Asuka Y, Tomaru N, Nisimura N, Tsumura Y, Yamamoto S
Laboratory of Forest Ecology and Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
Mol Ecol. 2004 May;13(5):1241-50. doi: 10.1111/j.1365-294X.2004.02118.x.
The within-population genetic structure of Fagus crenata in a 4-ha plot (200 x 200 m) of an old-growth beech forest was analysed using microsatellite markers. To assess the genetic structure, Moran's I spatial autocorrelation coefficient was calculated. Correlograms of Moran's I showed significant positive values less than 0.100 for short-distance classes, indicating weak genetic structure. The genetic structure within the population is created by limited seed dispersal, and is probably weakened by overlapping seed shadow, secondary seed dispersal, extensive pollen flow and the thinning process. Genetic structure was detected in a western subplot of 50 x 200 m with immature soils and almost no dwarf bamboos (Sasa spp.), where small and intermediate-sized individuals were distributed in aggregations with high density because of successful regeneration. By contrast, genetic structure was not found in an eastern subplot of the same size with mature soils and Sasa cover, where successful regeneration was prevented, and the density of the small and intermediate-sized individuals was low. Moreover, genetic structure of individuals in a small-size class (diameter at breast height < 12 cm) was more obvious than in a large-size class (diameter at breast height >/= 12 cm). The apparent genetic structure detected in the 4-ha plot was therefore probably the result of the structure in the western portion of the plot and in small and intermediate-sized individuals that successfully regenerated under the favourable environment. The heterogeneity in genetic structure presumably reflects variation in the density that should be affected by differences in regeneration dynamics associated with heterogeneity in environmental conditions.
利用微卫星标记分析了一处4公顷（200米×200米）老龄山毛榉林样地中日本水青冈的种群内遗传结构。为评估遗传结构，计算了莫兰指数I空间自相关系数。莫兰指数I的相关图显示，短距离类别的显著正值小于0.100，表明遗传结构较弱。种群内的遗传结构是由有限的种子传播形成的，可能会因种子阴影重叠、二次种子传播、广泛的花粉流动和间伐过程而减弱。在一个50米×200米的西部亚样地中检测到了遗传结构，该亚样地土壤不成熟且几乎没有矮竹（笹属植物），由于成功更新，小尺寸和中等尺寸个体高密度聚集分布。相比之下，在相同大小的东部亚样地中未发现遗传结构，该亚样地土壤成熟且有笹属植物覆盖，成功更新受阻，小尺寸和中等尺寸个体的密度较低。此外，小尺寸类个体（胸径<12厘米）的遗传结构比大尺寸类个体（胸径≥12厘米）更明显。因此，在4公顷样地中检测到的明显遗传结构可能是样地西部以及在有利环境下成功更新的小尺寸和中等尺寸个体中结构的结果。遗传结构的异质性大概反映了密度的变化，而密度变化应受与环境条件异质性相关的更新动态差异的影响。
