Genetic and Environmental Components of Morphological Variation in Gall-Forming Aphids (Homoptera, Aphididae, Fordinae) in Relation to Climate

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Abstract
Samples of galls induced by 3 spp. of aphids (Aphidoidea, Fordinae) were collected throughout the range of the host trees, Pistacia [P. atlantica, P. palaestina and P. khinjuk], in Israel. Nineteen morphological characters were measured on 9 alate aphids per gall. The total variance of each character was partitioned by analysis of variance into several components, estimating the relative magnitude of environmental and genetic effects on them. The relation of morphological variation to climate was studied by means of factor analysis and multiple regression. Variation of aphids within galls contributed relatively little to total variance. Since all aphids within a gall are parthenogenetic offspring of a single female, this component measures non-genetic variation. Variation between gall means (measuring the effect of differences among fundatrix genotypes) constituted a major part of total variation. Variation between locality means was significant in 2 spp. [Geoica utricularia (Pass.) and Slavum wertheimae (H.R.L.)] but not in the 3rd [Baizongia pistaciae (L.)]. Locality means of morphological measurements (size in particular) were negatively correlated with temperature, in the 2 former species. Some of the evidence suggests that this trend, which was found to be independent of geographical proximity, may be maintained by a selective advantage to larger aphids in colder environments.