Geographic Pattern of Bryophyte Species Richness in China: The Influence of Environment and Evolutionary History

Xiaotong Song,Xiulian Chi,Qinggang Wang,Wenzhuo Fang,Xiaoming Shao

doi:10.3389/fevo.2021.680318

Xiaotong Song, Xiulian Chi + Show 3 more

Open Access

https://doi.org/10.3389/fevo.2021.680318

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Abstract

How contemporary environment interacts with macroevolutionary processes to generate the geographic pattern of bryophyte species is still unresolved. China is very rich in bryophytes, with more than 3,000 bryophytes covering 70% of the families in the world. In this study, we assessed the effects of the contemporary environment (average temperature of the coldest season TCQ, precipitation of the warmest season PWQ, and elevational range) and the recent diversification rates (estimated as mean species number per genus, MSG) on the geographical pattern of species richness for bryophytes and two groups (i.e., liverworts and mosses) in China. We compiled the provincial level distribution of bryophyte species and estimated the geographic pattern of the recent diversification rate by MSG for species in China. Univariate, multivariate regressions and path model analyses were used to assess the relationships between species richness, MSG, and their potential environmental drivers. Species richness of all bryophytes and liverworts significantly increased with the increase of MSG, either in regressions or path analyses, indicating that provinces with high bryophyte richness were mainly inhabited by species (especially liverworts) from lineages with particularly high MSG. In contrast, the species richness of mosses was insignificantly decreased with MSG in univariate regression or insignificantly increased with MSG in path analysis. Both species richness and MSG of all bryophytes and liverworts increased with the increase in energy and water availability. In contrast, for mosses, the species richness significantly increased with the increase of energy and water availability, while MSG decreased with the increase of energy and water availability. The MSG of liverworts increase with the increase of elevational range but the MSG of mosses decrease with the increase of elevational range. Our study suggests that the humid tropical and subtropical mountains in China are not only diversity hotspots for bryophytes, but also cradles for high recent diversification of liverworts, and refuges for mosses to hold many monotypic and oligotypic genera.

Highlights

The huge spatialvariation in species richness and mechanisms underlying it have always been a hot topic of concern to ecologists and biogeographers (Rosenzweig, 1995)
We found that many mountainous provinces with a humid climate such as Yunnan, Sichuan, Xizang, Guizhou, Fujian, Taiwan have a large number of monotypic moss genera (Supplementary Figure 3)
We found that elevational range have a positive influence on the geographic pattern of MSG of liverworts, suggesting that habitat heterogeneity in mountains facilitated the recent speciation of liverworts

Summary

Introduction

The huge spatialvariation in species richness and mechanisms underlying it have always been a hot topic of concern to ecologists and biogeographers (Rosenzweig, 1995). The contemporary environmental factors such as energy, water availability and habitat heterogeneity have been regarded as potential drivers of species richness pattern (Allen et al, 2002; Currie et al, 2004; Stein et al, 2014; Rana et al, 2019). The species richness of a region is determined by the evolutionary processes of speciation, dispersal and extinction (Mittelbach et al, 2007). The positive species richness-energy/water/habitat heterogeneity relationships must reflect evolutionary history (Rana et al, 2019). Habitat heterogeneity can increase species richness by promoting the speciation rate and reducing species extinction (Turner, 2004; Fjeldsa et al, 2012; Hughes and Atchison, 2015)

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Discussion

Conclusion