DISSERTATION RESEARCH: Ecological Role of Fish in Southwestern Streams

在一个生态群落中具有较强影响的物种在其他环境条件下的影响可能是有限的，但决定物种相互作用强度的因素往往不清楚。鱼类控制着许多水系的重要特征。美国西南部的本土鱼类是测试非生物和生物因素对物种相互作用影响的理想选择，因为单一物种广泛分布在炎热的沙漠和凉爽的山脉的异质地貌中。这些溪流中的本地鱼类正在减少；因此，了解它们丧失的影响是至关重要的。为了评估环境背景如何影响西南溪流中物种的相互作用，这项研究将调查两个相关但功能不同的鱼类物种--斑点叉尾鱼和克拉克鱼--对沿海拔梯度的生态系统过程的影响。这一梯度将使研究这些物种对关键溪流过程的影响，如初级生产和有机质的产生，在从温暖的水、低沙漠溪流到凉水、高山溪流的条件下。利用在单一溪流中控制鱼类身份的大规模围栏和在多个溪流中的小规模鱼类围栏，这项研究将估计鱼类对生态系统特性的影响，并评估环境背景如何改变这些影响。该项目还将跟踪鱼类栖息地的使用情况，以了解对生态系统过程的影响是否在溪流中是不同的。了解改变生态系统中物种重要性的因素将为管理机构提供特别有价值的信息，管理机构必须制定可持续的做法来利用和保护这些生态资源。

A species with a strong influence in one ecological community may have a limited influence under other environmental conditions, but the factors determining the strength of species interactions are often unclear. Fish control important characteristics of many stream systems. Native fishes of the American southwest are ideal for testing the influence of abiotic and biotic factors on species interactions because single species are broadly distributed throughout a heterogeneous landscape of hot deserts and cool mountains. Native fishes are declining in these streams; thus, understanding the effects of their loss is vital. To assess how environmental context affects species interactions in Southwestern streams, this study will investigate the influence of two related, but functionally different fish species, Catostomus insignis and Catostomus clarki, on ecosystem processes along an elevational gradient. This gradient will enable examination of the effects of these species on critical stream processes such as primary production and organic matter generation under conditions ranging from warm water, low desert streams to cool water, high mountain streams. Using large-scale enclosures controlling fish identity in a single stream combined with small-scale fish exclosures in multiple streams, this study will estimate the effects of fish on ecosystem properties, and assess how environmental context modifies them. The project also will track fish habitat use to understand if effects on ecosystem processes are heterogeneous within the stream. Understanding the factors modifying species importance in ecosystems will provide information particularly valuable for management agencies, which must develop sustainable practices to use and protect these ecological resources.