Rosenberg Noah A, Hirsh Aaron E
Program in Molecular and Computational Biology, University of Southern California, 1042 W. 36th Pl., DRB 289, Los Angeles, CA 90089, USA .
Genetics. 2003 Aug;164(4):1677-82. doi: 10.1093/genetics/164.4.1677.
Genealogies from rapidly growing populations have approximate "star" shapes. We study the degree to which this approximation holds in the context of estimating the time to the most recent common ancestor (T(MRCA)) of a set of lineages. In an exponential growth scenario, we find that unless the product of population size (N) and growth rate (r) is at least approximately 10(5), the "pairwise comparison estimator" of T(MRCA) that derives from the star genealogy assumption has bias of 10-50%. Thus, the estimator is appropriate only for large populations that have grown very rapidly. The "tree-length estimator" of T(MRCA) is more biased than the pairwise comparison estimator, having low bias only for extremely large values of Nr.
快速增长种群的系谱近似呈“星状”。我们研究了在估计一组谱系的最近共同祖先时间（T(MRCA)）的背景下，这种近似的成立程度。在指数增长的情况下，我们发现，除非种群大小（N）与增长率（r）的乘积至少约为10⁵，否则源自星状系谱假设的T(MRCA)的“成对比较估计器”会有10% - 50%的偏差。因此，该估计器仅适用于增长非常迅速的大种群。T(MRCA)的“树长估计器”比成对比较估计器偏差更大，仅在Nr值极大时偏差较小。
