Taxonomic studies on the nematodes of the subfamily Radopholinae Allen & Sher, 1967

Abstract

This study is focused on the group of migratory endoparasitic nematodes of the subfamily Radopholinae Allen & Sher, 1967. The project aimed to refine the taxonomy of the subfamily and to provide a stable classification of the group. Evolutionary relationships of species within the subfamily Radopholinae, particularly the two most important genera Radopholus and Achlysiella, were evaluated. Phylogenetic analyses of all species of Radopholus and Achlysiella were carried out using morphological data. Original and GenBank sequences of ITS1-5.8-ITS2 and D2 and D3 expansion fragments of the 28S ribosomal RNA genes of five species of Radopholus and three species of Achlysiella were analysed. Bayesian inference, maximum likelihood and maximum parsimony approaches were employed. The results showed that while morphological data could not provide enough reliable resolution, molecular data sets showed that the subfamily Radopholinae Allen & Sher, 1967 and its genera Radopholus Thorne, 1949 and Achlysiella Hunt, Bridge & Machon 1989 each formed well-supported groupings. Radopholinae was shown to have a closer affinity with Hoplolaimidae (sensu De Ley & Blaxter, 2002) than with other nematode families, and therefore should be placed within family Hoplolaimidae, instead of the traditional placement within family Pratylenchidae. The present study confirmed the existence of obese mature females of A. magniglans and A. trilineata and supported the placement of five species of Radopholus in Achlysiella as A. magniglans, A.trilineata, A. brevicaudata, A. capitata and A. vacua as originally proposed by Ebsary (1991). A new species, Achlysiella uriarrae to be called n.sp., is described. Finally, a taxonomic revision of the subfamily Radopholinae is proposed.