Universidade Federal do Pampa, BR 472 km 592, Uruguaiana, RS 97500-000, Brazil.
Zoology (Jena). 2013 Oct;116(5):286-92. doi: 10.1016/j.zool.2013.07.002. Epub 2013 Aug 28.
Chromosomal rearrangements such as inversions can facilitate speciation even in the presence of gene flow. The present study aims to analyze the karyotypic variation in six populations of Geophagus brasiliensis from southern Brazil. All specimens showed 2n=48 chromosomes, but three karyotypes were found to have one, two or three pairs of submetacentric chromosomes. Although G. brasiliensis did not exhibit variation in the diploid number, it presented a wide interpopulational variation mainly regarding the karyotype formula and specific chromosomal markers. Differences in the location of the major and minor rDNA loci were observed among the populations. Moreover, different patterns were observed in the distribution of the constitutive heterochromatin, presenting intra- and interpopulational variation. This supports the hypothesis that this taxon represents a complex species or that cryptic species are included in this group, indicating a possibleprocess of sympatric speciation. By potentially restricting gene flow between heterokaryotypes, the segregating chromosome rearrangements we describe for G. brasiliensis may play a role in diversification in this species complex.
染色体倒位等结构重排即便在基因交流存在的情况下也能促进物种形成。本研究旨在分析巴西南部六个丽体鱼属（Geophagusbrasiliensis）种群的染色体组型变异。所有标本均显示 2n=48 条染色体，但发现有三种核型分别具有一对、两对或三对亚中部着丝粒染色体。虽然丽体鱼属的二倍体数目没有发生变化，但在染色体组型公式和特定的染色体标记方面表现出广泛的种群间变异。在种群间观察到主要和次要 rDNA 位点的位置存在差异。此外，在组成性异染色质的分布上观察到不同的模式，表现出种内和种间变异。这支持了这样一种假设，即该分类单元代表一个复杂的物种，或者该组中包含隐生种，表明存在一个可能的同域物种形成过程。我们描述的丽体鱼属的分离染色体重排在潜在上可能限制了异核型之间的基因流，因此可能在该物种复合体的多样化中发挥作用。
