濒危植物格木天然种群的表型多样性及变异

【目的】通过对濒危植物格木在我国中心分布区种群的果荚和种子表型性状测量分析,研究其表型多样性及变异规律,结合地理气候信息探讨影响表型变异的关键因子,为格木天然种群的遗传多样性保护恢复和引种栽培提供科学依据。【方法】对8个格木天然种群114个单株的13个果荚及种子表型性状进行测量,利用巢式方差分析、多重比较、相关性分析、主成分分析、聚类分析等分析方法,探讨格木天然种群的表型多样性水平、进化和适应性潜力、表型变异规律、表型分化水平、种群聚类特征及其与地理气候因子的相关性。【结果】格木表型多样性水平中等,13个性状的Shannon-Wiener指数在1. 911 1(种形指数)～2. 103 9(果荚周长)之间,平均2. 027 8;8个种群的Shannon-Wiener指数在0. 920 9(P6)～1. 885 6(P8)之间,均值为1. 474 7。格木表型性状离散程度较轻,13个性状的变异系数在7. 544 6%(种子长)～18. 868 5%(果荚面积)之间,均值为12. 410 9%; 8个种群的变异系数在8. 852 9%(P1)～13. 984 8%(P5)之间,均值为12. 410 9%。13个表型性状的极大值为极小值的1. 395 2(种形指数)～2. 805 6(每荚种子数)倍,均值为1. 791 7。巢式方差分析表明,格木13个表型性状在种群间和种群内均存在极显著差异(P<0. 01),说明这些性状在种群间和种群内均存在丰富的变异;种群内的变异(40. 387 1%)远大于种群间(11. 948 9%)。种群平均表型分化系数为21. 857 9%,各性状的分化系数变化幅度在7. 476 5%(种形指数)～38. 674 0%(果荚宽)之间。相关性分析表明,13个表型性状之间大多存在显著或极显著相关,果荚宽度、种子周长等性状和温度指标呈负相关,与纬度呈正相关,格木在气温高、降雨量大的地区往往具有小果荚、小种子的特征,随着温度指标降低和纬度增加,格木果荚及种子有变大的趋势。格木13个表型性状可提炼为4个主成分,累积贡献率为87. 382%。8个天然群体基于欧氏距离可分为3类:第1类2个种群呈现果荚小、种子小的特征,该类表型主要出现在格木分布区的南端;第2类5个种群呈现果荚大、种子大的特征,该类表型主要出现在格木分布区的北部,仅1个种群位于分布区的南部;第3类1个种群呈现果荚小、种子少、种子大而薄的特征,该类表型出现在格木南北分布区的中间衔接部。【结论】格木的表型多样性处于中等水平,在个体上存在较为丰富的变异。在群体及物种水平上,格木表型性状离散程度较轻,各个性状分布相对集中,较为稳定,不易发生群体分化,拥有特殊表型的格木单株具有较高的保存价值。果荚及种子大小进化及适应性潜力相对较大,种形指数最不易产生变异。种群内的变异是格木表型变异的主要来源,格木的种质资源收集保存可减少种群数量,增加种群内个体数量,并优先收集有特殊表型的单株。广西省容县和龙圩区的格木种群是格木遗传多样性保护及种质资源收集保存的重点区域。年均温等温度因子是影响格木表型及分布的最主要因子。果荚及其中种子的大小是格木种群间聚类的主要依据。

Phenotypic Diversity and Variation in Natural Populations of Erythrophleum fordii,an Endangered Plant Species

【Objective】 The phenotypic traits of pod and seed from an endangered plant Erythrophleum fordii were measured to investigate the phenotypic diversity and variation pattern of populations.And combing with geographical and climatic information, the factors affecting the phenotypic variation were discussed.This study provides a basis for genetic diversity conservation, restoration, and cultivation of E.fordii.【Method】 The phenotypic characteristics of thirteen pods and seeds from 114 individuals of eight natural populations were measured.Nested analysis of variance, multi-comparison, correlation analysis, principal components analysis, and cluster analysis were used to study phenotypic diversity,evolution and adaptive potential, patterns of phenotypic variation, level of phenotypic differentiation, cluster of populations, and the correlation between phenotypic traits and climate factors, respectively.【Result】 E.fordii showed a modest level of phenotypic diversity, the range of Shannon-Wiener index is from 1.911 1 (Shape index of seed) to 2.1039 (Perimeter of pod)with an average of 2.0278.The range of Shannon-Wiener index of eight populations is from 0.9209 (P6) to 1.8856 (P8) with an average of 1.4747.The range of variation of variance among the 13 traits was from 7.5446%(Length of seed)to 18.8685%(Area of pod)with an average of 12.4109%.The range of variation of variance among the eight populations was from 8.8529%(P1) to 13.9848%(P5) with an average of 12.4109%.The range of times of maximum and minimum was from 1.3952(Shape index of seed) to 2.8056(Number of seeds in pod)with an average of 1.7917.Analysis of nested variance showed that there was a significant differences (P<0.01) among and within populations, suggesting that abundant variation among and within populations.The within-population variation( 40.3871%) was much larger than the among-population variation(11.9489%);and the average phenotypic population differentiation coefficient was 21.8579% with a range from 7.4765%(Shape index of seed)to 38.6740%(Width of pod).Correlation analysis revealed that there were significant correlations among most phenotypic traits.The significantly negative correlation between the width of pod, length of seed and perimeter of seed was detected, whereas, there were significantly positive correlations between width of pod and latitude.The pod and seed were mostly found small in the areas with high temperature and rainfall in general, and the size of pod and seed became bigger and bigger along with the increase of the latitude and the decrease of the temperature.Principal component analysis showed that the four principal components added up to 87.382% of the variation.The eight natural populations were divided into three groups by UPGMA cluster analysis based on Euclidean distance calculated from phenotypic traits.The first group was comprised of populations with small pods and small seeds, which are located in the south of the natural distribution.The second group has characteristics of big pods and big seeds, which are located in the north of the natural distribution, and only one population is located in the south of the distribution.Populations with small pods, big and thin seeds are located in the middle of the distribution, belonging to the third group.【Conclusion】 E.fordii has the modest level of phenotypic diversity, there were abundant variations among and within populations.The degree of phenotypic variation was slight and stable, and there was low level of population differentiation in E.fordii.Within-population variation was the main source of variation.For germplasm collection and preservation, the number of populations can be reduced while the number of individual trees within populations can be increased, especially the individuals with unique phenotypic characteristics.Rongxian and Longxu of Guangxi are the most important regions for genetic conservation and germplasm collection.Temperature was the most important factor affecting the phenotypic traits and distribution of E.fordii.Pod and seed sizes are the basis for populations clustering .