Primates and their pinworm parasites: the cameron hypothesis revisited

A morphologically based cladistic analysis of the Enterobiinae, which includes most of the Oxyuridae parasitic in Primates, allows a reevaluation of the Cameron's hypothesis of close coevolution with cospeciation between hosts and parasites. Each of the three genera separated in the Enterobiinae fits with one of the suborders defined in Primates: Lemuricola with the Strepsirhini, Trypanoxyuris with the Platyrrhini, and Enterobius with the Catarrhini. Inside each of the three main groups, the subdivisions observed in the parasite tree also fit with many of the subdivisions generally accepted within the Primate order. These results confirm the subgroups previously described in the subfamily and support Cameron's hypothesis in its aspect of association by descent. Although the classification of the Enterobiinae generally closely underlines the classification of Primates, several discordances also are observed. These are discussed case by case, with use of computed reconstruction scenarios. Given that the occurrences of the same pinworm species as a parasite for several congeneric host species is not the generalized pattern, and given that several occurrences also are observed in which the speciations of the parasites describe a more complex network, Cameron's hypothesis of a slower rhythm of speciation in the parasites can be considered partly refuted. The presence of two genera parasitic on squirrels in a family that contains primarily primate parasites also is discussed. The cladistic analysis does not support close relationships between the squirrel parasites and suggests an early separation from the Enterobiinae for the first (Xeroxyuris), and a tardy host-switching from the Platyrrhini to the squirrels for the second (Rodentoxyuris).