Manipulation of Pistacia spp. by gall-forming aphids: Evolution of complex interactions

Across their wide distribution, Pistacia spp. are accompanied by a remarkable group of gall-forming aphids (Homoptera: Fordinae). The aphids induce several gall types on leaves and buds. Their life cycle is complex and includes migration between different host plants and sexual and asexual reproduction phases. We examined the phylogenetic association of 14 Fordinae species from the Levant based on sequences of the mitochondrial genes CO I and II (1952 bp). A single, most parsimonious cladogram revealed three lineages for the Fordinae: Fordini, Baizongiini, and a new group that includes Smynthurodes betae (West). The aphids have evolved toward better plant manipulation, inducing stronger sinks, and gaining higher reproductive success. The finding of similar gall types induced on different Pistacia hosts suggests aphids frequently shift hosts and control gall morphology. The intimate relationships between the aphids and their hosts may assist in taxonomic identification of Pistacia species, hybrids, and varieties.