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.

Howard 9726502 十年的研究表明，地蟋蟀（Allonemobius fasciatus 和 A. socius）通过同种精子优先顺序进行生殖隔离。 换句话说，这两个物种在自然界中很少产生杂交种，因为一个物种的精子在另一物种雌性的生殖道中运作不良。 这是生物学家对生殖隔离两个密切相关物种的特征有清楚了解的极少数情况之一。 这种生殖障碍的遗传控制将通过数量性状基因座（QTL）作图研究进行评估。 这是一项相对较新的技术，允许生物学家枚举和定位控制复杂性状（例如同种精子优先顺序）的基因（或 QTL）。 作图群体将足够大，足以检测对同种精子优先顺序影响很小的 QTL。 因此，这项研究将能够清楚地评估影响较大的基因和影响较小的基因对生殖隔离发展的作用。 一旦确定了 QTL，将单独检查每个 QTL 的影响。 通过精心设计的遗传杂交，来自 A. fasciatus 的单个 QTL 将被引入 A. socius 中，反之亦然。 如此产生的蟋蟀将允许在脱离其通常遗传背景的情况下研究QTL，从而直接测试QTL在控制同种精子优先权中的作用。 最后，最近的研究表明，同种精子的优先顺序进化得很快，并且常常可能是不同种群之间出现的第一个生殖障碍。 因此，了解这种屏障如何影响密切相关物种之间的重叠区域非常重要。 将通过遗传和人口统计建模方法分析同种精子优先级对重叠区域的影响。 生物学家对物种形成——新物种形成的过程以及地球上生命多样性的过程——的了解相对较少。 这是人类保护物种多样性努力的一个严重缺陷，除非不断产生新物种，否则这种努力就不可能成功。 事实证明，了解密切相关的物种之间生殖障碍的遗传基础特别困难。 这一困难可归因于两个因素：1）生殖隔离的多面性使得很难确定隔离两个物种的性状，2）直到最近才出现剖析复杂性状所需的工具。 对于A. fasciatus 和A. socius来说，第一个困难是经过十年的艰苦研究而克服的。 第二个困难已被遗传学的最新进展所克服，这些进展导致了几乎可以在任何生物体中进行定位的标记的开发。 映射标记可以监测基因组不同区域对生殖障碍的影响。将目前对 Allonemobius 系统的理解与遗传学的这些新进展相结合，将为生殖障碍的遗传学提供前所未有的见解。 特别是，拟议的研究将确定 A. fasciatus 和 A. socius 之间的生殖隔离是由少数具有重大影响的基因控制还是由许多具有较小影响的基因控制。 这种区别是一场持续了一个多世纪的争论的核心，对于理解种群的空间分离是否是物种形成所必需的以及物种形成所需的时间是长还是短至关重要。 最后，同种精子优先顺序的遗传控制研究归结为生育问题的遗传控制研究。 因此，这项研究提供的对不孕不育的见解将与包括人类在内的许多生物体相关。