Abstract:

How large-scale patterns of species diversity emerge is a central yet controversial issue in ecology and biogeography. Despite the long history of studies the mechanisms driving species diversity patterns in space remain poorly known. Using distribution data of all gymnosperm species in China, we assessed the influence of environmental factors on spatial patterns of species diversity in China. Further, we evaluated the proportion of gymnosperms in local floras. We found that species diversity of gymnosperms decreases along a south-north axis. Hengduan Mountains, with the highest species diversity, is a hotspot of gymnosperms. Species diversity patterns differ significantly between the gymnosperm subclasses. In particular, the species diversity pattern of Pinidae is similar to that of all species combined, while the species diversity of Gnetidae is highest in the drylands of northwestern China. In contrast, Cycadidae is restricted to southern China. Environmental heterogeneity and precipitation are the best predictors of species diversity patterns of all gymnosperms combined, followed by temperature anomaly since the Last Glacial Maximum (LGM), elevational range and energy. That different factors predict species diversity patterns of different gymnosperm subclasses, may reflect the differences in their evolutionary history and physiological adaptions. The ratio of gymnosperm to angiosperm species diversity is lower in the warm and humid eastern and southern parts of China, and increases towards the drylands in western and northern parts. Environmental energy and precipitation were good predictors of the ratio of gymnosperms to angiosperms. Specifically, the ratio decreases with increase of energy and decrease of precipitation suggesting that angiosperms may have stronger competitive ability in warm and humid regions while gymnosperms adapt better to dry and cold environments.

Key words: Pinidae, Gnetidae, Cycadidae, contemporary climate hypothesis, past climate change, species diversity pattern