Diet breadth has been linked to an array of ecological and evolutionary processes, including speciation and extinction, response to environmental change, nutrient cycling, and multi-trophic interactions. Global analyses have demonstrated significant variance in the breadth of hosts consumed by herbivorous species, in which narrow diet breadths are less common at higher latitudes. However, herbivores have traditionally been characterized as having highly specialized dietary niches, feeding from a single family or handful of species. Further, while the evolution of angiosperms has been credited with the diversification of consumer taxa, considerably less attention has been paid to the co-evolutionary dynamics associated with sister clades, like gymnosperms, that frequently co-occur in natural ecosystems. Here, we use a large scale, historic dataset of Lepidoptera host plant associations to quantify diet breadth for a highly generalized fauna. In doing so, we consider diet breadth in multiple dimensions and at multiple scales to assess the relationships between host plant use, functional traits, and network structure.
Results/Conclusions
We measure diet breadth for a total of 283 herbivorous species representing 20 families of Lepidoptera, a grand sum of 213,503 caterpillars. Across all herbivore species a total of 28 tree genera were recorded as host plants, including both angiosperm and gymnosperm taxa. The majority of herbivores were dietary generalists, whereas a relatively small subset (13%) specialized on two or fewer tree genera. Species from Erebidae were the most generalized herbivores, comsuming over 12 different tree genera on average and frequently feeding on both angiosperms and gymnosperms. Surprisingly, the ability to crossover and feed from angiosperms and gymnosperms was relatively common in certain families and contributed to an increase in network connectance among terrestrial ecozones.