Wed, Aug 17, 2022: 8:45 AM-9:00 AM
516B
Background/Question/MethodsPollination is often driven by the exchange of floral nutritional resources for pollen transfer. Bees for example rely on pollen as their main source of proteins and lipids for reproduction and development. Yet pollen protein and lipid quality vary widely between plant species, requiring bees to select their diet among the nutritional landscape. Our previous research hypothesized that host-plant pollen protein:lipid ratios (P:L) may shape broad patterns of bee species’ foraging behavior, and that groups of particular bee and host-plant taxa may occupy nutritional niches. To test this hypothesis, we observed bee-flower interactions in eight Great Basin and Eastern Sierra wildflower communities along an elevation gradient from 1550-2850m. We systematically sampled pollen-collecting bees to create bee-flower visitation networks, and chemically analyzed the protein and lipid concentrations of host-plant pollen from ~100 species, and pollen loads from ~80 bee species. We conducted PCA on the bee-flower interaction matrix, and using linear regression on their respective scores, asked 1) if plants offering nutritionally similar pollen share bee visitors, and 2) if bees collecting nutritionally similar pollen loads share host-plants. We then conducted a modularity analysis on the metanework to determine 3) if pollen nutrition of the bees and flowers differed between modules.
Results/ConclusionsWe found that the distribution of nutritional content of floral pollen was generally similar between sites, even with significant plant species turnover, indicating that wildflower communities offer similar nutritional landscapes across sites. Supporting our hypotheses, our metanetwork and subnetworks at each site across space and time indicate that plants offering similar pollen nutrition generally share a similar community of bee visitors, and that bees who collect pollen loads of similar macronutrient content tend to visit nutritionally similar host-plants. Yet the variation in bees’ pollen foraging strategies indicates that they can exhibit foraging flexibility among host-plants to balance the macronutrient profile of their pollen collection. Strikingly, the major modules of our metanetwork are delineated by plant species and bee species with similar pollen P:L within, and distinct differences in P:L between modules. This is the first evidence that major interacting partners in bee-flower visitation networks can exhibit distinct nutritional niches over space and time. This finding offers new insight into how reward composition at the community level mediates bee foraging strategies and interactions between co-flowering plant species. This study presents a novel approach to understanding how the macronutrient content of floral rewards drives the dynamics of plant-pollinator communities.
Results/ConclusionsWe found that the distribution of nutritional content of floral pollen was generally similar between sites, even with significant plant species turnover, indicating that wildflower communities offer similar nutritional landscapes across sites. Supporting our hypotheses, our metanetwork and subnetworks at each site across space and time indicate that plants offering similar pollen nutrition generally share a similar community of bee visitors, and that bees who collect pollen loads of similar macronutrient content tend to visit nutritionally similar host-plants. Yet the variation in bees’ pollen foraging strategies indicates that they can exhibit foraging flexibility among host-plants to balance the macronutrient profile of their pollen collection. Strikingly, the major modules of our metanetwork are delineated by plant species and bee species with similar pollen P:L within, and distinct differences in P:L between modules. This is the first evidence that major interacting partners in bee-flower visitation networks can exhibit distinct nutritional niches over space and time. This finding offers new insight into how reward composition at the community level mediates bee foraging strategies and interactions between co-flowering plant species. This study presents a novel approach to understanding how the macronutrient content of floral rewards drives the dynamics of plant-pollinator communities.