Entomopathogenic nematodes of the genera Steinernema and Heterorhabditis, along with their bacterial symbionts from the genera Xenorhabdus and Photorhabdus, respectively, are important biological control agents against agricultural pests. Rapid progress in the development of genomic tools has catalyzed a transformation of the systematics of these organisms, reshaping our understanding of their phylogenetic and cophlylogenetic relationships. In this review, we discuss the major historical events in the taxonomy and systematics of this group of organisms, highlighting the latest advancements in these fields. Additionally, we synthesize information on nematode-bacteria associations and assess the existing evidence regarding their cophylogenetic relationships.

Experimental Biology Research Group Institute of Biology Faculty of Sciences University of Neuchâtel Neuchâtel 2000 Switzerland

Faculty of Agriculture and Technology University of South Bohemia Studentská 1668 České Budějovice 37005 Czech Republic

Institute of Entomology Biology centre of the Czech Academy of Sciences Branišovská 31 České Budějovice 37005 Czech Republic

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