Collaborative Research: Postmating Reproductive Isolation Among Drosophila arizonae and Drosophila mojavensis

新物种起源的关键事件是生殖隔离的形成。然而，一个物种是如何分裂成两个生殖隔离的生物群体的，人们知之甚少。果蝇属的果蝇一直是物种形成研究的一个模式系统。这些研究主要集中在前交配或合子后分离机制，或那些决定雄性和雌性是否交配以及它们是否分别产生可存活和可育后代的过程。在物种形成的研究中，在授精和卵子受精之间发生的许多事件在很大程度上被忽视了。然而，最近的研究表明，对成功生殖至关重要的精子、精液和女性生殖道特征正在迅速分化。研究人员假设，这种差异会导致遗传差异种群的成员杂交时繁殖成功率降低，他们提出了一系列实验来明确验证这一假设，使用D. arizonae和它的兄弟物种D. mojavensis，两者都是北美特有的。由于来自不同地理区域的mojavensis被认为是早期物种，研究人员将利用自然发生的生殖隔离连续体来验证他们的预测。初步资料表明，不同居群间被测性状差异显著。通过在不同种群和具有已知繁殖特征的物种之间进行实验室杂交，研究人员将确定这些特征如何导致对新物种形成至关重要的繁殖障碍。这些实验结果可能对新物种的形成具有重要意义。

0075307 PitnickThe crucial event for the origin of new species is the formation of reproductive isolation. How one species splits into two reproductively isolated groups of organisms, however, is poorly understood. Fruitflies of the genus Drosophila have been a model system for studies of speciation. These studies have focused on premating or postzygotic isolating mechanisms, or those processes that determine whether or not males and females mate and whether or not they produce viable and fertile offspring, respectively. The multitude of events occurring between insemination and egg fertilization has been largely ignored in studies of speciation. Recent work, however, indicates that sperm, seminal fluid, and female reproductive tract characteristics that are of central importance for successful reproduction are rapidly divergent. The investigators postulate that this divergence will cause diminished reproductive success whenever members of genetically differentiated populations interbreed, and they propose a series of experiments to explicitly test this hypothesis using D. arizonae and its sibling species D. mojavensis, both endemic to North America. Because D. mojavensis from different geographic regions are considered to be incipient species, the investigators will take advantage of a naturally occurring continuum of reproductive isolation for testing their predictions. Preliminary data indicate that populations of D. mojavensis differ significantly in the traits to be measured. By conducting laboratory crosses between members of different populations and species with known reproductive characteristics, the investigators will determine how these characteristics lead to reproductive barriers central to the formation of new species. Results of these experiments may have important implications for the formation of new species.