Selection on a Genetic Polymorphism Counteracts Ecological Speciation in a Stick Insect
Selection on a Genetic Polymorphism Counteracts Ecological Speciation in a Stick Insect
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DOI：
10.1016/j.cub.2015.05.058
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发表时间：
2015-08-03
期刊：
影响因子：
9.2
通讯作者：
Nosil, Patrik
中科院分区：
文献类型：
--
作者：
Comeault, Aaron A.;Flaxman, Samuel M.;Nosil, Patrik
选择与性状遗传结构（如连锁、显性和上位性）之间的相互作用可以驱动或限制物种形成[1-3]。尽管越来越多的证据表明，物种形成可以进展到“中间”阶段，人口发展只有部分生殖隔离研究描述的选择机制，对物种形成施加限制比那些描述司机更罕见。竹节虫Timema cristinae提供了一个系统的例子，在该系统中，部分生殖隔离已经在适应不同宿主植物环境的种群之间进化，部分原因是对模式多态性的趋异选择[4，5]。在这里，我们演示了如何选择一个绿色/blanistic颜色多态性抵消在这个系统中的物种形成。具体来说，宿主之间的趋异选择不会发生在颜色表型上，因为黑素T。Cristinae在两种宿主物种的茎上都是隐蔽的，对真菌病原体具有抗性，并且具有交配优势。使用遗传杂交和全基因组关联作图，我们量化了图案和颜色多态性的遗传结构，说明了它们的简单遗传控制。我们使用这些经验的结果，以发展一个基于个人的模型，显示如何黑化表型作为一个“遗传桥梁”，增加生活在不同的主机上的人口之间的基因流。我们的研究结果表明，如何选择的性质的变化，性状和性状遗传结构的方面，可以对当地的适应和物种形成的约束。
The interplay between selection and aspects of the genetic architecture of traits (such as linkage, dominance, and epistasis) can either drive or constrain speciation [1-3]. Despite accumulating evidence that speciation can progress to "intermediate" stages with populations evolving only partial reproductive isolation studies describing selective mechanisms that impose constraints on speciation are more rare than those describing drivers. The stick insect Timema cristinae provides an example of a system in which partial reproductive isolation has evolved between populations adapted to different host plant environments, in part due to divergent selection acting on a pattern polymorphism [4, 5]. Here, we demonstrate how selection on a green/melanistic color polymorphism counteracts speciation in this system. Specifically, divergent selection between hosts does not occur on color phenotypes because melanistic T. cristinae are cryptic on the stems of both host species, are resistant to a fungal pathogen, and have a mating advantage. Using genetic crosses and genome-wide association mapping, we quantify the genetic architecture of both the pattern and color polymorphism, illustrating their simple genetic control. We use these empirical results to develop an individual-based model that shows how the melanistic phenotype acts as a "genetic bridge" that increases gene flow between populations living on different hosts. Our results demonstrate how variation in the nature of selection acting on traits, and aspects of trait genetic architecture, can impose constraints on both local adaptation and speciation.