Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
Evolution. 2010 Jan;64(1):116-25. doi: 10.1111/j.1558-5646.2009.00808.x. Epub 2009 Aug 3.
A central problem in evolutionary biology is to understand how spatial and temporal variation in selection maintain genetic variation within and among populations. Brown anole lizards (Anolis sagrei) exhibit a dorsal pattern polymorphism that is expressed only in females, which occur in "diamond,""bar," and intermediate "diamond-bar" morphs. To understand the inheritance of this polymorphism, we conducted a captive breeding study that refuted several single-locus models and supported a two-locus mode of inheritance. To describe geographic variation in morph frequencies, we surveyed 13 populations from two major islands in The Bahamas. Morph frequencies differed substantially between major islands but were highly congruent within each island. Finally, we measured viability selection on each island to test two hypotheses regarding the maintenance of the polymorphism: (1) that spatial variation in selection maintains variation in morph frequencies between islands, and (2) that temporal variation in selection across years maintains variation within islands. Although bar females had relatively lower survival where they were rare, our data do not otherwise suggest that selection varies spatially between islands. However, diamond-bar females were subject to positive frequency-dependent selection across years, and the relative fitness of bar and diamond females alternated across years. We propose that this polymorphism is maintained by temporal variation in selection coupled with the sheltering of alleles via a two-locus inheritance pattern and sex-limited expression.
进化生物学中的一个核心问题是理解空间和时间上的选择变化如何在种群内和种群间维持遗传变异。棕树变色龙（Anolis sagrei）表现出一种仅在雌性中表达的背纹多态性，存在“钻石”、“条纹”和中间“钻石-条纹”形态。为了理解这种多态性的遗传，我们进行了一项圈养繁殖研究，该研究反驳了几个单基因座模型，并支持了双基因座遗传模式。为了描述形态频率的地理变异，我们调查了巴哈马群岛的两个主要岛屿的 13 个种群。主要岛屿之间的形态频率差异很大，但在每个岛屿内高度一致。最后，我们在每个岛屿上测量了生存力选择，以检验关于多态性维持的两个假设：（1）选择的空间变化维持了岛屿之间形态频率的差异，（2）多年来选择的时间变化维持了岛屿内的差异。尽管条纹雌变色龙在它们稀少的地方生存能力相对较低，但我们的数据并没有表明选择在岛屿之间存在空间差异。然而，钻石-条纹雌变色龙在多年间受到正频率依赖选择的影响，条纹和钻石雌变色龙的相对适合度在多年间交替变化。我们提出，这种多态性是由选择的时间变化与通过双基因座遗传模式和性别限制表达来保护等位基因共同维持的。
