Dissertation Research: Environmental Causes and Behavioral Tactics Determining Variation in Vertical Migration: Midday Stratification in a Pelagic Zooplankton

Diel垂直迁徙(DVM)是指淡水湖泊和海洋中不同种群的每日上下运动。这些长时间的迁徙造成浮游动物密度的每日局部波动，因此直接影响对浮游植物的捕食率和向鱼类种群的能量转移。实地研究和数值模拟已经确定了浮游动物产量最大化的生态条件，以及对替代DVM行为施加的生存、生长和繁殖限制。因此，在现场观察到的DVm的变化似乎是适应性的。然而，导致DVM这种变异的机制尚不清楚，主要是因为人们对遗传变异相对于环境变化的重要性知之甚少。这项研究的目的是：(1)确定种群中遗传不同的个体在野外是否具有不同的DVM分布；(2)在实验室中，确定遗传不同的个体是否以相同的方式对旨在模拟田间条件的实验环境做出反应，以及这些反应在不同环境中是否相似。研究目标将有助于了解浮游动物大型水蚤层积行为变异的原因。由于层化行为在很大程度上决定了栖息地的范围，本研究不仅提供了DVM的机制，而且提供了关于基本浮游动物生态、栖息地选择的决定因素以及多态维持的数据。最后，了解浮游动物DVM的机制意味着更好地了解影响鱼类食物利用率和浮游植物捕食率的行为。

Diel vertical migration (DVM) is the daily up and down movement of diverse populations in both freshwater lakes and oceans. These long migrations cause daily, local fluctuations in zooplankton density, therefore directly affecting grazing rates on phytoplankton and energy transfer to fish populations. Field research and numerical simulations have identified both the ecological conditions under which zooplankton production can be maximized, along with the constraints on survival, growth and reproduction imposed on alternative DVM behaviors. Accordingly, it appears that variation in DVM, observed in the field, is adaptive. However, mechanisms causing such variation in DVM are unknown, largely because little is known about the importance of genetic variation relative to environmental change. The objectives of this study are: (1) to determine whether genetically different individuals in a population have different DVM distributions in the field (2) the laboratory, determine whether genetically different individuals respond in the same way to experimental environments designed to simulate field conditions, and whether those responses are similar in different environments. The study objectives will provide an understanding of the causes of variability in stratification behavior of the zooplankter Daphnia galeata mendotae. Since stratification behavior largely determines habitat range, this study offers insight into not only mechanisms of DVM but also data on basic zooplankton ecology, determinants of habitat choice, along with maintenance of polymorphisms. Finally, understanding mechanisms of zooplankton DVM means a better understanding of behaviors influencing food availability for fish and grazing rates on phytoplankton.