Beyond latitude: Temperature,productivity and thermal niche conservatism drive global body size variation in Odonata |
| |
Authors: | Laura Anna Mähn Christian Hof Roland Brandl Stefan Pinkert |
| |
Affiliation: | 1. Department of Animal Ecology, Faculty of Biology, University of Marburg, Marburg, Germany;2. Terrestrial Ecology Research Group, Department of Life Science Systems, TUM School of Life Science, Technical University of Munich, Freising, Germany;3. Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA |
| |
Abstract: | Aim So far, latitudinal body size clines have been discussed primarily 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 hypothesized 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 levels. For the distribution data, we integrated expert range maps and ecoregional ranges based on all available occurrence records. To distinguish between long-term and 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 components 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 conclusions 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 and weak latitude–size relationships. Our results reinforce the importance of body size as a determinant of species distributions and responses to climate change. |
| |
Keywords: | Bergmann's rule body size comparative analysis ecogeographical rule ectotherm niche conservatism Odonata resource availability thermoregulation trait–environment relationship |
|
|