Colombo P C
Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Ciudad Universitaria, Buenos Aires, Republica Argentina.
Hereditas. 2000;133(3):189-93. doi: 10.1111/j.1601-5223.2000.00189.x.
Deviation from formal null models and the comparisons between age classes are amongst the most direct methods of demonstrating ongoing natural selection. We have sampled 207 males from a population of the grasshopper Leptysma argentina at the onset and the end of the adult life span for this species; generations are synchronical and do not overlap. The karyotypic frequencies for a fusion (F) and a supernumerary segment (s1) were examined. The young male sample was heterogeneous and did not fit to the Hardy-Weinberg proportions, whereas the aged male sample did not deviate from H-W expectations in both analyses. Likewise, the young male sample showed fitness heterosis for the s1 carriers that are fusion homozygotes. We interpreted the significant results of karyotype frequency in both samples as the result of survival selection. Evidently natural selection acts on male adult viability as well as on other fitness components prior to adult survival, thus changing karyotype frequencies between generations. Likewise, we also detected a strong interaction between polymorphisms, whereas heterosis for s1 heterozygotes might be contributing to the maintenance of the s1 polymorphism. The actual target of selection remains unidentified.
偏离形式上的零模型以及不同年龄组之间的比较是证明正在进行的自然选择的最直接方法之一。我们从阿根廷细角蝗种群中在该物种成年寿命开始和结束时对207只雄性进行了采样；世代是同步的且不重叠。对一个融合（F）和一个额外片段（s1）的核型频率进行了检查。年轻雄性样本是异质的，不符合哈迪-温伯格比例，而老年雄性样本在两项分析中均未偏离哈迪-温伯格预期。同样，年轻雄性样本显示出对于作为融合纯合子的s1携带者的适应性杂种优势。我们将两个样本中核型频率的显著结果解释为生存选择的结果。显然，自然选择作用于成年雄性的生存能力以及成年生存之前的其他适应性成分，从而改变世代间的核型频率。同样，我们还检测到多态性之间有强烈的相互作用，而s1杂合子的杂种优势可能有助于维持s1多态性。选择的实际目标仍未确定。
