title: Redescription of Robustodorus megadorus with Molecular Characterization and Analysis of Its Phylogenetic Position within the Family Aphelenchoididae.
abstract: Based on a new record of the rare species Robustodorus megadorus from Utah, the generic diagnosis was amended to include the following characters: a labial disc surrounded by six pore-like sensilla; the absence of a cephalic disc; a lobed cephalic region devoid of annulation; a hexagonal inner cuticular structure of the pouch surrounding the stylet cone; large stylet knobs, rounded in outline and somewhat flattened on their lateral margins; a large spermatheca with an occluded lumen and lacking sperm; the excretory pore located between the median bulb and nerve ring. The stylet orifice consists of an open, ventral, elongate slit or groove. These characters distinguish the genus from the closely related genus Aphelenchoides. A lectotype and paralectotypes were designated. Results of phylogenetic analyses of the 18S and D2-D3 of 28S rRNA gene sequences revealed that R. megadorus occupies a basal position within one of the two main clades of the subfamily Aphelenchoidinae and shares close relationships with a species group of the genus Aphelenchoides that includes A. blastophthorus, A. fragariae, A. saprophilus, A. xylocopae, and A. subtenuis. Several specimens in our collection of R. megadorus were infected with Pasteuria sp. as were some of the paralectotypes.
authors.affiliation: Zoological Institute, Russian Academy of Sciences, St. Petersburg 199034, Russia.
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Ryss
authors.affiliation: School of Plant Sciences, University of Arizona, Tucson, AZ 85721.
authors.forename: Michael A
authors.initials: MA
authors.lastname: McClure
authors.affiliation: Department of Biology, Utah State University, Logan, UT 84322.
authors.forename: Claudia
authors.initials: C
authors.lastname: Nischwitz
authors.affiliation: Department of Biology, Utah State University, Logan, UT 84322.
authors.forename: Christine
authors.initials: C
authors.lastname: Dhiman
authors.affiliation: Plant Pest Diagnostic Center, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. ; Center of Parasitology of A. N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, Moscow 117071, Russia.
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Subbotin
keywords: Aphelenchoides megadorus; DNA; Pasteuria; Robustodorus megadorus; morphology; phylogeny; scanning electron microscopy