Modeling the relative importance of ecological factors in exotic invasion: the origin of competitors matters, but disturbance in the non-native range tips the balance

SA XIAO; RAGAN M. CALLAWAY; RYAN GRAEBNER; JOSÉ L. HIERRO; DANIEL MONTESINOS

ECOLOGICAL MODELLING

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 335 p. 39 - 47

0304-3800

Successful exotic plantinvasions are likely to be caused by multiple, non-mutually exclusive mechanisms,and it is exceptionally difficult to weight the relative importance of these mechanisms identified in differentexperiments. To this end we used individual-based models to explore how integrating empiricalresults from experiments might help to elucidate the relative importance of seed origin, biogeographicdifferences in competitive outcomes, and disturbance in exotic plant invasion. We integrated resultsfrom (1) competition experiments between Centaurea solstitialis derived from populations in the nonnativerange (California), the native range (Spain), and co-occurring native species from both ranges, (2)seed production by Centaurea plants from the different ranges grown in a common-garden environment,and (3) responses to disturbance experiments with plants from different native and non-native ranges.Californian C. solstitialis reached slightly higher abundances than its Spanish counterparts in every scenario,mainly due to higher seed production of Californians than their Spanish conspecifics, indicating thepotential importance of evolutionary changes in the non-native range. In the absence of disturbance, grassspecies native to Europe showed stronger competitive effects on C. solstitialis than grass species nativeto North America, suggesting that release from competition in the native range may have some explanatorypower for successful C. solstitialis invasion. However, the intensity of competition depended on thedisturbance regime used in models. When intense disturbance was incorporated into the model, C. solstitialiswas favored, with plants from Californian seed sources reaching higher densities than plants fromSpanish seed sources. Our results are consistent with the idea that disproportional positive responses todisturbance in California, relative to those in the invader?s native range of Spain, may be an importantfactor in the dominance of C. solstitialis in its non-native ranges. It is not clear why disturbance wouldhave more beneficial effects on the invader in its non-native range, but the powerful effects of disturbanceappear to interactin subtle ways with biogeographic differences in evolutionary trends, competitiveintensities, life histories, and reproductive rates.