The Drivers of Cytonuclear Discordance

细胞核不一致的驱动因素

• 批准号: RGPIN-2014-06460
• 负责人: Murphy, Robert
• 金额: $ 1.97万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=567820
• 关键词: Drivers; Cytonuclear; Discordance

Closely related individual females of wild species of animals, such as mothers and daughters, sisters and cousins, often occur nearer to one another in nature rather than being broadly mixed among more distantly related females. Given time, a diversity of female lineages emerges and in most species of animals this nearness pattern is broken by the side-by-side occurrence of distantly related females in a very narrow geographic zone of only a few kilometers or less. This so-called genetic discordance, which we detect from DNA passed strictly from mother to daughter, results in a pattern that is not unlike World War I battle trenches. In contrast to female patterns, breeding among females and males results in an absence of a clear pattern when considering characters passed from both parents to their offspring. The difference between the patterns of closely related females and those of characters passed from both parents is one form of what is termed cytonuclear discordance. In broadly distributed species, the distant contact zones of matrilines may be only 6km or less across. The discordance may even be restricted to a single arroyo. Curiously, on the narrow peninsula of Baja California, Mexico, most species of animals show a pattern of cytonuclear discordance in the middle of the peninsula. Some species share up to four such contact zones. The occurrence of contact zones in multiple species reflects a common history. In the case of Baja California, an ancient ephemeral seaway likely isolated once continuous populations. After the seaway disappeared, the populations reunited. These animals have now lived side-by-side for more than 3 million years but without the mixing of maternal lineages. In some regions, such as near the southern tip of the peninsula, populations may have been in contact for much longer periods of time, perhaps 8 million years but still keep the discordance. A key focus of my research is to determine why this common pattern of discordance is so universal among animals on the peninsula. In other words, why have females not dispersed more than 6km in the 3+ million years they have had to do so? After all, this small distance translates to female lineages not moving more than an unbelievable 2mm/year! One explanation for the pattern, also termed cytonuclear discordance, suggests that the lineages do not mix because their energy-producing molecular machinery does not work efficiently when divergent lineages mix. By analogy, this phenomenon is like trying to put a square peg of one lineage into a round hole of another. Another possibility is that females aggressively protect their families against intrusions from more distantly related females, and this novel explanation, which is analogous to battle-lines, I call the sisterhood hypothesis. To make the situation complex, both of these mechanisms may work together in concert. I will use a suite of cutting edge experiments and technology, initially with tree lizards, to evaluate cytonuclear discordance and the sisterhood hypothesis. I will also explore the relative roles played by each of these mechanisms in maintaining the pattern of side-by-side maternal lineages. My experiments range from determining the relatedness of nearby females on trees—mother-daughter, sisters, cousins, or more distantly related—to sophisticated models of the energy-producing machinery (enzymes). The analyses have implications for not only understanding how species evolve, and the natural role aggressive female behaviour might play in their evolution, but also for conservation and management initiatives. For example, the translocations of individual animals from one site to another more often than not fails and perhaps cytonuclear discordance best explains the problem.

野生动物物种中的近亲个体雌性，如母亲和女儿，姐妹篇和堂兄弟姐妹，在自然界中经常彼此靠近，而不是广泛地混合在亲缘关系较远的雌性中。随着时间的推移，雌性谱系的多样性出现了，在大多数动物物种中，这种近距离模式被打破，因为在一个非常狭窄的地理区域内，只有几公里或更少的远距离雌性并排出现。这种所谓的遗传不一致性，我们从严格从母亲传给女儿的DNA中检测到，导致了一种与第一次世界大战战壕相似的模式。与雌性模式相反，雌性和雄性之间的繁殖导致在考虑从父母双方传递给后代的特征时缺乏明确的模式。亲缘关系密切的雌性个体的模式与从双亲遗传而来的性状模式之间的差异，就是所谓的细胞核不协调的一种形式。在广泛分布的物种中，母系的远距离接触区可能只有6公里或更短。这种不协调甚至可能仅限于一条河流。奇怪的是，在墨西哥下加利福尼亚州的狭窄半岛上，大多数动物物种在半岛中部表现出细胞核不一致的模式。一些物种共享多达四个这样的接触区。多个物种接触带的出现反映了一个共同的历史。在下加利福尼亚的情况下，一个古老的短暂的海道可能孤立曾经连续的人口。在海上航道消失后，人口重新聚集。这些动物已经并肩生活了300多万年，但没有混合母系血统。在某些地区，如半岛南端附近，种群可能已经接触了更长的时间，也许有800万年，但仍然保持着不一致。我研究的一个重点是确定为什么这种常见的不一致模式在半岛的动物中如此普遍。换句话说，为什么女性在300多万年的时间里没有分散超过6公里？毕竟，这个小距离意味着女性血统每年的移动不会超过令人难以置信的2毫米！对这种模式的一种解释，也被称为细胞核不一致，表明谱系不能混合，因为当不同的谱系混合时，它们产生能量的分子机制不能有效地工作。打个比方，这种现象就像试图把一个血统的方栓插入另一个血统的圆孔。另一种可能性是，雌性积极地保护她们的家庭免受来自远亲雌性的入侵，这种新颖的解释，类似于战线，我称之为姐妹关系假说。为了使情况复杂化，这两种机制可能协同工作。我将使用一套尖端的实验和技术，首先用树蜥蜴，来评估细胞核不一致性和姐妹关系假设。我还将探讨这些机制中的每一个在维持并排母系模式中所起的相对作用。我的实验范围从确定树上附近雌性的亲缘关系母女、姐妹篇、堂兄弟姐妹或更远的亲缘关系到复杂的能量生产机器（酶）模型。这些分析不仅对了解物种如何进化以及攻击性雌性行为在其进化中可能发挥的自然作用具有影响，而且对保护和管理举措也具有影响。例如，个体动物从一个位点到另一个位点的易位往往失败，也许细胞核不一致最能解释这个问题。