Present status and future of nematode systematics

Since phylogenetic systematics became generally accepted and especially since informatics and molecular techniques for phylogenetic analysis were developed, systematics has undergone a conceptual and methodological revolution. Taxonomy, on the contrary, suffered a decline. Poor descriptions, too much routine work and low citation rates hampered it. As a result, the discipline became less attractive to young scientists. With only a small fraction of the biodiversity known, this situation will lead to serious problems in the future in all those fields of nematology depending on a correct identification of species. Phylogenetic analyses of nematodes have been mainly based on morphology, supplemented with developmental characters, but in recent years molecular methods have provided entirely new data sets. Phylogenetic estimates derived from independent data may provide new insights in character homologies through reciprocal illumination. Classifications of nematodes were often biased according to the expertise of the author and were only recently based on the principles of phylogenetic systematics. Recently, molecular and morphological data have been used to support a new overall classification with only (presumably) monophyletic taxa. In this classification plant, as well as animal, parasitic taxa are hierarchically downgraded in accordance with their phylogenetic history. Species occupy an important position in all aspects of biology, therefore the species concept matters. It determines, for example, the outcome of biodiversity assessments, distribution patterns, etc. However, several problems remain to be solved before a consensus will be reached about the choice of a concept. Future research in nematode systematics should comprise well-focused taxonomy based on a combination of classical and modern methods in a way that can raise the interest of young scientists as well as of funding agencies. It should be realised that, with the dwindling present taxonomic expertise, this is a very urgent matter.