattern of reticulate relationship exists in B. commelynoideum and its allied species. The chromosome numbers of four populations of B. commelynoideum and a closely related species B. rockii H. Wolff are reported. The results showed that the chromosome number of B. commelynoideum has abundant variations in both chromosome ploidy (2x; 4x; 6x) and basic chromosome number (x = 5; x = 6). Population DXS (x = 6), which has the different basic chromosome number, should represent a different kind of cryptic speciation in B. commelynoideum. The karyological evidence, together with the molecular data, indicated that the existence of at least three cryptic species in B. commelynoideum. This kind of genetic differentiation without morphological divergence might be caused by stabilizing selection imposed by the extreme environmental conditions of the alpine area.