TABLE CONTENTS

SESSION FIVE – CURRENT TRENDS IN NEMATODE PHYLOGENY,
EVOLUTION AND CLASSIFICATION
CONVENORS: JAMES BALDWIN & LYNN CARTA
Molecular Phylogenetic Perspectives for Character Classification and
Convergence: Framing Some Issues with Nematode Vulval Appendages
and Telotylenchid Tail Termini
Carta, L., Z. Handoo & A. Skantar
USDA-ARS Nematology Laboratory, Beltsville, MD 20705
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 requires 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.
5 th International Congress of Nematology, 2008 17