Population Biosystematic And Conservation Biology Of Cycas Debaoensis

All Cycas in China have been given the First Grade Conservation Status, and among which Cycas debaoensis is the endemic species to Southwestern China. Studies of population ecology, morphology and DNA sequences of the intergenic spacer atpB-rbcL of cpDNA were performed on C. debaoensis, with an attempt to discuss its geographic distribution, morphological and genetic diversity. Based on these results, the strategies for the conservation of this species have been proposed.Geographically, C. debaoensis is limited to the boder of GuangXi and YunNan province. Thirteen wild populations of the species including three new found were investigated, and can be ranged into two Groups of karst type and sand type according to the soil types they grow on. The populations of the karst type are scattered in isolated limesone hills, while the populations of sand type distribute along the Gula boundary river between GuangXi and YunNan province.The morphological characteristics of all the populations of the karst type and some populations of the sand type from the south Gula river(450-1100m) has no difference with that of the type population in Fuping village, Debao county(750-900m). They all have tripinnate leaves and more lobes of megasporophylls(each side 17-25). However, a few characteristics such as bipinnate(rare simply pinnate) leaves and less lobes of megasporophylls(each side 11-19) distinguish the north populations of Gula boundary river areas(230-400m) from the type population. That is to say, there are two recognized morphological ecotype in Cycas debaoensis. But the haplotype relationships of the interecotypes based on the sequencing of the intergenic spacer atpB-rbcL of cpDNA, are not consistent with the morphology distinction. The two morphological ecotypes share the common cpDNA haplotypes, and the wild populations of the two ecotypes are geographically continuous. This results suggest that that the morphology of Cycas debaoensis is diverse.Compared with other species of C. micholitzii Complex, the ecotype distinguished from the type population of C. debaoensis share more common with C. multifrondis in morphology. Besides, it has been said that the original habitat of C. multifrondis is also at the boder between GuangXi and YunNan province. So, it can be inferred that the populations from north Gula river, which are morphologically distinguished from the type population of C. debaoensis, might be the wild populations of C. multifrondis. Anyway, this conclusion needs more evidences and studies before further discussions about the affinity of C. debaoensis and C. multifrondis to be made.55 individuals from the above populations were sampled for sequences of the intergenic spacer atpB-rbcL of cpDNA, and only 5 haplotypes were detected totally. In the total 5 haplotypes, Hb and Hc are the common haplotypes, the others are just harbored by each one of the individuals. All the populations of the karst type and some populations from south part of Gula river share the mainly common one haplotype, while other populations share another one haplotype. But the populations from north Gula river harbore both the two common haplotypes. Thus, the area which these north populations inhabit today may be considered as current center or possible refugia during the Quaternary glacier of C. debaoensis.In situ strategy should be emphasized in conservation of C. debaoensis. Based on studies of the morphology and cpDNA sequencing, three three ESUs (ESU1-3) are designated. The gradation of conservation priority is ESU1, ESU2 and ESU3. For the most differentiated ESU1, it should be given the highest priority to its conservation. The second priority should be given ESU2, because it inculds the type population. Finally the Group3 should also be taken into account in in situ conservation. Population NY and CY, FP and NH, BW is emphases in each ESU, respectively.As for ex situ conservation of C. debaoensis, three ESUs must be separately managed. Ex situ to enhance diversity through transplant or reintroduction from each other is not advisable, in order to avoid loss of critical adaptive features and the possibility of compromised long-term viability due to outbreeding depression. It should be also avoided to introduce the cultivated individuals to the wild populations of C. debaoensis from the neighboring villages, because most of them are purchased from different areas.The ESUs designated should also be considered in the forthcoming project of restore C. debaoensis to avoid reintroduction from different areas.