Biotic interactions and the maintenance of a Daphnia hybrid species complex

水蚤的杂交种出现在许多湖泊中。然而，人们对水蚤杂交成功的因素知之甚少。在两个实验室（康斯坦茨D大学，EAWAG Dübendorf CH）的联合项目中，我们希望研究生物相互作用在水蚤杂交复合体维持中的可能作用。Daphnia hyalina、D. galeata和它们的杂交种出现在博登湖（德国-瑞士-奥地利边境）和格赖芬湖（瑞士）。在博登湖，亲种更为丰富，而在格赖芬湖，杂交种占主导地位。这两个湖泊在重要方面（形态，营养状态）不同，这是反映了不同的生物对水蚤的影响。与博登湖相比，格赖芬湖的水蚤更经常暴露于低质量的食物（有毒的蓝绿色），并且没有鱼类捕食的避难所（由于缺氧的低水层）。这两个湖泊之间的差异，在无脊椎动物捕食制度和水蚤寄生虫负载是非常可能的。除了实地取样方案外，我们还想从这两个湖泊中收集大约50个水蚤克隆（亲本种和杂交种，最近的克隆和从沉积物芯中孵化的老克隆）。这些克隆将用于实验室的生活史实验，以测试低质量食物的影响。鱼类利它素，无脊椎动物捕食者利它素和原生动物寄生虫。食品质量和无脊椎动物捕食者实验将在康斯坦茨进行;寄生虫和鱼类实验将在杜本多夫进行。（p）

Hybrids of the water flea Daphnia occur in many lakes. However, little is known about the factors that cause the success of Daphnia hybrids. In a joint project of two laboratories (University Konstanz D, EAWAG Dübendorf CH), we want to study the possible role of biotic interactions in the maintenance of a Daphnia hybrid complex. Daphnia hyalina, D. galeata and their hybrids occur in Bodensee (German-Swiss-Austrian Border) and in Greifensee (Switzerland). The parent species are more abundant in Lake Constance, while hybrids dominate in Greifensee. Both lakes differ in important aspects (morphometry, trophic state), which is reflected by different biotic influences on Daphnia. Compared to Lake Constance, Daphnia in Greifensee are more often exposed to low quality food (toxic blue-greens) and have less of a refuge from fish predation (due the anoxic hypolimnion). Differences between both lakes in the invertebrate predation regime and in parasite load of Daphnia are very probable. Besides field sampling programmes, we want to establish a collection of about 50 Daphnia clones from both lakes (parent species and hybrids, recent clones and old clones hatched from sediment cores). These clones will be used for life history experiments in the laboratory which test the influences of low quality food. of fish kairomones, of invertebrate predator kairomones and of a protozoan parasite. Food quality and invertebrate predator experiments will be done in Konstanz; parasite and fish experiments will be done in Dübendorf. (p)