Genetic differentiation and heterozygosity in pinyon pine associated with resistance to herbivory and environmental stress

At Arizona's Sunset Crater Pinus edulis colonizing the cinder fields are faced with a highly stressful environment. Many of these pinyons suffer chronic, intense insect herbivory that reduces plant growth and eliminates female cone production. Herbivory among pinyons growing in neighboring sandy-loam soils is minimal. Numerous trees within the heavily infested cinder field population suffer relatively low herbivory and maintain normal growth and reproduction. Resistant trees display significant genetic differences and are more heterozygous for two enzymes associated with herbivory than susceptible trees. Cinder-soil pinyons exhibit significant genetic differences and are more heterozygous for an enzyme associated with environmental stress than the neighbouring sandy-loam soil pinyons. -from Authors