MORPHOLOGICAL ADAPTATION TO HOST PLANTS IN UROLEUCON (HOMOPTERA: APHIDIDAE)

The morphology of host-specific Old World Uroleucon (Homoptera: Aphididae) species is related to features of their host plant species (Asteraceae and Campanulaceae) by canonical correlation analysis. Aphid species on pubescent host species have longer rostra and shorter hind tarsi, adaptations for feeding and walking on hirsute surfaces. Also, aphid species on taller hosts are larger. The positive relationship between rostrum length and host trichome density is further supported by simple regression analyses on two species complexes. Regression parameters differ between groups, suggesting different responses to different trichome types. This morphological adaptation involves characters used extensively by taxonomists and could result in convergence obscuring phylogenetic relationships of herbivore taxa and, particularly, the relation of herbivore phylogeny to host phylogeny.