日本産エンレイソウ属植物4種の交配・受粉機構  [in Japanese] Breeding and pollination systems of four Japanese Trillium species  [in Japanese]

Several breeding experiments were conducted to clarify the breeding and pollination systems of four Japanese Trillium (Liliaceae) species, i.e., T. kamtschaticum, T. apetalon, T. tschonoskii and T. smallii, in their natural habitats. Based on bagging experiment prior to flowering, all four species showed self-compatibility and also no significant differences in seed set compared to open pollinated individuals. Although no effective wind pollination occurred in all four species, pollination accounted for 46% of seed set in T. kamtschaticum. Field observations of insect visits also confirmed that no insect pollination was taking place in T. apetalon and T. smallii. Several Coleoptera and Diptera were observed visiting T. kamtschaticum and T. tschonoskii. However, their activities were low and infrequent. Accordingly, it was suggested that insect pollination in T. kamtschaticum was imperfect and the observed fecundity level resulted from the complementary contributions of both outbreeding and inbreeding systems. Furthermore, sufficient cross- and self-pollination by hand did not also show any significant differences in seed set from open-pollinated individuals in all four species. This fact indicates that seed set in these species is determined not by the frequency of pollination, including pollinator visiting, but by the resources of the plant itself. Consequently, although these four species substantially possess the possibility of both outbreeding and inbreeding, inbreeding proved to be the dominant breeding system. However, subsequent resource limitation allows only certain levels of fecundity regardless high fertilization levels, and as a result guarantees continuous yearly flowering and fruiting.