Experimental taxonomy of Silene section Elisanthe (Caryophyllaceae): crossing experiments

Silene section Elisanthe is a well‐defined group containing (in Europe) the following species: S. alba, S. diclinis, S. dioica, S. heuffelii and S. marizii (dioecious perennials or biennials) and S. noctifloara (a self‐compatible hermaphrodite annual). Crosses were attempted among these species, and between these species and members of other Silene sections. Crosses among the first five species revealed partial cross‐incompatibility with moderate hybrid fertility. S. alba proved especially incompatible with S. diclinis. S. noctiflora would not cross at all with other members of the section. It is suggested that S. noctiflora evolved from a dioecious precursor of S. alba, the species to which it is most similar in morphology, distribution and habitat; hybrid sterility, even without incompatibility, would have assured mutual isolation. Crosses with species from other sections of Silene have usually either failed consistently or revealed high cross‐incompatibility with hybrid sterility. Those crosses which were successful have all been within the boundaries of the old genus Melandrium, or with Lychnis species.