Bee-mediated pollination is driven by the exchange of nutritional resources for pollen transfer. Therefore, the nutritional content of pollen (protein and lipid concentrations) may shape interactions with bees and co-flowering plant species. Our previous research indicated that high pollen protein:lipid ratios (P:L) shape bumble bee foraging choice. Other bee species likely vary in their preferred P:L, raising the possibility that within communities, groups of particular bee taxa may occupy nutritional niches. To understand how pollen nutrition connects plants and pollinators, we observed bee-flower interactions throughout the growing season in Sierra Nevada (NV, CA) wildflower communities along an elevation gradient from 1550-2850m. We systematically sampled pollen-collecting bees to create bee-flower visitation networks, analyzed host-plant pollen nutrition, and collected bees’ pollen loads to analyze nutritional foraging targets. From the networks, we asked if 1) plants offering similar pollen nutrition, or P:L values, shared bee visitors, 2) bees that collected similar pollen nutrition shared host-plant species, and 3) if specific groups of bees and host-plants that frequently interact form nutritional niches. Preliminary data from one site indicate that bees with similar nutritional targets share pollen host-plant species, yet plants with similar pollen nutrition did not necessarily share bee visitors. This finding offers new insight into how reward composition mediates indirect interactions between co-flowering species, and that bees may achieve preferred nutrition by visiting host-plants offering complementary nutrient rewards. This study presents a novel approach to understanding how nutritional rewards drive the dynamics of plant-pollinator communities, while providing a nutritional perspective for pollinator conservation.
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