Flow Regime and the Structure and Productivity of Macroinvertebrate Communities in Tropical Streams

本研究旨在探讨哥斯达黎加热带干燥森林溪流中水流状况对大型无脊椎动物群落的生态和进化意义。原始的热带流域是测试水流对河流群落影响的理想地点，因为大多数温带河流没有季节性的温度和光周期以及高泥沙和泥沙负荷的混合影响，而且许多具有常年水流制度的原始小河流可供研究。这项研究将量化大型无脊椎动物的群落结构，以及在六条多年生溪流的杂乱栖息地中所有广泛和常见的大型无脊椎动物的生活史、特征和生产量。这项研究将侧重于这些参数在长时间(6个月)的恒流(枯季)和丰水期(雨季)以及在雨季出现短期洪涝缺陷时的时间变化。这项研究的中心假设是：溪流大型无脊椎动物群落不会因物种过饱和(在没有干扰的情况下)，并且可能能够承受长期的非生物稳定而不会损失多样性，即不存在“溪流底栖动物悖论”。本研究项目的主要目的是：(1)量化大型无脊椎动物相对丰度和物种组成的季节变化，并检验流量作为解释这种变化的协变量的有效性；(2)记录大型无脊椎动物生活史中季节性的程度，并评估地域性作为对水流状况的适应；(3)评估风暴在解释大型无脊椎动物群落结构季节变化方面的相对重要性；(4)评估空间尺度(即斑块大小)在底栖群落演替研究中的作用；以及(5)评估干扰在维持河流群落多样性方面的作用。

This research focuses on the ecological and evolutionary significance of flow regime to macroinvertebrate communities in tropical dry forest streams of Costa Rica. Pristine tropical watersheds are ideal sites for testing the effects of flow on stream communities because the confounding effects of seasonality in temperature and photoperiod and high silt and sediment load associated with most temperate streams are absent, and many pristine small streams with perennial flow regimes are available for study. The research will quantify macroinvertebrate community structure and the life history characteristics and production of all widespread and common species of macroinvertebrates in riffle habitat of six perennial streams. The study will focus on temporal changes in these parameters in response to prolonged (6 month) periods of both constant (dry season) and elevated (wet season) flow as well as to short-term flood flaws during the wet season. The central hypothesis of the study is that: stream macroinvertebrate communities are not oversaturated with species (in the absence of disturbance) and may be capable of withstanding long periods of abiotic stability without loss of diversity, i.e. there is no "paradox of the stream benthos". The principal objectives of this research project are to: (1) quantify seasonal variation in the relative abundance and species composition of macroinvertebrates and test the utility of flow as a covariate for explaining this variability; (2) document the extent of seasonality in macroinvertebrate life histories and evaluate sesonality as an adaptation to flow regime; (3) evaluate the relative importance of storms in explaining seasonal variability in macroinvertebrate community structure (4) assess the role of spatial scale (i.e. patch size) in studies of benthic community succession; and (5) evaluate the role of disturbance in maintaining the diversity of stream communities.