Niches of nine mangrove species in a -colonized area of Dongzhai Harbor, Hainan Island, China.

The distribution of mangroves is influenced by the environment. We aimed to understand the ecological adaptability of various mangrove species within the range of the exotic species, Buch.-Ham., in Dongzhai Harbor, Hainan Island, China. We used three niche breadth indexes (Simpson, Levins, and Shannon-Weiner) and two niche overlap indexes (Pianka and Levins) to quantitatively determine the niche characteristics of nine mangrove species. The results showed that the order of the niche breadth values of mangrove species was as follows: (Linn.) Blanco >  Sheue et al. >  (L.) Poir. >  (Forsk.) Vierh. Hailanci >  >  (L.) Engl. > a Griff >  (Perr.) C. B. Rob. >  (Lour.) Poir. Pearson correlation analysis revealed that the niche breadth of each population was significantly correlated with the importance value of the population in the whole sample (R = R = 0.771, R = 0.644,  < .05). The nine mangrove species were divided into three groups by Bray-Curtis cluster analysis; the groups were similar to the distribution of mangrove species in the natural state as determined by tide level. Niche similarity analysis showed that the niche similarity of most mangroves ranged between 0.5 and 0.8 and that the species pairs -, - and were characterized by large niche similarity ratios. Although it had a moderate niche breadth, had a relatively broad niche overlap with mangroves in the mid- and low-tide zones (, , , and ), a moderate overlap with and , only a slight overlap with , and no overlap with . There was no obvious linear relationship between niche width and niche overlap of mangroves. Due to its inefficiency in utilizing certain resources and relatively high degree of resource selection, it seems likely that will not pose a threat to the survival of native plants, let alone completely replace native species.