Rise of herbaceous diversity at the southeastern margin of the Tibetan Plateau: First insight from fossils

The Hengduan Mountains region (HMR) on the southeastern Tibetan Plateau, supports a high diversity of herbs, particularly in its subalpine to alpine ecosystems, due altitude and cool temperate climate. Current understanding formation such herbaceous richness is based chiefly molecular phylogenies; however, direct geological evidence lacking because herbs are rarely preserved as macroscopic fossils. In this study, we present abundant fossil fruits seeds from late Pliocene Heqing Basin southern HMR. Our systematic analysis shows presence at least 18 species belonging 11 genera, that is, Ranunculus, Corydalis, Rumex, Polygonum, Chenopodium, Stellaria, Fragaria, Astragalus, Aster, Carex, Schoenoplectus, which Polygonum most followed by Astragalus. This finding throws first light rise region. We interpret local assembly these resulting rapid pre-Pliocene diversifications many groups As nowadays grow primarily meadows few occur subaquatic plants, suggest an open meadow hosting some scattered shrubs vicinity vegetated wetland during Pliocene. provides past treeless vegetation within HMR thus improves our knowledge evolution uplift-induced climate cooling monsoon-associated precipitation seasonality potentially key driving forces for opening