Photoperiod and variation in life history traits in core and peripheral populations in the damselfly Lestes sponsa

In order to predict evolutionary responses to environmental changes one needs to identify the evolutionary potential in terms of genetic variation of traits and of the traits' plasticity. We studied genetic variance in life history traits and their reaction norms in response to manipulated photoperiods in central, northern, and northernmost peripheral populations of the damselfly Lestes sponsa (Hansemann). After the central-marginal hypothesis, it is predicted that central populations will express the highest genetic variance. Northern and northernmost populations showed the highest development and growth rates. All populations expressed shorter development and accelerated growth when raised in a northern compared with a central latitude photoperiod. The slopes of reaction norms differed between regions resulting in a region-by-photoperiod interaction. There was genetic variation in development time; however, it did not differ across regions. There was no genetic variation in growth rate or in the plasticity of development time and growth rate to photoperiod. Results did not support the central-marginal hypothesis. However, evidence was found that the development time has the potential to evolve at similar rates across study regions. In contrast, the growth rate seems to be genetically constrained for further evolution, probably because of a strong past directional selection on this trait. The presence of low genetic variation in the slope of the reaction norms could be a result of stabilising selection imposed by seasonality.