观光木片断化居群的遗传多样性和交配系统

doi:10.3724/SP.J.1003.2012.09083

摘要/Abstract

摘要：

观光木(Tsoongiodendron odorum)是我国特有的濒危植物, 有居群较小、间断分布的特点。为探讨生境片断化对观光木居群的遗传多样性和交配系统的影响, 我们采用8对微卫星引物对采自广东南昆山的观光木片断化居群的61个成株和15个家系共780个种子进行了基因分型, 调查了5个空间隔离的斑块中观光木的两代遗传多样性以及各个层次(居群、斑块及个体)的交配系统参数。结果显示: 片断化生境中观光木成株遗传多样性水平适中(H_E= 0.522), 种子遗传多样性比成株稍低(H_E= 0.499), 但没有显著的差异, 近交系数在种子中也没有显著的升高, 暗示生境片断化并没有侵蚀观光木的遗传多样性; 多位点交配系统分析(MLTR)结果表明, 该片断化生境中观光木为高度异交树种(t_m = 1.000), 只有较少的双亲近交(biparental inbreeding)和相关性交配(correlated mating)事件发生, 但有效花粉供体(effective pollen donor)数目较少(N_ep为3.7-5.4); 5个斑块间异交率差异不明显, 但小的斑块有效花粉供体相对较多; 另外, 观光木个体之间的异交率存在明显差异, 少数个体存在自交现象。这些结果为濒危物种观光木的长期保护提供了重要的遗传学信息。

关键词: Tsoongiodendron odorum, 生境片断化, 多位点交配系统分析, 保育遗传学, 微卫星

Abstract

Habitat fragmentation is one of the most serious threats to plant diversity. In general, fragmentation negatively impacts the genetic variability of plant populations due to increased random genetic drift, inbreeding, and reductions in gene flow. To investigate the effect of habitat fragmentation on genetic diversity and the mating system of Tsoongiodendron odorum, in this study, we analyzed genetic diversity and the mating system in hierarchical levels at the population, stands, and the individual scales in a fragmented T. odorum population. We sampled and mapped 61 adult individuals from the population. Using eight microsatellite loci, we genotyped a total of 780 seeds from 15 maternal trees for the mating system analysis. The results revealed moderate levels of genetic diversity in both adults (H_E= 0.522) and seeds (H_E= 0.499) with no significant differences between the two ontogenic stages. In addition, we did not observe a significant increase in the seeds inbreeding coefficient. Results from the multilocus mating system analysis indicated that T. odorum was an outbreeding species with a multilocus outcrossing rate (t_m) of 1.000. A small number of biparental inbreeding and correlated mating events were detected in this fragmented population. We found a small number of effective pollen donors (N_ep is between 3.7 and 5.4), which seems to be a common character of insect-pollinated canopy trees. Minor differences in outcrossing rates were detected among stands, and more pollen donors were found in smaller stands. However, outcrossing rate was significantly different among individuals, and a few selfing events were detected in some seed trees. These results may provide fundamental information required to establish long term conservation strategies for this endangered tree which is endemic to China.

Key words: Tsoongiodendron odorum, habitat fragmentation, multilocus mating system analysis, conservation genetics, microsatellite

王霞, 王静, 蒋敬虎, 康明 (2012) 观光木片断化居群的遗传多样性和交配系统. 生物多样性, 20, 676-684. DOI: 10.3724/SP.J.1003.2012.09083.

Xia Wang, Jing Wang, Jinghu Jiang, Ming Kang (2012) Genetic diversity and the mating system in a fragmented population of Tsoongiodendron odorum. Biodiversity Science, 20, 676-684. DOI: 10.3724/SP.J.1003.2012.09083.

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链接本文: https://www.biodiversity-science.net/CN/10.3724/SP.J.1003.2012.09083

https://www.biodiversity-science.net/CN/Y2012/V20/I6/676

图/表 7

参考文献 39

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斑块 Stand	成株数目 No. of adults	采种成株 No. of seed trees	果实数目 No. of fruits	种子数目 No. of seeds
NKS1	5	1	4	60
NKS2	13	3	9	134
NKS3	20	7	26	389
NKS4	16	3	11	168
NKS5	7	1	2	29
总计 Total	61	15	52	780

斑块 Stand	成株数目 No. of adults	采种成株 No. of seed trees	果实数目 No. of fruits	种子数目 No. of seeds
NKS1	5	1	4	60
NKS2	13	3	9	134
NKS3	20	7	26	389
NKS4	16	3	11	168
NKS5	7	1	2	29
总计 Total	61	15	52	780

引物 Primer	成株 Adults					种子 Seeds					总计 Total
引物 Primer	NKS1	NKS2	NKS3	NKS4	NKS5	NKS1	NKS2	NKS3	NKS4	NKS5	总计 Total
TOD1	1	3	3	3	2	2	3	3	3	1	3
TOD2	2	3	3	4	3	3	3	4	4	3	4
TOD5	3	6	6	9	5	5	7	7	6	4	9
TOD6	4	5	6	5	4	4	5	6	5	4	6
TOD8	2	1	2	3	2	1	3	3	2	1	3
TOD11	2	2	2	3	3	2	3	2	3	2	3
TOD12	2	2	3	3	3	3	4	3	3	2	5
TOD52	4	6	9	9	5	9	7	10	8	2	15
总计 Total	20	28	34	39	27	29	35	38	34	19	48

引物 Primer	成株 Adults					种子 Seeds					总计 Total
引物 Primer	NKS1	NKS2	NKS3	NKS4	NKS5	NKS1	NKS2	NKS3	NKS4	NKS5	总计 Total
TOD1	1	3	3	3	2	2	3	3	3	1	3
TOD2	2	3	3	4	3	3	3	4	4	3	4
TOD5	3	6	6	9	5	5	7	7	6	4	9
TOD6	4	5	6	5	4	4	5	6	5	4	6
TOD8	2	1	2	3	2	1	3	3	2	1	3
TOD11	2	2	2	3	3	2	3	2	3	2	3
TOD12	2	2	3	3	3	3	4	3	3	2	5
TOD52	4	6	9	9	5	9	7	10	8	2	15
总计 Total	20	28	34	39	27	29	35	38	34	19	48

生活史 Stage	斑块 Stands	样本 Sample size (N)	等位基因数 No. of alleles per locus (A)	等位基因丰富度 Allelic richness per locus (A_R)	观测杂合度 Observed heterozygosity (H_O)	预期杂合度 Expected heterozygosity (H_E)	近交系数 Inbreeding coefficient (F_IS)
成株 Adults	NKS1	5	2.50	2.30	0.588	0.464	-0.267*
	NKS2	13	3.50	2.39	0.450	0.454	0.009
	NKS3	20	4.25	2.58	0.621	0.547	-0.134*
	NKS4	16	4.89	2.76	0.610	0.575	-0.061
	NKS5	7	3.88	2.68	0.542	0.568	0.047
	平均 Average	12.2	3.80	2.54	0.569	0.532	-0.070
种子 Seeds	NKS1	60	3.63	2.38	0.652	0.496	-0.315*
	NKS2	134	4.38	2.48	0.597	0.518	-0.150*
	NKS3	389	4.75	2.50	0.542	0.538	-0.007
	NKS4	168	4.25	2.59	0.654	0.571	-0.143*
	NKS5	29	2.38	1.97	0.455	0.370	-0.229*
	平均 Average	156	3.88	2.38	0.581	0.532	-0.092