Genetic control of fruit polymorphism in the Genus Fedia (Valerianaceae) in the light of dimorphic and trimorphic populations of F. pallescens

The genus Fedia consists of three species (F. cornucopiae, F. graciliflora and F. pallescens) of winter annual herbs, endemic to the western Mediterranean Basin. The deciduous terminal fruits of these taxa are polymorphic in the development of their pericarp and/or calyx, and each population is dimorphic or more rarely trimorphic. The three main fruit types are dispersed in several manners, and are specialized for either epizoochory or myrmecochory. On the basis of our experimental study of dimorphic and trimorphic populations of F. pallescens subsp. pallescens, a genetic model is presented in order to explain the control of this intrapopulational polymorphism. It is postulated that two diallelic loci are tightly linked on the same chromosome in a functional supergene. One allele of each locus displays a dominance effect in the heterozygous state. Within the four possible homologous allelic segments, only two are present in the dimorphic populations, three in the trimorphic ones, and are otherwise associated in diverse combinations in the remaining taxa of the genus. Similar examples of fruit polymorphism are already documented in the tribe Valerianeae, subtribe Fediinae. The hypothesis is put forward that this fruit polymorphism is a synapomorphy for the subtribe.