快速适应性进化是物种适应新环境的关键策略之一。种间杂交是物种快速进化的一种重要方式，可在极短时间内产生新基因型/性状以适应变化环境。申请者前期以淡水生态系统关键种水蚤(Daphnia)为模式生物，发现水蚤长刺溞复合种亲本D. galeata有快速扩张能力，可扩散至正在富营养化的中/寡营养湖泊，并与本地种D. dentifera发生杂交，成为新环境的优势种群，提示水蚤杂交是应对水体富营养化的重要策略之一。但水蚤杂种对水体富营养化的适应机制不明。本研究拟采用水蚤单克隆培养技术，诱导培育水蚤杂种；研究杂种/亲本在富/中/寡营养水体中的表型差异，探讨杂种对富营养化的适应性特征；研究杂种/亲本在富/中/寡营养水体中的基因表达差异，期望揭示杂种应对水体富营养化的关键信号通路。研究结果不仅为研究水体富营养化下物种的快速进化提供重要依据，还将有助于阐明基因交换/重组在适应性进化中的重要作用。

Rapid evolution is an important strategy to adapt to the changing environments. Interspecies hybridization can produce new genotypes/traits in a short time to adapt to changing environments. By using water flea Daphnia which is a keystone species in the freshwater ecosystem as a model organism, we found that parental D. galeata showed a rapid expansion, could spread to eutrophicating lakes in the Western China, and then hybridized with local D. dentifera and became the dominant taxa in this species complex. Therefore, it suggested that Daphnia hybridization is an important strategy to cope with the lake eutrophication. In this proposal, we will: 1) produce the Daphnia hybrid clones; 2) investigate how the hybrid and parental clones’ responses to different water trophic conditions; 3) detect the differentially expressed genes of hybrid/parents in different water trophic conditions and then to explore the key signaling pathways of hybrids in response to the lake eutrophication. These results will not only provide an important basis for studying the rapid evolution in the text of lake eutrophication, but also help us to understand the role of gene exchange/recombination in the adaptive evolution.