The role of colonization in the dynamics of patchy populations of a cyclic vole species
- 302 Downloads
The crash phase of vole populations with cyclic dynamics regularly leads to vast areas of uninhabited habitats. Yet although the capacity for cyclic voles to re-colonize such empty space is likely to be large and predicted to have become evolved as a distinct life history trait, the processes of colonization and its effect on the spatio-temporal dynamics have been little studied. Here we report from an experiment with root voles (Microtus oeconomus) specifically targeted at quantifying the process of colonization of empty patches from distant source patches and its resultant effect on local vole deme size variation in a patchy landscape. Three experimental factors: habitat quality, predation risk and inter-patch distance were employed among 24 habitat patches in a 100 × 300-m experimental area. The first-born cohort in the spring efficiently colonized almost all empty patches irrespective of the degree of patch isolation and predation risk, but this was dependent on habitat quality. Just after the initial colonization wave the deme sizes in patches of the same quality were underdispersed relative to Poisson variance, indicating regulated (density-dependent) settlement. Towards the end of the breeding season local demographic processes acted to smooth out the initial post-colonization differences among source and colonization patches, and among patches of initially different quality. However, at this time demographic stochasticity had also given rise to a large (overdispersed) variation in deme sizes that may have contributed to an overshadowing of the effect of other factors. The results of this experiment confirmed our expectation that the space-filling capacity of voles is large. The costs associated with transience appeared to be so low, at least at the spatial scale considered in this experiment, that such costs are not likely to substantially constrain habitat selection and colonization in the increase phase of cyclic patchy populations.
KeywordsDispersal Extinction Habitat selection Immigration Population cycle
We thank all the volunteers that helped during field work at the Landscape Ecological Field Station, Campus Evenstad. The project was founded by The Research Council of Norway (project 182612).
- Andreassen HP, Hertzberg K, Ims RA (1998) Space use responses to habitat fragmentation and connectivity in the root vole Microtus oeconomus. Ecology 79:1223–1235Google Scholar
- Andreassen HP, Stenseth NC, Ims RA (2002) Dispersal behaviour and population dynamics of vertebrates. In: Bullock JM, Kenward RE, Hails RS (eds) Dispersal ecology. Cambridge University Press, Oxford, pp 237–256Google Scholar
- Barrett GW, Peles JD (eds) (1999) Landscape ecology of small mammals. Springer, New YorkGoogle Scholar
- Hanski I (1999) Metapopulation ecology. Oxford University Press, OxfordGoogle Scholar
- Ims RA, Hjermann DØ (2001) Condition-dependent dispersal. In: Clobert J, Danchin E, Dhondt AA, Nichols JD (eds) Dispersal. Oxford University Press, Oxford, pp 203–216Google Scholar
- Ims RA, Yoccoz NG (1997) The study of transfer processes in metapopulations: emigration, dispersal and colonization. In: Hanski I, Gilpin ME (eds) Metapopulation dynamics: ecology, genetics and evolution. Academic Press, San Diego, pp 247–265Google Scholar
- Steen H (1994) Low survival of long distance dispersers of the root vole (Microtus oeconomus). Ann Zool Fenn 31:271–274Google Scholar
- Stenseth NC, Lidicker WZ (eds) (1992) Animal dispersal. Small mammals as a model. Chapman & Hall, LondonGoogle Scholar
- Tast J (1966) The root vole, Microtus oeconomus (Pallas), as an inhabitant of seasonally flooded land. Ann Zool Fenn 3:127–170Google Scholar