Star Bastiaan, Stoffels Rick J, Spencer Hamish G
Department of Zoology, Allan Wilson Centre for Molecular Ecology and Evolution, University of Otago, 9054 Dunedin, New Zealand.
Genetics. 2007 Jul;176(3):1625-33. doi: 10.1534/genetics.107.071639. Epub 2007 May 4.
Environmental heterogeneity has long been considered a likely explanation for the high levels of genetic variation found in most natural populations: selection in a spatially heterogeneous environment can maintain more variation. While this theoretical result has been extensively studied in models with limited parameters (e.g., two alleles, fixed gene flow, and particular selection schemes), the effect of spatial heterogeneity is poorly understood for models with a wider range of parameters (e.g., multiple alleles, different levels of gene flow, and more general selection schemes). We have compared the volume of fitness space that maintains variation in a single-deme model to the volume in a two-deme model for multiple alleles, random selection schemes, and various levels of migration. Furthermore, equilibrium allele-frequency vectors were examined to see if particular patterns of variation are more prevalent than first expected. The two-deme model maintains variation for substantially larger volumes of fitness space with lower heterozygote fitness than the single-deme model. This result implies that selection schemes in the two-deme model can have a wider range of fitness patterns while still maintaining variation. The equilibrium allele-frequency patterns emerging from the two-deme model are more variable and strongly influenced by gene flow.
长期以来，环境异质性一直被认为是大多数自然种群中存在高水平遗传变异的一个可能解释：在空间异质环境中的选择可以维持更多变异。虽然这一理论结果在参数有限的模型（例如，两个等位基因、固定基因流和特定选择方案）中已得到广泛研究，但对于参数范围更广的模型（例如，多个等位基因、不同水平的基因流和更一般的选择方案），空间异质性的影响仍知之甚少。我们比较了在单种群模型中维持变异的适应度空间体积与在多种等位基因、随机选择方案和不同迁移水平的两种群模型中的适应度空间体积。此外，还研究了平衡等位基因频率向量，以查看特定的变异模式是否比最初预期的更为普遍。与单种群模型相比，两种群模型在杂合子适应度较低的情况下，能为更大体积的适应度空间维持变异。这一结果意味着，两种群模型中的选择方案可以具有更广泛的适应度模式，同时仍能维持变异。两种群模型中出现的平衡等位基因频率模式更具变异性，且受基因流的影响很大。
