Data for: Beyond latitude: Temperature, productivity, and thermal niche conservatism drive global body size variation in Odonata

Aim: So far, latitudinal body size-clines have been primarily discussed in the context of thermoregulation, sensu Bergmann. However, body size patterns are ambiguous in ectotherms and this heterogeneity remains poorly understood. We tested whether Bergmann’s rule and the resource availability rule which states that energetic requirements determine species’ body size, apply to damselflies and dragonflies (Odonata). Furthermore, we hypothesised that the contrasting effects of thermoregulation and resource availability (e.g. productivity) can obscure the overall gradient in body size variation. Location: Global Time period: Contemporary Major taxa studied: Odonata Methods: Using data for 43% of all odonate species described so far, we tested our hypotheses in phylogenetically and spatially comparative analyses at assemblage and species level. For the distribution data, we integrated expert range maps and ecoregional ranges based on all available occurrence records. To distinguish between long-term versus evolutionarily recent responses of environmental drivers in body size, we constructed a phylogenetically informed classification of all odonate species and decomposed the body size into its phylogenetic and specific component for our subset of species. Results: We documented a weak positive relationship between body length and latitude but found strong and contrasting effects for temperature between dragonflies and damselflies and consistent positive effects for productivity that explained 35%–57% of body size variation. Moreover, we showed a strong phylogenetic signal in sized-based thermoregulation that shaped the distribution of dragonflies, but not of damselflies. Main conclusion: We concluded that temperature, productivity, and conservatism in size-based thermoregulation synergistically determine the distribution of ectotherms, while the taxon-specific importance of these factors can lead to contrasting results and weak latitude–size relationships. Our results reinforce the importance of body size as a determinant of species distributions and responses to climate change.