Examining the Relationship between Aquatic Insect Assemblages and Water Variables by Ordination Techniques

以排序技術分析河川水棲昆蟲群聚及水質變數之關係

徐崇斌(Chorng-Bin Hsu) ； 楊平世(Ping-Shih Yang)

《台灣昆蟲》 25卷2期 (2005/06) Pp. i+67-85

https://doi.org/10.6661/TESFE.2005007

摘要

Aquatic insects were sampled quarterly at five sites along the upper Keelung River, which runs through the Taipei metropolitan area and receives various forms of pollution and anthropogenic disturbances, between August 1996 and April 1997 to examine the distribution patterns of aquatic insects and their relationships with the water variables using univariate and multivariate analyses. Upstream sites 1 to 3 significantly differed from the downstream sites 4 and 5 in the number of taxa, density, Shannon diversity index, and the proportion of dominant taxon in the univariate analyses. Baetis spp. was the dominant taxon (14.22%) and Chironomidae was the dominant family (21.78%) in the entire study reach. The results of canonical correspondence analysis (CCA), a eigenanalysis-based ordination, were compared with the results of non-metric multidimensional scaling (MDS), a distance-based ordination. Differences in aquatic insect assemblages at the first three sites were only found by the multivariate approaches, not by the univariate approach. High number of taxa and abundances at the three upstream sites contributing to variances in the aquatic insect assemblages were perceived on the CCA ordination diagrams. However, the common taxa at the three sites also increased the community similarities and formed an upstream group of samples separate from the downstream group in the MDS plots. Differences in the results between the univariate and multivariate analyses at the three upstream sites were mainly caused by the limited distributions of some taxa, such as Epeorus erratus, Amphinemura sp., Protonemura sp., and Rhyacophila spp. at site 1. In the CCA, conductivity and biochemical oxygen demand (BOD) on axis 1 and water temperature and pH on axis 2 were the water variables that best explained about 42.9% of the variance in aquatic insect assemblages on the first two axes. In the MDS, chemical oxygen demand (COD) and BOD showed the highest correlation with aquatic insect assemblages in the upper Keelung River.

關鍵字

community structure ； Keelung River ； canonical correspondence analysis ； multidimensional scaling

並列摘要

本研究自1996年8月至1997年4月間，在基隆河上游五個樣站進行每季採樣，以瞭解水棲昆蟲的分佈型式及其與水質變數之關係。由單變質分析方法顯示，分類群數量、密度、Shannon歧異度指標與優勢分類群比例，在上游3個樣站與下游2樣站間具有顯著之差異。全河域以Baetis spp.為優勢分類群（佔14.22%），搖蚊科（Chironomidae）則為最優勢的科（21.78%）。多變質分析以典型對應分析（canonical correspondence analysis, CCA）及多維空間尺度（multidimensional scaling, MDS）二種方法比較，結果顯示在上游3個樣站間水棲昆蟲組成的差異僅能以多變質分析方法區辦。高物種數及豐度增大了上游樣站中水棲昆蟲群聚的變異，而反應於CCA的排序圖中。而上游樣站共同物種的存在，亦增加樣站間群聚的相似度，在MDS的排序圖上形成上游與下游兩個不同群組的分佈形態。由於部份物種呈現侷限分布，如Epeorus erratus、Amphinemura sp.、Protonemura sp.及Rhyacophila spp.僅在第一樣站記錄，為主要造成上游三個樣站中單變質與多變質分析結果差異的原因。CCA指出在第一軸上的電導度與生化需氧量（biochemical oxygen demand, BOD）與第二軸上之水溫及酸鹼值為解釋此河段水棲昆蟲群聚變異最佳的水質變數，解釋的變異量約為42.9%。MDS顯示化學需氧量（chemical oxygen demand, COD）及BOD，與水棲昆蟲群聚所構成之排序圖具有最高之相似性。

並列關鍵字

群聚結構 ； 基隆河 ； 典型對應分析 ； 多維空間尺度