title: Contrasting Patterns of Species Richness and Functional Diversity in Bird Communities of East African Cloud Forest Fragments.
abstract: Rapid fragmentation and degradation of large undisturbed habitats constitute major threats to biodiversity. Several studies have shown that populations in small and highly isolated habitat patches are prone to strong environmental and demographic stochasticity and increased risk of extinction. Based on community assembly theory, we predict recent rapid forest fragmentation to cause a decline in species and functional guild richness of forest birds combined with a high species turnover among habitat patches, and well defined dominance structures, if competition is the major driver of community assembly. To test these predictions, we analysed species co-occurrence, nestedness, and competitive strength to infer effects of interspecific competition, habitat structure, and species' traits on the assembly of bird species communities from 12 cloud forest fragments in southern Kenya. Our results do not point to a single ecological driver of variation in species composition. Interspecific competition does not appear to be a major driver of species segregation in small forest patches, while its relative importance appears to be higher in larger ones, which may be indicative for a generic shift from competition-dominated to colonisation-driven community structure with decreasing fragment size. Functional trait diversity was independent of fragment size after controlling for species richness. As fragmentation effects vary among feeding guilds and habitat generalists, in particular, tend to decline in low quality forest patches, we plead for taking species ecology fully into account when predicting tropical community responses to habitat change.
authors.affiliation: Nicolaus Copernicus University in Toruń, Chair of Ecology and Biogeography, Pl-87-100 Toruń, Poland.
authors.forename: Werner
authors.initials: W
authors.lastname: Ulrich
authors.affiliation: Ghent University, Department of Biology, Terrestrial Ecology Unit, B-9000 Ghent, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Lens
authors.affiliation: Department of Life Sciences, Imperial College London, Silwood Park, Buckhurst Road, Ascot, Berkshire, SL5 7PY, United Kingdom.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Tobias
authors.affiliation: Technische Universität München, Department of Ecology and Ecosystem Management, Terrestrial Ecology Research Group, D-85354 Freising, Germany.
authors.forename: Jan C
authors.initials: JC
authors.lastname: Habel
mesh_terms: D000351:Africa, Eastern; D000818:Animals; D044822:Biodiversity; D001717:Birds; D003247:Conservation of Natural Resources; D017753:Ecosystem; D065928:Forests; D011157:Population Dynamics; D014329:Tropical Climate