Annual variation in the topology of a southern California plant-pollinator interaction network

The past decade has seen a surge of interest in the study of plant-pollinator interaction networks. Several studies have described universal features of these mutualistic networks, including asymmetric specialization and nested community structure. However, there has been no attempt to document annual variation in community-scale patterns of species interactions, and to test whether such variation influences community structure. Here I present the results of a three year study of a montane meadow plant-pollinator community from southern California, and show that network topology varied, such that pollinators did not interact with plant species similarly across the three years. Furthermore, the composition of the “generalized” core group of species varied between years, as did the number and identity of those species involved in “specialized” relationships. However, the community remained highly nested across in all three years. These results suggest that nested community structure might be resilient to annual variation in plant-pollinator interactions, however the reproductive and evolutionary consequences of such temporal variation needs to be explored.