http://planet.uwc.ac.za/nisl/Gwen's%20Files/Biodiversity/Chapters/Info%20to%20use/Chapter%207/HotSpotTropForestMyers.pdf

Threatened biotas: "hot spots" in tropical forests.

Introduction.- Western Melanesia.- Eastern Melanesia.- The Subtropical Islands in the New Zealand Region.- Micronesia.- Central Polynesia.- Western Polynesia.- Eastern Polynesia.- Northern Polynesia: The Hawaiian Islands.- The Oceanic Islands in the Eastern Pacific.- The Future of Island Vegetation.

Vegetation of the tropical Pacific islands

Tropical rain forests do not always have a high diversity in tree species. In some cases, most of the trees in the canopy layer are a single species. This results in a low diversity among the other canopy tree species (fig. 1). Increasing dominance by one canopy species has little effect on the diversity of subcanopy trees (fig. 2). Such single-dominant forests are of two types: the dominant either persists at the site beyond one generation or it does not. In forests with a persistent dominant species (type I), one species may achieve dominance either by colonizing most of a large open patch and persisting thereafter or by gradually replacing the existing residents. The latter could take place either because the dominant is the species most resistant to deleterious physical or biotic conditions or because it is superior in competition to all others. One possible mechanism enabling one species to replace and exclude many others is the possession of an ectomycorrhizal (EM) association. Most tropical tree sp...

Low-Diversity Tropical Rain Forests: Some Possible Mechanisms for Their Existence

Insects are a major force in most ecosystems, yet in studies of biodiversity they often receive less attention than birds, mammals and plants. Two papers this week redress the balance. Novotny et al. studied some 500 species of lepidopteran caterpillars, beetles and fruit flies across 75,000 km2 of rain forest in Papua New Guinea. They found that most species of herbivorous insects were widely distributed. Species richness was high, as expected in the tropics, but the species found did not alter much even over hundreds of kilometres. Dyer et al. reached rather different conclusions from their work on hundreds of thousands of host-specificity feeding records for butterfly and moth caterpillars from areas ranging from Canada to Brazil. They found that the average number of tree species on which an insect species feeds was fewer in the tropics than in temperate parts of the New World, a confirmation of the latitudinal gradient in ecological specialization much discussed by biologists since the time of Darwin and Wallace. With apparently contradictory results such as these two reports, though, the discussion may run and run. A study of about 500 species of lepidopteran caterpillars, beetles and fruit flies details that that most species of herbivorous insects are widely distributed over 75,000 km2 of contiguous lowland rain forest in Papua New Guinea. Thus, although species richness was high, the species found did not alter much even over hundreds of kilometres despite habitat discontinuities and different geological terrains. Recent advances in understanding insect communities in tropical forests1,2 have contributed little to our knowledge of large-scale patterns of insect diversity, because incomplete taxonomic knowledge of many tropical species hinders the mapping of their distribution records3. This impedes an understanding of global biodiversity patterns and explains why tropical insects are under-represented in conservation biology. Our study of approximately 500 species from three herbivorous guilds feeding on foliage (caterpillars, Lepidoptera), wood (ambrosia beetles, Coleoptera) and fruit (fruitflies, Diptera) found a low rate of change in species composition (beta diversity) across 75,000 square kilometres of contiguous lowland rainforest in Papua New Guinea, as most species were widely distributed. For caterpillars feeding on large plant genera, most species fed on multiple host species, so that even locally restricted plant species did not support endemic herbivores. Large plant genera represented a continuously distributed resource easily colonized by moths and butterflies over hundreds of kilometres. Low beta diversity was also documented in groups with differing host specificity (fruitflies and ambrosia beetles), suggesting that dispersal limitation does not have a substantial role in shaping the distribution of insect species in New Guinea lowland rainforests. Similar patterns of low beta diversity can be expected in other tropical lowland rainforests, as they are typically situated in the extensive low basins of major tropical rivers similar to the Sepik–Ramu region of New Guinea studied here.

/pdf/low-beta-diversity-of-herbivorous-insects-in-tropical-2y5dotetz6.pdf

Low beta diversity of herbivorous insects in tropical forests.

Early and mid Holocene tool-use and processing of taro (Colocasia esculenta), yam (Dioscorea sp.) and other plants at Kuk Swamp in the highlands of Papua New Guinea

K. Paijmans

Papers

New Guinea vegetation

New Guinea vegetation