CONICET | Buscador de Institutos y Recursos Humanos

Many contemporary theories on invasion success share the prediction that successful invaders are somehow fundamentally different from native species. MacDougall et al. (2009) propose that success can result from either fitness differences that favors the dominance of the invader, or niche differences that allow the invader to establish despite lower average fitness. Rather than stabilizing coexistence, such fitness differences drive competitive exclusion and can be approximated by species average growth rate differences. Based on MacDougalls model, we assessed these drivers of invasion success by comparing native and exotic woody plants both in terms of (1) niche differences (presence and abundance along environmental gradients of water and nutrients) and (2) functional traits predictors of relative growth rate (an indirect measurement of fitness) at the mountain woodlands of Córdoba. Our approach considered the dominant woody species in the study area. We found that there is a broad overlap in species distribution along gradients (low niche differentiation), but with strong differences in their functional attributes. Exotic species characteristics suggest an acquisitive strategy in resource uptake and water use (higher growth rates and competitive ability), while natives show more conservative attributes. Our results suggest that invasion success in the area is not related to niche differences but rather to morpho-functional differences linked to higher fitness. This likely higher competitive ability showed by the exotic species is expected to promote species replacement in the community. Moreover, if replacement of native by exotic species occurs, ecosystem fluxes such as the hydrological cycle might be altered.