Sammendrag

A complete diallel cross was made among nine Betula pendula trees growing in a natural population and a trial was planted on agricultural soil at one site. This exceptional trial has provided estimates of genetic parameters that can only be estimated in complete diallels. Traits measured were height and diameter during a period of 37 years, and assessments were made of bud burst, leaf abscission and rust infection at the early ages. All traits showed genetic variation and the variance components of general combining ability (GCA) effects were dominating, with heritability estimates of 0.16 and 0.23 for height and diameter at age six years. The best-growing families could be identified at that age. At age 37 years, when the trial had been thinned twice, the offspring from the highest and lowest ranked parent for growth contributed with 19% and 6% of the total volume of the stand, respectively. The GCA effects were also highly significant for the assessment traits, but with an interaction with year for bud burst. High values of estimates of genetic correlations proved that bud burst, leaf abscission and rust infection are interrelated, and also to some extent with growth traits. Families with an early bud burst were tallest, were less affected by the rust fungus and kept their leaves later in the autumn.

Sammendrag

Temperature during seed maturation can induce an epigenetic memory effect in growth phenology of Norway spruce (Picea abies (L.) Karst.) that lasts for several years. To quantify the epigenetic modifications induced by natural climatic variation, common garden experiments with plants originating from different provenances and seed years were performed. Plants from warmer seed years showed delayed phenology with later bud flush, bud set and growth cessation. This effect was quantified by linear models of phenology traits as a function of climate indices for the origin and seed year of the plants. Significant effects of the temperature during seed production (seed year) was found for the bud set in seedlings in their first growing season and for bud flush and growth cessation in the 7th-8th growing season from seed. The models suggest that growth start and growth cessation are delayed 0.7–1.8 days per 100 additional degree days experienced by the seed during embryo development and seed maturation. Models that include factors that are known to induce epigenetic effects could be used to better predict future performance of forest reproductive material.

Til dokument

Sammendrag

Despite sophisticated mathematical models, the theory of microevolution is mostly treated as a qualitative rather than a quantitative tool. Numerical measures of selection, constraints, and evolutionary potential are often too loosely connected to theory to provide operational predictions of the response to selection. In this paper, we study the ability of a set of operational measures of evolvability and constraint to predict short‐term selection responses generated by individual‐based simulations. We focus on the effects of selective constraints under which the response in one trait is impeded by stabilizing selection on other traits. The conditional evolvability is a measure of evolutionary potential explicitly developed for this situation. We show that the conditional evolvability successfully predicts rates of evolution in an equilibrium situation, and further that these equilibria are reached with characteristic times that are inversely proportional to the fitness load generated by the constraining characters. Overall, we find that evolvabilities and conditional evolvabilities bracket responses to selection, and that they together can be used to quantify evolutionary potential on time scales where the G‐matrix remains relatively constant.