Plant-parasitic nematodes are of major social and economic importance as it is estimated to be responsible for a reduction of the global food production by ≈13%. The advent of a large phylogenetic frameworks has shed light on the evolution of plant parasitism within this group of animals.
About 550 million years ago, nematodes and nematomorphs (their closest relatives) started to diverge. Nowadays we observe large difference in terms of speciation and abundances: whereas dedicated surveys in freshwater streams are required to collect nematomorphs, every square meter of terrestrial soil harbors 2–20 million nematodes. Whereas by far most nematomorphs fully depend on arthropods as a primary food source, the trophic ecologies among nematodes are more diverse include bacterivory, fungivory, omnivory, predation, and animal and plant parasitism. In this review Casper Quist, Geert Smant and Johannes Helder (Wageningen University) show that at least four independent major lineages of plant parasites have evolved from fungivorous ancestors. Ribosomal DNA frameworks with sequence data from more than 2,700 nematode taxa combined with detailed morphological information allow for explicit hypotheses on the origin of agronomically important pests, such as root-knot, cyst, and lesion nematodes.