Sasabe M, Takami Y, Sota T
Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan.
Heredity (Edinb). 2007 Jun;98(6):385-91. doi: 10.1038/sj.hdy.6800952. Epub 2007 Feb 28.
Marked diversification of genital morphology is common in internally fertilizing animals. Although sexual selection may be the primary process controlling genital evolution, factors promoting genital evolution are controversial, and the genetic background of genital morphology is poorly understood. We analyzed the genetic basis of species-specific genital morphologies in carabid beetles of the subgenus Ohomopterus (genus Carabus, Carabidae) using two parapatric species with hybrid zones. Biometric analyses on experimental F(1) and backcross populations revealed that inheritance of genital morphology is polygenic. Applying Lande's modification of the Castle-Wright estimator to population means and variances to estimate the minimum number of genes involved, we found that a relatively small number of loci is responsible for species differences in genital morphology. In addition, joint-scaling tests indicated that the additive genetic effect accounts for most interspecific differences in genital traits, but dominance and epistatic genetic effects also play roles. Overall, the genetic basis of male and female genitalia is fairly simple, enabling these traits to respond quickly to selection pressures and to diverge rapidly. Our results provide insight into the diversification of genital morphology in carabid beetles, and will hopefully stimulate further studies on the genetic basis of genitalia, such as mapping of quantitative trait loci affecting species-specific genital morphology.
显著的生殖器形态多样化在体内受精动物中很常见。虽然性选择可能是控制生殖器进化的主要过程，但促进生殖器进化的因素仍存在争议，而且人们对生殖器形态的遗传背景了解甚少。我们利用两个具有杂交带的邻域分布物种，分析了地鳖甲属（步甲科，地鳖甲属）凹眼地鳖亚属物种特异性生殖器形态的遗传基础。对实验性F(1)和回交群体的生物统计学分析表明，生殖器形态的遗传是多基因的。应用兰德对卡斯尔 - 赖特估计量的修正方法，根据群体均值和方差来估计涉及的基因最少数量，我们发现相对较少的基因座决定了生殖器形态的物种差异。此外，联合尺度检验表明，加性遗传效应占生殖器性状种间差异的大部分，但显性和上位性遗传效应也起作用。总体而言，雄性和雌性生殖器的遗传基础相当简单，使得这些性状能够快速响应选择压力并迅速分化。我们的研究结果为地鳖甲生殖器形态的多样化提供了见解，并有望激发对生殖器遗传基础的进一步研究，例如对影响物种特异性生殖器形态的数量性状基因座进行定位。
