Invasive species are well known to have a variety of negative ecological impacts on native ecosystems. Reduction in the abundance and diversity of native species is a commonly reported negative impact by invasive species. While the impacts of invasive plants have been well documented to affect community-level inter-specific diversity, relatively few studies have examined their impact on population-level intra-specific diversity. Here we examine the impact of an invasive plant on the intra-specific diversity of a native dominant plant in a mixed grass prairie ecosystem. Little bluestem (Schizachyrium scoparium) is a commonly occurring graminoid in the mixed grass prairies of the southern Great Plains, an ecosystem invaded by the exotic King Ranch bluestem (Bothriochloa ischaemum). We specifically asked: (1) Does an invasive grass negatively impact the abundance of a native grass? (2)How do changes in native grass abundance affect intra-specific trait variation and diversity? We quantified the impact of B. ischaemum on the abundance and functional trait diversity of S. scoparium across a gradient of invasion.
Results/Conclusions
We found that the invasive grass Bothriochloa ischaemum had a significant negative effect on total abundance of the native grass Schizachyrium scoparium (R2 = 0.47, p = 0.0065). Additionally, the presence of the invader had a negative effect on the height of the natives growing nearby (R2 = 0.12, p = 0.031). There was no effect of B. ischaemum invasion on the other functional traits (specific leaf area and leaf dry matter content). Further, B. ischaemum invasion did not influence the variance of native S. scoparium traits, nor was there an effect on the trait composition of S. scoparium across the invasion gradient. These results suggest that while invasive B. ischaemum negatively impacts the abundance of native S. scoparium, there is no effect on the intra-specific variation and diversity of invaded versus uninvaded plots.