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Scaling in stream communities
Peter E Schmid1, Mutsunori Tokeshi, Jenny M Schmid-Araya
1School of Biological Sciences, Queen Mary, University of London, London E1 4NS, UK. p.e.schmid@qmul.ac.uk
Proceedings. Biological Sciences
|February 8, 2003
Summary
Stream invertebrate communities show consistent body size scaling relationships across seasons, suggesting habitat complexity, not just energy, influences their structure. This reveals how species size distributions are shaped by environmental factors.
Area of Science:
- Ecology
- Stream Ecology
- Community Ecology
Background:
- Understanding scaling relationships between population density (N) and body size (W) is crucial for resource use analysis.
- Previous research on these scaling relationships has yielded controversial results regarding their form.
Purpose of the Study:
- To investigate the form and temporal consistency of population density-body size scaling relationships in stream invertebrate communities.
- To explore the influence of habitat complexity on species-size spectra and community organization.
Main Methods:
- Analysis of an extensive dataset of 602 invertebrate species from two stream communities (Seebach, Austria and Mynach, Wales).
- Application of ordinary least squares (OLS), bisector (OLS(BIS)), and quantile regressions to analyze N-W relationships.
- Examination of species-size spectra using seasonally collated data and fractal dimension (D) for habitat complexity.
Main Results:
- Seasonal OLS(BIS) regressions showed slopes not departing from -1, indicating seasonally convergent scaling unrelated to energetic constraints.
- Species-size spectra exhibited 'central tendencies' rather than right-skewed distributions, reflecting community phyletic composition.
- Body-mass spectra differed between communities; Seebach showed bimodal convergence, while Mynach displayed seasonally shifting unimodality.
- Large invertebrate body-size spectra scaled with seasonal habitat complexity, suggesting its role in constraining community structure.
Conclusions:
- Stream invertebrate communities exhibit seasonally convergent body-size scaling relationships.
- Habitat complexity, particularly fractal dimension, significantly influences the organization of stream benthos, especially for larger species.
- The findings offer an alternative explanation for body-size scaling, emphasizing habitat structure over purely energetic constraints.