Mode of Colonization and Patterns of Life History in Some North American Conifers

Abstract

The predictions of the optimality models by Stearns and Crandall, on the relationship between colonization and life history patterns in forest canopy species were examined on thirty-four coniferous forest tree species of North America. Data on several life historical traits such as, age of flowering, seed size, interval between large seed crops, life span, and maximum height were analyzed using analysis of covariances and phenotypic correlations. The results suggested that colonizing (pioneer) species had larger seeds and shorter life span; while, non-colonizing (climax) species had smaller seeds and longer life span. These results largely supported the theoretical conclusions of Stearns and Crandall. It is hypothesised that the association and divergence, both in life history and colonization patterns among coniferous forest tree species might have occurred as a result of competition for light under the forest canopy, leading to major shifts in the ontogenetic pathways during the evolutionary history of the genera.