The spatial population dynamics of insects exploiting a patchy food resource: A model study of local persistence

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The spatial population dynamics of insects exploiting a patchy food resource: A model study of local persistence (EN)

Halley, J. M. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών και Τεχνολογιών. Τμήμα Βιολογικών Εφαρμογών και Τεχνολογιών (EL)
Halley, J. M. (EN)

1. We have studied the density-dependent persistence of four tephritid flies on patches of their host vegetation using a semi-analytic model. The model takes into account density dependence, environmental stochasticity and immigration. Basic statistical methods were used to parameterize the model for data collected in our field study. We have assumed that the extinction process is due mainly to a fluctuation of the amount of resources. 2. The model was used to predict local extinction probability. For all species, these predictions were compared to, and found to be in reasonable agreement with, the observed levels of local extinction. 3. The model can also be used to estimate the effects of increasing fragmentation on a given fly species. The occupancy of larger patches is strongly dependent on initial conditions. Initially-occupied large patches can last a long time, irrespective of isolation, but unoccupied ones must be colonized first, requiring that the patch be reasonably close to the source of dispersers. Small patches, irrespective of initial conditions, will, on average, only be occupied if it lies close to a large 'mainland' patch or group of patches; that is, its isolation is less than the 'dispersal distance' for that species. 4. On the scale of the field system studied, immigration is the dominant factor determining persistence. The rate of immigration appears to be proportional to the area of a patch, but the isolation of almost all patches (distance to the next patch) is significantly less than the measured dispersal distance of all the species studied. Further studies will be needed to confirm what our model has to say about the relative importance of migration in more highly fragmented habitats. (EN)

local extinction (EN)

Journal of Applied Ecology (EN)



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