Computerized key to the genus Bursaphelenchus Fuchs, analysis of species clusters based on morphology, using information of insect vectors and associated plants, with a revision of the genus.

The genus Bursaphelenchus includes B. xylophilus (Steiner et Buhrer, 1934) Nickle, 1981, which is of world economic and quarantine importance. Distinction among several species of the pinewood nematodes species complex (PWNSC) is often difficult. Besides standard morphology, morphometrics and molecular biology, new tools are welcome to better understand this group. The computerized (or e-) key of this genus, presented in this communication, includes 74 species (complete list of valid species of the world fauna) and 35 characters, that were used by the taxonomic experts of this group, in the original descriptions. Morphology of sex organs (male spicules and female vulval region) was digitized and classified to distinguish alternative types. Several qualitative characters with overlapping character states (expressions) were transformed into the morphometric indices with the discontinuous ranges (characters of ratios of the spicule dimensions). Characters and their states (expressions) were illustrated in detail and supplied by brief user-friendly comments. E-key was created in the BIKEY identification system (Dianov & Lobanov, 1996-2004). The system has built-algorithm ranging characters depending on their diagnostic values at each step of identification. Matrix of species and the character states (structural part of the e-key database) may be easily transformed using statistical packages into the dendrograms of general phenetic similarities (UPGMA, standard distance: mean character difference). It may be useful in the detailed analysis of taxonomy and evolution of the genus and in its splitting to the species groups based on morphology. The verification of the dendrogram using the information on the species links with insect vectors and their associated plants, provided an opportunity to recognize the five clusters (xylophilus, hunti, eremus sensu stricto, tusciae and piniperdae sensu stricto), which seem to be the natural species groups. The hypothesis about the origin and the first stages of the genus evolution is proposed. A general review of the genus Bursaphelenchus is presented.

Computerized key of the genus genus Laimaphelenchus Fuchs, 1937

The Order Aphelenchida contains several genera of economic importance, namely Aphelenchoides and Bursaphelenchus. Nematode species belonging to these 2 genera frequently co-habit with other genera such as Laimaphelenchus. It is therefore important to clearly distinguish them, as well as understand the group´s biodiversity. A computerized, or e-key, for the genus Laimaphelenchus Fuchs has been developed in the BiKey Identification system (Dianov & Lobanov, 1996-2004). The e-key includes 14 species and 34 characters (from 2 to 6 character states each). It also includes the built-in algorithm ranging characters according their diagnostic values to minimize the number of the diagnosis steps (average number of steps is 2.7; values are re-calculated at each step). The most important characters (as calculated by BiKey) are: length of posterior branch of the female genital system; excretory pore position; vulval anterior flap shape; number pairs of mail tale papillae; male bursa shape (ventral view); number of tail tip setae in female; female tail tip stub shape; presence of mucro on tail tip in male. Key is pictorial (image-operating), multientry, as other BiKey products.

A synopsis of the genus Bursaphelenchus Fuchs, 1937 (Aphelenchida: Parasitaphelenchidae) with keys to species

The 75 valid species of the genus Bursaphelenchus are listed together with their synonyms. Diagnostic characters and their states are discussed and illustrated. Tabular and traditional text keys are provided for the genus. Two new subspecies are proposed to distinguish populations of B. piniperdae and B. poligraphi, as described by Rühm (1956), from the original descriptions of these species published by Fuchs (1937). Known records of Bursaphelenchus species with their associated natural vectors, plants and plant families are given. Dendrograms of species relationships (UPGMA, standard distance: mean character difference) based on combined taxonomic characters and also on spicule characters only, are provided. Discussion as to whether the species groups are natural or artificial (and therefore purely diagnostic) is based on their relationships in the dendrogram and the vector and associated plant ranges of the species. Of the six species groups distinguished, two appear to represent natural assemblages, these being the xylophilus-group (with ten species) and the hunti-group (seven species), of which two, B. cocophilus and B. dongguanensis, form the cocophilus-cluster which is separated on the dendrogram from the main clusters. The remaining four species groups appear to be artificial and purely diagnostic in function, namely the aberrans-group (four species); the eidmanni-group (six species); the borealis-group (five species), and the piniperdae-group (43 species). Two new subspecies, both in the piniperdae-group, viz. B. piniperdae ruehmpiniperdae n. subsp. and B. poligraphi ruehmpoligraphi n. subsp., are proposed and diagnosed from B. piniperdae piniperdae and B. poligraphi poligraphi the respective type subspecies. Bursaphelenchus dongguanensis is regarded as being a valid member of the genus and its transfer to Parasitaphelenchus is rejected.

The History of Expansion of the Genus Bursaphelenchus (Nematoda: Aphelenchida: Parasitaphelenchidae)

Because of globalization and removal of geographical barriers, frequent biological invasions of introduced species become an urgent environmental problem. According to the Convention on Biological Diversity (CBD), precise identification of dangerous aggressive species at the early stages of their invasion to new regions is the most important component of the environmental control and monitoring. To resist the potential environmental hazard, the precise data are required on the current distribution and history of expansion of pests that are of global economic importance.

Review of the genus Bursaphelenchus Fuchs, 1937 (Nematoda, Aphelenchida) with some conclusions on the host-parasite and vector-parasite evolution.

INTRODUCTION AND GOALS: Genus Bursaphelenchus includes several pests of the world importance for the rural economy, the most dangerous are the Bursaphelenchus xylophilus (the pinewood nematode caused decline of the pine trees in south Asia and in one spot area in Europe, Portugal, Peninsula de Setubal) and the Bursaphelenchus cocophilus, causing the decline of coco-palm plantations in Carribean and Latin American regions. The peculiarity of the host-parasite association of the genus that the nematode life cycle includes three trophic components: plant (mostly a tree), insect vector and a fungus. Goals of the presentation is to list all species of the world fauna and all efficient diagnostic characters, then create the identification tool and analyze the similarity of species and possible ways and causes of the host-parasite evolution of the group. RESULTS: Complete list of species with synonymy and a catalogue of all efficient diagnostic characters with their states, selected from papers of the most experienced taxonomists of the genus, are given for the genus Bursaphelenchus. List of known records of Bursaphelenchus species with names of natural vectors and plants and their families is given (for world pests the most important groups of trees and insects are listed). The tabular, traditional and computer-aided keys are presented. Dendrograms of species relationships (UPGMA, standard distance: mean character difference) based on all efficient taxonomic characters and separately on the spicule characters only, are given. Discussion whether the species groups are natural or purely diagnostic ones is based on the relationships dendrograms and the vector and associated plant ranges of Bursaphelenchus species; the xylophilus species group (B. xylophilus, B. abruptus, B. baujardi, B. conicaudatus, B. eroshenkii, B. fraudulentus, B. kolymensis, B. luxuriosae; B. mucronatus), the hunti group (B. hunti, B. seani, B. kevini and B. fungivorus) are probably the natural ones. CONCLUSIONS: The parasitic nematode association includes three trophic components: plant, insect vector and fungus. The initial insect-plant complex Scolytidae-Pinaceae is changeable and only in rare occasions the change of the preferred vector to Cerambycidae (the xylophilus group), Hymenoptera (the hunti group) led to formation of the natural species-groups. From the analysis it is clear that although the vector range is changeable it is comparatively more important for the evolution of the genus Bursaphelenchus than associations with plants at the family level. Data on the fungi species (3rd component in natural Bursaphelenchus associations) are insufficient for the detailed comparative analysis.

Progress in the use of scanning electron microscopy (SEM) applied to the taxonomy of the genus Bursaphelenchus (Nematoda: Parasitaphelenchidae)

The scanning electron microscope (SEM) has been a major tool in detailed morphological observations of plant parasitic nematodes during the last 30 years, efficiently complementing light microscopical (LM) studies. Nematodes are extremely difficult to observe and characterize due to their small size (aprox. 1 mm long) and paucity of morphological characters, so detailed surface observations of several organs and nematode regions are of the highest value. Among plant parasitic nematodes, one of the most devastating species is the “pinewood nematode” (PWN), Bursaphelenchus xylophilus, which has been a major problem for forest species, and in particular pines, in Asia (Japan, China, Korea) and has been recently detected in the European Union (Portugal). B. xylophilus belongs to a closely related, morphologically similar group of species, within the genus Bursaphelenchus, and designated by the “xylophilus group”. SEM has become a crucial tool in observing several genital characters of males and females, such as male genital papillae, male copulatory spicules, female vulval flap and female genital papillae.s In this presentation, we will show how SEM has been utilized to observe and characterize the shape of the vulval flap, the presence/ absence of papillae near the flap, and confirm the presence and the arrangement of the male genital papillae. LM is also used in this work to show its value as a complementary tool to SEM, in both genital characteristics and other, general, characters of the genus Bursaphelenchus, such as the male bursa and cephalic region.