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Published on: January 13, 2023
The problem of using fixed-area subsampling methods to estimate macroinvertebrate richness: a case study with
Raphael Ligeiro1, Wander Ferreira, Robert M Hughes
1Departamento de Biologia Geral, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. ligeirobio@gmail.com
Environmental Monitoring and Assessment
|August 30, 2012
Summary
Fixed-area subsampling in freshwater macroinvertebrate studies can overestimate or underestimate taxonomic richness. Fixed-count methods are recommended for reliable richness estimates, especially when sample sizes vary.
Area of Science:
- Ecology
- Freshwater Biology
- Environmental Science
Background:
- Subsampling is common for processing freshwater macroinvertebrate samples.
- Fixed-count and fixed-area subsampling methods are currently employed.
- Fixed-area methods are still in use despite potential limitations.
Purpose of the Study:
- To evaluate the reliability of macroinvertebrate taxonomic richness estimates from fixed-area subsampling.
- To compare fixed-area versus fixed-count approaches for ecological studies.
Main Methods:
- Used a dataset from 18 tropical stream sites with varying human disturbance levels.
- Processed a standard number of subsampling quadrats (fixed-area approach).
- Analyzed collection curves and correlated quadrat number with taxonomic richness.
Main Results:
- Processing 12 quadrats (half the sample) stabilized collection curves for many sites.
- The number of quadrats needed for 80% richness was negatively correlated with the number of individuals per sample.
- Fixed-area subsampling can lead to overestimation in samples with many individuals and underestimation in samples with few.
Conclusions:
- Fixed-area subsampling alone is not recommended for accurately measuring taxonomic richness.
- Fixed-count approaches are encouraged for more reliable taxonomic richness assessments in macroinvertebrate studies.
- Sample size (number of individuals) significantly impacts the representativeness of fixed-area subsampling efforts.
