Snider Sunny B, Gilliam James F
Department of Zoology, North Carolina State University, Raleigh, North Carolina 27695-7617, USA.
Ecology. 2008 Jul;89(7):1961-71. doi: 10.1890/07-0715.1.
Immigration, emigration, migration, and redistribution describe processes that involve movement of individuals. These movements are an essential part of contemporary ecological models, and understanding how movement is affected by biotic and abiotic factors is important for effectively modeling ecological processes that depend on movement. We asked how phenotypic heterogeneity (body size) and environmental heterogeneity (food resource level) affect the movement behavior of an aquatic snail (Tarebia granifera), and whether including these phenotypic and environmental effects improves advection-diffusion models of movement. We postulated various elaborations of the basic advection diffusion model as a priori working hypotheses. To test our hypotheses we measured individual snail movements in experimental streams at high- and low-food resource treatments. Using these experimental movement data, we examined the dependency of model selection on resource level and body size using Akaike's Information Criterion (AIC). At low resources, large individuals moved faster than small individuals, producing a platykurtic movement distribution; including size dependency in the model improved model performance. In stark contrast, at high resources, individuals moved upstream together as a wave, and body size differences largely disappeared. The model selection exercise indicated that population heterogeneity is best described by the advection component of movement for this species, because the top-ranked model included size dependency in advection, but not diffusion. Also, all probable models included resource dependency. Thus population and environmental heterogeneities both influence individual movement behaviors and the population-level distribution kernels, and their interaction may drive variation in movement behaviors in terms of both advection rates and diffusion rates. A behaviorally informed modeling framework will integrate the sentient response of individuals in terms of movement and enhance our ability to accurately model ecological processes that depend on animal movement.
迁入、迁出、迁移和再分布描述了涉及个体移动的过程。这些移动是当代生态模型的重要组成部分，了解移动如何受到生物和非生物因素的影响对于有效模拟依赖于移动的生态过程至关重要。我们研究了表型异质性（体型大小）和环境异质性（食物资源水平）如何影响一种水生蜗牛（大瓶螺）的移动行为，以及纳入这些表型和环境效应是否能改进移动的平流扩散模型。我们提出了各种对基本平流扩散模型的细化作为先验工作假设。为了检验我们的假设，我们在高食物资源处理和低食物资源处理的实验溪流中测量了单个蜗牛的移动。利用这些实验性移动数据，我们使用赤池信息准则（AIC）检验了模型选择对资源水平和体型大小的依赖性。在低资源条件下，大型个体比小型个体移动得更快，产生了一种低峰态的移动分布；在模型中纳入体型依赖性提高了模型性能。与之形成鲜明对比的是，在高资源条件下，个体作为一个群体一起向上游移动，体型大小差异基本消失。模型选择分析表明，对于该物种，种群异质性最好用移动的平流成分来描述，因为排名靠前的模型在平流中纳入了体型依赖性，但在扩散中没有。此外，所有可能的模型都纳入了资源依赖性。因此，种群和环境异质性都影响个体移动行为和种群水平的分布核，它们的相互作用可能在平流速率和扩散速率方面驱动移动行为的变化。一个基于行为的建模框架将整合个体在移动方面的感知反应，并增强我们准确模拟依赖于动物移动的生态过程的能力。
