Novel ecosystems support substantial avian assemblages: the case of invasive alien Acacia thickets
Article first published online: 6 SEP 2013
© 2013 The Authors. Diversity and Distributions published by John Wiley & Sons Ltd.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Diversity and Distributions
Volume 20, Issue 1, pages 34–45, January 2014
How to Cite
Rogers, A. M., Chown, S. L. (2014), Novel ecosystems support substantial avian assemblages: the case of invasive alien Acacia thickets. Diversity and Distributions, 20: 34–45. doi: 10.1111/ddi.12123
- Issue published online: 14 DEC 2013
- Article first published online: 6 SEP 2013
- National Research Foundation of South Africa
- Biological invasions;
- body size;
- conservation value;
- local–regional assemblages;
- novel ecosystems
Altered habitats may form entirely novel ecosystems that support new combinations of species. How indigenous species use invaded areas is, however, not well understood. Here, we investigate the value of Australian Acacia thickets as novel ecosystems in the Western Cape of South Africa by surveying bird assemblages within them.
Western Cape Province of South Africa.
Birds were surveyed quantitatively in a variety of Acacia thickets in the south-western Western Cape in three seasons to examine species richness, abundance and functional diversity. We also examined the extent to which avian diversity was related to differences in patch-level vegetation structure.
Significant variation was observed in assemblage richness, density and biomass across sites. Diversity increased with productivity, but declined with stem density and canopy cover. On average, Acacia thicket patches were used by c. 20 species (with a regional richness of 76 species), had a mean density of 7.78 birds ha−1 and a mean biomass of 0.224 kg ha−1. The most abundant feeding guilds were the mixed feeders and insectivores.
Acacia thickets in the Western Cape support a large subset of the region's birds with the most abundant species being small mixed feeders. Compared with other habitat types, Acacia thickets support avian assemblages with species richness and density similar to some natural sites in the region, but lacking typical nectarivores. Extrapolation to the area transformed by invasive acacias in the Cape Floristic Region suggests that these novel ecosystems support c. 22 million individual birds or 621 tonnes of avian biomass.