Rainforests, Null models
The period of research in tropical rainforests of Mount Kupe in Cameroon and of Palo Seco in Panama spanned five years, preceded and followed by a series of shorter visits to rainforests in Australia, Africa, Asia and Central America. Data have been acquired along elevational gradients according to sampling designs aimed at testing predictions at the community level. Although difficult to implement under field conditions, this approach yielded structured data sets instead of purely descriptive species accounts based on haphazard collections.
When the number of species studied simultaneously or other constraints preclude manipulative experiments, null models provide a statistical approach to compare an observed pattern with patterns expected to occur in the absence of a specific process, e.g., interspecific interactions or response to an environmental constraint. I further developed existing null models for environmental gradients to better account for community-level processes and applied the refined tests to the Mount Kupe data set.
With the publication of the gradient distributions in the journal Ecology (80:976-988), I deliberately invited reanalyses. Almost two decades after its publication, the incidence matrix of the Kupe distributions resurrected as a reference data set within the (in)famous controversy about checkerboard distributions, initiated with Diamond’s publication of assembly rules and continuing with the major protagonists still involved (Chapter 9, Species along a Gradient in Sanderson & Pimm, 2015. Patterns in Nature: The Analysis of Species Co-Occurrences, University of Chicago Press). A review of community structures along elevational gradients in tropical montane forests (Willig & Presley, J. Trop. Ecol. 2016) cited my Mount Kupe data set as the only one concerning amphibians and reptiles, highlighting the challenge of acquiring good quality data in this type of environment.
Hofer, U., Bersier, L.-F. & Borcard, D. 2004. Relating niche and spatial overlap at the community level. Oikos 106: 366-376.
Hofer, U., Baur, H. & Bersier, L.-F. 2003. Ecology of three sympatric species of the genus Chamaeleo (Sauria: Chamaeleonidae) in a tropical upland forest in Cameroon. Journal of Herpetology 37(1): 203-207
Hofer, U., & Bersier, L.-F. 2001. Herpetofaunal diversity and abundance in tropical upland forests of Cameroon and Panama. Biotropica 33(1): 142-152
Hofer, U., Bersier, L.-F. & Borcard, D. 2000. Ecotones and gradient as determinants of herpetofaunal community structure in the primary forest of Mount Kupe, Cameroon. Journal of Tropical Ecology 16: 517-533.
Hofer, U., Bersier, L.-F. & Borcard, D. 1999. Spatial organization of a herpetofauna on an elevational gradient revealed by null model tests. Ecology 80(3): 976-988.
Nguyen, N., & Hofer, U. 2004. Estimates of the herpetofaunal diversity in the Shipstern Nature Reserve, Belize. Report on behalf of the International Tropical Conservation Fund (ITCF).