The species-specific physical and biological restrictions a propagule must overcome to accomplish successful colonization. Similarly, the term colonization should be used for incidents of immigration that are followed by establishment of a viable population. It should be emphasized that dispersal per se does not deal with events that occur after a movement has been completed and the term “effective dispersal” should be used for events of dispersal followed by successful establishment. The term immigration is dispersal from the perspective of the recipient locality regardless of the source – the arrival of new individuals to an area previously not occupied by that species.
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The term dispersion refers to the fine-scale spatial distribution pattern of organisms, and migration is in some cases equivalent to dispersal, though it typically refers to a particular (directional and synchronized) type of movement. Because of the variety of disciplines involved with the study of movements of organisms, the term is often misused and confused with a plethora of movement terms. The movement of disseminules away from their source, either their place of birth or their breeding site. Thus, the use of sensitivity analyses to characterize the potential influence of dispersal-related hypotheses on model results is an essential step in modeling dispersal. We stress that, given the difficulties in estimating dispersal parameters, dispersal modeling typically involves the integration of multiple sources of information. We dedicated this article to the introduction of some of the commonly used approaches to estimate movement at various spatial resolutions, including mesocosm studies, focal animal sampling, multistate models, spatial capture–recapture models, correlated abundances, spatial dynamic occupancy models, integrated population models, and genetic and isotope analysis. Therefore, dispersal processes are often poorly understood, particularly for rare and/or elusive species. Despite its importance, dispersal is also one of the hardest parameters to estimate. Adult flukes produce eggs, and larvae in the snail hosts are produced over long periods, months, or even many years, leading to dispersal in time.Īdam Duarte, Ivana Mali, in Encyclopedia of Ecology (Second Edition), 2019 Abstractĭispersal is a vital life-history strategy that has implications for gene flow, resource competition, population dynamics, and species’ distributions. In many species, special flotation devices of the tail prolong the duration of floating ( Figure 3). They actively swim and keep afloat by means of their tails and can thus be dispersed over long distances by water currents.
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Larvae (cercariae) are often forcibly ejected into the respiratory currents of the snails in which they have developed, bringing about dispersal away from the host. Trematode larvae illustrate that all three aspects of dispersal can be brought about by the same stage. Three aspects of dispersal are important: dispersal over short distances away from an individual host, dispersal in space and range extension over larger distances, and dispersal in time. For parasites, a third point is important: dispersal may reduce the chances of hosts becoming overinfected. Dispersal is important for any species, whether free-living or parasitic, because a population restricted to one small area risks becoming extinct if conditions become unfavorable and because dispersal reduces inbreeding and the loss of evolutionary adaptability.