Galla Stephanie J, Johnson Jeff A
Department of Biological Sciences and Institute of Applied Science, University of North Texas, 1155 Union Circle, Denton, TX 76203, USA.
Department of Biological Sciences and Institute of Applied Science, University of North Texas, 1155 Union Circle, Denton, TX 76203, USA.
Mol Phylogenet Evol. 2015 Mar;84:1-13. doi: 10.1016/j.ympev.2014.12.012. Epub 2014 Dec 29.
Life history strategies can influence the effective population size (Ne) of loci differently based on their mode of inheritance. Recognizing how this may affect the rate of lineage sorting among marker types is important for studies focused on resolving phylogenetic relationships among recently divergent taxa. In this study, we use gene tree, coalescent-based species tree, and isolation-with-migration analyses to explore the differences between marker types (autosomal, Z-linked, and mitochondrial) in resolving phylogenetic relationships among North American prairie grouse (Tympanuchus). We found that Z-linked loci were more likely to identify monophyletic relationships among prairie grouse species compared to autosomal and mtDNA loci in both species and gene tree analyses, with species tree analyses outperforming gene trees. These results were further supported with isolation-with-migration analyses, where Z-linked loci largely followed a strict isolation model while autosomal loci were more likely to fit a model with gene flow between species following population divergence. While accounting for differences in inheritance pattern (or Ne) for marker type, results suggest that additional factors, such as strong sexual selection and sex-biased introgression (i.e., male-biased postzygotic hybrid behavioral isolation or "unsexy son"), may further explain the decreased diversity levels and increased rate of lineage sorting observed with the Z-linked loci relative to autosomal and mtDNA loci. In fact, to our knowledge no hybrid male prairie grouse have been observed breeding in the wild, yet hybrid females along with backcross females are known to produce viable offspring. Overall, this study highlights that more work is needed to determine how complex models of gene flow (i.e., sex biased introgression) and differences in the effective size among marker types based on differing life history strategies influence divergence date estimation and species delimitation.
生活史策略会根据基因座的遗传模式对有效种群大小（Ne）产生不同影响。认识到这如何影响不同标记类型间的谱系分选速率，对于专注于解析近期分化类群间系统发育关系的研究很重要。在本研究中，我们使用基因树、基于溯祖理论的物种树以及隔离与迁移分析，来探究北美草原松鸡（Tympanuchus）不同标记类型（常染色体、Z染色体连锁和线粒体）在解析系统发育关系上的差异。我们发现，在物种和基因树分析中，与常染色体和线粒体DNA基因座相比，Z染色体连锁基因座更有可能识别出草原松鸡物种间的单系关系，物种树分析的表现优于基因树分析。隔离与迁移分析进一步支持了这些结果，其中Z染色体连锁基因座很大程度上遵循严格的隔离模型，而常染色体基因座更有可能符合种群分化后物种间存在基因流的模型。在考虑标记类型的遗传模式（或Ne）差异时，结果表明，其他因素，如强烈的性选择和性别偏向的基因渗入（即雄性偏向的合子后杂种行为隔离或“不性感的儿子”），可能进一步解释了相对于常染色体和线粒体DNA基因座，Z染色体连锁基因座观察到的多样性水平降低和谱系分选速率增加的现象。事实上，据我们所知，尚未观察到野生杂交雄性草原松鸡进行繁殖，但已知杂交雌性以及回交雌性会产生可存活的后代。总体而言，本研究强调需要开展更多工作，以确定基因流的复杂模型（即性别偏向的基因渗入）以及基于不同生活史策略的标记类型间有效大小差异如何影响分歧时间估计和物种界定。
