Balanced Dispersal Between Spatially Varying Local Populations: An Alternative To The Source‐Sink Model

Abstract

Analysis of long-term monitoring data on breeding collared flycatchers (Ficedula albicollis Temm.) has revealed equal numbers of immigrations and emigrations between neighboring populations of different sizes. Dispersal patterns were close to patterns simulated under a conditional dispersal and with populations near saturation level. Local growth rates of the 11 sites were computed and did not support the idea that the observed balanced exchanges could be the result of a source-sink system. This is the first empirical evidence for a system of discrete habitat patches with component populations that exist as simultaneous sources and sinks to their neighbors. Dispersal propensities were inversely related to population sizes, which showed little variation in time. These results are consistent with recent modeling of dispersal as an evolutionarily stable strategy, and they demonstrate that dispersal can be an active phenomenon requiring neither the dominance hierarchies nor the temporal instability generally invoked by ecological and population genetic models. We note a parallel to the concept of Ideal Free Distributions and discuss implications for the evolution of dispersal mechanisms in fragmented populations.

Integrating across Life‐History Stages: Consequences of Natal Habitat Effects on Dispersal

“…Yet this assumption is rarely likely to be true in nature. Evidence from some systems indicates that the proportion of dispersers from a given habitat may be in versely related to conspecific density or affected by dif ferences in habitat condition so that individuals disperse to and away from sites proportionally to achieve an ideal free distribution (Doncaster et al 1997;Diffendorfer 1998;Haugen et al 2006). Our review suggests that patch en vironment can affect the development of connectivity be tween local sites by generating repeatable differences be tween types of patches and the probability that individuals leave their natal patch.…”

‘Heritability’ of dispersal propensity in a patchy population

“…Offspring sex and local habitat quality, measured by breeding population size and mean number of fledglings per nest in a plot, were also included as explanatory variables because these variables have previously been shown to affect dispersal propensity in this population (for sex-biased dispersal, conspecific attraction and use of local reproductive success for emigration and immigration decisions, see Pärt & Gustafsson 1989;Pärt 1990;Doncaster et al 1997;Doligez et al 1999Doligez et al , 2002Doligez et al , 2004. Because plot area and number of boxes are strongly positively correlated to plot population size, using these variables instead of population size did not change the results (see electronic supplementary material E11).…”

Causes and consequences of animal dispersal strategies: relating individual behaviour to spatial dynamics

“…In their study, movement out of a patch was greater when the population density was low and more variable due to demographic stochasticity, both characteristics of small patches. Patch size is likely to be a phenomenological description of patch carrying capacity, which has Doligez et al (2003) also been predicted to be negatively correlated with dispersal rate (McPeek & Holt, 1992 ;Doncaster et al, 1997). Covariation between patch size, population size and average degree of relatedness introduces further confounding variables.…”