The area-independent effects of habitat complexity on biodiversity vary between regions

• Published in: Ecology letters Vol. 6; no. 2; pp. 126 - 132
• Main Authors: Johnson, Mark P., Frost, Natalie J., Mosley, Matthew W. J., Roberts, Malcolm F., Hawkins, Stephen J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.02.2003
• Subjects: Fractal; Gastropoda; heterogeneity; lottery; spacing; topography; ANE, Irish Sea, Isle of Man; British Isles, England; ANE, British Isles, England
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1046/j.1461-0248.2003.00404.x

Potential explanatory variables often co‐vary in studies of species richness. Where topography varies within a survey it is difficult to separate area and habitat‐diversity effects. Topographically complex surfaces may contain more species due to increased habitat diversity or as a result of increased area per se. Fractal geometry can be used to adjust species richness estimates to control for increases in area on complex surfaces. Application of fractal techniques to a survey of rocky shores demonstrated an unambiguous area‐independent effect of topography on species richness in the Isle of Man. In contrast, variation in species richness in south‐west England reflected surface availability alone. Multivariate tests and variation in limpet abundances also demonstrated regional variation in the area‐independent effects of topography. Community composition did not vary with increasing surface complexity in south‐west England. These results suggest large‐scale gradients in the effects of heterogeneity on community processes or demography.