Still D W, Kim D-H, Aoyama N
Department of Horticulture, Plant and Soil Science, California State Polytechnic University, Pomona, 3801 W Temple Avenue, Pomona, CA 91768, USA.
Ann Bot. 2005 Sep;96(3):467-77. doi: 10.1093/aob/mci199. Epub 2005 Jul 1.
Echinacea angustifolia is a widespread species distributed throughout the Great Plains region of North America. Genetic differentiation among populations was investigated along a 1500 km north-south climatic gradient in North America, a region with no major geographical barriers. The objective of the study was to determine if genetic differentiation of populations could be explained by an isolation-by-distance model or by associations with climatic parameters known to affect plant growth and survival.
Historical climatic data were used to define the nature of the climatic gradient and AFLP markers were used to establish patterns of population genetic differentiation among ten Echinacea populations collected from North Dakota to Oklahoma. A total of 1290 fragments were scored using six EcoRI/MseI and three PstI/MseI primer combinations. Assessment of the correlation between climatic, genetic and geographic distances was assessed by Mantel and partial Mantel tests.
PstI/MseI combinations produced significantly fewer fragments, but a larger percentage was unique compared with EcoRI/MseI markers. Using estimates of F(ST), populations in Oklahoma and southern Kansas were identified as the most divergent from the other populations. Both the neighbour-joining tree and principal co-ordinate analysis clustered the populations in a north-south spatial orientation. About 60% of the genetic variation was found within populations, 20% among populations and the remaining 20% was partitioned among groups that were defined by the topology of the neighbour-joining tree. Significant support was found for the isolation-by-distance model independent of the effects of annual mean precipitation, but not from annual mean temperature and freeze-free days.
Echinacea angustifolia populations exhibit genetic divergence along a north-south climatic gradient. The data support an isolation-by-distance restriction in gene flow that is independent of annual mean precipitation.
狭叶松果菊是一种广泛分布于北美大平原地区的物种。在北美一个没有重大地理障碍的地区，沿着一条1500公里的南北气候梯度对种群间的遗传分化进行了研究。该研究的目的是确定种群的遗传分化是否可以用距离隔离模型来解释，或者是否与已知影响植物生长和存活的气候参数有关。
利用历史气候数据来定义气候梯度的性质，并使用AFLP标记来确定从北达科他州到俄克拉何马州采集的10个松果菊种群间的遗传分化模式。使用六种EcoRI/MseI和三种PstI/MseI引物组合对总共1290个片段进行了评分。通过Mantel检验和偏Mantel检验评估气候距离、遗传距离和地理距离之间的相关性。
与EcoRI/MseI标记相比，PstI/MseI组合产生的片段明显较少，但独特片段的百分比更高。根据F(ST)估计，俄克拉何马州和堪萨斯州南部的种群与其他种群差异最大。邻接法树和主坐标分析都将种群按南北空间方向聚类。约60%的遗传变异存在于种群内，20%存在于种群间，其余20%则分布在由邻接法树的拓扑结构定义的组间。发现距离隔离模型得到了显著支持，该模型独立于年平均降水量的影响，但不受年平均温度和无霜天数的影响。
狭叶松果菊种群沿南北气候梯度表现出遗传分化。数据支持基因流中与年平均降水量无关的距离隔离限制。
