Abstracts (first author)
Genetic and phenotypic variation in developmental rate across geographic regions: a photoperiod driven latitude compensating mechanism?PDF
Genetic and phenotypic variation in developmental and growth rates along latitudinal gradients may benefit our understanding of the evolution of latitudinal compensating mechanisms. I explored compensatory developmental mecha¬nisms with respect to photoperiod in central, northern and northernmost peripheral populations of a damselfly Lestes sponsa. In addition, genetic variance in developmental and growth rate was evaluated across the populations. L. sponsa is strictly univoltine with egg overwintering throughout its geographic distribution. The role of photoperiod on the expression of larval development was evaluated under controlled laboratory conditions. Larvae from each region were grown in both high and low latitude photoperiod. All three populations shortened development time and accelerated growth as a response to high latitude photoperiod (phenotypic plasticity present). The slopes of reaction norms differed between populations. There was a genetic differentiation between populations and this resulted in a genotype-by-environment interaction in development time and growth rate. Genetic variance (Vg) in development time was significant, however it did not differ across populations. Vg in growth rate was non-significant. Reaction norms in development time and growth rate also showed non-significant Vg. Results supported the presence of countergradient variation in development time and growth rate as seasonally more time stressed populations took shorter time for development and grew faster than less time stressed populations. Slopes of reaction norms indicated that the latitude compensating mechanism was mediated by photoperiod. While growth rate seems to be genetically constrained for further evolution, development time has a potential to evolve, though, at a similar rate across study regions. Reaction norms seem to be canalized with respect to photoperiod.