Submitted to: International Congress of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: March 14, 2008
Publication Date: July 13, 2008
Citation: Carta, L.K., Handoo, Z.A., Skantar, A.M. 2008. Molecular phylogenetic perspectives for character classification and convergence: Framing some issues with nematode vulval appendages and telotylenchid tail termini [abstract]. Proceedings of the Fifth International Congress of Nematology, July 13-18, 2008, Brisbane, Australia. p. 17.
Characters flagged as convergent based on newer molecular phylogenetic trees inform both practical identification and more esoteric classification. Nematode morphological characters such as lateral lines, bullae and laciniae are quite independent structures from those similarly named in other organisms like fish and insects. Within nematodes, naming and classifying similar morphological structures and refining them within independent phylogenetic frameworks often require qualification, formal definition, or novelty in character names. Micrographs and drawings of vulval appendages were analyzed from the literature and considered within frameworks of an 18S phylogenetic tree and ecological associations. Three major vulval appendage classes based on composition, position and orientation included membranes, flaps, and epiptygmata. They were distributed across subsets of terminal and phylogenetically distant taxa that were almost exclusively commensal or parasitic. For instance epiptygmata were present within Aphelenchida, Tylenchida, Rhabditida and Enoplida. In another study, a more refined 18S molecular phylogeny based upon 18 taxa of plant-parasitic Telotylenchidae (Tylenchida) stunt nematodes and two relatives was constructed. Relatively thickened hyaline tail termini in Telotylenchidae were mapped on the tree, demonstrating a mosaic distribution among taxa with shorter hyaline tails. Phylogenetic similarity was demonstrated between Trophurus minnesotensis, with a long hyaline tail, and the relatively short-tailed Quinisulcius acutus. Overlapping measurements of hyaline tail termini support the notion that Paratrophurus could be synonymized with Tylenchorhynchus. Phylogenetic support was found for the presence of Pratylenchoides ritteri within the Merliniinae. Epiptygmata in these distinctly classified taxa may provide further support for the taxonomically upsetting notion of a possible new family for a Pratylenchoides. Expanded molecular phylogenetic trees with ultrastructural and possibly developmental comparisons are needed to refine these tail and vulval characters before using them to amend current classifications.