Centre for Ecological and Evolutionary Synthesis (CEES)Department of Biosciences, University of Oslo P.O.Box 1066, Blindern, NO-0316, Norway.
School of Aquatic and Fishery Sciences, University of Washington Box 355020, Seattle, Washington, 98195-5020.
Ecol Evol. 2014 Jan;4(2):144-56. doi: 10.1002/ece3.918. Epub 2013 Dec 18.
Divergent selection pressures induced by different environmental conditions typically lead to variation in life history, behavior, and morphology. When populations are locally adapted to their current environment, selection may limit movement into novel sites, leading to neutral and adaptive genetic divergence in allopatric populations. Subsequently, divergence can be reinforced by development of pre-or postzygotic barriers to gene flow. The threespine stickleback, Gasterosteus aculeatus, is a primarily marine fish that has invaded freshwater repeatedly in postglacial times. After invasion, the established freshwater populations typically show rapid diversification of several traits as they become reproductively isolated from their ancestral marine population. In this study, we examine the genetic and morphometric differentiation between sticklebacks living in an open system comprising a brackish water lagoon, two freshwater lakes, and connecting rivers. By applying a set of microsatellite markers, we disentangled the genetic relationship of the individuals across the diverse environments and identified two genetic populations: one associated with brackish and the other with the freshwater environments. The "brackish" sticklebacks were larger and had a different body shape than those in freshwater. However, we found evidence for upstream migration from the brackish lagoon into the freshwater environments, as fish that were genetically and morphometrically similar to the lagoon fish were found in all freshwater sampling sites. Regardless, few F1-hybrids were identified, and it therefore appears that some pre-and/or postzygotic barriers to gene flow rather than geographic distance are causing the divergence in this system.
不同环境条件下的分歧选择压力通常会导致生活史、行为和形态的变化。当种群适应其当前环境时，选择可能会限制它们向新栖息地的移动，从而导致异地种群的中性和适应性遗传分化。随后，通过发展有性前和有性后基因流障碍，分化可以得到加强。三刺鱼，Gasterosteus aculeatus，是一种主要的海洋鱼类，在冰期后多次入侵淡水。入侵后，建立的淡水种群通常会在与祖先海洋种群生殖隔离时迅速多样化几种特征。在这项研究中，我们研究了生活在一个由咸水泻湖、两个淡水湖和连接河流组成的开放系统中的刺鱼的遗传和形态差异。通过应用一组微卫星标记，我们解开了个体在不同环境中的遗传关系，并确定了两个遗传种群：一个与咸水有关，另一个与淡水有关。“咸水”刺鱼比淡水中的鱼更大，体型也不同。然而，我们发现有证据表明有从咸水泻湖向上游迁移到淡水环境的情况，因为在所有淡水采样点都发现了与泻湖鱼类在遗传和形态上相似的鱼类。尽管如此，很少有 F1 杂种被识别出来，因此，在这个系统中，似乎是一些有性前和/或有性后基因流障碍而不是地理距离导致了分化。
