Connectivity and homogenisation of population sizes: an experimental approach in Lacerta vivipara
Article first published online: 6 JAN 2004
Journal of Animal Ecology
Volume 73, Issue 1, pages 179–189, January 2004
How to Cite
Lecomte, J., Boudjemadi, K., Sarrazin, F., Cally, K. and Clobert, J. (2004), Connectivity and homogenisation of population sizes: an experimental approach in Lacerta vivipara. Journal of Animal Ecology, 73: 179–189. doi: 10.1111/j.1365-2656.2004.00796.x
- Issue published online: 6 JAN 2004
- Article first published online: 6 JAN 2004
- Received 14 February 2003; accepted 24 July 2003
- density dependence;
- environmental stochasticity;
- habitat fragmentation;
- two-patch system
- 1At regional scales, dispersal is known to prevent metapopulation extinction by buffering stochastic processes. Theory predicts that connectivity, through density-dependent dispersal rates, should spatially homogenize population density and synchronize local population dynamics in the long term. However, empirical evidence for the effect of connectivity on synchrony and local population dynamics remains scarce.
- 2We experimentally manipulated connectivity in order to investigate the homogenisation effect on population size. The experimental design consisted of 16 patches of common lizard populations (Lacerta vivipara), half of which were connected by dispersal. The design allowed us to identify candidates for dispersal in unconnected patches.
- 3We found that population sizes became spatially more and more homogeneous with time in connected patches, whereas extinctions or demographic explosions were observed in unconnected patches. Juvenile dispersal was density-dependent in connected patches but not in unconnected ones. These results suggest that the loss of connection modifies population functioning by influencing how dispersal is determined by local conditions.
- 4Finally, population explosions in unconnected patches were followed by a sharp decrease in population size. So non-extinct, unconnected populations did not stabilize. This could be due to over-compensatory density dependence.
- 5Population viability analysis models suggest that environmental stochasticity and catastrophic events, in addition to the density-dependent process, are required to explain population size variation and extinction.