Intensive land-use and high native fruit availability reduce fruit removal of the invasive Solanum mauritianum in South Africa

Abstract

Invasive plant species threaten ecosystems worldwide. Management of invasive plants considerably benefits from an understanding of the processes that drive invasive spread, like seed dispersal. In the subtropics, many invasive species rely on vertebrate frugivores for dispersal. In turn, frugivore distribution across the landscape depends on habitat and fruit availability. Therefore, the loss of habitat owing to land-use change, and low fruit availability may reduce the local frugivore abundance and thereby impact invasive fruit removal and spread. However, the interplay among these factors remains poorly understood. In the intensively used agricultural landscape in KwaZulu-Natal, eastern South Africa, we investigated the effects of land-use and native and invasive fruit availability on frugivore abundance and analyzed how potential changes translate into fruit removal rates of the invasive fleshy-fruiting shrub Solanum mauritianum Scopoli (Solanaceae). Increasing land-use intensity reduced frugivore abundance, which in turn reduced fruit removal rates of the invasive species. Increasing native fruit availability did not influence frugivore abundance, but reduced fruit removal rates of S. mauritianum, indicating a fruit preference of frugivores for the simultaneously fruiting native species. In conclusion, fruit removal of the species is highest in locations with low land-use and low native fruit availability. Thus, these areas should be priority areas for invasive species management. Additionally, plantings of native fruiting species may provide alternative preferred food resources, reduce invasive fruit removal and ultimately improve invasive species management.