DOI: 10.5061/dryad.jq2bvq8b3
title: Global warming pushes the distribution range of the two alpine ‘glasshouse’ Rheum species north- and upwards in the Eastern Himalayas (EH) and the Hengduan Mountains (HM)

description: Alpine plants’ distribution is being pushed higher towards mountaintops
 due to global warming, finally diminishing their range and thereby
 increasing the risk of extinction. Plants with specialized ‘glasshouse’
 structures have adapted well to harsh alpine environments, notably to the
 extremely low temperatures, which makes them vulnerable to global warming.
 However, their response to global warming is quite unexplored. Therefore,
 by compiling occurrences and several environmental strata, we utilized
 multiple ensemble species distribution modeling (eSDM) to estimate the
 historical, present-day, and future distribution of two alpine
 ‘glasshouse’ species Rheum nobile Hook. f. & Thomson and R.
 alexandrae Batalin. Rheum nobile was predicted to extend its distribution
 from the Eastern Himalaya (EH) to the Hengduan Mountains (HM), whereas R.
 alexandrae was restricted exclusively in the HM. Both species witnessed a
 northward expansion of suitable habitats followed by a southerly retreat
 in the HM region. Our findings reveal that both species have a
 considerable range shift under different climate change scenarios, mainly
 triggered by precipitation rather than temperature. The model predicted
 northward and upward migration for both species since the last glacial
 period which is mainly due to expected future climate change scenarios.
 Further, the observed niche overlap between the two species presented that
 they are more divergent depending on their habitat, except for certain
 regions in the HM. However, relocating appropriate habitats to the north
 and high elevation may not ensure the species’ survival, as it needs to
 adapt to the extreme climatic circumstances in alpine habitats. Therefore,
 we advocate for more conservation efforts in these biodiversity hotspots.
description: We focused on the entire
 geographic distribution ranges of the two species (Figure 1D). For this,
 the past field (1937–2020) (Supplementary Table S1) datasets were compiled
 and cross-checked with the herbarium records from the National Herbarium
 and Plant Laboratories (KATH, Nepal) and Kunming Institute of Botany, CAS
 (KUN, China) to construct the geographic distribution of both species. In
 addition to past field and herbarium collections, we also ground-validated
 occurrence points (from 2015 to 2022) through GPS in the field and
 cross-checked with the online databases of the Chinese National Herbarium
 (PE; http://pe.ibcas.ac.cn/en/), Chinese Virtual Herbarium (CVH;
 http://www.cvh.ac.cn/), the Global Biodiversity Information Facility
 (GBIF.org, 2021), the Royal Botanical Garden at Edinburgh (RBGE, United
 Kingdom; http://data.rbge.org.uk/search/herbarium/) and the Herbarium at
 the University of Tokyo (TI, Japan;
 http://umdb.um.u-tokyo.ac.jp/DShokubu/). While compiling the occurrence
 datasets, we mainly focused on geographic coordinates recorded by the
 different resource persons during the field. So, the occurrence points
 from the other herbarium specimens and online databases were discarded in
 the datasets.  With the use of predictive environmental
 variables and a given species distribution model, we used the
 standardized approach in ODMAP (Overview, Data, Model, Assessment and
 Prediction) (Zurell et al., 2020) protocol structure (Supplementary
 Methods). The ensemble of SDMs was implemented using the R-package
 ‘Biomod2’ (Thuiller et al., 2020).