Breeding system of a plesiomorphic floral type: an investigation of small flowered Streptocarpus (Gesneriaceae) species

Six different floral morphologies can be found among the ca. 146 species of Streptocarpus occurring in Africa and Madagascar. One of these, a simple, small pouch type, was found to be plesiomorphic for the genus after mapping these floral types onto a molecular phylogeny. The breeding systems and population structure of three species possessing the plesiomorphic small floral morphology, S. micranthus, S. ibityensis and S. lanatus, have been investigated using nuclear microsatellite markers. Significant deviations from panmixia were found both at the between and within population level (S. micranthus θ = 0.708, f = 0.786; S. ibityensis, θ = 0.173, f = 0.138; S. lanatus, θ=0.539, f = 0.646). As a florally diverse genus, Streptocarpus is unusual in having a predominantly selfing, mixed mating breeding system as a plesiomorphic condition.