A native annual forb locally excludes a closely related introduced species that co-occurs in oak-savanna habitat remnants.

摘要: Despite the ubiquity of introduced species, their long-term impacts on native plant abundance and diversity remain poorly understood. Coexistence theory offers a tool for advancing this understanding by providing framework to link short-term individual measurements with population dynamics directly quantifying niche average fitness differences between species. We observed that pair closely related functionally similar annual plants different origins-native Plectritis congesta Valerianella locusta-co-occur at community scale but rarely local direct interaction. To test whether and/or preclude local-scale coexistence, we parameterized models competitor results from controlled outdoor pot experiment, where manipulated densities each evaluate hypothesis exhibit environmental dependency, leading community-scale coexistence despite competitive exclusion, replicated experiment water availability treatment determine if key limiting resource alters prediction. Water impacted vital rates intensities intraspecific versus interspecific competition P. V. locusta. influence our model predicts competitively excludes locusta in across conditions because an absence stabilizing combined difference fitness, although advantage weakens drier conditions. Further, field data demonstrated have negative effect seed conclude limits abundances direct-interaction scale, posit may rely spatially dependent mechanisms maintain site scale. In outcome study demonstrates mechanistically how species limit invader.