Co-occurrence-based measure of species' habitat specialization: robust, unbiased estimation in saturated communities
Version of Record online: 20 SEP 2011
© 2011 International Association for Vegetation Science
Journal of Vegetation Science
Volume 23, Issue 2, pages 201–207, April 2012
How to Cite
Botta-Dukát, Z. (2012), Co-occurrence-based measure of species' habitat specialization: robust, unbiased estimation in saturated communities. Journal of Vegetation Science, 23: 201–207. doi: 10.1111/j.1654-1103.2011.01347.x
- Issue online: 14 MAR 2012
- Version of Record online: 20 SEP 2011
- Manuscript Accepted: 9 AUG 2011
- Manuscript Received: 7 JUL 2009
- Niche width;
- Species pool;
- Whittaker's β;
Large vegetation plot databases enable the estimation of niche width from species co-occurrence data. Different indices have been proposed for this purpose, but do not give unbiased (i.e. independent of species pool size) and robust estimates over a wide range of conditions. The aims of the paper are to: (1) demonstrate the limitations of different methods, and (2) propose a new algorithm that results in unbiased and robust estimates.
Whittaker's β-diversity, calculated from raw data, is an unbiased niche width measure only if the relationship between γ-diversity and local richness is linear. However, this requirement is satisfied only in specific conditions, if both γ-diversity and local richness are linear functions of the species pool size with zero intercept. I propose the use of Beals smoothing to estimate species pools. It has been proved through analysis of simulated data that Whittaker's β calculated from species pool data is an unbiased estimate of niche width. I have shown that the robustness of the estimate can be improved by excluding extremely species-rich plots. The relative role of methodological decisions during niche width estimation was explored through analysis of a large field data set (>8000 relevés).
The proposed algorithm results in robust, unbiased estimation, even in saturated communities, thus it avoids the drawbacks of the co-occurrence-based niche width measures proposed earlier.