活血丹小尺度空间遗传结构

活血丹(Glechoma lonituba)是唇形科活血丹属的多年生克隆草本植物。采用简单重复序列区(ISSR)分子标记技术,比较分析了3个不同斑块活血丹的遗传多样性、克隆多样性以及小尺度空间遗传结构,并探讨其与生境异质性、繁殖体传播和人为干扰的相关性。结果表明:1)活血丹物种水平的遗传多样性很低,各斑块的遗传多样性较低,以水渠边斑块最高,平葛村斑块次之,竹林下斑块最低。2)活血丹物种水平的克隆多样性较高,各斑块活血丹的克隆多样性以水渠边斑块最大,平葛村斑块次之,竹林下斑块最低。3)遗传分化系数Gst为0.7129,表明活血丹的遗传变异大部分存在于斑块间;斑块间的基因流较小,仅为0.2004。4)空间自相关分析表明活血丹一定的空间距离下存在显著的空间遗传结构,竹林下斑块在100cm时存在显著性正相关,其X轴截矩为205.994cm;平葛村斑块在200cm时存在显著性正相关,其X轴截矩为235.388cm;水渠边斑块在150cm时存在显著性正相关,其X轴截矩为240.336cm。应用软件SPAGeDi 1.2软件对各斑块的空间遗传结构进行量化,表明平葛村斑块具有最强的空间遗传结构,水渠边和竹林下斑块的空间遗传结构较弱。活血丹的遗传结构、克隆结构及空间分布格局受到其繁殖体传播特征、人为干扰和繁殖权衡的影响,是其对生境异质性的适应结果。

Fine-scale spatial genetic structure of Glechoma longituba

Fine-scale spatial genetic structure, which indicates nonrandom spatial distribution of genotypes or genetic diversity, has important consequences for population biology. The study of fine-scale spatial genetic structure can provide an understanding of the key processes and mechanisms involved in the maintenance of plant populations. Glechoma longituba is a perennial herbaceous clonal plant species that belongs to the Labiatae family. Glechoma longituba is a herb of medicinal importance that is widely distributed in China, and its phenotypic characteristics vary among different habitats. The genetic diversity, clonal diversity, and fine-scale spatial genetic structure of Glechoma longituba plants collected from three different patches (Shuiqubian, Pinggecun, and Zhulinxia) with different habitats were analyzed using inter-simple sequence repeat (ISSR) molecular markers. In addition, the correlation with habitat heterogeneity, propagule propagation, and human disturbance were also examined in the study. The results indicated the following: 1) Genetic diversity of Glechoma longituba at the species level was relatively low (percentage of polymorphic loci, P=31.15%; Shannon informative index, I=0.1601; Nei''s index, h=0.1096). Genetic diversity of Glechoma longituba was highest in Shuiqubian patch (P=21.31%, I=0.0965, h=0.0627), followed by Pinggecun patch (P=8.20%, I=0.0354, h=0.0226), and Zhulinxia patch (P=3.28%, I=0.0120, h=0.0073). 2) Clonal diversity of Glechoma longituba at the species level was relatively high (number of genets, G=73; ratio of genets to ramets, G/N=0.2332; Simpson''s diversity index, D=0.8843; genotypic evenness, E=0.8192). The clonal diversity of Glechoma longituba was highest in Shuiqubian patch (G=60, G/N=0.5660, D=0.9693, E=0.8747), followed by Pinggecun patch (G=10, G/N=0.1087, D=0.8430, E=0.9075), and Zhulinxia patch (G=3, G/N=0.0260, D=0.2642, E=0.3599). 3) Genetic differentiation coefficient (G_st) was 0.7129, which indicated that most of the genetic variation existed among patches, whereas little genetic variation existed within patches. The estimated gene flow was as low as 0.2004. 4) Spatial autocorrelation analysis showed that the autocorrelation coefficient of Glechoma longituba in Zhulinxia patch was significantly positive at a distance of 100 cm with an X-intercept of 205.994 cm but significantly negative at a distance of 350 cm. The autocorrelation coefficient in Pinggecun patch was significantly positive at a distance of 200 cm with an X-intercept of 235.388 cm but significantly negative at a distance of 450 cm. The autocorrelation coefficient in Shuiqubian patch was significantly positive at a distance of 150 cm with an X-intercept of 240.336 cm but significantly negative at a distance of 350 cm. Analysis with SPAGeDi 1.2 software showed that the strength of spatial genetic structure in Pinggecun patch was greater than those in Shuiqubian and Zhulinxia patches. The Sp ratio (used to compare the extent of spatial genetic structure among populations) for Pinggecun, Shuiqubian, and Zhulinxia patches was 0.0944, 0.0558, and 0.0556, respectively. The genetic diversity, clonal diversity, and fine-scale spatial genetic structure of Glechoma longituba are affected by propagule dispersal characteristics, human disturbance, and trade-off between investment in sexual reproduction and clonal propagation and might be a consequence of adaptation to habitat heterogeneity.