Variation in diet breadth and specialization fundamentally influences how species interact with the abiotic and biotic components of their environment. Consequently, understanding the drivers of this variation is key to understanding numerous ecological and evolutionary processes and will be an important component in developing predictive tools as ecological networks respond to environmental change. While certain theoretical underpinnings of the factors driving specialization have been established for some time, the recently gained investigative power derived from combining mechanistic theory of ecological networks with large data sets allows us to more concretely develop and test hypotheses. Using wild bees and plant-pollinator networks as our study system, we endeavor to extend the scope of such studies to include mutualistic interactions, an important consideration given global losses in pollinator populations. In our study, mechanistic models of adaptive foraging in pollinators are leveraged against intercontinental data sets of pollen loads on wild bees. Using this dual approach we specifically ask: how does organismal phenology interact with temporal resource density to drive specialization or generalization in foraging and consumption?
Results/Conclusions
Building upon recent advances in mechanistic modeling of plant-pollinator interactions, we modified the underlying structure of plant-pollinator networks to include temporal plasticity in their topology, mimicking the seasonal flux in plant-pollinator interactions. This is accomplished by assigning phenomenological functions to govern the phenology of both plant and pollinator natural history, thereby also regulating potential pollination interactions across time. Using this modeling framework, we modeled different types of resource seasonality by producing treatments with varying levels of temporal resource overlap. Results indicate that while temporal resource overlap plays little role in driving specialization in bees with extended foraging times, reduced overlap drives clear tendencies towards specialization as bee foraging times decrease. Theoretical results are corroborated empirically using pollen load data taken from shorter (genus Andrena) and longer (genus Lasioglossum) flight span bees across environments with both high and low temporal resource overlap. Overall, results indicate the important role that phenology can play in determining diet breadth and the structure of ecological networks.