WHAT THE EVIDENCE SAYS
Surveys across 30 eastern Amazon streams related Odonata assemblages to habitat integrity and water quality. More preserved streams supported greater representation of Zygoptera, while more degraded conditions favored relatively tolerant Anisoptera. Community composition changed along the degradation gradient even where simple species-count responses were less diagnostic.
WHY IT MATTERS / OUR READ
A biological indicator can lose sensitivity when it is reduced to total richness. Composition—and which ecological strategies replace which others—may reveal degradation before a headline count makes the change obvious.
CAVEATS / UNCERTAINTY
This is an observational regional study, and odonate responses integrate several correlated environmental changes. Taxon-specific composition should complement, not replace, direct measurements of riparian condition and water quality.
SOURCE
Journal of Insect Conservation · Original evidence
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