Congruent phylogenetic relationships of Melaphidina aphids (Aphididae: Eriosomatinae: Fordini) according to nuclear and mitochondrial DNA data with taxonomic implications on generic limits

Melaphidina aphids (Rhus-gall aphids; Eriosomatinae: Fordini) comprise five genera from eastern Asia and one monotypic genus from eastern North America. Melaphidina are unique in feeding on plant species of Rhus subgenus Rhus (Anacardiaceae), on which they form galls during the summer. The phylogenetic relationships among some species of Melaphidina aphids remain controversial. In this study, we sought to resolve the backbone phylogeny of Melaphidina aphids by sampling 15 accessions representing all six genera, all species, and all subspecies except Meitanaphis microgallis using 20 gene regions: five nuclear genes as well as 13 protein-coding genes and two rRNA genes of the mitochondrial genome. Phylogenetic analyses included Bayesian and maximum likelihood methods. Independent analyses of nuclear and mitochondrial genes returned congruent topologies, and analyses of all gene regions combined showed well-supported relationships among Melaphidina species. In particular, these were: (1) Nurudea (excluding N. ibofushi) is sister to a clade composed of the five remaining genera; (2) the monotypic North American genus Melaphis is sister to a clade comprising the four remaining genera; and (3) (Schlechtendalia + N. ibofushi) is sister to the clade (Floraphis (Meitanaphis + Kaburagia). Our results support the transfer of Meitanaphis flavogallis to Kaburagia as an additional subspecies or species, and the recognition of Floraphis as a distinct genus. This study provides important molecular resources for subsequent evolutionary studies using more nuclear genes on the Melaphidina aphids and their close allies.