|其他摘要||To understand the systematics and evolution of the genus Maianthemum s. l. (include Maianthemum s. str. and Smilacina), an integrative study was undertaken by means of morphological, cytological and molecular phylogenetic approaches. Moreover, both ethnobotanical survey of Maianthemum and population ecology of Maianthemum atropurpureum were conducted in northwestern Yunnan Province, SW China. The primary results are summarized as follows:
Leaf epidermis of 30 species from Maianthemum and related genera were investigated with both light microcopy (LM) and scanning electron microscopy (SEM) methods. No distinct epidermal variation was observed within Maianthemum species, whereas differences were found among genera of the tribe Polygonatae. The shapes of adaxial epidermal cells of Maianthemum are usually polygonal or irregular, with the anticlinal walls straight, arched, while those of daxial epidermal cells are usually irregular with the anticlinal walls simulate, sinuous to sinuate. The stomatal apparatus in all species were observed only on abaxial epidermis except for M. trifolium, without accessory cells. Under SEM, the inner margin of the outer stomatal rim is nearly smooth, sinulate or sinuous, and the cuticular membrane of the leaf epidermis is striated, sometimes striated to wrinkled, occasionally granular or scalelike. The stomatal apparatus are sunken, protuberant or equal to epidermis cells.
Chromosomal numbers and karyotypes of 10 species of Maianthemum from China were reported in this study. Three species were investigated cytologically for the first time. All species have a chromosome set of 2n = 36, except four species having polyploids in some populations: M. bifolium, M. atropurpureum, M. fuscum, and M. racemosum. The basic chromosome number of the genus was confirmed to be x = 18 and the genus is suggested to have been paleo-polyploidized. The results also showed striking variation of karyotype in different species, as in the numbers of metacentric, submetacentric, and acrocentric chromosomes as well as in the number of satellites. Three modes of unimodal, bimodal, and trimodal were recognized based on the number of clear gaps in chromosome length variation. The unimodal variation (without gap) was found in M. dahuricum from NE China, the bimodal variation (with one gap) in M. tatsienense, and almost the species from SW China have the trimodal variation (with two gaps). Our molecular study also supported similar results. In addition, the chromosome variation is also reflected from the karyotypic asymmetry. Maianthemum dahuricum from NE China has a 2B-type, M. japonicum and M. nanchuanense from NE to C China have a 2C-type, while species from SW China almost show 3B and 3C-types. Results of this cytological study provide a better understanding of phylogenetic relationships as well as chromosome evolution in the genus.
Forty-eight samples representing twenty-eight species of Maianthemum together with eleven from close taxa as outgroup were sequenced including both chloroplast and nuclear markers (trnL-F, rps16, rpl16, psbA_trnH, rbcL, ndhF, and ITS). Phylogenetic analysis of the molecular data robustly supported the monophyly of Maianthemum including both Maianthemum sensu stricto and Smilacina, and provided a moderate phylogeny for several clades within the genus. Species from the high mountains of southwestern China to the Himalayas formed a well supported clade, which characterized by large and colorful flowers, hairy stems and leaves. Maianthemum tatsienense and M. stenolobum form a clade which has a distribution from southwestern to central China. Species with linear petals form a well supported clade, which distributed from Japan, northeastern to central China. The North American M. racemosum is sister to a clade including the tropic American species with a relatively low support. Many important morphological characters were not consistent with the molecular data, e.g. rhizome, representing a sympodial aggregation consisting of several individual rhizome units. But we also found some characters, such as the ratio of filament and anther in length, the degree of stigma dehiscent, were related to DNA evidences. Maianthemum showed recent or fast radiation in the high mountains of southwestern China, and complex intercontinental relationships in the Northern Hemisphere.
In Gongshan and Zhongdian county of Yunnan, M. atropurpureum was the most common species collected traditionally as so-called “Zhu-ye-cai” by local residents. In order to evaluate on the impacts of harvesting, population ecology of M. atropurpureum, including population density, height and basic diameter of ramets, biomass, ramets flowering/m2, were investigated in ten patches of Gongshan and Zhongdian. The results reveal that populations of M. atropurpureum in Gongshan are less affected by local collection and gathering than those in Zhongdian.
In Northwest Yunnan, including Lujiang Prefecture (Liuku, Fugong, Gongshan) and Deqing Prefecture (Weixi, Zhongdian and Deqin), three kinds of key informants, that is, collectors, vendors and restaurateurs, were interviewed. Vernacular name(s), price, harvest, frequency, and trade mechanisms and amount, were recorded. The availability, seasonal and yearly changes of Maianthemum resources and marketing were documented through semi-structured interviews. In Fugong, a participant observation was undertaken for understanding the collection behavior and process.
M. atropurpureum and M. purpureum are generally harvested and sold in Northwest Yunnan. In Weixi, however, M. tatsienense, M. forrestii and M. henryi were also found in the marketplace. In local communities, M. atropurpureum was more popular and better sold than M. purpureum. Seasonality and resource availability were considered as the main reasons resulting in price instability, supply-and-demand balance, and tourism as the other factors. The price of Zhu-ye-cai fluctuated from 1-16 yuan RMB per kilogram.
In Zhongdian, the resource of Zhu-ye-cai was declining at an unexpected rate, being speeded up by degradation and destruction of fir old-growth. To some extent, local tourism stimulates and motivates the existing over-harvesting and consumption. In comparison, there was a great exploitive potential, with abundant resource in Fugong and Gongshan.|