Current climate overrides past climate change in explaining multi-site beta diversity of Lauraceae species in China

  Background  We aimed to characterise the geographical distribution of Sørensen-based multi-site dissimilarity (β_sor) and its underlying true turnover (β_sim) and nestedness (β_sne) components for Chinese Lauraceae and to analyse their relationships to current climate and past climate change.

  Methods  We used ensembles of small models (ESMs) to map the current distributions of 353 Lauraceae species in China and calculated β_sor and its β_sim and β_sne components. We tested the relationship between β_sor, β_sne and β_sim with current climate and past climate change related predictors using a series of simultaneous autoregressive (SAR_err) models.

  Results  Spatial distribution of β_sor of Lauraceae is positively correlated with latitude, showing an inverse relationship to the latitudinal α-diversity (species richness) gradient. High β_sor occurs at the boundaries of the warm temperate and subtropical zones and at the Qinghai-Tibet Plateau due to high β_sne. The optimized SAR_err model explains β_sor and β_sne well, but not β_sim. Current mean annual temperature determines β_sor and β_sne of Lauraceae more than anomalies and velocities of temperature or precipitation since the Last Glacial Maximum.

  Conclusions  Current low temperatures and high climatic heterogeneity are the main factors explaining the high multi-site β-diversity of Lauraceae. In contrast to analyses of the β-diversity of entire species assemblages, studies of single plant families can provide complementary insights into the drivers of β-diversity of evolutionarily more narrowly defined entities.