| 1. |
- Jackson, A L, et al.
(författare)
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Consumer-resource matching in a food chain when both predators and prey are free to move
- 2004
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 106:3, s. 445-450
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Tidskriftsartikel (refereegranskat)abstract
- The classical theory of the ideal free distribution (IFD) predicts that the spatial distribution of consumers should follow the distribution of the resources they depend on. Here, we study consumer-resource matching in a community context. Our model for the community is a food chain with three levels. We study whether the primary consumers are able to match resources both under predation risk and in its absence. Both prey and predators have varying degrees of knowledge of the global and local resource distribution. We present two versions of the model. In the "resource maximising" model, the consumers consider the availability of their resource only. In the "balancing" model, individual consumers minimise predation risk per unit of resource that they can gain access to. We show that both models can lead to perfect matching of consumers on resources and predators on consumers, assuming that individuals have full knowledge of the whole environment. However, when the consumers' information and freedom of movement are greater than those of the predators, then the predators generally undermatch the consumers. In the opposite case, we observe overmatching and high consumer movement rates. Furthermore, undermatching of predators on consumers tends to induce overmatching of consumers on resources.
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| 2. |
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| 3. |
- Ranta, E, et al.
(författare)
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Size of environmental grain and resource matching
- 2000
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 89:3, s. 573-576
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Tidskriftsartikel (refereegranskat)abstract
- For most animals their foraging environment consists of a patch network. In random environments there are no spatial autocorrelation at all, while in fine-grained systems positive autocorrelations flip to negative ones and back again against distance. With increasing grain size the turnover rate of spatial autocorrelation slows down. Using a cellular automaton with foragers having limited information about their feeding environment we examined how well consumer numbers matched resource availability, also known as the ideal free distribution. The match is the better the smaller the size of the environmental grain. This is somewhat contrary to the observation that in large-grained environments the spatial autocorrelation is high and positive over long distances. In such an environment foragers, by knowing a limited surrounding, should in fact know a much larger area because of the spatially autocorrelated resource pattern. Yet, when foragers have limited knowledge, we observed that the degree of undermatching (i.e., more individuals in less productive patches than expected) increases with increasing grain size.
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| 4. |
- Ripa, Jörgen, et al.
(författare)
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Biological filtering of correlated environments: towards a generalised Moran theorem
- 2007
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 116:5, s. 783-792
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Tidskriftsartikel (refereegranskat)abstract
- Many species from diverse taxa are known to display synchronous fluctuations across vast geographical ranges. It is often thought that climate factors influencing the growth of conspecific populations are correlated over large distances and hence produce the synchronous population dynamics - an effect known as the Moran effect. However, for species embedded in a food web the Moran effect needs not necessarily influence the focal species directly, but can act indirectly through other species. Such an indirect synchronization can also occur in an age-structured population, where the correlated environment of one age-class causes synchronous fluctuations of another. Here, we investigate this indirect Moran effect. We find first of all that synchrony is readily transferred through food webs or between age classes, which complicates the identification of the underlying synchronizing factor. Secondly, we find puzzling cases, where synchrony is enhanced as it is filtered through a food web or between age-classes. Our results also apply to systems of different species, but with closely matching dynamics.
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