Standing chromosomal variation in Lake Whitefish species pairs: the role of historical contingency and relevance for speciation
Standing chromosomal variation in Lake Whitefish species pairs: the role of historical contingency and relevance for speciation
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DOI：
10.1111/mec.13816
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发表时间：
2017-01-01
影响因子：
4.9
通讯作者：
Bernatchez, Louis
中科院分区：
文献类型：
--
作者：
Dion-Cote, Anne-Marie;Symonova, Radka;Bernatchez, Louis
染色体变化在物种形成中的作用仍然是一个有争议的话题，尽管与分歧相关的人口条件应该促进它们的出现。我们测试了染色体变化和物种形成之间的潜在关系，通过研究两个湖白鲑（白鲑clupeaformis）血统，最近殖民冰后期湖泊后allopatry。一个矮小的湖沼物种从正常的底栖物种反复进化，成为生殖隔离。湖白鱼杂交经历有丝分裂和减数分裂不稳定，这可能是由于结构不同的染色体。出于这一观察，我们测试的假设，染色体组织不同的白鲑物种对使用细胞遗传学。虽然染色体和基数是保守的物种之间（2n = 80，NF = 98），我们观察到广泛的细微核型性状的多态性。我们描述了与异染色质和重复DNA相关的染色体内差异，并测试了三个同域物种对之间的平行性。多变量分析支持这一假设，在亚染色体标记水平的分化主要出现在异地。然而，我们没有发现证据之间的物种对湖泊，殖民化效应或殖民化后的分化相一致的平行。报道的染色体内多态性似乎并没有发挥核心作用，在驱动正常和侏儒湖白鲑之间的适应性分歧。我们讨论了如何在湖白鱼系统染色体分化可能有助于不稳定的有丝分裂和减数分裂染色体分离的杂交，如前所述。这里检测到的染色体结构仍然难以测序和组装，证明了细胞遗传学作为理解物种形成的基因组基础的补充方法的价值。
The role of chromosome changes in speciation remains a debated topic, although demographic conditions associated with divergence should promote their appearance. We tested a potential relationship between chromosome changes and speciation by studying two Lake Whitefish (Coregonus clupeaformis) lineages that recently colonized postglacial lakes following allopatry. A dwarf limnetic species evolved repeatedly from the normal benthic species, becoming reproductively isolated. Lake Whitefish hybrids experience mitotic and meiotic instability, which may result from structurally divergent chromosomes. Motivated by this observation, we test the hypothesis that chromosome organization differs between Lake Whitefish species pairs using cytogenetics. While chromosome and fundamental numbers are conserved between the species (2n = 80, NF = 98), we observe extensive polymorphism of subtle karyotype traits. We describe intrachromosomal differences associated with heterochromatin and repetitive DNA, and test for parallelism among three sympatric species pairs. Multivariate analyses support the hypothesis that differentiation at the level of subchromosomal markers mostly appeared during allopatry. Yet we find no evidence for parallelism between species pairs among lakes, consistent with colonization effect or postcolonization differentiation. The reported intrachromosomal polymorphisms do not appear to play a central role in driving adaptive divergence between normal and dwarf Lake Whitefish. We discuss how chromosomal differentiation in the Lake Whitefish system may contribute to the destabilization of mitotic and meiotic chromosome segregation in hybrids, as documented previously. The chromosome structures detected here are still difficult to sequence and assemble, demonstrating the value of cytogenetics as a complementary approach to understand the genomic bases of speciation.