The Status of the Members of the Aphis asclepiadis Species Group (Hemiptera: Aphididae) in the United States of America

In North America, there is a morphologically defined group of Aphis species that use Cornus spp. as primary host plants and also are associated with plants in the family Apiaceae. We refer to them collectively as the Aphis asclepiadis species group and attempt to elucidate the taxonomic status of its members using sequences of mitochondrial cytochrome oxidase 1 (Cox1) and nuclear elongation factor 1-α (EF1α1) genes. The Bayesian phylogenetic analyses of the combined data of these two genes strongly supported a clade composed of the A. asclepiadis species group. This group includes the following North American native species: A. asclepiadis, A. carduella, A. decepta, A. impatientis, A. neogillettei, A. nigratibialis, A. saniculae, A. thaspii, and A. viburniphila, and the related exotic species, A. salicariae. Bayesian phylogenetic and Maximum Parsimony Network nested all the collections that match the diagnostic characters described for A. asclepiadis and A. carduella, and the ones described for A. nigratibialis. Moreover, the range of pair-wise distances between collections of A. asclepiadis and A. carduella are 0.00-0.73 and 0.00-0.87% for Cox1 and EF1α1, respectively. Therefore, we conclude that A. asclepiadis Fitch 1851 is a senior synonym of A. carduella Walsh 1863, syn. nov. In addition, all the sequences of species morphologically identified as A. impatientis matched almost 100%. Biological studies showed that Aphis impatientis is a heteroecious species that alternates between Cornus and Impatiens. We also found that morphological characterization of the sexual morph is useful to differentiate species that feed on Cornus spp. as primary host plants.