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Reduced Introgression of Sex Chromosome Markers in the Mexican Howler Monkey (Alouatta palliata × A. pigra) Hybrid Zone
International Journal of Primatology ( IF 2.5 ) Pub Date : 2018-09-14 , DOI: 10.1007/s10764-018-0056-4
Liliana Cortés-Ortiz 1 , Marcella D Baiz 1 , Javier Hermida-Lagunes 2 , Francisco García-Orduña 2 , Ariadna Rangel-Negrín 2 , Dawn M Kitchen 3 , Thore J Bergman 1, 4 , Pedro A D Dias 2 , Domingo Canales-Espinosa 2 ,
Affiliation  

Interspecific hybridization allows the introgression or movement of alleles from one genome to another. While some genomic regions freely exchange alleles during hybridization, loci associated with reproductive isolation do not intermix. In many model organisms, the X chromosome displays limited introgression compared to autosomes owing to the presence of multiple loci associated with hybrid sterility or inviability (the “large X-effect”). Similarly, if hybrids are produced, the heterogametic sex is usually inviable or sterile, a pattern known as Haldane’s rule. We analyzed the patterns of introgression of genetic markers located in the mitochondrial (control region) and nuclear (autosomal microsatellites and sex chromosome genes) genomes of two howler monkey species (Alouatta palliata and A. pigra) that form a natural hybrid zone in southern Mexico, to evaluate whether the large X-effect and Haldane’s rule affect the outcomes of hybridization between these sister species. To identify the level of admixture of each individual in the hybrid zone (N = 254) we analyzed individuals sampled outside the hybrid zone (109 A. pigra and 39 A. palliata) to determine allele frequencies of parental species and estimated a hybrid index based on nuclear markers. We then performed a cline analysis using individuals in the hybrid zone to determine patterns of introgression for each locus. Our analyses show that although the hybrid zone is bimodal (with no known F1 s and few recent generation hybrids) and quite narrow, there has been extensive introgression in both directions, and there is a large array of admixed individuals in the hybrid zone. Mitochondrial and most autosomal markers showed bidirectional introgression, but some had biased introgression toward one species or the other. All markers on the sex chromosomes and a few autosomal markers showed highly restricted introgression. This pattern is consistent with the hypothesis that the sex chromosomes make a disproportionate contribution to reproductive isolation, and our results broaden the taxonomic representation of these patterns across animal taxa.

中文翻译:

墨西哥吼猴 (Alouatta palliata × A. pigra) 杂交区性染色体标记的渐渗减少

种间杂交允许等位基因从一个基因组渗入或移动到另一个基因组。虽然一些基因组区域在杂交过程中自由交换等位基因,但与生殖隔离相关的基因座不会混合。在许多模式生物中,由于存在与杂交不育或不存活性相关的多个基因座(“大 X 效应”),与常染色体相比,X 染色体显示出有限的基因渗入。类似地,如果产生杂交种,异配性通常是不可行的或不育的,这种模式被称为霍尔丹规则。我们分析了位于两种吼猴物种(Alouatta palliata 和 A. pigra) 在墨西哥南部形成一个自然杂交区,以评估大 X 效应和霍尔丹规则是否影响这些姐妹物种之间杂交的结果。为了确定杂交区(N = 254)中每个个体的混合水平,我们分析了在杂交区外采样的个体(109 A. pigra 和 39 A. palliata)以确定亲本物种的等位基因频率并估计基于混合指数在核标记上。然后,我们使用混合区中的个体进行了克隆分析,以确定每个基因座的基因渗入模式。我们的分析表明,虽然混合区是双峰的(没有已知的 F1 s 和很少的最近一代杂交种)并且非常狭窄,但在两个方向上都有广泛的基因渗入,并且在混合区中有大量混合个体。线粒体和大多数常染色体标记显示双向基因渗入,但有些基因渗入偏向于一个物种或另一个物种。性染色体上的所有标记和一些常染色体标记都显示出高度受限的基因渗入。这种模式与性染色体对生殖隔离做出不成比例贡献的假设一致,我们的结果扩大了这些模式在动物分类群中的分类学代表性。
更新日期:2018-09-14
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