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Mapping functional traits: comparing abundance and presence-absence estimates at large spatial scales
Tim Newbold1, Stuart H M Butchart, Cağan H Sekercioğlu
1United Nations Environment Programme, World Conservation Monitoring Centre, Cambridge, United Kingdom. Tim.Newbold@unep-wcmc.org
Plos One
|September 7, 2012
Summary
Mapping bird community composition using species ranges is effective, though local abundance data could improve accuracy. This study tested range-overlap methods against independent data, finding it the best available approach for trait-based community ecology. Further data is needed for precise estimates.
Area of Science:
- Ecology
- Biodiversity Science
- Computational Biology
Background:
- Quantifying biological community composition increasingly relies on functional traits.
- Trait-based mapping is emerging but lacks validation against independent data.
Purpose of the Study:
- To test the accuracy of commonly used and novel methods for mapping functional trait composition of bird communities in the Western Hemisphere.
- To compare range-overlap methods with those incorporating abundance data against independent community composition data.
Main Methods:
- Calculated community-weighted mean of trait values, functional richness, and functional divergence for four traits (body mass, generation length, migratory behavior, diet).
- Compared four mapping methods, including range-overlap and three abundance-informed approaches, using Western Hemisphere bird data.
- Validated maps against independent American Christmas Bird Count (CBC) data.
Main Results:
- The commonly-used range-overlap method showed the best fit with observed community composition (21/22 correlations positive; R(2) median 0.33).
- Overall correspondence between mapped and observed communities was positive (62/73 correlations) but varied widely by metric and method (R(2) median 0.12).
- The range-overlap method performed best despite its assumption of equal species abundance.
Conclusions:
- Overlaying species range maps is the most effective currently available method for estimating trait-based community composition patterns due to data limitations.
- While effective, the range-overlap method's accuracy varies, highlighting the urgent need for local species abundance data.
- Improved abundance data will enable more accurate trait-based community assessments and ecological mapping.
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