Population differences in early life-history traits in grayling

In this paper we test population differences in early life-history traits i n three grayling Thymallus thymallus populations. The grayling shared ances tors some 80-90 years ago. We performed common-garden experiments at three temperatures (mimicking population-specific summer temperatures), and measu red survival and growth rates during early development. We found significan t additive genetic variance in size (length and yolk-sac volume) measured a t hatching, swim-up and termination of the experiment, and significantly di fferent reaction norms for growth rate and survival during the period of fi rst feeding. In general, each population did best at the temperature experi enced in nature. These differences in early life-history traits suggest tha t natural selection has resulted in local adaptation in a time period of 13 -18 generations.