Orr H Allen
Department of Ecology and Evolution, University of Chicago, 1103 E. 57 th St, Chicago, IL, 60637.
Evolution. 1989 Jan;43(1):180-189. doi: 10.1111/j.1558-5646.1989.tb04216.x.
Hybrids between D. pseudoobscura bogotana and D. pseudoobscura pseudoobscura are fertile except for males produced in one of the two reciprocal crosses. As there is no premating isolation between these subspecies, nonreciprocal male sterility represents the first step in speciation. Genetic analysis reveals two causes of hybrid F sterility: a maternal effect and incompatibilities between chromosomes within males. The maternal effect appears to play the greatest role in hybrid sterility. The X chromosome has the largest effect on fertility of any chromosome, a ubiquitous result in analyses of hybrid sterility and inviability in Drosophila. This effect is entirely attributable to a region comprising less than 30% of the X chromosome. These results are compared to those from a similar study of D. pseudoobscura-D. persimilis hybrids, an older and more reproductively isolated species pair in the same lineage. Such comparisons may allow one to identify the genetic changes characterizing the early versus late stages of speciation.
波哥大伪暗果蝇和伪暗果蝇之间的杂交种是可育的，但在两个正反交组合之一中产生的雄性除外。由于这些亚种之间没有交配前隔离，非相互雄性不育代表了物种形成的第一步。遗传分析揭示了杂种F不育的两个原因：母体效应和雄性体内染色体之间的不相容性。母体效应似乎在杂种不育中起最大作用。X染色体对生育力的影响在所有染色体中最大，这在果蝇杂种不育和 inviability分析中是一个普遍的结果。这种影响完全归因于一个占X染色体不到30%的区域。将这些结果与对伪暗果蝇-拟暗果蝇杂种的类似研究结果进行比较，这是同一谱系中一个较老且生殖隔离程度更高的物种对。这样的比较可能使人们能够识别出表征物种形成早期和晚期阶段的遗传变化。
