Habitat-independent spatial structure in populations of some forest birds in eastern North America
Article first published online: 20 AUG 2012
© 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society
Journal of Animal Ecology
Volume 82, Issue 1, pages 145–154, January 2013
How to Cite
Ricklefs, R. E. (2013), Habitat-independent spatial structure in populations of some forest birds in eastern North America. Journal of Animal Ecology, 82: 145–154. doi: 10.1111/j.1365-2656.2012.02024.x
- Issue published online: 17 JAN 2013
- Article first published online: 20 AUG 2012
- Manuscript Accepted: 6 JUL 2012
- Manuscript Received: 5 MAR 2012
- University of Missouri
- Alexander von Humboldt Foundation
- community ecology;
- forest birds;
- geographic ranges;
- host–pathogen coevolution;
- population distributions;
- spatial ecology
- The extent to which populations fill available ecological space is critical to evaluating niche-based theories of community assembly, but habitat suitability for populations is difficult to assess. The absence of a species from areas of otherwise suitable habitat might indicate localized species-specific influences, including biological interactions with competitors, consumers or pathogens, on local population persistence.
- I used Bray–Curtis ordination axis scores, based on the distributions of forest birds across census plots in eastern North America, as proxies of general features of habitat suitability to predict local abundances of each species of small land bird. I then applied spatial analysis to identify significant spatial structure (Moran's I) in residuals (positive or negative) from predicted local densities, which would indicate localized species-specific influences on population size.
- Fifty-eight of 79 species exhibited no significant spatial structure in residual abundances, indicating that the ordination axes reflect most of the spatial variation in environmental conditions and habitat characteristics that influence population distribution and density or that samples were too small to detect significant spatial variation. Twenty-one species exhibited significant habitat-independent spatial structure of residuals within distances of 100 km. Aggregations of residuals for these species were independently located, for the most part, and thus probably unrelated to general features of the environment that affect many species.
- Among factors considered as potential causes of spatial anomalies, positive density dependence (Allee effects), intraspecific social aggregation and area sensitivity in response to forest fragmentation find little support in this analysis. Because of the species-specific nature of these clustered residuals, specialized pathogens are potential candidates to drive spatial anomalies in host abundance.