Latitudinal gradients and climatic controls on reproduction and dispersal of the non-native mangrove Sonneratia apetala in China

High reproductive and dispersal capacity allow invasive plant species to spread and establish, out-compete and occupy new niches. Sonneratia apetala, a species used in afforestation projects in southern China, was introduced from Bangladesh in 1985. This species has the capacity to colonize in mangrove mudflats and invade natural mangrove community of China. However, its effectiveness to do so may change with latitude. Aiming to provide reproduction evidence on S. apetala invasiveness from the perspective of fruit and seed properties, we conducted in situ observations of fruit and seed properties of 12 S. apetala populations across the latitudinal gradient from Haikou (19.60 degrees N) to Quangang (25.25 degrees N, current latitudinal limit for this species). Fruits per tree decreased with increasing latitude (R-2 = 0.47; p < 0.0001); fruit weight (R-2 = 0.28; p < 0.0001) and volume (R-2 = 0.27; p < 0.0001) varied quadratically relative to latitude. However, seed quantity per fruit, weight and volume were not correlated with latitude. The relationship between fruit and several climatic factors showed that mean annual precipitation, mean annual low temperature and mean annual irradiance had significant effects on these properties. Fruit floating percentages suggested decreases with time but was markedly site specific. Accordingly, the dispersing potentials were high in low latitude regions with small and light fruits but with big quantity; while they were weak in high-latitude regions where medium size fruits might resist the cold in winter. The mid-latitude sites with large fruits and great germination percentage resulted in good performance and establishment, where the species invasiveness should be noted.

Automated summary

The study conducted in situ observations of fruit and seed properties of Sonneratia apetala across a latitudinal gradient from Haikou to Quangang in southern China. It found that fruit quantity decreased with increasing latitude, while fruit weight and volume varied quadratically relative to latitude. Seed quantity, weight, and volume were not correlated with latitude. Climatic factors such as precipitation, low temperature, and irradiance had significant effects on fruit properties.