The status of the members of the Aphis carduella species group (Hemiptera, Aphididae) in the United States of America

In North America, there are some Aphis species that uses Cornus as a primary host plant that are associated with native Aphis species that feed on plants of the family Apiaceae. We refer to them collectively as the Aphis carduella 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-a (EF1a1) genes. A Bayesian phylogenetic analysis of the concatenated Cox1 and EF1a1 data strongly supported a clade composed of members of the A. carduella species group. This group includes those native to North America: A. asclepiadis, A. carduella, A. decepta, A. impatientis, A. neogillettei, A. nigratibialis, A. saniculae, A. thaspii and A. viburniphila, and the exotic species, A. salicariae. Bayesian phylogenetic and Maximum Parsimony Network nested all individuals that match the diagnostic characters described for A. asclepiadis and A. carduella, and those described for A. nigratibialis. Moreover, the range of pair-wise distances estimated from Kimura 2-parameter between collections of A. asclepiadis and A. carduella is 0.00-0.73% and 0.00-0.87% for Cox1 and EF1a1 respectively. The pair-wise distance value obtained with COI does not differ from other highly polyphagous Aphis species. This data leads us to conclude that A. asclepiadis Fitch 1851 is a senior synonym of A. carduella Walsh 1863, syn. nov., and A. impatientis is not a monoecious species.