Résumé
The three speciesNeisseria meningitidis, Neisseria gonorrheae, andNeisseria lactamicaare often regarded as highly recombining bacteria.N. meningitidishas been considered a paradigmatic case of the “semiclonal model” or of “epidemic clonality,” demonstrating occasional bouts of clonal propagation in an otherwise recombining species. In this model, occasional clonality generates linkage disequilibrium in the short term. In the long run, however, the effects of clonality are countered by recombination. We show that many data are at odds with this proposal and thatN. meningitidisfits the criteria that we have proposed for predominant clonal evolution (PCE). We point out that (i) the proposed way to distinguish epidemic clonality from PCE may be faulty and (ii) the evidence of deep phylogenies by microarrays and whole-genome sequencing is at odds with the predictions of the semiclonal model. Last, we revisit the species status ofN. meningitidis, N. gonorrheae, andN. lactamicain the light of the PCE model.