Breeding system and crossability in JapaneseEpimedium (Berberidaceae)

A series of experimental pollinations involving six species ofEpimedium provided strong evidence for an outbreeding system and no internal (postmating, postpollination) barrier to hybridization in the taxa concerned. Self-pollinations of four species,E. diphyllum, E. trifoliatobinatum, E. grandiflorum andE. sempervirens indicated high self-incompatibility (at most 5.4%, usually 0% in capsule-set). Field experiments in a population revealed the occurrence of cross-pollination. On the other hand, interspecific cross-pollinations showed high crossability at any combination of species (33.3%–100% in capsule-set). Furthermore, the interspecific F₁s obtained germinated at a high rate (usually more than 20%) and three of them, which bloomed, are highly fertile (more than 68.6% in pollen viability). The results were discussed in connection with the isolating mechanisms between the species ofEpimedium.