- Moran, N. A. and T. G. Whitham
Here, we examine the ability of colonizers to select appropriate hosts when colonization occurs long before feeding, and when traits available as cues may be least associated with host quality. In the life cycle of the aphid Pemphigus betae, autumn migrants select among host trees (Populus angustifolia and natural hybrids with P. fremontii) far in advance of the spring feeding stages, while trees are in a very different physiological condition. In order to estimate host quality, we censused successful and aborted galls on 34 trees in a Utah canyon during seven consecutive years, thus obtaining tree-specific rates of stem-mother survivorship. We estimated attractivity of these trees by censusing autumn migrants during 3 yr. Both survivorship and attractivity varied among trees, and differences among trees persisted across years. Tree-specific colonization rates were positively related to gall establishment.