物种间杂交指两个不同物种之间进行交配后，发生物种间基因交换/重新组合，由此产生新基因型, 从而显著改变群体的遗传结构。在环境胁迫下，杂交所产生的新基因型可获得更多生存机会。申请者前期以枝角类浮游生物水蚤属(Daphnia) 为模式生物，发现1）不同生态环境下，水蚤群体的遗传结构存在巨大差异；2）当生态环境恶化时，水蚤杂交比例会显著增加；3）水蚤群体的种间杂交可显著改变群体的遗传结构。这些研究提示，物种间杂交是环境胁迫下物种得以延续的重要策略。为检验这一假说，本研究将利用可精确分辨水蚤群体中不同类群差异特征的15个微卫星遗传位点，对8个天然或人工湖泊的水蚤群体样本进行基因型分析，重点探讨生态环境对杂交的影响，以及新栖息地水蚤杂种对变化环境的响应。期望证实生态环境可影响群体的种间杂交，且种间杂交产生的后代更适应变化下的生态环境。本研究将有助于阐明基因交换/重新组合在适应性进化中的重要作用。

Interspecific hybridization (i.e. crossing between two different species) is a creative evolutionary force that forms novel genotypes, and then significantly changes the population structure. Hybrids will allow rapid adaptation to new environments, when unfavourable conditions arise. Our previous studies, by using hybrid complexes of zooplanktonous cladocerans of the genus Daphnia, indicated that the population structure showed significant differences among different environments and the proportion of hybrids increased when the environmental conditions deteriorated. In addition, the hybridization could change the Daphnia population structure significantly. These results suggest that hybridization is an important strategy for the survivor of the species in the unfavourable environments. The present proposal, by using 15 advanced microsatellite loci, will investigate Daphnia population structure from 8 different lakes (natural or artificial) to address the open questions of if the environments effect on the hybridization and how the hybrids response to the changing environments. We expect that the hybrids will success in the changing environments. The proposed combination of intensive field sampling and advanced molecular technology will advance our understanding of the role of hybridization in the changing environments and, more generally, of genetic exchange in adaptive evolution.