Much of ecology has been concerned with understanding the patterns of diversity, species interactions, and the mechanisms underlying species coexistence. In novel ecosystems, for example, understanding the seemingly stable coexistence of native and exotic species has gained importance in light of rapid environmental change. There is increasing evidence to suggest that facilitation, specifically ant-plant dispersal mutualisms, affects plant community structure by influencing seed recruitment, competition, local diversity, and possibly coexistence. However, it could be argued that these mutualisms may also be facilitating the invasion of exotic plants into native communities by disturbing soils and/or dispersing exotic seeds. To address this, a two-year study was conducted in the herbaceous understory of York gum-jam woodlands in the Southwest Western Australian Ecoregion. These communities are composed of a mosaic of annual forbs and grasses of native and exotic origin and face growing threats from fragmentation, native species removal, and extensive land-use change. Field surveys were conducted during the 2016 and 2017 winter and spring growing seasons (July to September) in three remnant reserves. Understory communities along the edge (typically high abundance of exotic plant species) and within the core (typically less invaded) of reserves were surveyed to characterize ant and plant communities. Above ground ant nests and adjacent, undisturbed plots were then opportunistically surveyed and mapped within these areas. Species composition and the proportional abundance of vegetation growing on nests were recorded within quadrats. The distance between “nest” and “non-nest” quadrats was standardized according to nest size. Soil was sampled within each quadrat to quantify differences in the soil profile of nests and undisturbed soil.
Results/Conclusions
Preliminary data analyses showed that species richness and diversity of vegetation growing on ant nests are higher compared to vegetation on undisturbed soil. Additionally, plant communities on ant nests had a higher proportion of exotic species compared to adjacent, undisturbed plots, suggesting that ants may be playing a role in facilitating the introduction of exotic plant species into the reserve. In systems where native and exotic plant species are stably coexisting, understanding the mechanisms contributing to this coexistence is vital. Understanding the processes by which species diversity is maintained and identifying the subsequent changes in ecological interactions involved in the formation of novel communities is crucial, as these communities may be an inevitable consequence of global environmental change.