Dissertation Research: Size-Refugia, Alternative States andTrophic Cascades in Pond Benthic Food Webs

[701120]莱博尔德有几个因素可以影响消费者对食物网的影响。在简单的食物链中，捕食者的影响随着生产力的增加而增加。然而，如果猎物在其生命史的某个时刻由于体型的原因可以从捕食者那里获得避难所，那么食物网的相互作用就会变得更加复杂。在这个提议中，研究人员将研究大小结构的猎物种群如何影响捕食者相互作用的强度，以及初始条件、物种组成和环境因素（如生产力）如何在很大程度上决定捕食者控制食物网的程度。正在进行的建模工作显示了所有这些因素如何影响食物网中捕食者的影响，特别是根据初始条件的潜在替代稳定状态。该模型的显著特征是为密歇根州南部的小型池塘底栖生物食物网开发的，并且似乎得到了支持，在那里，蜗牛Helisoma trivolis只在小的时候容易受到捕食者（主要是半足类，Belostoma fluineum，水蛭和掠食性甲虫）的影响，而另一种常见的蜗牛Physella gyrina在所有大小上都容易受到影响。一个大型的中观实验将检验基于猎物物种身份和多样性、初始密度和生产力的模型预测。生物和非生物调查范围广泛的池塘，和封闭/封闭实验将被用来进一步阐明这些影响。这项研究的结果将揭示生态学中关于物种相互作用强度的各种问题，这些问题与形态、环境和初始条件有关。

9701120 Leibold Several factors can influence the impacts of consumers in food webs. In simple food chains, the impact of predators increases with productivity. If prey can attain a refuge from predation due to size at some point in its life history, however, the food web interactions become more complex. In this proposal, the investigators will examine how size-structured prey populations may influence the strength of interactions of predators, and how initial conditions, species composition, and environmental factors (e.g., productivity) may greatly determine the degree to which predators can control the food web. An ongoing modeling effort shows how all of these factors can influence the effects of predators in food webs, with particular reference to potential alternative stable states depending on initial conditions. The salient features of the model were developed for, and appear to be upheld in small pond benthic food webs of southern Michigan, where the snail, Helisoma trivolis, is only susceptible to predators (primarily the Hemipteran, Belostoma flumineum, leeches, and predatory beetles) when small, whereas another common snail, Physella gyrina, is susceptible at all sizes. A large mesocosm experiment will examine the predictions of the model based on prey species identity and diversity, initial densities, and productivity. Biotic and abiotic surveys of a wide range of ponds, and enclosure/exclosure experiments m situ will be employed to further elucidate these effects. Results from this study should shed light into a variety of questions in ecology concerning the strength of species interactions in relation to morphological, environmental, and initial conditions.