Dispersal In Population Dynamics Research Articles

Sex, personality and conspecific density influence natal dispersal with lifetime fitness consequences in urban and rural burrowing owls.

There is a growing need to understand how species respond to habitat changes and the potential key role played by natal dispersal in population dynamics, structure and gene flow. However, few studies have explored differences in this process between conspecifics living in natural habitats and those inhabiting landscapes highly transformed by humans, such as cities. Here, we investigate how individual traits and social characteristics can influence the natal dispersal decisions of burrowing owls (Athene cunicularia) living in urban and rural areas, as well as the consequences in terms of reproductive success and apparent survival. We found short dispersal movements among individuals, with differences between urban and rural birds (i.e., the former covering shorter distances than the latter), maybe because of the higher conspecific density of urban compared to rural areas. Moreover, we found that urban and rural females as well as bold individuals (i.e., individuals with shorter flight initiation distance) exhibited longer dispersal distances than their counterparts. These dispersal decisions have effects on individual fitness. Individuals traveling longer distances increased their reproductive prospects (productivity during the first breeding attempt, and long term productivity). However, the apparent survival of females decreased when they dispersed farther from their natal territory. Although further research is needed to properly understand the ecological and evolutionary consequences of dispersal patterns in transformed habitats, our results provide information about the drivers and the consequences of the restricted natal movements of this species, which may explain its population structuring through restricted gene flow between and within urban and rural areas.

On a possible origin of the fat-tailed dispersal in population dynamics

Populations do not remain fixed in space. Their distribution changes continuously due to the impact of environmental factors, such as wind, and/or due to self-motion of individuals. A cornerstone for understanding mechanisms of dispersal is identification of factors affecting the dispersal curve, in particular, its rate of decay at large distance. The standard random walk approach resulting in a dispersal curve with a ‘thin’ Gaussian tail was eventually opposed by the theory of Lévy flights, which predicts a more realistic ‘fat’ tail with a lower rate of decay. However, here we argue that the Gaussian large-distance asymptotics is more an artefact of an oversimplified description of the dispersing population rather than an immanent property of the random walk diffusion. Specifically, we show that, when some inherent population structure is taken into account, diffusion results in a dispersal curve with either exponential or power law rate of decay. Our theoretical results appear to be in a very good agreement with some available data.