What is the basis for mortality in infested pinyon pine trees?

Abstract

The rise in mortality in the population of pinyon pine trees ( Pinus edulis) in the southwestern area of Colorado has resulted in an almost 1 O year study in attempt to determine the basis for the increase in the death of some of these trees. It was discovered that these trees were under an insect infestation, namely by the mountain pine beetle, Dendroctonus ponderosae. The general supposition for the susceptibility of the infested individuals was that the mortality had some genetic basis. This hypothesis was a result of an ecological assessment of the study sites that showed the existence of healthy trees adjacent to infested trees. Thus, in order to obtain some data to support this hypothesis, starch gel electrophoresis was employed. The polymorphic enzymes, 0-glycerate dehydrogenase and peroxidase, that were extracted from pinyon pine needles, were used as arbitrary, genetic markers. It was expected that healthy pinyon trees would be a heterozygous banding pattern, since heterozygosity had, in many cases, been correlated with the successful individuals within a given population. On the other hand, the infested trees were expected to be a homozygous for the same markers. In this particular study, this correlation between the genotype and the health of resistant and susceptibility pinyon individuals was not established. It was possible that there might not be a correlation, rather other factors, for example water stress, may have attributed to the rise in mortality.