Lost in worm space: phylogeny and morphology as road maps to nematode diversity

The taxonomic impediment in nematology is expanding rather than receding: in the past decade estimates of nematode species richness have increased by several orders of magnitude, while the number of active nematode taxonomists has continued to decline steadily. In order to survive as a discipline in the new century, nematode taxonomy will therefore have to i) prioritise taxa that are relevant to other scientific investigations, ii) provide identification and classification tools that are easily applicable by nonspecialists, and iii) focus on revealing patterns of relatedness rather than on compiling exhaustive catalogues of species, since the latter will never remotely reach completion. Traditional morphological studies based on light microscopy do not meet these needs because they provide insufficient character resolution and require too much specialist knowledge. Phylogenetic approaches are more promising, especially when incorporating molecular sequence data as well as other non-traditional character suites.