Plant species that bloom concurrently are often visited by groups of shared pollinators. This sets up a situation where either plants may be competing with each other to get pollinators services from insects, or they could be facilitating each other by attracting more pollinators. One plant species member of a group of co-flowering wildflowers in the Southern Sierra Nevada of California (genus Clarkia in the family Onagracea) is known to experience facilitation. Specifically, when the species Clarkia xantiana is found growing with other Clarkia, as opposed to on its own, it receives a greater number of pollinator visits. The question that then arises is how do these co-flowering species share pollinators?
By examining networks of plant-pollinator interactions of four Clarkia speciesat multiple sites, I asked the following questions:
I. Pollinator Resource Partitioning (a) Do co-flowering species partition pollinator resources? (b) Does co-flowering influence visitation rates?
II. Spatial and Temporal Variation in Plant-Pollinator Interaction Networks (a) Are temporal and spatial variation in the network of plant-pollinator interactions driven by biotic (plants or pollinators) or abiotic (rainfall, geographic location) factors? (b) Does the floral community composition influence specialization of plant-pollinator interactions?
III. Specialization of Plant-Pollinator Interactions (a) Is ecological specialization determined by floral morphology, floral community context, or relative abundance of flowers? (b) Are plants and flower-visitors mutually specialized? (c) Does the degree of specialization of plants or pollinators change from year to year?
Our results suggest that: (i) the four co-flowering species do, indeed, partition their pollinator resources based on floral shape and in part by forming exclusive interactions between species plant and bee pairs, (ii) Co-flowering does not necessarily result in higher visitation, (iii) spatial and temporal variation are predominantly driven by biotic factors, (iv) floral community composition does influence specialization, (v) ecological specialization is not determined by floral morphology or relative abundance of flowers, (vi) plants and their pollinators are, indeed, mutually specialized, and (vii) the degree of specialization of neither plants or pollinators is consistent from one year to the next.
Publications with more detailed results and analyses are in preparation. If you would like to see current manuscripts please contact me.