Island Biogeography Theory: Emerging Patterns and Human Effects

Islands are conventionally (and narrowly) referred to as isolated lands in surrounding waters. However, in broad senses and when loosely defined, ‘islands’ also include insular areas or entities such as mountain tops, lakes (e.g., potholes in northern Great Plains in North America), oasis (in deserts), and springs (especially in deserts) that support unique species assemblages relative to surrounding habitats (e.g., Brown, 1978; Lomolino et al., 2006). Mostly because of the insular nature, habitats on oceanic islands are often different from those on the nearest mainland even when latitudes (climates) and the sizes (areas) are the same. For example, islands often support unique species assemblages with proportionally more rare and endemic species with small population sizes (e.g., reduced body size or the so-called insular dwarfism and dispersal). Partly because of their unique features (e.g., isolation) and conservation values, islands are extremely attractive for intensive efforts in exploration, research, and conservation (e.g., Kalmar and Currie, 2006). Island biogeography studies the biogeography of the isolated units mentioned in the preceding text, especially in the context of species diversity and related patterns and ecological processes. As a major advance and guide in related research arena on islands, MacArthur and Wilson (1967) developed the theory of island biogeography (next section) based on observations of many earlier naturalists made during their explorations around the world. To date, this relatively simple heuristic model has paved the ground and continues to inspire many individuals for further exploration and in some cases has resulted in with much greater effort and investment in such research.