A Study On The Reproductive Ecology Of Satyrium Ciliatum Ldl. (Orchidaceae)

In the nearly 20,000 species of the Orchidaceae, Satyrium ciliatum Ldl. is the only species which has been reported to display two separate sexual forms, the female form and the hermaphroditic form. An intensive research on the reproductive ecology of this species, therefore, may shed some light on our understanding of the evolution of the reproductive systems in the Orchidaceae. In this work, the breeding system and productive ecology of S. ciliatum were investigated. The results are summarized as follows: 1. Only hermaphroditic form and male sterile form were discovered in populations of Satyrium ciliatum, and the male sterile form was always found to grow together with the hermaphroditic form. The male sterile form appeared in six populations of the 16 populations investigated, accounting for about 38% of the total. The percentage of male sterile individuals within a population varied markedly between populations, ranging from 1% to 78%, and exceeding 50% in only one population. 2. Breeding system experiments conducted in a population of Satyrium ciliatum including both male sterile form and hermaphroditic form have shown that both forms were apomicts, and the formation of mature embryos was independent of pollination. This is the first time to find the coexistence of both male sterile apomictic biotype and hermaphroditic biotype within a same population in the Orchidaceae. 3. The floral structure varied greatly in Satyrium Ciliatum. This species could be divided into six biotypes based on the gender and morphology of the flower: short-spurred female, long-spurred female and three-petaled female small-flowered hermaphrodite, big-flowered hermaphrodite, short-spurred hermaphrodite. 4. Some significant differences were found in reproduction success and ecological preferences between the short-spurred female biotype and the small-flowered hermaphrodite biotype. 1) The short-spurred male sterile biotype could endure more disadvantageous environmental conditions than the small-flowered hermaphrodite one. 2) The short-spurred form blossomed earlier than the small-flowered biotype. 3) Although the short-spurred male sterile biotype produced more fruits on average, no significant difference was found between these two biotypes as to the average number of embryos of an individual plant. 4) The distribution strategies of source of the two biotypes exhibited both advantages and disadvantage.