Long Tristan A F, Pischedda Alison
Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
Proc Biol Sci. 2005 Sep 7;272(1574):1781-7. doi: 10.1098/rspb.2005.3165.
Modification of offspring sex ratios in response to parental quality is predicted when the long-term fitness returns of sons and daughters differ. One factor that may influence a mother's sex allocation decision is the quality (or attractiveness) of her mate. We investigated whether the sex ratios of offspring produced by female Drosophila melanogaster are biased with respect to the age of the males to which they are mated, and whether there is an adaptive basis for this phenomenon. We found that females mated to old males (13 d post-eclosion) initially produced a greater proportion of daughters than did females mated to young males (1 d post-eclosion). This pattern does not appear to be due to a systematic difference in the numbers or mortality of the X- and Y-bearing sperm originating from old and young fathers, as the overall sex ratios of all offspring produced from a single copulation did not differ between broods fathered by the two types of males. The sons of older males fared worse in competitive mating assays than did the sons of younger males, while daughters of old and young males were of comparable fitness. These results suggest that there is an adaptive basis for the observed sex ratio modification.
当儿子和女儿的长期适应性回报不同时，预计后代性别比例会因亲本质量而发生改变。影响母亲性别分配决策的一个因素可能是其配偶的质量（或吸引力）。我们研究了雌性黑腹果蝇所产后代的性别比例是否因与之交配的雄性年龄而产生偏差，以及这种现象是否有适应性基础。我们发现，与老龄雄性（羽化后13天）交配的雌性最初产生的女儿比例高于与年轻雄性（羽化后1天）交配的雌性。这种模式似乎并非源于来自老龄和年轻父亲的携带X和Y染色体精子数量或死亡率的系统性差异，因为单次交配产生的所有后代的总体性别比例在由这两种雄性作为父亲的后代之间并无差异。在竞争性交配试验中，老龄雄性的儿子比年轻雄性的儿子表现更差，而老龄和年轻雄性的女儿适应性相当。这些结果表明，观察到的性别比例改变存在适应性基础。
