Abundance-asymmetry in conspecific aggregation and interspecific interaction

Abstract

In natural communities, species abundance has intrinsic associations with spatial pattern of species and interspecific interaction. However, how these associations contribute to species coexistence remains largely controversial. We expect that common species suffer stronger interspecific competition, which limits their population growth rates. Rare species tend to increase strength of intraspecific competition relative to interspecific competition via stronger aggregation than common species, which facilitates their coexistence with other species. To test this hypothesis, we examined interspecific interaction and conspecific aggregation for adult trees (DBH≥ 10 cm) in a 25-ha forest dynamics plot in Changbaishan, northeast China, and further evaluated their relationships with species abundance. Our results showed that interspecific spatial associations were mostly negative, and common species showed more significant repulsion than rare species, which indicated obvious abundance-asymmetry in interspecific association. In addition, the abundance-dependent conspecific aggregation contributed to abundance-independent local dominance among species via adjusting the proportion of conspecific vs. heterospecific trees at local scale (~5 m), which would facilitate the coexistence between rare and common species. These results suggest that the strength of interspecific interactions in community-level mainly depends on common species, and the prevalent conspecific aggregation in plant communities is crucial to the survival of rare species and long-term species coexistence. Our study uncovers the underlying coexistence mechanisms about the abundance-dependent spatial distribution of species, and provides further insights into the community assembly rules in temperate forests.