Plant reproductive success in highly fragmented Valais vineyard landscapes: a quasi-experimental approach

Abstract

The ongoing intensification of agriculture has led to habitat loss, degradation and fragmentation with their concomitant negative effects on biodiversity. For plant populations relying on pollinators those processes are expected to have severe effects on individual fitness due to limited pollinator numbers or reduced accessibility in isolated habitat patches. Intensively managed vineyards represent an ideal study system due to their near-binary habitats (vineyards with and without ground vegetation) and their high variation in habitat configuration on a landscape-scale. Here we investigated the effects of habitat quality and the degree of habitat fragmentation on fitness-related variables in four plant species (Lotus corniculatus, Trifolium pratense, Centaurea jacea and Sinapis alba) and the relationships with pollinator abundance. Habitat quality, i.e. the amount of ground vegetation significantly affected pollinator visitation rate and reproductive success of plants. Interestingly, habitat amount and the degree of fragmentation had no detectable effects on plant reproductive success, most likely due to the high mobility of pollinator species. Overall these results indicate that the reproductive success of a plant is mainly determined by local habitat quality, i.e. the local management of a vineyard, and to a lower degree by factors acting on the landscape scale.