Bergmann’s Rule describes an increase in the body size of endothermic animals with decreasing environmental temperatures. However, in ectothermic insects including moths, some of the few existing studies investigating size patterns along temperature gradients do not follow the Bergmann’s Cline. Intraspecific differences in moth sizes along spatiotemporal temperature gradients are unknown from the Palaeotropics, hindering general conclusions and understanding of the mechanism responsible. We measured intraspecific forewing size differences in 28 Afrotropical moth species sampled in 3 seasons along an elevational gradient on Mount Cameroon, West/Central Africa. Size increased significantly with elevation in 14 species but decreased significantly in 5 species. Additionally, we found significant inter-seasonal size differences in 21 species. Most of these variable species had longer forewings in the transition from the wet to dry season, which had caterpillars developing during the coldest part of the year. We conclude that environmental temperature affects the size of many Afrotropical moths, predominantly following prevailingly following Bergmann’s Cline. Nevertheless, the sizes of one-third of the species demonstrated a significant interaction between elevation and season. The responsible mechanisms can thus be assumed to be more complex than a simple response to ambient temperature.

Animals respond to climatic change by adapting or by altering distributional patterns. How an animal responds is influenced by where it is positioned within its geographic range; the probability of extirpation is increased near range boundaries. Here, we examine the impact of Holocene climatic fluctuations on a small mammalian herbivore, the bushy-tailed woodrat (Neotoma cinerea), at five locations within south central Idaho and northwestern Utah. Previous work demonstrated that woodrats adapt to temperature shifts by altering body size. We focus here on the relationship between body mass, temperature, and location within the geographic range. Body mass is estimated by measuring fossil fecal pellets, a technique validated in earlier work. Overall, we find the predicted phenotypic response to climate change: animals were larger during cold periods, and smaller during warmer episodes. However, we also identify several time periods when changes in environmental temperature exceeded the adaptive flexibility of N. cinerea. A smaller-bodied species, the desert woodrat (N. lepida) apparently invaded lower elevation sites during the mid-Holocene, despite being behaviorally and physically subordinate to N. cinerea. Analysis of contemporary patterns of body size and thermal tolerances for both woodrat species suggests this was because of the greater heat tolerance of N. lepida. The robust spatial relationship between contemporary body size and ambient temperature is used as a proxy to reconstruct local climate during the Holocene.