Clines in ecologically important traits across environmental gradients provide evidence of historical natural selection. Arabidopsis kamchatica ssp. kamchatica (Brassicaceae) is a perennial herb and is distributed widely along altitude (30 - 3000m) in the Japanese Alps. However, its subspecies kawasakiana is an annual herb and lives only under 100m. To understand ecological and physiological basis of altitudinal adaptation, we studied altitudinal cline in life-history and hervivory-defense traits for total 38 populations of those subspecies in and around several mountain regions of the Japanese Alps, by laboratory common-garden experiments.

We found altitudinal clines in many traits including flowering and germination timing; flower, seed and trichome production; and glucosinolate concentration. These results clearly indicate that various traits have been adapted to altitude by historical natural selection, and facilitate our understanding to the biological mechanism of altitudinal adaptation. We have already exploited the advantage of the close relation of the focal species to the model plant A. thaliana for studying genetic basis of adaptation in those traits and Hirao et al. will present the recent results elsewhere.