Plant-plant interactions in a subtropical coastal community

Abstract

In subtropical coastal dune ecosystems, biotic interactions can play a pivotal role in shaping species distribution patterns and community dynamics. We evaluated the influence of three dominant shrub species on plant species richness, plant abundance, and community composition, assessing their interaction roles (facilitation, neutrality, interference) in plant communities in southern Brazil. We selected 15 isolated individuals of each of the three most common shrub species in this environment, Guapira opposita, Dodonaea viscosa and Vitex megapotamica. We sampled all woody plants and bromeliads both under the canopy of each individual of the three shrub species and in a paired open site near each shrub. We compared species richness, plant abundance, and interaction strength between the two microhabitats (under the canopy and open area). Plant abundance and richness were higher under the canopy of G. opposita, indicating its role as a facilitator. V. megapotamica exhibited mild facilitation, with a small effect on abundance and no effect on richness, while Dodonaea viscosa acted as an interferer, with lower pant abundance under its canopy than in open sites. Community composition differed among shrub species and open sites, as well as across different shrubs. Our study reveals a wide spectrum of plant-plant interactions influencing plant community structure and dynamics..