Elevational patterns of phylogenetic structure of angiosperms in a biodiversity hotspot in eastern Himalaya

Aims The tropical niche conservatism (TNC) hypothesis and the out of tropics (OTT) propose mechanisms generating patterns species diversity across warm-to-cold thermal gradients at large spatial scales. These two hypotheses both integrate ecological biogeography-related evolutionary factors, but they predict opposite for phylogenetic structure. Mount Namjagbarwa possesses one longest elevational flowering plant in world. We aim to analyse structure plants this mountain, investigate underlying causes emergence patterns. Location Mt. located eastern edge Himalaya. Methods Species distribution data were extracted from specimen records online sources, literature, herbarium our fieldwork. Bioclimatic CHELSA database. was divided into 100-m belts, which grouped three elevation segments (100–2000 m, 2000–4000 m 4000–5200 m) analysis. calculated metrics each belt. relationships with climatic factors analysed using generalized additive models structural equation models. Results A typical hump-shaped pattern richness observed along gradient Namjagbarwa. However, showed a zig-zag segments, has different formation mechanisms. Temperature tolerance played important roles throughout entire Main conclusions Neither TNC nor OTT alone can fully explain floristic assembly are better explanation low middle elevations respectively. Potential region alternate between convergence conservatism. study likely be common This is preserving potential mountain biodiversity. more studies needed determine