Trichoptera larvae and water quality parameters of streams Canonical correspondence analysis (CCA) was used to determine the variance of species-environment relations. According to this analysis, 49.5% of the variance was described by the first two axes of the relation between species and environmental variables (r = 1.000) (Table 4), and pH, ammonia-nitrogen (NH 3 -N), and water temperature were the variables that best explained Trichoptera distribution. CCA demonstrated that variables such as pH were positively correlated with the first axis, whereas ammonianitrogen was negatively correlated with the first axis. The second CCA axis was mainly correlated with water temperature. According to the second axis, pH and water temperature were positively related to the distribution of some species (e.g., Ecnomus sp., Polyplectropus sp., Pseudoneureclipsis sp., Hydropsyche camillus, H. askalaphos, Cheumatopsyche sp., C. tramota, Potamyia sp., and Stenopsyche siamensis). Also, the distributions of the species in the lower left corner of the plot (e.g., Rhyacophila inaequalis, Amphipsyche meridiana, Hydropsyche pallipenne, Potamyia phaidra, Cheumatopsyche dubitans, and Marilia sumatrana) were negatively correlated with ammonianitrogen (Figure 37).

Published as part of Seetapan, Kriengkrai & Prommi, Taeng On, 2022, The larvae of caddisfly species (Insecta, Trichoptera) in northern Thai streams and their relationships to environmental variables, pp. 301-324 in Zootaxa 5222 (4) on page 315, DOI: 10.11646/zootaxa.5222.4.1, http://zenodo.org/record/7466720