From individuals to communities: How singleton invasive pine saplings lead to biodiversity change in the Brazilian Cerrado hotspot

Abstract

AbstractQuestionsHow do newly established species interact with existing assemblage members to alter local biodiversity? This question is especially topical given growing concerns about increased temporal turnover levels relative to background rates. Pine (Pinus spp.), a major invasive taxon in the Southern Hemisphere, is progressively dominating remaining fragments of the Brazilian savanna (Cerrado), a biodiversity hotspot. Because the Cerrado's diversity is linked to habitat heterogeneity we argue that the impact of these invasive singleton pines will be mediated by differences in local habitat structure. Here we use isolated invasive pines (Pinus elliottii) in the Cerrado as a study system to test the prediction that changes in the diversity of native communities, in the presence of newly established exotic individuals, will be greatest in the dominant vegetation layer of a habitat.LocationItirapina Ecological Station, southeast of Brazil.MethodsWe used a stratified random survey in 5 m × 5 m pairs of plots invaded by a single pine individual, each matched by control uninvaded plots; both shrub and grass vegetation layers were sampled in both habitats. In total, 300 plots were sampled, 114 in the shrub‐dominated campo sujo and 186 in the grass‐dominated campo úmido.ResultsOver 400 plant species were recorded. In both habitats, we detect marked shifts in species richness of the dominant vegetation layer. In line with our prediction, the nature of these changes is mediated by local habitat structure. We find significantly reduced species richness in the shrub layer of the shrub‐dominated habitat, but elevated species richness in the grass layer of the grass‐dominated habitat in invaded sites (vs. control). In the grass layer of campo úmido, pine initially decreases dominance thus allowing more species to colonize the plots.ConclusionsThe shape of the diversity vs. establishment time relationship is layer‐dependent, with a significant relationship between dominance/evenness and pine size in the grass layer but no relationship in the shrub layer. Our results show that, although complex, the consequences for local biodiversity of non‐native species establishment are not haphazard and thus contribute to the understanding of species co‐existence.