Testing multiple hypotheses for the high endemic plant diversity of the Tibetan Plateau

Abstract

Aim The Tibetan Plateau harbours the highest alpine and endemic plant diversity in the world, attributed to rapid diversification during the plateau uplift and Quaternary climate fluctuations. However, there is little understanding of which hypotheses associated with these geological and climatic processes garner strong support as explanations for the observed diversity patterns. Here, we test support for hypotheses related to uplift and climate changes that could account for the high endemicity and phylogenetic diversity of the world’s highest plateau. Location Tibetan Plateau (TP). Time period Neogene, Quaternary and current period. Major taxa studied Tibetan endemic seed plants. Methods We collated data on endemic seed‐plant distribution based on county‐level mapping from published monographs and online databases. We calculated species richness (SR) and phylogenetic diversity for endemic herbs, shrubs, trees, and all plants for 0.5‐degree × 0.5‐degree grid cells covering the TP. We derived environmental and evolutionary predictors to evaluate eight biogeographical hypotheses associated with plateau uplift and climate fluctuations, and used partial regression analysis and mixed conditional autoregressive (CAR) models to assess the relative contribution of each predictor to the extant diversity of the TP. Results We found plateau uplift independently explained more variance in diversity than climate fluctuations, but there were also strong interaction effects. The full CAR models including all predictors explained 37%–75% of the total variation across diversity measures and life forms. The predictor representing the montane museum hypothesis explained the most variation (c. 25%), but each predictor explained at least 6%. Main conclusions These results demonstrate that both the plateau uplift and Quaternary climate fluctuations had large impacts on current patterns of species diversity, but the influence of plateau uplift was more pronounced than that of climate changes. Our study suggests that plateau uplift and climate changes are the original drivers of complex biogeographical processes accounting for the biodiversity of the TP.

Sky islands as foci for divergence of fig trees and their pollinators in southwest China

“…The Quaternary ice ages have had major impacts on both tropical and temperate organisms, redistributing species and causing extinctions, fragmenting and rejoining populations, and generating opportunities for divergence and speciation (Batalha‐Filho, Cabanne, & Miyaki, ; Liu et al, ; Pinheiro et al, ; Wang, Chen, et al, ; Yu, Deane, et al, ). In mountainous areas, where orogenesis creates barriers to dispersal, the impacts of Quaternary climate changes are complex, with varying outcomes for different taxa (Yu, Deane, et al, ). In the case of the sky islands of SW China, their complex topography and range of elevations has clearly favoured survival, differentiation and speciation over extinction, and resulted in an area of exceptional species richness.…”

“…The Quaternary ice ages have had major impacts on both tropical and temperate organisms, redistributing species and causing extinctions, fragmenting and rejoining populations, and generating opportunities for divergence and speciation (Batalha-Filho, Cabanne, & Miyaki, 2012; Liu et al, 2013;Pinheiro et al, 2011;Wang, Chen, et al, 2015b;Yu, Deane, et al, 2019a). In mountainous areas, where orogenesis creates barriers to dispersal, the impacts of Quaternary…”

“…Factors that shape the dynamics of populations and their divergence over time have combined to determine current levels of biodiversity (Avise, 2000). Among these factors, tectonic movements have played an important role in the genesis of biodiversity because they can create geographical dispersal barriers such as mountain ranges or major river systems that isolate populations and lead to species diversification (Achimon, Johnson, Cocucci, Sersic, & Baranzelli, 2018;Cheng et al, 2016;Yu, Deane, et al, 2019a;Zhang, Zheng, & Ge, 2007). Climate oscillations, especially the Quaternary glacial-interglacial cycles, are also seen as drivers of population divergence (Ibrahim, Nichols, & Hewitt, 1996) when retreat to glacial refugia generates fragmentation and isolation facilitates divergence and speciation (Hewitt, 2000(Hewitt, , 2004.…”

Concealed truth: Modeling reveals unique Quaternary distribution dynamics and refugia of four related endemic keystone Abies taxa on the Tibetan Plateau

“…The Tibetan Plateau (TP) is one of the world's major hotspots of plant species diversity, harboring 12,000 species of vascular plant, including 3,673 endemic species (Wen, Zhang, Nie, Zhong, & Sun, ; Yu et al, ; Zhang et al, ). From a geographical standpoint, the TP is unique (Favre et al, ; Liu et al, ): Over time, great fluctuations in temperature (Liu et al, ; Shen et al, ) and precipitation (Liu et al, ; Shen, Piao, Cong, Zhang, & Jassens, ) have occurred, in addition to the effects of elevation on generating different climatic conditions (Favre et al, ).…”

“…The Tibetan Plateau (TP) is one of the world's major hotspots of plant species diversity, harboring 12,000 species of vascular plant, including 3,673 endemic species (Wen, Zhang, Nie, Zhong, & Sun, 2014;Yu et al, 2019;Zhang et al, 2016). From a geographical standpoint, the TP is unique (Favre et al, 2015;Liu et al, 2016):…”