The usual positive inter-specific relationship between range size and abundance of local populations can have notable exceptions in Afrotropical montane areas, where range-restricted bird species are unusually abundant. We tested how the area occupied locally by passerines and their geographic range size relate to local abundances along a tropical elevational gradient of Mt Cameroon, West-Central Africa. Data on bird assemblages were collected at six forested elevations (350, 650, 1100, 1500, 1850 m, 2200 m a.s.l.) using a standardised point count at 16 locations per elevation. Elevational ranges of birds were compiled from published sources and their geographic range sizes were determined as the occupancy of 1° x 1° grid cells. The observed relationship between local abundance and geographic range size within the entire passerine assemblage on Mt Cameroon disagrees with the most frequently reported positive pattern. However, the patterns differ among elevations, with positive trends of the abundance-range size relationship in lowland changing to negative trends towards higher elevations. Interestingly, the total assemblage abundances do not differ much among elevations and population size estimates of species occupying different parts of the gradient remain relatively constant. These patterns are caused by relatively high abundances of montane species, which might be a result of long-term ecological specialization and/or competitive release in species-poor montane locations and possibly facilitated by an extinction filter. Our data suggest that montane species' abilities to maintain dense populations might compensate for less area available near mountain tops and help these populations to circumvent extinction.

Center for Macroecology Evolution and Climate Natural History Museum of Denmark University of Copenhagen 2100 Copenhagen Denmark

Department of Ecology Faculty of Science Charles University Prague Viničná 7 12844 Praha 2 Czech Republic

IRTC International Research and Training Center Yaoundé Cameroon

Mount Cameroon National Park Buea Cameroon

Zobrazit více v PubMed

Proc Natl Acad Sci U S A. 2009 Nov 17;106 Suppl 2:19737-41 PubMed

J Anim Ecol. 2006 Nov;75(6):1426-39 PubMed

Q Rev Biol. 2010 Mar;85(1):3-25 PubMed

J Appl Ecol. 2010 Feb;47(1):5-14 PubMed

Proc Natl Acad Sci U S A. 1970 Dec;67(4):1715-21 PubMed

Science. 1988 Sep 16;241(4872):1455-60 PubMed

Biol Lett. 2009 Aug 23;5(4):492-4 PubMed

Oecologia. 1980 Jan;45(3):385-389 PubMed

Nature. 2014 May 8;509(7499):222-5 PubMed

J Appl Ecol. 2014 Aug;51(4):849-859 PubMed

Proc Biol Sci. 2000 Oct 7;267(1456):1947-52 PubMed

Functional and Phylogenetic Structure of Forest Bird Assemblages Along an Afrotropical Elevational Gradient

High Inter-Specific Diversity and Seasonality of Trunk Radial Growth in Trees Along an Afrotropical Elevational Gradient

Cophylogeny, narrow host breadth and local conditions drive highly specialized bird-haemosporidian associations in West-Central African sky islands

Spatiotemporal pattern of specialization of sunbird-plant networks on Mt. Cameroon

Traits and ecological space availability predict avian densities at the country scale of the Czech Republic

Biomass, abundances, and abundance and geographical range size relationship of birds along a rainforest elevational gradient in Papua New Guinea

Flying between raindrops: Strong seasonal turnover of several Lepidoptera groups in lowland rainforests of Mount Cameroon