Water temperature drives local variability in the life cycle of Onychogomphus forcipatus (Odonata: Gomphidae) in a Mediterranean river

Geographic variation in life history traits of dragonflies has been extensively studied, mainly along latitudinal clines, but life history variation at a local scale has received less attention. We describe the life cycle differences between two populations of Onychogomphus forcipatus unguiculatus (Odonata: Gomphidae) located in close proximity in a small Mediterranean river basin in the northeast of the Iberian Peninsula. While the larval growth pattern recorded in the middle course of the river showed an exclusively univoltine pattern, the one found in one of its tributaries revealed a mixed pattern of uni- and semivoltinism. The difference in water temperature between these sites, especially during the cold months, is probably the environmental factor underlying the differences in voltinism. Given the spatial proximity between the two populations, 7.5 km apart on a straight line, our finding suggests phenotypic plasticity of this taxon as the mechanism of adjustment of its life cycle to small variations in water temperature. Overall, our results may help to understand how this species can respond to variations in water temperature under climate change or other human-mediated impacts.