Local adaptation and rapid evolution of aphids in response to genetic interactions with their cottonwood hosts

Several studies have demonstrated the ecological consequences of genetic variation within a single plant species.  For example, these studies show that individual plant genotypes support unique composition of the plants’ associated arthropod community. By contrast, fewer studies have explored how plant genetic variation may influence evolutionary dynamics in the plant’s associated species.  Here, we examine how aphids respond evolutionarily to genetic variation in their host plant. We conducted two experiments to examine local adaptation and rapid evolution of the free-feeding aphid Chaitophorus populicola across genetic variants of its host plant, Populus angustifolia. To test for local adaptation, we collected tree cuttings and aphid colonies from three sites along an elevation / climate gradient and conducted a reciprocal transplant experiment. In general, home aphids (aphid transplanted onto trees from the same site) produced 1.7-3.4 times as many offspring as foreign aphids (aphids...