Landscape fragmentation and agricultural context impact pollination services to native annual plants in critically endangered Australian woodlands

Abstract Context Agricultural intensification leads to habitat loss and fragmentation, disrupting plant-pollinator interactions directly and indirectly, through changes in landscape configuration and altered land-use practices. This has detrimental consequences for the persistence of plants, pollinators, and the ecosystem services they provide. Objectives We investigated the drivers by which landscape and agricultural context (what crops are being grown) impact pollination services and the reproductive success of native plant species in remnant vegetation within an agricultural mosaic landscape. Specifically, we evaluate the direct and indirect effects of landscape fragmentation (remnant size and edge effect) and the crop type adjacent to natural remnants on bee communities and native plants’ seed production. Methods We combined bee community surveys with field pollination experiments on four native annual plant species in core and edge remnants in the York gum-Jam woodlands of SW Western Australia, an endangered ecosystem. For each remnant, we recorded remnant size, adjacent crop type (canola or wheat), and local community predictors (floral abundance, canopy cover, and organic ground cover). We assessed how landscape and local community predictors influence bee communities and reproductive success in our focal plant species, to evaluate variation in pollination services across highly fragmented and isolated vegetation remnants. Results Bee abundance was higher in remnants adjacent to canola than wheat. Native bee abundance decreased, however, from the core to the edge of remnants adjacent to canola (but not wheat), suggesting a possible pollinator dilution effect next to flowering canola fields. Canola directly and indirectly increased seed production of the focal plant species, mediated by changes in bee abundance. Species-specific responses at the local scale resulted in higher pollen limitation in areas with abundant floral resources and low bee abundance. Conclusions Adjacent crop type, position within remnants, and remnant size are all associated with variation in bee abundances and plant reproduction. At local scales, variation in floral abundances relates to pollination services. Our findings indicate that adjacent crop type, combined with the abundance of bees (generalist insect pollinators) in remnant vegetation, impacts the reproductive success of native plants persisting in remnants of an endangered annual plant system within an intensively managed agricultural landscape.