Beukeboom L W, Ellers J, Van Alphen J J
Institute of Evolutionary and Ecological Sciences, University of Leiden, PO Box 9516, NL-2300 RA Leiden, The Netherlands.
Heredity (Edinb). 2000 Jan;84 ( Pt 1):29-36. doi: 10.1046/j.1365-2540.2000.00628.x.
In species with single-locus complementary sex determination (sl-CSD), sex is determined by multiple alleles at a single locus. In the haplodiploid Hymenoptera, sl-CSD results in females, if individuals are heterozygous at the sex locus, and in males, if individuals are hemizygous (haploid males) or homozygous (diploid males). Several hymenopteran species have been shown to have sl-CSD, but in several others sl-CSD is absent and the phylogenetic distribution remains unclear. In the family Braconidae, all four species tested so far were shown to possess sl-CSD. In this study, inbreeding experiments were used to test for the presence of sl-CSD in two species belonging to a subfamily of the Braconidae, Asobara tabida and Alysia manducator (Alysiinae). In both species inbreeding experiments showed no difference in brood size or sex ratio compared to the (outbred) control group. Furthermore, the sex ratios found in the inbreeding treatment differed significantly from the sex ratios expected under sl-CSD. Therefore, we conclude that sl-CSD is absent in these species. This study is the first to show the lack of sl-CSD in species of the Braconidae family and that hymenopteran sex-determining mechanisms can vary, even within a family.
在具有单基因座互补性性别决定（sl-CSD）的物种中，性别由单个基因座上的多个等位基因决定。在单倍二倍体膜翅目昆虫中，如果个体在性别基因座上是杂合的，sl-CSD会导致产生雌性；如果个体是半合子（单倍体雄性）或纯合子（二倍体雄性），则会产生雄性。已经证明几种膜翅目昆虫物种具有sl-CSD，但在其他几种物种中不存在sl-CSD，其系统发育分布仍不清楚。在茧蜂科中，到目前为止测试的所有四个物种都被证明具有sl-CSD。在本研究中，采用近亲繁殖实验来测试茧蜂科一个亚科的两个物种——塔比阿索茧蜂和食蚜茧蜂（蚜茧蜂亚科）中是否存在sl-CSD。在这两个物种中，与（远交）对照组相比，近亲繁殖实验在产卵量或性别比例上均未显示出差异。此外，在近亲繁殖处理中发现的性别比例与sl-CSD预期的性别比例有显著差异。因此，我们得出结论，这些物种中不存在sl-CSD。本研究首次表明茧蜂科物种中缺乏sl-CSD，并且膜翅目昆虫的性别决定机制可能不同，即使在一个科内也是如此。
