Nematology, 2008, Vol. 10(3), 405-431 Trichodoridae (Nematoda: Triplonchida) from the Tara National Park, Serbia, and proposal of Trichodorus pseudobursatus n. sp. ∗ Wilfrida DECRAEMER 1,2, , Milan RADIVOJEVIC´ 3 and Eduardo DE LA PEÑA 4,5 1 Royal Belgian Institute of Natural Sciences, Vautierstraat 29, 1000 Brussels, Belgium 2 Department of Biology, Nematology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium 3 Plant Protection Institute, Faculty of Agriculture, Nemnjina 6, 11080 Beograd, Serbia 4 Institute for Agricultural and Fisheries Research, Burg. Van Gansberghelaan 96, 9820 Merelbeke, Belgium 5 Department of Biology, Terrestrial Ecology Unit, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium Received: 13 August 2007; revised: 12 November 2007 Accepted for publication: 12 November 2007 Summary – A survey for plant-root parasites in Tara National Park, Serbia, revealed the widespread occurrence of Trichodoridae, present in nearly one-third of the samples. Several species appeared to belong to the Trichodorus aequalis species complex sensu Loof (1973). The taxonomic value of the observed variations in diagnostic features within this species complex is discussed. A new species Trichodorus pseudobursatus n. sp. is described. It is characterised by males with a nearly straight habitus, two ventromedian cervical papillae anterior to the secretory-excretory pore, medium-sized and mostly straight spicules with wider manubrium continuous with the blade; blade with a smooth narrower part with a few bristles at mid-spicule, followed by a wider striated posterior part devoid of bristles. Females are characterised by a large, well developed pear-shaped vagina with medium-sized, rounded triangular and well separated vaginal sclerotised pieces in lateral optical view. In addition to the diagnostic morphological features, differentiation of the new species from other Serbian morphotypes of the Trichodorus sparsus species complex was supported by canonical discriminant analyses (CDA). Additional information is provided for T. sparsus and three T. aff. sparsus morphotypes from Serbia. The discovery of the genus Trichodorus in Serbia represents a new geographical record. Keywords – canonical discriminant analysis, description, morphology, morphometrics, taxonomy, Trichodorus aequalis species complex, Trichodorus sparsus. Serbia occupies a central position within the Balkan They represent the first records of trichodorid species Peninsula, a world centre of biodiversity. Its nematofauna, from Serbia. Taxonomic analysis revealed the presence however, is poorly known and since Serbia is mainly an of Trichodorus species belonging to the Trichodorus agricultural country, focus lies on plant-parasitic nema- aequalis complex sensu Loof (1973). Identification to todes. From 2002 until the present time, Milan Radivo- species level is difficult. Populations appear rather similar, jevic´ carried out a survey of plant-root parasitic nema- although showing small differences in diagnostic morpho- todes in the Tara National Park, the most westward of logical features and measurements, the extremes of which all national parks in Serbia. It is very diverse in habitat suggest different species when compared with intra- and and extends over a surface of about 20 000 ha at 1000 m interspecific ranges known within the genus. Loof (1973) a.s.l. mean altitude. Tara National Park is recognised as a sanctuary for wildlife and accommodates numerous rare mentioned that species of the T. aequalis complex (at that and/or endemic species as it escaped quaternary glaciation time T. aequalis Allen, 1957, T. sparsus Szczygiel, 1968 and was located near the tertiary Panonian Sea (Miocene). and T. hooperi Loof, 1973) are more variable in morpho- Even today, the park area has a mild, humid, continental logical and morphometric features compared to other Tri- climate, supporting rich vegetation, primarily forests. chodorus species (for example in stylet and spicule length, So far, populations of trichodorid species have been variation in number of precloacal supplements, position of found in 14 (nearly one-third) of the localities sampled. ventromedian cervical papillae in relation to the secretory- ∗ Corresponding author, e-mail: [email protected] © Koninklijke Brill NV, Leiden, 2008 405 Also available online - www.brill.nl/nemy W. Decraemer et al. excretory pore and distance between them and the vagina Materials and methods shape in female). Until now, taxonomic papers hardly ever make an ex- The whole territory of Tara is situated within the UTM plicit statement of the species concept used, which means grid CP quadrant of 100 × 100 km; codes 66-86 refer that the hypothesis ‘a new species’ cannot be tested (Dod- to 10 × 10 km unit quadrants, while the letters A to Z son & Lee, 2006). Without knowing if the author(s) used, of the code refer to the 25 sample stations in the 2 × 2 for example, the biological, morphological or phyloge- km sampling units. Habitats sampled include forests, pre- netic species concept, citing the most commonly used dominantly mixtures of spruce, fir and beech, as well as ones, we have no precise idea of what the author meant meadows and transition zones. Single point samples were by ‘species’ and we cannot test the boundaries of the taken, using a spade, per 4 km2 unit, from all over the ter- designated species. Barely distinguishable morphological ritory, as a block of about 1 kg soil from up to 20 cm groups, such as recently separated sibling species, can depth. Nematodes were extracted by sieving the super- show clear genetic divergence and reproductive isolation natant of soil mixed with water, followed by the Baermann yet the reverse also occurs. Another confounding problem funnel technique, hot-fixed with TAF (Courtney et al., in the use of morphological characters is that they can be 1955), then slowly transferred to glycerin prior to mount- affected by phenotypic plasticity in response to environ- ing on glass slides. Morphometrics were obtained using mental factors, as well as by morphological stasis. an Olympus BX50 compound microscope equipped with To obtain a better understanding of the taxonomic value image-capture software. Drawings and photographs were of the observed differences in diagnostic features within made with a Reichert Polyvar microscope using interfer- this group and to be able to understand what the author(s) ence contrast. Morphological data of females and males considered to be a species, the T. aequalis species group from all populations were analysed using a forward step- will be discussed, based upon the study of type specimens, wise canonical discriminant analysis (Genstat 8.0). An voucher material and Serbian populations. In a later stage, unidentified juvenile specimen of Trichodorus was found molecular data will be added. at Barski dol location 76N: mixed forest of mainly spruce Although species of the T. aequalis species complex and beech forest on limestone. are gonochoristic, mating experiments to test reproductive isolation between putative species are hardly realistic; OTHER MATERIAL STUDIED mixed populations are common and trichodorids are difficult to culture on agar plates. In Trichodoridae, the Trichodorus aequalis, specimens from Alaska, courtesy morphological species concept is currently the concept in E. Bernard. vogue. Consequently, species are defined on the basis of T. coomansi De Waele & Carbonell, 1983, holotype particular essential features, whereby there is no proof of male, slide RUG284, paratypes, slide RUG285, RUG288, gene flow but morphological distinctiveness is considered Nematode Collection, Ghent University, Ghent, Belgium. as a surrogate to lineage independence. Moreover, testing T. giennensis Decraemer, Roca, Castillo, Peña-Santiago the hypothesis of a new species using the morphological & Gomez-Barcina, 1993: paratype specimens, slides species concept is easier than testing new species based RIT397, RIT417 from the Nematode Collection of the on the phylogenetic species concept, where it is often Royal Belgian Institute of Natural Sciences, Brussels, difficult to determine the polarity of the characters, several Belgium. features being probably convergent. T. hooperi: paratypes, slides WT1627, WT1632, WT1635 This contribution presents an overview of the T. ae- from the Nematode Collection of the Agricultural Univer- qualis species complex based on data from the litera- sity of Wageningen, courtesy P. Loof. ture, type material and other specimens. A new species, T. orientalis De Waele & Hashim, 1984, holotype female, Trichodorus pseudobursatus sp. n., is described and il- slide RUG269-272, paratypes, slides RUG 269, RUG 273 lustrated. Additional support for its differentiation from from the Nematode Collection, Ghent University, Ghent, closely related species based on morphometric data is Belgium and voucher specimens from the Nematode substantiated by canonical discriminant analyses. Three Collection of the Royal Belgian Institute of Natural different morphotypes of T. aff. sparsus from Serbia are Sciences, Brussels, Belgium. described and additional data are given for Trichodorus T. parorientalis Decraemer & Kilian, 1992, paratypes, sparsus. slides RIT378, RIT 379 from the Nematode Collection of 406 Nematology Trichodoridae from Serbia the Royal Belgian Institute of Natural Sciences, Brussels, recorded T. aequalis from the rhizosphere of Rhododen- Belgium. dron obtusum from Japan but the author could not con- T. paucisetosus Bernard, 1992, paratypes,