Eco-Evolutionary Dynamics of Generalist and Specialist Pollinators Facing Plant Diversity Changes

Changes in plant diversity and abundance due to land-use modifications can induce plant-pollinator trophic cascades, potentially leading to long-term shifts in pollination services. Our ability to mediate such loss of pollination services through informed landscape management is limited by insufficient understanding of long-term adaptations of wild pollinators to land-use, especially when accounting for rapid evolution of traits involved in plant-pollinator interactions. To address this issue, we here use a conceptual trait-based eco-evolutionary model to explore how shifts in plant abundance within agricultural landscapes affect: (1) pollinator populations through bottom-up cascades, and (2) plant populations through top-down effects of eco-evolutionary pollinator responses. Our results align with the expectation that specialist pollinators tend to be vulnerable to plant abundance changes over ecological timescales. This vulnerability is exacerbated by limited evolutionary adaptation of specialist pollinators. In contrast, generalists are more resilient to ecological change due to their broader tolerance and, notably, a better capacity for adaptive responses. Such adaptive responses can, however, lead to a significant loss of functional diversity, potentially outweighing the compensatory effects of evolutionary rescue in mitigating negative land-use change impacts. For specialists, the loss of functional diversity equals the loss of species diversity in our model. By contrast, the loss of functional diversity for pollinators with a more generalised feeding strategy, especially for moderate generalists, may exceed the loss of species diversity to the point that the functional properties of pollinators completely overlap. Our findings demonstrate how resource specialisation influences eco-evolutionary responses of pollinators to land-use changes. To ensure stable pollination services, conservation and landscape management strategies must account for limited adaptive capacity of specialists while acknowledging the risk of adaptive loss of functionality in generalists.