Genetic lineages of the invasive Aegilops triuncialis differ in competitive response to neighboring grassland species

Abstract

Competitive dynamics between native and exotic species can influence both the success of exotics in the novel environment as well as diversity and abundance of native species. Invasive species are often characterized by multiple introductions in the novel range, which can lead to population differentiation for invasion characteristics. Here we use two invasive lineages of the exotic grass, Aegilops triuncialis L., to determine if these lineages differ in their response to competitors and in their persistence in the invaded range. We find that one lineage is negatively affected by competitor presence in both flowering phenology and reproductive output, while the other lineage shows no response in either trait. Furthermore, we find that the two lineages were introduced at different times and are each capable of replacing the other as the most abundant lineage of a given county. Our results demonstrate that genetic lineage is a more important determinant of competitive response than neighbor identity, and that the two lineages may employ alternate invasion mechanisms. Because management techniques are decided upon based on traits that confer invasiveness, our results highlight the importance of considering intraspecific variation in the invaded range.