Latitudinal variability and driving factors of functional diversity in Pinus thunbergii communities across sea-islands in Eastern China

Aims The Pinus thunbergii communities is widespread across islands in both Yellow Sea and East China Sea. The objective of this study is to examine the latitudinal pattern of functional diversity and abiotic and biotic drivers of P. thunbergii communities. Our aims are to advance understanding of whether the zonal character of latitude oriented pattern of biodiversity still holds in the same community type across the highly isolated and fragmented landscape. Methods We investigated community structure and measured plant functional traits across 60 P. thunbergii communities in 27 islands, spanning 13 degree in latitudes of Eastern China. Linear regression was used to analyze the relationships between functional diversity of the P. thunbergii community and each of the biotic factors (the dominance of P. thunbergii and species diversity) and abiotic factors (annual mean temperature, total solar radiation and aridity index). The relative importance of abiotic and biotic factors on the functional diversity of P. thunbergii communities was determined by using the generalized linear model and variance decomposition. Important findings With the increasing latitude, the dominance of P. thunbergii, species richness, and functional richness, functional dispersion and Rao's quadratic entropy (Rao0 of stem traits alone and stem and leaf traits in combination decreased significantly but those of leaf traits did not show clear trend, across P. thunbergii communities. The dominance of P. thunbergii, species richness and climatic factors jointly explained 63%, 47% and 39% of variation in each of functional richness, functional dispersion and Rao(2 of the combination of leaf and stem traits, and 56%, 67% and 53% of variation in each of functional richness, functional dispersion and Rao(2 of stem traits, but small variations in leaf traits (21%-30%). Species richness and Simpson diversity significantly increased but Shannon-Wiener diversity significantly decreased leaf functional richness. Aridity significantly increased functional diversity of stem traits and the combination of leaf and stem traits. Annual mean temperature significantly decreased functional dispersion and Rao(2 of wood traits. These results indicate that there is a clear latitudinal pattern of functional diversity in P. thunbergii communities across islands. Climate and species richness play the key roles for shaping the latitudinal variations in functional diversity of P. thunbergii communities across islands in Eastern China.