Renaud Fortuner

Usefulness of morphological data for the study of nematode biodiversity

Public interest in biodiversity has never been so high, but the necessary inventory of existing species is hindered by the scarcity of taxonomists able to characterise and describe new species (α-taxonomy). This situation is particularly worrisome in nematology where only a small fraction of the estimated 105 to 108 existing species has been described and where experienced taxonomists are fast disappearing while the few that are still active find it increasingly difficult to publish morphological descriptions and to get financial support for biodiversity studies. The present disregard for α-taxonomy is said to originate from the excessive reliance by funding agencies and academic authorities on the Impact Factors attributed to scientific journals by ISI (Institute for Scientific Information). Molecular studies gave back some support and prestige to taxonomy, but that approach suffers from some limitations and it cannot be used alone for reaching taxonomic conclusions. In addition, any described DNA sequence should always be linked to a named species whose morphology has been correctly described by a trained taxonomist. The authors call for a renewed interest in α-taxonomy. Electronic publication according to the Code of Zoological Nomenclature would be one solution, but journals and authors seem reluctant to accept it. A variant would be to publish on paper only the diagnosis of the new species. The complete descriptions could be deposited in an Internet database but the setting-up of such a database would be a costly enterprise that would require several years of work by a team composed of morphological and molecular taxonomists and computer scientists.

Genisys and computer-assisted identification of nematodes

Identification of species for the study of biodiversity in the phylum Nemata is defined as being able to identify any of the 12 000 described species of nematodes, and being able to recognise when the specimen under study belongs to a species unknown to science. Moreover, this large-scale identification must be done by biologists who are not expert taxonomists. It is argued that printed identification aids are too rigid and unreliable, and molecular identification aid is too limited, to be used in this context. Only computer identification tools are flexible, reliable, and general enough to give a non-taxonomist the possibility to identify any species. However, a review of existing tools and approaches shows that they fall short of reaching this objective. The functionality of a general identification system that could overcome the problems and difficulties encountered in the use of computerised tools is then described. This system (which has been described by the authors in several articles under the name of Genisys) would include a general database with all the characters from all the published descriptions of nematodes species and a set of integrated identification tools. Some of these tools would export the data into formats usable by existing identification and systematics tools. Other tools would have to be developed to support new approaches. A guidance tool would help the non-expert user by suggesting the successive computerised tools to be used during an identification session or by directing the user to other approaches, such as molecular identification in the case of heteroderids or some Meloidogyne species. L’identification des especes pour l’etude de la biodiversite dans le phylum Nemata est definie comme la possibilite d’identifier n’importe laquelle des 12 000 especes decrites du groupe et d’etre capable de reconnaitre que le specimen etudie appartient a une espece non encore decrite. En outre, ce type d’identification a grande echelle doit pouvoir etre pratique par des biologistes qui ne sont pas des taxinomistes. Il est montre que les aides imprimees a l’identification sont trop rigides et trop peu fiables et que l’identification moleculaire est encore de portee trop limitee pour etre utilisables dans ce contexte. Seuls les outils d’identification assistee par ordinateur sont suffisamment flexibles, fiables et generaux pour permettre a un non taxinomiste d’accomplir les identifications definies plus haut. Pourtant, une revue des outils existants et des approches utilisees montre qu’ils sont incapables d’atteindre l’objectif fixe. La fonctionnalite d’un systeme d’identification general capable de resoudre les problemes souleves par l’utilisation d’outils informatises est ensuite decrite. Ce systeme (decrit par les auteurs du present article sous le nom de Genisys) doit comprendre une base de donnees avec tous les caracteres inclus dans les descriptions publiees des especes connues et un ensemble d’outils d’identification integres. L’un de ces outils devrait permettre d’exporter les donnees sous des formats utilisables par les outils existants d’identification et de systematique. D’autres outils devraient etre developpes pour mettre en œuvre de nouvelles approches. Un outil de guidage aiderait le non-specialiste en lui suggerant les outils informatiques a utiliser successivement dans le cadre d’une session d’identification ou en le dirigeant vers d’autres approches telles que l’identification moleculaire dans le cas de certains Heteroderides et d’especes de Meloidogyne.

On the morphometric identity of populations of Helicotylenchus pseudorobustus (Steiner, 1914) Golden, 1956 (Tylenchida: Hoplolaimidae)

Helicotylenchus microlobus is considered to be a junior synonym of H. pseudorobustus by several authors while others consider it as valid. To clarify the status of both species, 39 samples collected from various countries were subjected to statistical analyses that showed they could be grouped into six groups. Topotypes of H. pseudorobustus and H. microlobus belong to two different groups. However, samples in the other groups were morphologically intermediate between these two groups. Characters used in the past to uphold the validity of H. microlobus were variable and overlapping from group to group. The 28 samples studied are identified as H. pseudorobustus . Helicotylenchus microlobus , H. bradys and H. phalerus are confirmed as junior synonyms of H. pseudorobustus . There was no complete congruence between the morphological groups and molecular groups proposed by other authors. For these, two MOTU (Molecular Operational Taxonomic Unit) are accepted within H. pseudorobustus .