Ancestral and monophyletic presence of diplostigmaty in Sebaea (Gentianaceae) and its potential role as a morphological mixed mating strategy

Summary•  Diplostigmaty, the presence of a primary (apical) stigma and secondary (mid‐stylar) stigmas along the style, is only known from the genus Sebaea (Gentianaceae). Early work indicated that the secondary stigmas provide a mechanism of autogamy, suggesting that it might ensure reproductive assurance. •  Here, we test the monophyly of this unique morphological trait. Using Bayesian methods, we infer a nuclear DNA phylogeny for 96 accessions, including c . 50% of the species from the genus Sebaea . With this phylogeny, we infer the distribution of ancestral states on critical nodes using parsimony and likelihood methods. •  The inferred nrDNA phylogeny shows that the genus Sebaea is divided in two statistically well‐supported clades, A and B, consistent with recent estimates. The most recent ancestor (MRCA) of clade A, except the most basal species ( Sebaea pusilla ), is resolved as diplostigmatic. No reversal to a single stigma is observed within this clade. •  We suggest that diplostigmaty is evolutionarily stable through time. We also discuss why this reproductive system is not found elsewhere than in Gentianaceae and the potential advantage of diplostigmaty as a stable mixed mating strategy.