Invasive Prosopis associated with large, but idiosyncratic, ecosystem changes and loss of native biodiversity across India

Non-native invasive species can have strong negative impacts on biodiversity and ecosystem processes across spatial scales. However, comprehensive understanding of the impacts of non-native plant invasions is biased by a disproportionate focus on individual components of complex impacts at small spatial scales. Thus, evaluating the impacts of invasive species across climate gradients and diverse biogeographic regions is exceptionally valuable. Our goal was to determine if different facets of community and ecosystem impacts of a global invader are consistent and correlated with each other across a wide range of ecosystem types. We quantified and integrated measurements of the characteristics of stands of woody perennials, understory soil properties, and understory vegetation related to the impact of the globally invasive tree, Prosopis juliflora, across a large rainfall gradient in India. We sampled seven sites in tropical deciduous forest, savanna, and shrub biomes invaded by Prosopis across India. Substantial decreases in native plant richness were consistently associated with Prosopis invasion, but Prosopis increased non-native plant richness and biomass, consistent with invasional meltdown. However, other than richness, most impacts on communities and ecosystem properties were highly variable among sites and path analysis revealed highly variable connections among stand structure, soil characteristics, and climate. Our regional scale patterns indicate that Prosopis has substantial but idiosyncratic impacts on native ecosystems and communities, and that different components of impact are poorly integrated. These results contribute to understanding of the highly variable impacts of even an exceptionally dominant invader, but experimentally identifying the mechnisms that underpin these impacts might be needed to extract generality from its conditional effects.