Abstrusomyzus: a new genus similar to Myzus

One of the serious problems in modern aphid systematics is that the generic classification of the family was constructed largely by European workers, based mostly on Eurasian species. We recently published a study of the North American species that had been placed in Ovatus by recent authors (Proc. Entomol. Soc. Wash. 101:39-56). Two things were of particular interest to us:

  1. There was clearly not a close relationship between the four native species of the genus and the single European introduction;
  2. One of the native North American species was known to feed on many different plants in several unrelated plant families, a condition that is unusual in aphids, and is suggestive of a nascent agricultural pest.

1. Phylogenetic Analysis
Our approach in this project was to run cladistic analyses of morphological characters, attempting to determine whether the four North American species were closely related to the other members of Ovatus and several Myzus species. Pictured at right is one of the cladograms from the paper. It shows that the four North American species, grouped together in the middle of the cladogram, do not belong to Ovatus, several species of which fall out more basally on the tree. Note that we used three species of Hyalomyzus as outgroups. Our results indicated that Eurasian Ovatus were closely related to the North American genus Hyalomyzus, but the four North American "Ovatus" species were not closely related to any of the species in the analysis. We concluded that a new genus was required for these four species, establishing four new combinations as follows:

 Research cladogram
  1. Abstrusomyzus leucocrini (Gillette & Palmer)
  2. Abstrusomyzus phloxae (Sampson)
  3. Abstrusomyzus reticulatus (Heie)
  4. Abstrusomyzus valuliae (Robinson)

A Potential New Pest?
Most aphids are extremely host specific, feeding on one or a few species of plants that are usually closely related. Many of the most pestiferous aphids known differ dramatically from this normal pattern by being polyphagous on plants in widely divergent families. Well-known polyphagous pests include the green peach aphid (Myzus persicae (Sulzer)), the potato aphid (Macrosiphum euphorbiae (Thomas)), and the cotton aphid (Aphis gossypii Glover). These aphids can cause serious problems even when they feed on a crop in low numbers, since they can transmit plant viruses between their phylogenetically disparate host plants. Very few polyphagous aphids are not pests. Thus we thought it important to study Abstrusomyzus phloxae, an oddly polyphagous species.

A. phloxae is so far known from the following plant families:

  • Apocynaceae
  • Asteraceae (=Compositae)
  • Brassicaceae (=Cruciferae)
  • Caryophyllaceae
  • Cyperaceae
  • Fabaceae (=Leguminosae)
  • Hydrophyllaceae
  • Liliaceae
  • Plantaginaceae
  • Polemoniaceae
  • Polygonaceae
  • Ranunculaceae
  • Rubiaceae
  • Violaceae

Abstrusomyzus phloxae on Plantago
Most of the plants from which this species is known are low-growing, or the aphid is found on the basal-most leaves. A notable exception is found in the populations in the eastern U.S. that seem to prefer to feed on Plantago. Here, the aphids feed on the new leaves in the middle of the rosette, and are tended by ants (Lasius alienus in Maryland). These ants build incredible huts or "sheds" out of sand and bits of soil, completely enclosing the young leaves and the aphids feeding on them.
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Last Updated: April 19, 1999