Regional diversity, local community structure and vacant niches: the herbivorous arthropods of bracken in South Africa

Abstract

Abstract. 1. Seventeen species of phytophagous arthropods (sixteen insects and one gall‐forming eryiophyid mite) were found feeding on the above‐ground parts of bracken (Pteridium aquilinum (L.) Khun.) in surveys throughout the geographic range of the plant in South Africa. A further thirteen species of insects may possibly feed on the plant in this region.2. Given the area over which bracken grows in South Africa, this is very close to the number of species expected on the plant, based on species‐area calculations and comparisons with bracken in other geographic regions.3. The species‐richness of bracken‐feeding arthropods in local communities reflects the size of the regional pool of species in different geographic areas. Local richness in South Africa is intermediate between that in south‐western U.S.A. and Britain.4. In both Britain and South Africa there is a weak tendency (0.05 < P < 0.07) for larger local patches of bracken to support more species of phytophages than small patches, with similar very shallow slopes (0.083 and 0.086) in plots of log species versus log area on both continents.5. The taxonomic composition of bracken‐feeding arthropods in South Africa is markedly different from that in other pants of the world, suggesting very different and largely independent evolutionary histories in different regions.6. There is no sign of convergence in the feeding niches of communities of bracken‐feeding arthropods in different parts of the world, and the pattern of feeding relationships is very different in South Africa to patterns observed elsewhere. Conspicuous vacant niches (ways of exploiting the plant that are observed in other geographic regions) are easily identified in the South African communities.

Species Richness of Reef-Building Corals Determined by Local and Regional Processes

“…The observation that many species compete weakly if at all (Schoener 1983 Compton, Lawton & Rashbrook 1989), and the emergence of non-equilibrial explanations for richness patterns (e.g. Diamond & Case 1986) have challenged the supremacy of competition as the primary organizing factor in ecological communities.…”

Local Communities of Arboreal Herbivores in Papua New Guinea: Predictors of Insect Variables

“…Research has often focused on predictors of insect species richness at the regional scale on particular hosts (see recent review in Jones and Lawton 1991) and on predictors of insect host-specificity within particular insect taxa (e.g., Futuyma 1991). Regional and local processes (sensu Cornell 1985) have been contrasted recently in studies of herbivore species richness (e.g., Cornell 1985, Compton et al 1989, Basset and Burckhardt 1992. At the regional scale, species richness is thought to be influenced predominantly by biogeographical processes such as past climatic history, speciation rates, widespread extinction, and geographical position of dispersal barriers and corridors.…”

Fern sporophagy in Coleoptera from the Juan Fernandez Islands, Chile, with descriptions of two new genera in Cryptophagidae and Mycetophagidae

“…Although Hendrix was referring mainly to root-, stemand foliage-feeders among the Hemiptera, Lepidoptera and Hymenoptera, our data suggest the same phenomenon to have occurred in these three mycophagous groups utilizing fern spores. Compton et al (1989) also supported this hypothesis by pointing out that the insect communities on associated with bracken in the U.S.A., Britain and South Africa have very different and largely independent evolutionary histories.…”