Organisms do not occur randomly in space. Any species of plant or animal may be found in some areas, while they are completely absent from others. Likewise, the individuals of any one species are distributed in relation to each other in distinct patterns. The reasons for the readily apparent nonrandomness of the spatial distribution patterns of organisms are numerous, and the patterns result from processes acting throughout the whole life cycle of the organism, and on various spatial scales. Although this spatial structuring of populations is often ignored in ecological theory, it has profound implications for the mediation of biological processes: interactions between individuals and across species all take place in space as well as in time, and an understanding of spatial patterns is basic to understanding real-life ecological processes. Indeed, patterns of spatial distribution play an important role in shaping a wide range of ecological dynamics, such as intra- and interspecific competition, mating systems, predation, population genetics, and the spread of contagious diseases.
This article presents an overview of how spatial patterns in the distribution of organisms are created, and how they influence the way ecological processes run their course in ecological communities, exemplified by predator-prey dynamics. These patterns are scale dependent: organisms which are distributed in one way when observed at a large spatial scale may be distributed very differently at closer scales. To accommodate this, the presentation is structured according to the main spatial scale of the patterns under discussion. The initial focus lies on the way organisms are distributed at a landscape level, at which spatial distribution is mainly influenced by topographical features and variation in habitat availability. The subsequent discussion moves the scale to patterns in the dispersion of individuals, which can be seen primarily as an effect of behavioral interactions with conspecifics and with those of predator and prey species. To conclude, large-scale regional distribution patterns are briefly discussed, in relation to how they may contribute to the observed spatial distribution patterns at smaller scales.
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