Studies of island biogeography are undergoing an invigorating transformation, from primarily ecological investigations founded in the equilibrium theory of MacArthur and Wilson (1967) toward a more general exploration of dynamic processes and patterns that span from generational to geological time ( Whittaker et al., 2008). Stuart, in Encyclopedia of Evolutionary Biology, 2016 Overview The question of invasive nonnative species is a separate major problem of island biogeography that is discussed in another chapter of this book. Species equilibria have not been detected among native species. Associated with the progressive and regressive phases of ecosystem development, different species assemblages also occur. The model also implies that after the plant biomass or biophilic nutrient climax, forest recovery yields successively less tall Metrosideros forests. The different kinds of dieback or canopy failure, depicted on the diagram as demographic events, reflect the habitat changes in terms of soil water and nutrient relations that occur over the long timescale. These may be synchronized over larger or smaller areas, depending on the disturbance regime, the cohort structure, and the aging pattern in the forest mosaic. With time, here estimated as 1 million years, the forest undergoes a number of generation turnovers in the form of canopy breakdown or gap formation and recovery. After that, a regression phase sets in very slowly, characterized by cation leaching, increasing occlusion of phosphorus ( Crews et al., 1995), formation of secondary aluminum (gibbsite) and iron (goethite) minerals, and advanced desilication ( Fox et al., 1991). Both, the volcanic ash and pahoehoe substrates, may achieve a “climax” in vegetation development in about 1000 to 5000 years in the rain forest climate. Here, the process of nudation can be a new pahoehoe lava flow or a volcanic ash blanket. The model addresses the concepts of climax as well as those of primary and secondary succession and habitat change with time in a single island biome, the montane tropical rain forest of Hawaii. This is diagrammatically portrayed in Fig. In connection with our long-term research on the native Metrosideros forest dieback in Hawaii, I introduced a model of ecosystem development based on the theory of succession ( Mueller-Dombois, 1986). Yet dynamic equilibria remain an area of ecological and biogeographical interest because an understanding of dynamic processes is essential for an improved theory of island biogeography. Both, the climax and species equilibrium concepts have been severely criticized. Clements proposed a final stabilization, called climax, while MacArthur and Wilson proposed a dynamic (final) species equilibrium as explained earlier. Other processes, such as the establishment and regeneration of populations (ecesis) after major disturbances (nudations), their “invasion” relative to “extinction” or their “final” assemblages in communities or ecosystems, also fall into the realm of biogeographical research. For example, the process of “dispersal” and “migration” of species among islands and their “adaptation” in terms of speciation were chosen as the main topics in a recent treatment of Hawaiian biogeography ( Wagner and Funk, 1995). All of these processes are of concern in biogeographic research. In his concept of succession, the early, influential American ecologist Clements (1916) recognized six processes:(a) nudation, (b) migration, (c) ecesis (establishment by reproduction), (d) competition, (e) reaction (habitat change through organisms), and (f) final stabilization, the climax community. These are listed as (a) dispersal, (b) invasion, (c) competition, (d) adaptation, and (e) extinction of species. MacArthur and Wilson (1967) speak of five fundamental processes as the most difficult to study in biogeography. The Theory of Successionīoth the island biogeography and biome theories thus outlined contain elements of succession or community and ecosystem development. Dieter Mueller-Dombois, in Encyclopedia of Biodiversity, 2001 II.C.
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