Intraspecific spatial niche differentiation: Evidence from Phyllostachys edulis

Abstract

Interspecific niche differentiation has attracted much more attention than intraspecific niche differentiation. If the intraspecific competition of invasive species is greater than the interspecific competition, it should reduce the invasive abilities of invasive species. Thus, it is important to understand how invasive species avoid or reduce the intraspecific competition. Phyllostachys edulis in southern China is more competitive than many trees. After it invades a community, it can displace other trees. In the current study, we tested whether the different aged bamboo plants (aged two to eight in two-yr increments) exhibited spatial segregation (spatial niche differentiation). The study was performed in the Ecological Station of Dagang Mountain (114°30′∼114°45′E, 27°30′∼27°50′N), about 200km east from Nanchang City, Jiangxi province, China. We recorded the planar coordinates of all the plants with diameter at breast height (DBH) ⩾3cm. We used the conditional probability (type-specific probability) surface to show the spatial niche differentiation. We also compared the DBH of four aged groups of bamboo plants. We used the Shapiro–Wilk test to test the normality of DBHs of each age group. If DBHs did not follow the Normal distribution, we used the Weibull function to fit these data. Then we used the Kolmogorov–Smirnov test to test whether any two aged groups of DBHs came from the same population. At the end, we used the generalized additive models (GAMs) and a local regression model (LOESS) to explore whether there is a correlation between DBHs and the corresponding planar coordinates. We found that there was significant spatial segregation in four aged groups based on the statistical test. Bamboo plants may reduce their intraspecific competition by spatial niche differentiation. We found that the DBHs approximated the Weibull distribution, and there were very weak relationships between the DBHs and the spatial locations. We concluded that different aged bamboo plants exhibited spatial segregation and may reduce their intraspecific competition by spatial niche differentiation.