Unsuccessful dispersal affects life history characteristics of natal populations: The role of dispersal related variation in vital rates

Jacques A Deere,Tim Coulson,Sarah Cubaynes,Isabel M Smallegange

doi:10.1016/j.ecolmodel.2017.10.010

Jacques A Deere, Tim Coulson + Show 2 more

Open Access

https://doi.org/10.1016/j.ecolmodel.2017.10.010

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Abstract

Individuals that disperse from one habitat to another has consequences for individual fitness, population dynamics and gene flow. The fitness benefits accrued in the new habitat are traded off against costs associated with dispersal. Most studies focus on costs at settlement and effects on settlement populations; the influence of dispersal to natal populations is assessed by monitoring change in numbers due to emigration. However, the extent to which natal populations are affected when individuals that invest in dispersal fail to disperse/emigrate is unclear. Here, we use an Integral Projection Model (IPM) to assess how developing into a disperser affects natal population structure and growth. We do so using the bulb mite (Rhizoglyphus robini) as a study system. Bulb mites, in unfavourable environments, develop into a dispersal (deutonymph) stage during ontogeny; these individuals are called dispersers with individuals not developing into this stage called non-dispersers. We varied disperser expression and parameterised IPMs to describe three simulations of successful and unsuccessful dispersal: (i) ‘no dispersal’ - dispersal stage is excluded and demographic data are from non-disperser individuals; (ii) ‘false dispersal’ - dispersal stage included and demographic data from non-disperser individuals are used; (iii) ‘true dispersal’ - dispersal stage included and demographic data are from individuals that go through the dispersal stage and from non-disperser individuals. We found that the type of dispersal simulation (no dispersal<false dispersal<true dispersal) and disperser expression increases generation time and reduces lifetime reproductive success and population growth rate. Our findings show that disperser individuals that fail to leave, can change the structure and growth of natal populations.

Highlights

The importance of dispersal on the ecology of populations can be substantial
Within each Integral Projection Model (IPM) simulation, for a given life stage the confidence intervals of the predicted size did not overlap with the confidence intervals of the predicted size of any other life stage, and predicted sizes followed the same level of size increase across life stages as observed values
The same differences in population biology values between the false and true dispersal IPMs were calculated with IPMs which had a linear deutonymph transition function (Fig. 3, grey lines). This was done to test whether the results we found were not due to the non-linearity of the deutonymph transition function and how it affected the approximation of the IPM; an effect which may be specific to our study system

Summary

Introduction

The importance of dispersal on the ecology of populations can be substantial (see Clobert et al, 2001). With the dispersal process come associated costs that are traded off against (potential) fitness benefits that are accrued in the new habitat at both the individual and (meta-) population level (see review by Bowler and Benton 2005; Bonte et al, 2012). Egy that increases individual fitness in a heterogeneous (spatial and temporal) landscape by the process of moving the organism into a new environment, whereby variability in expected fitness between different habitat patches drives the evolution of dispersal (Bowler and Benton, 2005). There is some support for a purely genetic control of dispersal, there is widespread evidence that dispersal can be conditional upon a variety of traits (e.g. statedependent, behavioural) and environmental conditions (McPeek and Holt, 1992; Clobert et al, 2004; Bowler and Benton, 2005).

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