Can you please post the following reply regarding the above issue? Thanks, -- Yaron. Yaron Ziv <[EMAIL PROTECTED]>
---------------------------------- Dear Natalia and Patrick, Indeed, the first (but not the simplest) 'metapopulation dynamics' model has been introduced by Levins (see references below; 1-3), where metapopulation means a population of populations maintained by between patch-balanced colonization-extinction rates (see two important books; 4, 5). In his original model, Levins assumes total colonization (or, immigration) rate to be frequency-dependent while total extinction rate to be frequency-independent. In a following model (the core-satellite), Hanski added frequency-dependence to the total extinction rate term (6). His frequency-dependence term relies on Brown and Kodrick-Brown's 'rescue-effect' concept (7) where extinction rate is reduced by increased fraction of occupied patches. (Note, however, that in their original paper, Brown and Kodrick-Brown relates to 'island biogeography' and show that total species extinction rate is also affected by the distance of the island to the mainland. In other words, the origination of the 'rescue effect' concept has to do with species-oriented issues and not with a single population demographic issues, such as source-sink dynamics.) I highly recommend Gotelli's papers on the four basic (conservative, according to Harrison; see below) models of 'metapopulation dynamics' (8, 9). As far as I know, the source-sink concept has been used for quite some time by ecosystem ecologists in terms of material transfer and directionality flux of resources. However, demographically, the source-sink terms have been coined by Pulliam (10, 11) to express fitness-related values (i.e., r > 0 is source; r < 0 is sink). (Note, however, that his original paper has to do with the optimal foraging theory and not with the later uses of these terms.) It is important to mention that a similar hypothesis was formulated earlier by Shmida and Ellner (the 'mass effect'; 12, but see also 13) to express the idea of constant, frequent dispersal of plant material (i.e., seeds) from one habitat to another that is not suitable for those plant species. In other words, those non-adapted plant species in the unsuitable habitat (i.e., with negative population growth values; later coined sinks) keep persisting in that habitat because of the continuous addition of propagules from the original habitat's populations (later coined sources). The "marriage" between metapopulation dynamics and source-sink dynamics comes from Harrison's papers (14, 15), where she reviews whether or not a "real" metapopulation dynamics exist and broadens the term 'metapopulation structure' to include different types, such as conservative, mainland-island/source-sink, non-equilibrium, patchy, and combined. 1. Levins, R. 1969a. Some demographic and genetic consequences of environmental heterogeneity for biological control. Bulletin of the Entomological Society of America 15:237-240. 2. Levins, R. 1969b. The effect of random variations of different types on population growth. Proceedings of the National Academy of Sciences U.S.A. 62:1061-1065. 3. Levins, R. 1970. Extinction. In: Some Mathematical problems in Biology. G. Gesternhaber (ed.). Providence, American Mathematical Society, pp. 77-107. 4. Hanski, I., and Gilpin, M. E. (eds.). 1997. Metapopulation Biology: Ecology, Genetics, and Evolution. San Diego, Academic Press. 5. Hanski, I. 1999. Metapopulation Ecology. Oxford, Oxford University Press. 6. Hanski, I. 1982. Dynamics of regional distribution: the core and satellite species hypothesis. Oikos 38:210-221. 7. Brown, J. H. and A. Kodric-Brown. 1977. Turnover rates in insular biogeography: effect of immigration on extinction. Ecology 58:445-449. 8. Gotelli, N. J. 1991. Metapopulation models: the rescue effect, the propagule rain, and the core-satellite hypothesis. American Naturalist 138:768-776. 9. Gotelli, N. J. and W. G. Kelley. 1993. A general model of metapopulation dynamics. Oikos 68:36-44. 10. Pulliam, H. R. 1988. Sources, sinks, and population regulation. American Naturalist 132:652-661. 11. Pulliam, H. R. and B. J. Danielson. 1991. Sources, sinks, and habitat selection: a landscape perspective on population dynamics. American Naturalist 137S:S50-S66. 12. Shmida, A. and S. Ellner. 1984. Coexistence of plant species with similar niches. Vegetatio 58:29-55. 13. Slatkin, M. 1974. Competition and regional coexistence. Ecology 55:128-134. 14. Harrison, S. 1991. Local extinction in metapopulation context: an empirical evaluation. In: Metapopulation Dynamics: Empirical and Theoretical Investigations. M. Gilpin and I. Hanski (eds.). San Diego, Academic Press Inc., pp. 73-88. 15. Harrison, S. and A. D. Taylor. 1997. Empirical evidence for metapopulation dynamics. In: Metapopulation Biology: Ecology, Genetics, and Evolution. I. Hanski and M. E. Gilpin (eds.). San Diego, Academic Press, pp. 27-42. Hope this helps clarifying the relationship between the different concepts, -- Yaron. -------------------------------- Yaron Ziv (PhD) The Spatial Ecology Lab Department of Life Sciences Ben-Gurion University Ber-Sheva 84105, ISRAEL On 18 May 2007, at 00:15, patfoley wrote: >Natalia, > >You may want to look at Ilkka Hanski's 1998 Book Metapopulation Ecology. > >In short, the source-sink concept was formulated by Brown and ...snip... >>explain in many text books. I would like to know if anyone has a clear idea >>about this subject. >> >>Thanks, >>Natalia
