Island Biogeography Dieter Mueller-Dombois, University of Hawai’i, Honolulu, HI, USA r 2001 Elsevier Inc All rights reserved This article is reproduced from the previous edition, volume 3, pp 565–580, r 2001, Elsevier Inc Clarification of Concepts Island Biogeography Biogeography is a scientific approach to understanding the distribution and abundance of living things, the biota, on our planet Island biogeographers are primarily interested in isolated areas and the study of fragmented life zones and their relation to the biota But what living things or biota are included? Nearly all groups are studied: plants, birds, insects, other animals, humans, fungi, fishes, disease organisms, and so on From this list it is clear that biogeography is not a single discipline Instead, it is a unifying principle for scientists of different disciplines The unifying principle is their interest in the distribution and abundance of the organisms with which they have a greater familiarity Thus, botanists, ornithologists, entomologists, mamologists, mycologists, and anthropologists can all come together and be unified by their interest of biogeography Biogeographic Scales The study of distribution and abundance of biota can be applied at any level of scale in space and time Spatial Scales Traditionally, biogeographers were, and still are, interested in biotic patterns occurring at global and intercontinental scales Geographically speaking, these are small scales that provide for broad overviews on maps or satellite images Scientists were concerned with distinguishing and mapping large-area distribution patterns, based on landscape physiognomy, such as tropical rain forests, deserts, savannas, and temperate grasslands, commonly called ‘‘biomes.’’ A parallel concern was to distinguish broad patterns of species distribution, which could be mapped as ‘‘biotic provinces,’’ areas distinguished as different centers of biodiversity with their ‘‘own’’ floras and faunas Lately, biogeographers have become concerned with distribution patterns occurring at more detailed spatial scales, such as within-archipelago migration patterns, or the distribution of biota along individual mountain slopes Moreover, the aspect of abundance versus rareness of species and other taxa has become of concern to biogeographers, an area treated traditionally by ecologists Timescales Present-day distribution and abundance patterns of biota are usually the result of past events and historical processes Historical processes that led to present-day distribution patterns of biota are often measured at geological timescales in millions of years Similarly long timescales are considered for biological evolution But organic evolution by mutations and hybridization can occur at any timescale Other timescales of biogeographic interest relate to the concepts of succession Encyclopedia of Biodiversity, Volume following disturbances and to phenological change Successional change in terms of primary succession, which refers to vegetation development on new geological surfaces, can be considered at long timescales involving hundreds and thousands of years Primary succession can also be related to soil development (¼ pedogenesis) Secondary succession, defined as following disturbances on already developed soils or previously vegetated substrates, may be considered at plant-demographic timescales, involving a few years, decades, or hundreds of years, if based on the life cycles of certain long-lived tree species Phenology relates to seasonal changes in biota The latter two biotic change-with-time conceptsFsuccession and phenologyFwere developed from ecological research in biogeography Thus, biogeography as a research approach to discover chronological changes overlaps with those aspects of ecology that deal with distribution and abundance of biota at successional and phenological timescales and also with evolutionary research that seeks to unveil migration patterns and phylogenetic relationships over long and short timescales Geobotany The term geobotany is derived from geographical botany, the biogeographical study of plants In an effort to clarify Central European and Anglo-American terminology in this broad study area, Mueller-Dombois and Ellenberg (1974) synthesized the specializations within the area of geobotany in tabular form, which is reproduced in Table Biogeography was originally understood as consisting primarily of phytogeography and zoogeography Today, following a review of recent textbooks (e.g., Cox and Moore, 1993; Hengeveld, 1990; Huggett, 1998; and others), one can consider all the ecological disciplines listed under Anglo-American equivalents (Table 1) as aspects of plant biogeography Three Inspiring Theories The Theory of Island Biogeography This theory, originally proposed by MacArthur and Wilson (1963, 1967), is practically synonymous with the concept of ‘‘island biogeography.’’ It proposes that species equilibria are formed on islands in relation to the size of land area and its distance from biotic source areas An equilibrium is suggested where the rate of invasion equals the rate of extinction of island biota These are the intersection points on Figure Curves sloping from the left to the abscissa represent decreasing rates of invasion of biota, from near to far source areas; curves sloping from the zero point on the abscissa up to the right ordinate represent increasing rates of extinction, from large to small islands The curves are based on a complicated http://dx.doi.org/10.1016/B978-0-12-384719-5.00080-0 395