|其他摘要||The morphological and cytological characters of the genus Begonia sect. Diploclinium were studied. The phylogenetic relationship of sect. Diploclinium together with other Begonia sections was discussed based on cladistics and molecular phylogenetic studies. The threatened status of Chinese Begonia sect. Diploclinium species was determined on the basis of IUCN Red List Categories and Criteria (Version 3.1). In addition, some notes on production biology and plant introdunction were inferred from the conducted conservation biology studies on sect. Diploclinium species especially on B. gulinqingensis. The main results are summarized as follows:
(1) Pollen morphology
High diversity existing in pollen morphology was shown in species of sect. Diploclinium. Among them, many shared similarities and might be much more closely related with species of other Begonia sections, and should be excluded from sect. Diploclinium. Thus, the size and sculpture on the surface of pollen are probably one of the best parameters to characterize sections of Begonia effectively. It was also suggested that the species with lager pollens could be more primitive, while those with smaller ones might be much advanced. The proposal of sect. Leprosae was not well supported.
(2) Seed micromorphology
High diversity in seed mircromorphology was also shown in species of sect. Diploclinium. Among them, many shared similarities and might be much more closely related with species of other Begonia sections, and should be excluded from sect. Diploclinium. Thus, the morphological features of seed are probably the other parameters to characterize sections of Begonia effectively. It was also suggested that the species with lager seeds could be more primitive, while those with smaller ones might be much advanced. The proposal of sect. Leprosae was also not well supported.
(3) Characters of leaf epidermis
Our study of characters of leaf epidermis under light microscope and scanning electron microscope indicated that high diversity exists in Chinese Begonia. Although the characters did not show its importance to the taxonomy at sectional level of the genus Begonia, it showed some value to the treatment of specific treatment. Additionally, stomatal group is discovered in B. peltatifolia and B. fenicis which might be adapt to the arid surroundings.
Based on this study and literature survey, we infer that aneuploidy and polyplodization have played an important role in the speciation of Chinese Begonia. X=15 is suggested to the basic chromosome number for Chinese Begonia. The other sections of Chinese Begonia might have evolved from sect. Coelocentrum by descending or ascending aneuploidy alteration.Our cytological studies also revealed high diversity in sect. Diploclinium. Among them, many shared similarities and might be much more closely related with species of other Begonia sections. Thus, the somatic chromosome number is probably not a good parameters to characterize sect. Diploclinium of Begonia effectively. The proposal of sect. Leprosae was also not well supported.
The Constant Index of the strict consensus tree was only 0.35, implying that there were too many non-homoplasy characters were used in cladistic analysis. So the key of phylogenetic studies of the examined taxa was to find out exact characters which could indicate actual evolutionary lineages.
(6) Molecular phylogeny
Based on both MP and Bayesian analysis using sequence data from internal transcribed spacer (ITS) regions of nuclear ribosomal, it was indicated that sect. Diploclinium based on morphology are polyphyletic. The sect. Leprosae was not supported as monophyletic. Thus the separation of the traditionally accepted sections according to the characters of ovary was not well supported. The existing infragenetic morphology-based system is imperfect. The evolutionary rate of the trnL-F might be too slow to analysis in Chinese Begonia species.
Based on the morphological, cytological and molecular phylogenetic studies, the sect. Diploclinium was considered an assemblage of taxa strictly around the type species (B. grandis), and reported here in its strict sense, while the traditionally acceptation based on morphology was in the large sense. The plants with tubers and the limestone habitats delimit sect. Diploclinium species from other sections of Begonia. Thus, A few taxonomic implications were inferred: B. leprosa, B. cavaleriei and other sect. Diploclinium s. l. species which share some characters should be excluded from sect. Diploclinium s. str. and incorporated to sect. Coelocentrum or a new section; B. crassirostris should be a member of sect. Sphenanthera; species with modarate to deep lobed leaves should be included in sect. Platycentrum or proposed as a new section; species with modarate to deep lobed leaves should be proposed as a new section; the situation of species from Taiwan remained unclear, it should need to be used in combination with other characters for separating taxa in this complex; two new species B. guaniana and B. gigabracteata were described and illustrated.
The evolution of pollens, seeds, and pattern of anticlinal walls of leaf epidermis were speculated. The evolution approach of pollens might be from large size to diminutive, from shallow sculpture on the surface to deep; the evolution of seeds might be from large size to diminutive; while the evolution of attern of anticlinal walls of leaf epidermis might be from straight, arched to undulant.
Finally, it was also suggested that the species of the sect. Coelocentrum might be primitive, while these of the sect. Diploclinium might be originated from the ancient species closely related with sect. Coelocentrum species. In correspondingly, sect. Reichenheimia which was also closely related with sect. Diploclinium might be more primitive than sect. Sphenanthera.
2 Conservation biology
Our studies on the conservation biology of Chinese Begonia sect. Diploclinium suggested that more than 70% species were in danger of extinct. The main factor threatening to the survival of the Chinese begonias was hunman activities which caused the disturbance or destruction of the habitats. In order to protect this resourse effectively, there are some details should be noted: more knowledge-transference to local people; proper collectiong methods in fieldword; introduction and reintroduction.
3 Production biology and introduction
Most of the the Chinese Begonia sect. Diploclinium species had two types of effective productive patterns: asexual and sexual production. It was not only useful to cultivate in greenhouse but also reintroduction in the field to increase the number of population. Some in situ and ex situ conservation studies were conducted by our research group and some results have been achieved.|