| Paphiopedilum micranthum, Paphiopedilum malipoense, and Changnienia amoena are three endangered orchid species in China. In the present study, the genetic diversity and population genetic structure of the three species were investigated using RAPD technique and morphological analysis. The main results are highlighted in the following.1. A total of 161 individuals representing 4 natural populations of P. micranthum in Yunnan and Guizhou. SW China were surveyed using 12 RAPD primers. At species level, the percentage of polymorphic bands (PPB) was 71.6 %, Nei's gene diversity (h) was 0.217 and Shannon index (I) was 0.3301. At population level, however, the means of the three indexes were 45.2 %, 0.1457 and 0.2204, respectively. These results indicated that the genetic diversity of P. micranthum was a bit lower than those of other out-cross orchid species. AMOVA showed that 20.31% of the genetic diversity resulted from differentiation among populations with remaining 79.69% residing within populations. The coefficient of gene differentiation (Gst) generated by POPGENE was 0.2958, indicating slightly higher population differentiation compared with other out-cross orchid species. Spatial autocorrelation analysis showed that significant spatial structure existed within each of two studied populations. No significant correlation between genetic distance and spatial distance was found.2. Based on 10 individuals of P. malipoense sampled from 2 populations located in Guizhou, much lower genetic diversity was found by RAPDs, with PPB = 49.5%, h = 0.1174, I= 0.1764 at species level, and PPB= 12.75%, h = 0.0486, 7=0.0712 at population level. Although great efforts had been made, the sample size was still small, and thus the results may be bias to some extent.3. A total of 216 individuals representing 11 natural populations of C. amoena located in Henan, Hubei, Hunan and Jiangxi provinces were surveyed using 16 RAPD primers. At species level, PPB was 80.7 %, h and I were 0.197 and 0.3116, respectively. At population level, the means of three indexes were 40.9%, 0.1247 and 0.1902, respectively. These results indicated that the genetic diversity of C. amoenawas lower than other out-cross orchid species. AMOVA showed that 43.48% of the genetic diversity existed among populations, while the Gst generated by POPGENE was 0.3580. Both suggested high level of genetic differentiation among populations in this species. No spatial structure within populations was revealed by spatial autocorrelation analysis. In addition, correlation did not exist between genetic distance and spatial distance.4. Morphological study on 7 populations of Changnienia amoena found medium variation within populations in 12 characters, with the CV values ranging from 0.022 to 0.300. The averages of observation values of all the characters in LS population were the highest among 3 studied populations (XN2, XN4 and LS). According to our statistic in XN4 population, the number of pseudo-bulbs did not show significant correlation with other characters.The factors leading to the endangerment of these orchid species were analyzed. based on our genetic studies and other information about P. micranthum, P. malipoense. and C. amoena. First, over collection of wild individuals is the direct cause for the rare and endangerment of these species, particularly P. malipoense. Second, the habitats suitable for orchid species have been seriously destructed and fragmented in recent decades. As a result, the number and sizes of the extant populations have decreased greatly, which in turn lead to further loss of genetic diversity and alternation of population genetic structure of these species. As to C. amoena, its low propagation ability also made it difficult to survive in the wild. On the bases of these findings, the following conservation strategies are proposed: (1) in situ conservation will be suitable for P. micranthum, because it possess high ability of clonal growth and sufficient genetic diversity. (2) In contrast, an ex situ strategy should be taken int... |
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