Winter temperature structures mangrove species distributions and assemblage composition in China. Issue 12 (4th October 2018) - Wu, Yingtong
Abstract: Aim: The identification of environmental variables associated with geographical range limits can shed light on the ecological and physiological constraints imposed by abiotic stresses. Mangrove forest is a coastal ecosystem restricted to the tropics and subtropics. However, the factors that influence fine‐scale assemblage composition of mangroves remain an open question. This study aimed to identify range‐limiting climate factor(s) associated with species composition that are likely to have influenced the evolution of mangroves. Location: China. Time period: 1950s–2013. Major taxa studied: True mangrove species. Methods: We collected species presence–absence data across 70 sites spread between 18 and 27°N in China to analyse the latitudinal diversity gradient in relationship to 25 climate variables. To examine the change in community composition along the diversity gradient, we analysed two components of beta diversity: turnover‐resultant dissimilarity and nestedness‐resultant dissimilarity. We used non‐metric multidimensional scaling to identify crucial climate factors associated with variation in mangrove assemblage composition. We also applied variance partitioning among taxonomic ranks to detect taxonomic signal in climatic tolerance of mangroves. Results: First, total species richness decreases with increasing latitude. Second, variation in mangrove assemblage composition is significantly correlated with winter temperature, exhibiting a nested subset structure in species composition and a gradual decrease in the number of thermophilic species with increasing latitude. Finally, mangrove species show a genus‐level signal in tolerance of winter temperature, whereas most other climate factors vary primarily among species within genera. Main conclusions: Winter temperature appears to constrain the current distributions of mangrove species, and tolerance of low air temperature is evolutionarily conservative at the genus level. These ecological and phylogenetic patterns collectively suggest that physiological constraints related to cold tolerance structure the nested pattern with respect to the latitude of mangrove assemblages at a regional scale.