Climate, species richness, and body size drive geographical variation in resource specialization of herbivorous butterflies
AbstractRevealing drivers of variation in resource specialization is a long-standing goal in ecological and evolutionary research. As a general prediction, the degree of resource specialization increases towards lower latitudes. Although herbivorous insects are one of the best-studied consumer groups, factors determining the degree of specialization on large spatial scales are poorly understood. Herein, we focused on the fundamental host breadth of 246 herbivorous butterfly species distributed across the Japanese archipelago. Using Bayesian Structural Equation Modeling based on information of pooled geographical occurrence and host use, we show that local butterfly communities tend to become more specialized towards higher latitudes, a pattern that is opposite to predictions from classical hypotheses. We also found that the pattern is mainly driven by factors related to climate, butterfly diversity, and body size in each community. Our results re-emphasize the importance of current climate as a regulating factor for butterfly host breadth and morphology.