Impact of climate on Odonata traits

Insects exhibit diverse colours between and within species that may function in thermoregulation, mate signalling, and predator-prey interactions. Variation in climate along latitudinal gradients may impact insects’ traits such as body size and colour. We quantified several phenotypic traits and asked whether variation in these traits can be explained by latitude and local climatic factors (temperature, precipitation, and humidity). We collected Australian odonate photographs from online databases, and measured colour and sexual dichromatism. Furthermore, we measured odonate body size and sexual size dimorphism. Bioclimatic variables were extracted from WorldClim and the Australian Government Bureau of Meteorology databases. Body size of odonates followed Bergmann’s (body size increases with latitude) and Rensch’s rule (sexual size dimorphism increases with body size when males are larger and decreases with body size when females are larger). We also found a significant correlation between precipitation and male body size. Moreover, body colour of odonates had no relationship with any of our predictors whereas precipitation, humidity, and body size were strongly correlated with sexual dichromatism. Overall, our study provides insight into how climatic factors relate to insect traits and will highlight the consequences of such variations under the changing climate.