Evolutionary consequences of interspecific hybridization: Daphnia resting egg banks as biological archives

尽管有许多关于动植物种间自然杂交的研究，但很少有研究涵盖足够长的时间来描述杂交谱系的起源和命运，或将种间基因流动水平与环境条件联系起来。在此，我们建议利用从康斯坦斯湖和格雷芬塞湖沉积物中分离的静止卵来扩展我们对水蚤物种复合体的种群遗传学研究。在1950年以前，两湖只发现了一种D. hyalina，后来D. galeata入侵两湖，导致了种间杂交。我们的初步数据为这两个种群的大规模杂交提供了证据，我们的目标是利用核和线粒体DNA数据描述20世纪（~100年）杂交（例如渗入）的后果。此外，我们将孵化不同时期（1960年、1970年、1990年和2000年）的个体，并在40年的时间内测试差异孵化和表型变异。这种结合种群遗传学和表型分析的方法，利用湖泊沉积物中的休眠卵，将使我们能够在过去的一个世纪中测量一个物种复合体的生殖隔离、基因流动和选择水平。

Despite many studies on natural interspecific hybridization among plants and animals, few cover long enough time periods to describe the origin and fate of hybrid lineages or to associate levels of interspecific gene flow with environmental conditions. Here we propose to extend our population genetic studies of a Daphnia species complex using resting eggs isolated from sediments of Lake Constance and Lake Greifensee. Initially, only one species (D. hyalina) was found in both lakes (before 1950), later on D. galeata invaded both lakes which resulted subsequently in interspecific hybridization. Based on our preliminary data which provide evidence for a massive hybrid sweep in both populations, we aim to describe the consequences of hybridization (e.g. introgression) during the course of the 20th century (~100 years) using nuclear and mitochondrial DNA data. In addition, we will hatch individuals from several time periods (1960¿s, 1970¿s, 1990¿s and 2000¿s) and test for differential hatching and phenotypic variation over a time period of 40 years. This combined approach of population genetics and phenotypic analyses using resting eggs from lake sediments will allow us to measure the level of reproductive isolation, gene flow, and selection in a species complex during the past century.