Species in nature vary greatly in how specialized they are in resource use. For example, some predator species are extremely specialized, eating only one species of prey, while others are extremely generalized, feeding on many different species. Trade-offs in resource use are often thought to play a critical role in the evolution of specialized species, because an adaptation for the use of one resource may prevent the efficient use of another resource. The evolutionary importance of such trade-offs in generalist species that use many resources is not well understood. This research examines the importance of trade-offs in the adaptation of floral traits to different pollinators (an important resource for plant reproduction) in a generalist plant, wild radish (Raphanus raphanistrum), using measurements of selection on floral traits by individual pollinator taxa. If selection by one pollinator opposes selection by another pollinator, then this indicates a trade-off, because a plant cannot be well-adapted to both pollinators at the same time.
Floral adaptation to pollinators can have important consequences for reproduction and population growth in native species. In addition, many organisms such as pathogens, major agricultural weeds (such as wild radish), and invasive species are generalists. Therefore, results from this study will have broader impacts on our understanding of adaptation in economically, medically, and environmentally important generalist organisms.
