DISTINGUISHING INTRAPOPULATIONAL CATEGORIES OF PLANTS BY THEIR INSECTFAUNAS - GALLS ON RABBITBRUSH

Within a population of rubber rabbitbrush, Chrysothamnus nauseosus, th e subspecies C. nauseosus consimilis and C. nauseosus hololeucus, and a third unidentified group were better segregated by their insect gall s, than by differences in plant morphology. This level of segregation was further increased when morphological measurements and counts of in sect galls were analyzed simultaneously. We interpret this result to m ean that plant morphology and insect distributions reflect two differe nt, perhaps overlapping, portions of the host's genome. By using both sets of characters concurrently, rather than either set independently, we increased the portion of the plant's genome being sampled and incr eased the probability of detecting differences among host genotypes. H ence, knowledge of the distributions of insect galls may be useful for augmenting the level of separation, obtained by morphological measure ments, among intrapopulational categories of plant genotypes. This app lication may be of greatest benefit when hybridization blurs morpholog ical distinctions among plant taxa, when morphological traits are high ly variable within genotypes, or when ephemeral morphological traits ( e.g., leaves, flowers) are not available for measurements.