Using Adapted Native Communities to Manage Established Invasive Plants

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Invasive plants often benefit from a change in eco-evolutionary context, escaping herbivores, pathogens and competing plants from their home range. Introduced into naïve native communities, they can spread rapidly, threatening native plant diversity and ecosystem functioning. Increasingly, studies have shown that native species sometimes adapt in response to the selection pressures imposed by an invasive plant. Here, we explore the concept of using these adapted native species to accelerate the evolutionary response of invaded native communities. Our target species was the invasive forb Verbena brasiliensis, which was introduced to Gulf and mid-Atlantic coasts more than a century ago and since has spread throughout the South-Central United States. We hypothesized that the longer V. brasiliensis was present in an area, the greater the likelihood of adaptation by co-occurring native species. Through a series of greenhouse studies, we showed that competition with V. brasiliensis reduced the growth of a group of co-occurring plants by 18% to 86%. One of the mechanisms of the invasive plant’s dominance was its ability to leverage an increase in available nutrients into much faster growth. We identified several soil microbial communities that suppressed the invasive plant’s growth, but their effectiveness faded when introduced into background soils with existing microbial communities. Similarly, we found that while native plant species from some locations were able to compete more effectively with V. brasiliensis than others, when the species were assembled into small native communities, the advantage did not always persist. Finally, contrary to our expectations, the distribution of adapted native communities did not fit the chronosequence of the invasive plant’s spread that we constructed from herbarium data. Our results show how shifts in community context can prevent the benefits of adapted native species from being effective when transported to new locations. The issue not only presents a practical challenge to using adapted native communities in invasive species management, but it also suggests a reason why some invasive plants persist. While adapted native species may emerge in some locations, changes in community context may prevent them from spreading readily.

Invasive plants, Eco-evolutionary dynamics, native adaptation, Verbena brasiliensis, invasive species management