Comparatively few studies have examined nodulation or rhizobial association in the basal legume tribe Crotalarieae. Within the Lotononis s. l. clade, Ardley et al. characterize the rhizobia associated with Listia, Leobordea and Lotononis s.s., and examine infection and nodule initiation in species of Listia. They find that the lupinoid nodules of Listia angolensis and L. bainesii have uniformly infected central tissue and develop in the outer root cortex, and infection occurs without root hair curling or the formation of infection threads. Five genera of rhizobia nodulate Lotononis s.l. hosts, but specificity has developed within Listia, which is nodulated only by species of Methylobacterium and Microvirga. The seasonally waterlogged habitat of Listia species may favour the development of symbiotic specificity.