Variations in species richness in tropical bird and other faunas
Diversification of tropical avifaunas are being studied as part of the research programme of Centre for Tropical Biodiversity. One of the major tasks done at the Zoological Museum has been the development of databases which allow accomodation of distributional data for large numbers of species on a continent-wide scale. Databases have been developed for analysing all African and South American breeding birds with a 1° spatial resolution, and some datasets have also been made for regional analysis (15' resolution) (J. Fjeldså, C. Rahbek, N. Burgess and H. de Klerk, with P. Williams, The Natural History Museum, London, and a broad network of experts abroad). Similar databases are being developed for African mammals, snakes (N. Burgess, C. Rahbek, J.B. Rasmussen) African frogs (N. Burgess, C. Rahbek, with A. Schiøtz, Grevinge), butterflies (with T. Larsen, London) and some plant groups (with the Botanical Museum, University of Copenhagen, and J. Lovett, University of York) (N. Burgess, coordinator). The databases cover altogether nearly 9,000 species. Several papers are in press and in progress, as well as cand.scient. projects by J. Dam and F. Brammer (South American birds) and J. Larsen (African mammals).
One of the aims with these unique datasets is to conduct comprehensive statistical analyses on determinants of species richness, evaluating to what extent species richness and range sizes are determined by different biological (macroecological) variables and non-biological parameters (latitude, longitude, elevational amplityde, climatic parameters etc.), at different spatial scales. The design of the theoretical and analytical framework was started in 1996 (C. Rahbek). A pilot study was made to examine the relationship between concentrations of narrowly endemic species and interannual variability in ground conditions (documented by ten years meteorological satellite imagery; J. Fjeldså, with Ornis Consult and EU Remote Sensing Unit, Ispra, Italy). Another more detailed analysis of the relationship between endemism and ecoclimatic stability was intiated for the Andean cloud forest zone (J. Fjeldså, with staff of Université Cathlique de Louvain, Belgium).
The variation in species richness on altitudinal gradients was analysed through critical reviews of the existing literature and using a database over all 3,087 species of breeding South American landbirds (C. Rahbek). Explanatory models for the mid-altitude peak of species richness are being evaluated through field studies in Africa (T. Romdal, L. Christiansen, M. Dehn, cand.scient. projects).