The Genetic Control and Evolutionary Significance of a Barrier to Interspecific Hybridization

种间杂交障碍的遗传控制和进化意义

• 批准号: 9726502
• 负责人: Daniel Howard
• 金额: $ 39.5万
• 依托单位: New Mexico State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-03-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9726502&HistoricalAwards=false
• 关键词: Genetic; Control; Evolutionary; Significance; Barrier

Howard 9726502 Ten years of research have demonstrated that the ground crickets, Allonemobius fasciatus and A. socius, are reproductively isolated by conspecific sperm precedence. In other words, the two species produce few hybrids in nature because sperm from one species operates poorly in the reproductive tract of females from the other species. This is one of the very few situations in which biologists have a clear understanding of the trait that reproductively isolates two closely related species. The genetic control of this reproductive barrier will be assessed through a quantitative trait loci (QTL) mapping study. This is a relatively new technique that allows biologists to enumerate and locate the genes (or QTLs) that control a complex trait, such as conspecific sperm precedence. The mapping populations will be large enough to detect QTLs that have even a small effect on conspecific sperm precedence. Thus the study will allow a clear evaluation of the role of genes with large effects and the role of genes with small effects on the development of reproductive isolation. Once QTLs have been identified, the effects of each will be examined on an individual basis. Through carefully designed genetic crosses, single QTLs from A. fasciatus will be introduced into A. socius and vice-versa. The crickets so produced will allow a QTL to be studied in isolation from its usual genetic background, and thereby directly test the role of the QTL in controlling conspecific sperm precedence. Finally, recent studies indicate that conspecific sperm precedence evolves quickly and may often be the first reproductive barrier to arise between diverging populations. Therefore, it is important to understand how such a barrier influences zones of overlap between closely related species. The effect of conspecific sperm precedence on zones of overlap will be analyzed through a genetic and demographic modeling approach. Speciation, the process by which new species are formed and ther efore the process responsible for the diversity of life on earth, is relatively poorly understood by biologists. This is a critical shortcoming in humanity's efforts to preserve species diversity, which cannot succeed unless new species continue to be generated. Reaching an understanding of the genetic basis of reproductive barriers between closely related species has proven particularly difficult. The difficulty can be attributed to two factors: 1) the multi-faceted nature of reproductive isolation makes it hard to identify the traits that isolate two species, and 2) the tools necessary to dissect complex traits were not, until recently, available. In the case of A. fasciatus and A. socius the first difficulty was overcome by ten years of painstaking research. The second difficulty has been overcome by recent advances in genetics that have led to the development of markers that can be mapped in virtually any organism. Mapped markers allow the effects of different regions of the genome on a reproductive barrier to be monitored. Combining the current understanding of the Allonemobius system with these new developments in genetics will provide unprecedented insight into the genetics of reproductive barriers. In particular, the proposed research will allow a determination of whether reproductive isolation between A. fasciatus and A. socius is controlled by a few genes of major effect or by many genes of small effect. This distinction is at the center of a debate that has raged for more than a century and is critical for understanding whether spatial separation of populations is necessary for speciation and whether the time required for speciation is large or small. Finally, the study of the genetic control of conspecific sperm precedence boils down to the study of the genetic control of fertility problems. Thus, the insights into infertility provided by this research will be relevant to many organisms, including humans.

霍华德9726502进行了十年的研究表明，地面板球，Allonemobius fasciatus和A. socius是通过特定精子优先级生殖分离的。 换句话说，这两个物种在自然界中产生的杂种很少，因为一个物种的精子在其他物种的女性生殖道中起作用很差。 这是生物学家对生殖隔离两个密切相关的物种的特征有清晰了解的极少数情况之一。 该生殖屏障的遗传控制将通过定量性状基因座（QTL）映射研究来评估。 这是一种相对较新的技术，它允许生物学家列举并定位控制复杂性状的基因（或QTL），例如特定的精子优先级。 映射种群将足够大，可以检测到对同种精子优先级影响的QTL。 因此，该研究将允许对具有较大作用的基因的作用以及对生殖隔离发展产生微小影响的作用的作用进行清晰的评估。 一旦确定了QTL，将对每个QTL进行单独检查。 通过精心设计的遗传杂交，将引入来自筋膜曲霉的单个QTL，并将其引入A. socius，反之亦然。 如此生产的板球将使QTL与通常的遗传背景分离，从而直接测试QTL在控制特定精子优先级中的作用。 最后，最近的研究表明，同种精子优先级会迅速发展，并且通常是在不同种群之间出现的第一个生殖障碍。 因此，重要的是要了解这种障碍如何影响密切相关物种之间重叠的区域。 同种精子优先考虑对重叠区域的影响将通过遗传和人口统计学建模方法分析。 物种形成的过程是生物学家对新物种形成的过程，以及导致地球生命多样性的过程。 这是人类保护物种多样性的努力的重要缺点，除非继续产生新物种，否则该物种多样性无法成功。 事实证明，了解密切相关物种之间生殖屏障的遗传基础的遗传基础特别困难。 难度可以归因于两个因素：1）生殖隔离的多方面性质使得很难识别分离两个物种的性状，而2）直到最近才能使用，剖析复杂性状所需的工具才能使用。 在筋膜曲霉和A. socius的情况下，第一个困难被十年艰难的研究克服了。 最近的遗传学进步已经克服了第二个困难，这导致了可以在任何生物体中映射的标记的发展。 映射的标记允许监测基因组不同区域对生殖屏障的影响。将对Allonemobius系统的当前理解与遗传学的这些新发展相结合，将为生殖屏障的遗传学提供前所未有的见解。 特别是，拟议的研究将确定筋膜曲霉和socius之间的生殖隔离是由一些主要作用的基因控制还是由许多效应的许多基因控制。 这种区别是一场辩论的核心，该辩论已经肆虐一个多世纪，对于了解种群的空间分离是否对于物种形成以及形成所需的时间是否大还是很小至关重要。 最后，对同种精子优先的遗传控制的研究归结为研究生育问题的遗传控制。 因此，这项研究提供的对不育症的见解将与包括人类在内的许多生物有关。