Contribution to the systematics of the genus Aphis (Hemiptera:Aphididae)

A phylogeny of the genus Aphis was built primarily from specimens collected in the Midwest of USA. A topology using UPGMA were constructed with 73 taxa and forty-one morphological characters with their character states of alate and apterae viviparous females. I identified four main groups: gossypii, asclepiadis, middletonii and fabae. Topologies of analyses performed using bootstrap Maximum Parsimony and MrBayes of cytochrome oxidase I (COI), nuclear elongation factor (EF1-∝) and primary endosymbiont Buchnera 16S (Buch 16S) were not congruent. MrBayes strongly supported most of terminal nodes of the phylogenetic trees. The phylogeny was strongly supported by detailed morphological characterization, EF1-∝ and combined sequences of COI and EF1-∝ with morphological characters. It was not supported by single analysis of COI or of Buch 16S. The topology constructed with morphological characters shows four main groups: gossypii, asclepiadis, middletonii and fabae. The same four groups are found in the phylogeny constructed from molecular data but the gossypii and fabae groups have differing set of species. My results showed that current genus Toxoptera should be a subgenus within Aphis. The current subgenus Bursaphis is a synonym of subgenus Aphis s. str. The phylogeny demonstrated the relationship of the North American species of the middletonii group to Xerobion. The current genus Xerobion Nevsky, 1928 is a senior synonym of Protaphis Borner 1952. Current genus Iowana Hottes, 1954 is a junior synonym of Aphis and it should be transferred to the subgenus Aphis s. str. My results show that the members of the gossypii group are: the North American species (A. forbesi, A. monardae, A. oestlundi, A. rubifolii, A. rubicola, and three new species A. elena, A. lythrum and A. syriaca); the European species (A. nasturtii, A. urticata and A. sedi), and the Asian species (A. agrimoniae, A. clerodendri, A. glycines, A. gossypii, A. hypericiphaga, A. ichigicola, A. ichigo, A. sanguisorbicola, A. sumire and A. taraxicicola). The North American taxa most closely related to A. gossypii are A. monardae, A. oestlundi, A. elena, A. lythrum and A. syriaca. The native A. monardae is valid species and not a synonym of A. gossypii. A novel morphological character was found to discriminate these species, the distance from the base of antennal segment III to the first secondary sensoria (DBIII). Aphis monardae has a monoecious holocyclic life cycle (apterous males and ovipara) on Monarda fistulosa. The COI sequence divergence range between A. gossypii and A. monardae is 2.7-3.04%. The cosmopolitan A. gossypii and A. sedi are cryptic species. Sequence divergences of COI and EF1-∝ between these species are less than 1% but the sodium channel para-type shows greater genetic distances range (0.84-1.84). In addition, several morphological characters will discriminate between these two species. I am retaining two species of the North American middletonii group, A. maidi-radicis and A. middletonii, as well as describing a new species, A. mediaty. Despite the low sequence divergences of COI among these species (less than 1%) I found morphological characters that are useful for species discrimination. The members of the asclepiadis group form a monophyletic clade strongly supported by COI, EF1-∝, Buch16S, and the combined data sets of molecular and morphological characters. Most of the members of this group are native species (A. asclepiadis, A. cornifoliae, A. decepta, A. impatientis, A. neogillettei, A. nigratibialis, A. saniculae, A. thaspii and A. viburniphila) and are related to the exotic species, A. salicariae. Molecular, morphological and biological work shows that A. asclepiadis Fitch, 1851 is a senior synonym of A. helianthi Monell 1879