Collaberative Research: Ultimate Causation of Insect Drift:An Evaluation of Active and Passive Models

生活在溪流底物上或底物内的昆虫大量地“漂”向下游，并有明显的夜间节律。昆虫漂移是流水的独特特性之一，尽管有许多研究，它仍然是一个挑战，也是一个谜。概念和技术的最新发展现在允许对生物漂移的原因，漂移进入的主动与被动程度以及生物与非生物原因的相对影响等问题进行协调一致的攻击。本研究旨在了解昆虫在觅食事件和被捕食风险的背景下的漂移。夜行性被捕食风险假说令人满意地解释了。漂移的发生有两种解释：一种是夜间觅食活动的被动和偶然结果，另一种是与资源枯竭有关的主动和有目的的栖息地寻找/分散过程。虽然被动模式被广泛接受，但来自最近工作的证据证明了被动机制的弱点和主动机制的重要作用。本研究结合现场取样、实验室和现场实验来解决五个目标，测试有关漂移行为机制的多种假设。它们的完成将导致对下游漂移的主动和被动解释的相对贡献的更好理解，下游漂移仍然是河流生态学中主要的、未解决的问题之一。

Insects living on or within the substrate of streams "drift" downstream in substantial numbers and with a pronounced nocturnal rhythm. Insect drift is one of the unique properties of running waters and, despite numerous studies, it remains both a challenge and a puzzle to lotic ecologists. Recent developments of concepts and techniques now allow for a concerted attack on the issues of why organisms drift, to what degree drift entry is active vs. passive, and the relative influence of biotic vs. abiotic causes. This research is directed toward the goal of understanding insect drift within the context of foraging events and risk of predation. Nocturnality has been satisfactorily explained by the risk of predation hypothesis. Two explanations exist for why drift occurs: as the passive and accidental consequence of nocturnal foraging activity, or as an active and purposeful process of habitat search/dispersal, related to resource depletion. While the passive model is widely accepted, evidence from recent work documents weaknesses in the passive mechanism and a significant role for an active mechanism. This research uses a combination of field sampling and laboratory and field experiments to address five objectives that test multiple hypotheses concerning the mechanism(s) underlying drift behavior. Their completion should lead to an improved understanding of the relative contributions of active and passive explanations of downstream drift, which remains one of the major, unresolved issues in river ecology.