Fleshy-fruited invasive shrubs indirectly increase native tree seed dispersal

VERGARA-TABARES, DAVID L.; BLENDINGER, PEDRO G.; TELLO, AGUSTINA; PELUC, SUSANA I.; TECCO, PAULA A.

OIKOS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022 vol. 2022

0030-1299

Biological invasions are one of the main threats to biodiversity and ecosystem functioningin the Anthropocene. Fleshy-fruited invasive plants establish mutualisticinteractions with native seed dispersers and may affect the mutualisms between nativepartners, negatively by disrupting plant dispersal through competition for seed dispersersor positively by facilitating seed dispersal via the attraction of fruit-eatinganimals. Moreover, the invaders? density in the neighborhood of native plants maymodulate the direction and/or magnitude of such effects on natives. In mountains ofcentral Argentina, the cessation of fruiting of the dominant native tree Lithraea molleoidesoverlaps with the beginning of the fruiting of invasive shrubs (Pyracantha spp.).This partial overlap allows for testing opposite predictions regarding the effect of invasivefruits on native seed dispersal. We compared frugivory by seed disperser birds onL. molleoides during non-overlapping and overlapping periods, at six sites that differedin Pyracantha shrub density (high, low and no-invasion). We counted frugivory during2 h on 15 individuals of L. molleoides at each site and period, totaling 360 h of observation.Frugivory on the native tree was similar among sites during the non-overlappingperiod and remained constant in both periods at non-invaded sites. At invaded sites,frugivory increased from non-overlapping to overlapping period and was greater athighly invaded sites. The resource provided by Pyracantha did not disrupt seed dispersalof the dominant native tree. Rather, it facilitated frugivory by seed dispersers andthis effect may be exacerbated with higher fruit availability of invasives. Our resultsprovide a counterview to the prevailingly negative impacts of invasive species on theseed dispersal of native species since the fruiting of invasive plants facilitated the seeddispersal of native species in a continental region contrasts with the mutualism disruptioncommonly observed in insular environments.