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Geographical names and the entities they represent act as a fundamental cornerstone across numerous disciplines. However, inconsistent geographical names and arbitrarily defined regional geographical scales are common, hindering cross-disciplinary communication and synthesis. The Pan-Tibetan Highlands, comprising the Tibetan Plateau, Himalaya, Hengduan Mountains and Mountains of Central Asia, is a case in point. To rectify these inconsistencies of terminology, we employed a multi-disciplinary approach to standardize the nomenclature of the Tibetan Plateau and the three adjacent mountain regions, defining their spatial extent using historical and contemporary perspectives. A literature meta-analysis indicated that ‘Tibetan Plateau’, ‘Himalaya’ and ‘Hengduan Mountains’ are the most suitable names for these regions in terms of both priority (earliest use) and popularity, whereas ‘Mountains of Central Asia’ emerges as appropriate for the mountain chains to the west of the Tibetan Plateau. The new term ‘Pan-Tibetan Highlands’ is proposed to replace the less precise and arguably misleading ‘High Mountain Asia’ for these regions collectively. Additionally, new geographical boundaries, applicable back through time, are proposed for each region, based on geological and geomorphological features. Using these new boundaries, the Pan-Tibetan Highlands area is 3.95 × 106 km2 with a mean elevation of 3,824 m, while the Tibetan Plateau is smaller (1.82 × 106 km2) and higher (4,465 m) than commonly assumed. Across the Pan-Tibetan Highlands, the proportion of protected areas is be far below the proposed 30% anticipated in the post-2020 Global Biodiversity Framework target with only a few exceptions. Additionally, the Hengduan Mountains showed the highest vascular plant species richness and endemism, followed by the Himalaya, Mountains of Central Asia and Tibetan Plateau. The obvious conservation gap in the Pan-Tibetan Highlands calls for urgent research-based optimization of conservation network. Our approach benefits quantitative spatial analysis by providing well-defined geographical scales for various fields, aiding cross-disciplinary comparisons and synthesis.

Additional file 1: Table S1. Statistics of the sequencing, assembly, and filtering of transcriptomes of samples of three varieties of the Rhododendron sanguineum complex. Table S2. Basic information of the transcriptome sequencing and alignment rates of 18 RNA libraries of two tissues of three varieties of the Rhododendron sanguineum complex. Table S3. BUSCO statistics for transcriptome assembly quality assessment of three varieties of the Rhododendron sanguineum complex. Table S4. Orthologous cluster statistics across three varieties of the Rhododendron sanguineum complex. Table S5. Identification and annotation of orthologous clusters across three varieties of the Rhododendron sanguineum complex. Table S6. List of the 40 predicted anthocyanin-associated genes and paralogs found in the Rhododendron sanguineum complex. Table S7. Primer information used for qRT-PCR validation of 12 gene paralogs involved in anthocyanin synthesis in three varieties of the Rhododendron sanguineum complex. Table S8. Statistical information of promoters for all genes among the Rhododendron sanguineum complex. Figure S1. BUSCO quality assessment results of transcriptome assemblies for three varieties of the Rhododendron sanguineum complex (a) and annotation of 15,164 orthologous cluster hits against six different databases (b). RsS – R. sanguineum var. sanguineum; RsH – R. sanguineum var. haemaleum; RsD – R. sanguineum var. didymoides. Figure S2. Annotation of the 15,164 one to one single copy orthologs among three varieties of the Rhododendron sanguineum complex through interrogation against three different databases. Figure S3. Phylogenetic and genetic clustering results for the three varieties of the Rhododendron sanguineum complex. Figure S4. Gene expression patterns of all 18 samples of three varieties of the Rhododendron sanguineum complex. Figure S5. Volcano plots of differentially expressed genes (DEGs) based on pairwise comparisons of the three varieties of the Rhododendron sanguineum complex. Figure S6. Heatmap and results of the functional enrichment of differentially expressed genes (DEGs) among the three varieties of the Rhododendron sanguineum complex. Figure S7. Hierarchical clustering of normalized expression levels of 23 candidate genes show distinct gene expression profiles in comparison of RsH and RsD. Variety code as in Figure S1. Red indicates high expression, and blue indicates low expression. Figure S8. Hierarchical clustering of normalized expression levels of 25 candidate genes show distinct gene expression profiles in comparison of RsH and RsS. Variety code as in Figure S1. Red represents high expression, and blue represents low expression. Figure S9. Hierarchical clustering of normalized expression levels of 12 candidate genes show distinct gene expression profiles in comparison of RsS and RsD. Variety code as in Figure S1. Red represents high expression, and blue represents low expression. Figure S10. A common layout of the promoter architecture of the 13 anthocyanin genes across varieties. Variety code as in Figure S1.