Genetic variability in two tree species, Acer platanoides L. and Betula pendula roth, with contrasting life-history traits

Genetic variation in adjacent Nordic populations of Acer platanoides L. and Betula pendula Roth was assessed by allozymes and in growth and phenology traits of juvenile trees grown in two field trials, and in growth chambers with free or restricted nutrient access. The objectives, based on the difference in the species' life-history traits, were to test the following hypotheses: (1) the population differentiation is higher in A. platanoides; (2) the genetic variability and (3) the phenotypic plasticity are larger in B. pendula. Analyses of variance revealed that, except for budburst, the growth and phenology traits generally supported the first hypothesis. The estimates of the coefficients of additive variance consistently disagreed with the second hypothesis. Allozyme data also supported the first hypothesis, but not the second. Finally, the phenotypic plasticity was larger in B. pendula.