Fundamental resource specialization of herbivorous butterflies decreases toward lower latitudes

Abstract

Revealing 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.

Environmental heterogeneity as a driver of terrestrial biodiversity on a global scale

“…Enquist et al (2019) indicated that climatic EH is the main driver of the global tree species abundance distribution, and more climatically stable regions have harbored rare species. The variation in resource specialization can shape the distribution pattern of terrestrial biodiversity for ground beetles, and climatic change can regulate the host breadth and morphology of ground beetles (Settele et al, 2012; Turlure et al, 2010; Nakadai et al, 2020). Thus, climatic EH could regulate terrestrial biodiversity, particularly for trees and ground beetles, which is consistent with our results.…”

Dataset of forewing length of Japanese and Taiwanese butterfly species

“…Forewing length can be regarded as an indicator of body size, which may constraint physiological parameters, such as resource exploitation and requirement (Hashimoto & Ohgushi, 2017), tolerance to environmental stresses (Clissold & Simpson, 2015), and dispersal ability (Chai & Srygley, 1990). Specifically, if researchers combined the information of this data paper with monitoring and census datasets including butterfly as a targeted taxa (e.g., the censuses of the National Survey of the Natural Environment and the Monitoring Sites 1,000 Project by the Ministry of the Environment in Japan), this data would provide opportunities to test biodiversity patterns across time and space (e.g., Nakadai et al, 2018;Nakadai, Nyman, Hashimoto, Iwasaki, & Valtonen, 2020). For example, the impact of climate change on geographical and phenological patterns of butterfly body size at the community-level can be tested.…”