Data from: The global distribution of diet breadth in insect herbivores

Understanding variation in resource specialization is important for
progress on issues that include coevolution, community assembly, ecosystem
processes, and the latitudinal gradient of species richness. Herbivorous
insects are useful models for studying resource specialization, and the
interaction between plants and herbivorous insects is one of the most
common and consequential ecological associations on the planet. However,
uncertainty persists regarding fundamental features of herbivore diet
breadth, including its relationship to latitude and plant species
richness. Here we use a global dataset to investigate host range for over
7,500 insect herbivore species covering a wide taxonomic breadth and
interacting with more than 2,000 species of plants in 165 families. We ask
whether relatively specialized and generalized herbivores represent a
dichotomy, rather than a continuum from few to many host families and
species attacked, and whether diet breadth changes with increasing plant
species richness towards the tropics. Across geographic regions and
taxonomic subsets of the data, we find that the distribution of diet
breadth is fit well by a discrete, truncated Pareto power law
characterized by the predominance of specialized herbivores and a long,
thin tail of more generalized species. Both the taxonomic and phylogenetic
distributions of diet breadth shift globally with latitude, consistent
with a higher frequency of specialized insects in tropical regions. We
also find that more diverse lineages of plants support assemblages of
relatively more specialized herbivores, and that the global distribution
of plant diversity contributes to, but does not fully explain, the
latitudinal gradient in insect herbivore specialization.