ABSTRACT
Genetic analyses of forest tree populations indicate the presence of substantial spatial patchiness within these populations, even when they occupy relatively homogeneous habitats. This genetic heterogeneity is most likely the result of patterns of seed dispersal. In wind-dispersed species, seed dispersal tends to be relatively limited, and most seeds of a given parent tree tend to land and germinate nearby. Genetic analyses have been carried out in two ponderosa pine populations using electrophoretically-detectable variation at several protein loci. Both populations show significant spatial heterogeneity. For example, within a continuous ponderosa pine stand in Boulder Canyon, Colorado, all trees occupying an area of approximately two ha. were mapped, and their genetic constitution was determined for seven polymorphic loci. Patchiness has been documented in patterns of cone production and in analyses of monoterpene composition of the xylem oleoresin. The results indicate that there are significant differences among tree clusters in cone production and oleoresin amount and composition.
