Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada.
Mol Ecol. 2012 Mar;21(6):1411-22. doi: 10.1111/j.1365-294X.2011.05465.x. Epub 2012 Jan 23.
Whether speciation can advance to completion in the face of initially high levels of gene flow is a very controversial topic in evolutionary biology. Extensive gene exchange is generally considered to homogenize populations and counteract divergence. Moreover, the role of introgressive hybridization in evolution remains largely unexplored in animals, particularly in freshwater zooplankton in which allopatric speciation is considered to be the norm. Our work investigates the genetic structure of two young ecological species: the pond species, Daphnia pulex and the lake species, Daphnia pulicaria. Phylogenetic and population genetics analyses were conducted on mitochondrial NADH dehydrogenase 5 (ND5) gene, the nuclear Lactate dehydrogenase (Ldh) gene and 21 nuclear microsatellite markers in 416 individuals from habitats with various degrees of permanence. The strong and consistent phylogenetic discordance between nuclear and mitochondrial markers suggests a complex evolutionary history of multiple independent habitat transition events that involved hybridization and introgression between lake and pond Daphnia. On the other hand, the low level of contemporary gene flow between adjacent populations indicates the presence of effective habitat isolating barriers. The Daphnia system provides strong evidence for a divergence-with-gene flow speciation model that involves multiple habitat transition events.
在基因流最初水平较高的情况下，物种形成是否能够完成，这是进化生物学中一个非常有争议的话题。广泛的基因交换通常被认为会使种群同质化，并抵消分歧。此外，在动物中，特别是在被认为是异域物种形成常态的淡水浮游动物中，种间杂交在进化中的作用在很大程度上仍未得到探索。我们的工作调查了两个年轻的生态物种的遗传结构：池塘物种，Daphnia pulex 和湖泊物种，Daphnia pulicaria。对来自具有不同持久性的生境的 416 个人的线粒体 NADH 脱氢酶 5（ND5）基因、核乳酸脱氢酶（Ldh）基因和 21 个核微卫星标记进行了系统发育和种群遗传学分析。核和线粒体标记之间强烈而一致的系统发育不和谐表明，存在涉及湖泊和池塘 Daphnia 之间杂交和基因渗入的多个独立生境过渡事件的复杂进化历史。另一方面，相邻种群之间的当代基因流水平较低表明存在有效的生境隔离障碍。Daphnia 系统为涉及多个生境过渡事件的具有基因流的分歧形成模型提供了有力证据。
