Genetic Diversity of Natural and Planted Populations of Tsoongiodendron Odorum from the Nanling Mountains

27 Mar Genetic Diversity of Natural and Planted Populations of Tsoongiodendron Odorum from the Nanling Mountains

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Abstract

迁地保护是珍稀濒危植物保护的重要措施。观光木(Tsoongiodendron odorum)是古老的孑遗树种, 被列为国 家二级重点保护植物, 营建迁地保护林是对其进行保护的重要手段, 但已经营建的迁地保护林每个种群目前只保 存下来几十株个体。为了评价这些迁地保护林的遗传多样性现状, 作者采用ISSR分子标记对南岭地区观光木3个 人工迁地保护种群和4个自然种群的遗传多样性进行了比较。结果显示: 16条ISSR引物共扩增出362个条带, 其中 301个为多态条带, 多态条带百分比(P)为83.2%, 各种群P值为37.9–62.2%, 平均为53.1%, 表明观光木在物种和种 群水平都具有较高的遗传多样性。自然种群总体P值和Shannon信息指数(I)(80.9%, 0.3629)均高于人工迁地保护种 群(66.6%, 0.2990), 说明人工迁地保护种群遗传多样性较低。种群结构分析表明3个人工迁地保护种群均有可能来 源于源口自然种群。 4个自然种群间遗传分化系数(GST)为0.2495, 表明自然种群间存在显著遗传隔离, 基因流受阻 和生态环境差异是造成种群遗传分化的主要原因。在今后的迁地保护工作中, 我们建议从不同生态地理区收集种 质材料, 并在不同生态类型区开展迁地保护工作, 同时开展观光木种群生态生殖生物学研究。

English Abstract

Ex situ conservation, complementary to in situ conservation, plays an important role in preservation and recovery of endangered species. Tsoongiodendron odorum is a relic species that was listed in the
Second Grade of the List of Wild Plants Under State Protection (First Batch) in China. For protection of its
genetic diversity, ex situ conservation populations have been established and managed outside of natural habitats in several nature reserves since 1980. However, only dozens of individuals are currently saved from
each planted population. To assess the actual protective effectiveness of these planted populations, we detected and compared the genetic diversity of three planted populations from Nanling Mountains with four
natural populations using ISSR markers. Overall, we detected 362 total ISSR discernible bands with 16 ISSR
primers, of which 301 were polymorphic. The percentage of polymorphic bands (P) was 83.2%. At the population level, the percent of polymorphic bands ranged from 37.9% to 62.2%, with an average value of
53.1%. This result showed that T. odorum had high genetic diversity both at population and species levels.
However, the percentage of polymorphic bands and Shannon information index (I) of ex situ conservation
populations (66.6% and 0.2990) were much lower than those of natural populations (80.9% and 0.3629). We
deduced that there was a narrow genetic base for plantations of T. odorum. Population structure analysis revealed that three planted populations could be collected from the same wild population (i.e., YK population).
The genetic variation of four natural populations (GST=0.2495) showed that there was significant isolation
among populations, which would limit gene flow and population differentiation among populations. We pre-sent suggestions on regulating seed collection from different natural habitats to establish planted populations
and strengthening research on the reproductive biology of T. odorum.