Phenotypic Selection on the Process of Gall Formation of a Tetraneura aphid (Pemphigidae)

Abstract

1. To clarify the evolutionary interactions between a galling aphid Tetraneura sp. and its host plant Ulmus davidiana var. japonica Nakai, we examined the pattern of phenotypic selection acting on the process of gall formation by multiple regression analyses and field experiments. 2. Two hypotheses have been advanced to explain variation in performance of gall insects within host plants. The «spatial heterogeneity hypothesis» postulates that size differences among leaves or shoots chosen by gall formers are primarily responsible for differential performance. The «synchronization hypothesis» emphasizes the effect of timing of insect attack relative to bud burst of the host plant as a source of the variation. 3. Multiple regression analysis showed that leaf size and shoot length did not contribute at all to fecundity in galls