Variation in floral morphology in a hybrid complex of Cyclamen in Sardinia

Background: Hybridisation is a key driver of plant speciation, and understanding ongoing hybridisation provides insights into the underlying process(es). We studied a hybrid complex in Mediterranean Cyclamen between the common C. repandum and rare C. balearicum in Sardinia. Aims: We analysed variation in the frequency and morphology of different floral types to assess the degree of hybridisation and analysed the ecological niche to identify factors that are likely to influence the maintenance of hybrid populations. Methods: We recorded the frequency of the different flower colour types in 45 populations and measured floral traits in 10 of them. We characterised the spatial extent and climatic niche of this hybrid complex. We analysed floral type variation in four traits (flower size, style and anther length, herkogamy) along a hybridisation gradient. Results: Hybrid populations occupy a wide area (ca. 1000 km2) on the north-west coast of the island. Sites dominated by hybrid floral types are ecologically marginal for the common parent. The C. repandum-like type is present in all populations and shows a decrease in style and anther lengths and herkogamy in populations containing a greater proportion of hybrids. Conclusions: This hybrid complex provides an ideal case of reproductive isolation owing to the differences in the ecological niche where different floral types are found.