Phylogenetic conservatism of fruit development time in Chinese angiosperms and the phylogenetic and climatic correlates

Abstract

QuestionsDocumenting the patterns and drivers of functional trait distributions at large spatial scales is key to our fundamental understanding of the composition of plant assemblages. However, phylogeographic patterns of fruit development time (FDT, the difference between flowering and fruiting dates) have remained unstudied. Here we compiled reproductive phenology (flowering and fruiting time) and species distribution data for 6838 angiosperm species in China to explore whether FDT is more phylogenetically conserved as latitude and elevation increase, whether the phylogenetic signal of FDT correlates with phylogenetic structure and potential climatic drivers across China, and whether the environmental determinants of phylogenetic signal of FDT differ between herbaceous and woody species. LocationChina MethodsWe divided China into 268 200 × 200 km grid cells and calculated the phylogenetic signals of FDT in each grid cell using pagel’s λ. We then regressed the phylogenetic signals of FDT as a function of either latitude or elevation, individually. We examined the relationship between phylogenetic signals of FDT and climate variables using both ordinary and spatial linear regressions. We also examined the relationship between the phylogenetic signal of FDT and either net relatedness index (NRI) or clade age of each grid-cell. ResultsWe found that phylogenetic signals in FDT increased as elevation and latitude increased. The Pagel’s λ of FDT was negatively correlated with clade age but positively correlated with NRI. Precipitation in the wettest quarter was the primary variable affecting the phylogenetic signal for herbaceous species, while minimum temperature of the coldest month and temperature seasonality were the two most important climatic factors for woody species. ConclusionsStrength of phylogenetic conservatism of FDT is greater at higher latitudes and elevations. The latitudinal and elevational patterns, where mean clade age of species lowers as temperature decreases, and angiosperm assemblages tend to be more phylogenetically clustered at higher elevations and higher latitudes, could be explained by the Tropical Niche Conservatism hypothesis. The phylogenetic signals of herbs and of woody plants are triggered by different climatic drivers. Our findings have important implications for the study of large-scale geographical gradients in plant species richness, phylogenetic diversity and community assembly.