Patterns of Genetic Variation in Swertia przewalskii, an Endangered Endemic Species of the Qinghai-Tibet Plateau |
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Authors: | Defang Zhang Shilong Chen Shengyun Chen Dejun Zhang Qingbo Gao |
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Institution: | (1) Laboratory of Qinghai-Tibet Biological Evolution and Adaptation, Northwest Plateau Institute of Biology, Chinese Academy of Sciences, 59 Xiguan Avenue, Xining Qinghai, 810001, P.R. China;(2) Graduate School, Chinese Academy of Sciences, Beijing, 100039, P.R. China |
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Abstract: | Swertia przewalskii Pissjauk. (Gentianaceae) is a critically endangered and endemic plant of the Qinghai-Tibet Plateau in China. RAPD and ISSR
analyses were carried out on a total of 63 individuals to assess the extent of genetic variation in the remaining three populations.
Percentage of polymorphic bands was 94% (156 bands) for RAPD and 96% (222 bands) for ISSR. A pairwise distance measure calculated
from the RAPD and ISSR data was used as input for analysis of molecular variance (AMOVA). AMOVA indicated that a high proportion
of the total genetic variation (52% for RAPD and 56% for ISSR) was found among populations; pairwise Φ
ST comparisons showed that the three populations examined were significantly different (p < 0.001). Significant genetic differentiation was found based on different measures (AMOVA and Hickory θB) in S. przewalskii (0.52 on RAPD and 0.56 on ISSR; 0.46 on RAPD and 0.45 on ISSR). The differentiation of the populations corresponded to low
average gene flow (0.28 based on RAPD and 0.31 based on ISSR), whereas genetic distance-based clustering and coalescent-based
assignment analyses revealed significant genetic isolation among populations. Our results indicate that genetic diversity
is independent of population size. We conclude that although sexual reproduction and gene flow between populations of S. przewalskii are very limited, they have preserved high levels of genetic diversity. The main factors responsible for the high level of
difference among populations are the isolation and recent fragmentation under human disturbance. |
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Keywords: | Swertia przewalskii genetic variation RAPD ISSR endemic plant Qinghai-Tibet Plateau |
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