Mateos Mariana, Vrijenhoek Robert C
Monterey Bay Aquarium Research Institute, Moss Landing, California 95039, USA.
Evolution. 2002 May;56(5):985-92. doi: 10.1111/j.0014-3820.2002.tb01410.x.
Crossing experiments revealed that a diploid hybridogenetic fish (genus Poeciliopsis) from the Río Mocorito (Sinaloa, Mexico) is trihybrid. Its haploid maternal genome is inherited clonally (i.e., hemiclonally), and it expresses a mixture of morphological traits found in the closely related species P. monacha and P. viriosa. Its haploid paternal genome is replaced in each generation by mating with males of a more distantly related sexual species, P. lucida. However, expression of mixed (monacha X viriosa) traits by this hemiclone is also consistent with retention of shared ancestral polymorphisms. If true, this hemiclonal lineage would be one of the few examples of an ancient asexual taxon. We used mitochondrial DNA and allozymes to test whether the maternal progenitor of the Mocorito hybridogen was a recent P. monacha X P. viriosa hybrid or a remnant of their most recent common ancestor. Our results clearly link the hemiclonal genome to contemporary P. monacha and therefore support the hypothesis of a recent origin. Additionally, our findings suggest that this unisexual fish may serve as a vehicle for introgression between two allopatric sexual species.
杂交实验表明，来自墨西哥锡那罗亚州莫科里托河的一种二倍体杂交起源鱼类（食蚊鱼属）是三杂种。它的单倍体母本基因组以克隆方式（即半克隆方式）遗传，并且表现出在近缘物种单色食蚊鱼和维里食蚊鱼中发现的形态特征的混合。它的单倍体父本基因组在每一代中通过与亲缘关系更远的有性物种亮食蚊鱼的雄鱼交配而被替换。然而，这种半克隆体对（单色食蚊鱼×维里食蚊鱼）混合特征的表达也与保留共同祖先的多态性相一致。如果属实，这种半克隆谱系将是古代无性分类群的少数例子之一。我们使用线粒体DNA和同工酶来测试莫科里托杂交起源物种的母本祖先是否是近期的单色食蚊鱼×维里食蚊鱼杂交种，或者是它们最近共同祖先的残余。我们的结果清楚地将半克隆基因组与当代的单色食蚊鱼联系起来，因此支持了近期起源的假说。此外，我们的研究结果表明，这种单性鱼可能是两个异域有性物种之间基因渗入的载体。
