Master in Ecology, Biodiversity and Evolution (EBE)
Training period proposal in M2
Year 2005-2006
Title: Dispersal in fragmented landscapes: good or bad?
Laboratory:
Name of the laboratory: CEHIDRO, Dept. Eng. Civil, Instituto Superior Técnico
Name of the research team: H.M. Pereira´s Group
Person in charge of the training period:
Name : Henrique Miguel Pereira
Phone : +351 218 418 343
Fax : +351 218 497 650
Email : hpereira@ist.utl.pt
Website : http://correio.fc.ul.pt/~hpereira/research/index.html
References in the field of study:
Bevers, M., and C. H. Flather. 1999. Numerically exploring habitat fragmentation effects on
populations using cell-based coupled map lattices. Theoretical Population Biology 55:61-76.
Casagrandi, R., and M. Gatto. 1999. A mesoscale approach to extinction risk in fragmented habitats.
Nature 400:560-562.
Cantrell, R. S., and C. Cosner. 1999. Diffusion models for population dynamics incorporating individual
behavior at boundaries: Applications to refuge design. Theoretical Population Biology 55:189-207.
Foley, P. 1994. Predicting Extinction Times from Environmental Stochasticity and Carrying-Capacity.
Conservation Biology 8:124-137.
Hanski, I. 1999. Metapopulation ecology. Oxford University Press, Oxford, UK.
Hanski, I. 2001. Population dynamic consequences of dispersal in local populations and
metapopulations. Pages 283-298 in J. Clobert, E. Danchin, A. A. Dhondt, and J. D. Nicholls,
editors. Dispersal. Oxford University Press, Oxford, UK.
Lens, L., S. Van Dongen, K. Norris, M. Githiru, and E. Matthysen. 2002. Avian Persistence in
Fragmented Rainforest. Science 298:1236-1238.
Pereira, H., G. C. Daily, and J. Roughgarden. 2004. A framework for assessing the relative
vulnerability of species to land-use change. Ecological Applications 14:730-742.
Pereira, H. M., and G. C. Daily. in press. Modeling Biodiversity Dynamics in Countryside Landscapes.
Ecology.
Pulliam, H. R. 1988. Sources, Sinks, and Population Regulation. American Naturalist 132:652-661.
Thomas, C. D. 2000. Dispersal and extinction in fragmented landscapes. Proceedings of the Royal
Society of London Series B-Biological Sciences 267:139-145.
Description of the training period:
In KISS models (Pereira et al. 2004, Pereira and Daily in press) species with a large ratio of
dispersal to population growth and with low affinity for human-modified habitats are
especially vulnerable to habitat destruction. The vulnerability of species with large dispersal
distances is a result of the source-sink structure of KISS models (Pulliam 1988, Cantrell
1999). In contrast, metapopulation theory predicts that species with high dispersal fare better
in fragmented landscapes (Hanski 1999) This difference occurs because metapopulation
theory considers multiple patches in a stochastic environment, and a species that does not
disperse at all is very vulnerable to local stochastic extinctions (Casagrandi 1999). Local
extinctions are particularly common when populations in the habitat patches are small (Foley
1994). Therefore there are two opposing forces acting on dispersal during habitat loss (Hanski
2001). On one hand, dispersal is risky in a fragmented landscape because some dispersing
individuals will fail to locate suitable habitat. On the other hand, dispersal may help sustain
metapopulations in fragmented landscapes by rescuing small populations from stochastic
extinctions. The question then is, which effect prevails in natural populations? Some studies
suggest that species with large dispersal are most affected by habitat loss (e.g. Thomas 2000)
while others have found the opposite pattern (Lens 2002). Clearly, more empirical studies,
and studies on a wider array of taxa using different cues of habitat suitability, are needed.
A thorough theoretical examination of this question has also been lacking. The student will
use an individual based-model programmed in C++, to compare the effect of dispersal
mortality with the rescue effect of dispersers into small population patches. The model can be
run from Mathematica and allows the following parameters to be set: geometry of the
landscape corresponding to a grid of n*m cells and each cell can correspond to a different
habitat class (typically two classes of habitat are used, suitable and non-suitable), dispersal
model (random-walk or directed), birth rate and mortality rate in each habitat class, homerange size (in number of cells), age at first breeding. The model is inspired in life cycles of
mammals and birds.
This training period can be followed with a PhD:
YES