Hybrid speciation in sparrows II: a role for sex chromosomes?
Hybrid speciation in sparrows II: a role for sex chromosomes?
复制标题
DOI：
10.1111/j.1365-294x.2011.05182.x
复制
发表时间：
2011-09-01
影响因子：
4.9
通讯作者：
Saetre, Glenn-Peter
中科院分区：
文献类型：
--
作者：
Elgvin, Tore O.;Hermansen, Jo S.;Saetre, Glenn-Peter
动物的同倍体杂交物种形成尚不清楚，主要是因为缺乏充分记录的病例。本文报道了家雀（Passer domesticus）、西班牙麻雀（P. hispaniolensis）及其拟杂交后代意大利麻雀（P. italiae）的多位点序列分析结果。意大利麻雀在遗传上介于家麻雀和西班牙麻雀之间，表现出家谱上的不一致性和来自任何一个假定亲本物种的等位基因的马赛克模式。与家雀和西班牙麻雀的常染色体变异相比，Z染色体的平均变异显著降低。此外，相对于常染色体，两种之间的差异在Z染色体上有所增加。这种变异和分化模式与Z连锁基因的减少渗入和/或更快的Z效应（Z上的适应性分化率增加）是一致的。f - st离群值检验与快速z型假说一致：五个z连锁位点中的两个（CHD1Z和PLAA）被确定为候选基因，在假定的亲本物种中受到积极的、分歧的选择。有趣的是，后两个基因在（杂交）意大利麻雀中显示出一种马赛克模式；即意大利麻雀在CHD1Z有固定的西班牙麻雀等位基因，在PLAA主要有家雀等位基因。因此，本研究提出的初步证据表明，性染色体可能在这种同倍体杂交物种形成中起重要作用。
Homoploid hybrid speciation in animals is poorly understood, mainly because of the scarcity of well-documented cases. Here, we present the results of a multilocus sequence analysis on the house sparrow (Passer domesticus), Spanish sparrow (P. hispaniolensis) and their proposed hybrid descendant, the Italian sparrow (P. italiae). The Italian sparrow is shown to be genetically intermediate between the house sparrow and Spanish sparrow, exhibiting genealogical discordance and a mosaic pattern of alleles derived from either of the putative parental species. The average variation on the Z chromosome was significantly reduced compared with autosomal variation in the putative parental species, the house sparrow and Spanish sparrow. Additionally, divergence between the two species was elevated on the Z chromosome relative to the autosomes. This pattern of variation and divergence is consistent with reduced introgression of Z-linked genes and/or a faster-Z effect (increased rate of adaptive divergence on the Z). F-ST-outlier tests were consistent with the faster-Z hypothesis: two of five Z-linked loci (CHD1Z and PLAA) were identified as candidates for being subject to positive, divergent selection in the putative parental species. Interestingly, the two latter genes showed a mosaic pattern in the (hybrid) Italian sparrow; that is, the Italian sparrow was found to be fixed for Spanish sparrow alleles at CHD1Z and to mainly have house sparrow alleles at PLAA. Preliminary evidence presented in this study thus suggests that sex chromosomes may play a significant role in this case of homoploid hybrid speciation.