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Summary: A new species of Aporcelinus , collected in a natural habitat of central Mexico, is described and illustrated, including molecular (D2-D3 28 S -rRNA) data. Aporcelinus zapotitlanensis sp. n. is characterised by its 1.19-1.43 mm long body, lip region offset by a deep constriction and 16.5-18.5 μ m broad, odontostyle 19.5-22 long, neck 325-368 μ m long, pharyngeal expansion 150-201 μ m long or 46-55% of the total neck length, uterus 130-167 μ m long and tripartite, V = 54-56, tail conical with finely rounded tip (30-37 μ m, c = 34-43, c′ = 1.2-1.4) lacking a distinct dorsal concavity, spicules 48-51 μ m long, and 11-12 spaced ventromedian supplements with one or two of them located within the range of the spicules. Molecular analyses confirm the monophyly of Aporcelinus and places the new species within a clade shared with A. infundibulicaudatus and A. amazonicus. [ABSTRACT FROM AUTHOR]

The evolutionary relationships of 82 species of tylenchid and aphelenchid nematodes were evaluated by use of sequence data of the D2 and D3 expansion fragments of the 28S ribosomal RNA genes. Nine automatic and one culled sequence alignments were analysed using maximum parsimony and Bayesian inference approaches. The molecular data sets showed that the order Tylenchida comprises lineages that largely correspond to two suborders, Hoplolaimina and Criconematina, and other taxonomic divisions as proposed by Siddiqi (2000). Several significant results also derived from our study include: i) the basal position of groups that include entomoparasitic nematodes within tylenchid trees; ii) paraphyly of the superfamily Dolichodoroidea sensu Siddiqi (2000); iii) evidence for a Pratylenchus, Hirschmanniella and Meloidogyne clade; and iv) lack of support for widely held traditional placement of Radopholus within Pratylenchidae and placement of this genus within Hoplolaimidae or Heteroderidae. Congruence and incongruence of molecular phylogeny and traditional classifications and morphological-based hypotheses of phylogeny of tylenchids are discussed. [ABSTRACT FROM AUTHOR]