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Population-level consequences of spatial interactions
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

How is the nature of populations governed by the movement decisions made by their members? This is the core question in this thesis. To answer this question, I first assume that s movement decisions are based on conditions in their local environment. Then I derive mathematical relationships that distil the character of individual movement events, and relate the sum of these events to the dynamical properties of the population. I find that the fate of populations depend delicately on the way resident individuals relocate in response to local conditions. This general conclusion is supported by results in the four papers constituting this thesis.

In the first paper we derive a deterministic approximation of a stochastic individual-based spatial predator-prey model. We show how general types of movement behaviors either stabilise or destabilise predator-prey dynamics. Based on experimental data on movement behaviors, we conclude that predator-prey dynamics are stabilised if the prey species respond stronger to predator presence than the predatory species respond to prey.

In the second paper we derive a new type of functional response that arise when there is a behavioral spatial “race” between predators and prey. Although fundamentally different from classical functional responses, the induced density-dependencies in reproduction rates are similar to those in Holling’s type II and DeAngelis-Beddington’s functional responses.

In the third paper we perform a novel systematic investigation of density-dependencies in population growth-rates induced by the spatial covariance in empirical predator-prey systems. We categorise three types of density dependencies: “lagged”, “direct” and “independent”, and find direct and especially lagged density-dependencies to be common. We find that the density-dependencies in most cases are destabilising, which is at odds with the wide-spread view that spatial heterogeneity stabilises consumer-resource dynamics. We also find dependencies of prey density to be more common than of predator density.

In the forth paper we consider the evolution of cooperation. We formulate a stochastic individual-based group-formation process and show that profit-dependent group disengagement is evolutionarily stable and allows the emergence of stable cooperative communities.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2013. , 29 p.
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-83194ISBN: 978-91-7459-776-9 (print)OAI: oai:DiVA.org:umu-83194DiVA: diva2:665821
Public defence
2013-12-12, KBC-huset, Lilla hörsalen, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research CouncilSwedish Research Council Formas
Available from: 2013-11-21 Created: 2013-11-20 Last updated: 2015-07-03Bibliographically approved
List of papers
1. Population-level consequences of heterospecific density-dependent movements in predator-prey systems
Open this publication in new window or tab >>Population-level consequences of heterospecific density-dependent movements in predator-prey systems
2014 (English)In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 342, 93-106 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we elucidate how small-scale movements, such as those associated with searching for food and avoiding predators, affect the stability of predator-prey dynamics. We investigate an individual-based Lotka-Volterra model with density-dependent movement, in which the predator and prey populations live in a very large number of coupled patches. The rates at which individuals leave patches depend on the local densities of heterospecifics, giving rise to one reaction norm for each of the two species. Movement rates are assumed to be much faster than demographics rates. A spatial structure of predators and prey emerges which affects the global population dynamics. We derive a criterion which reveals how demographic stability depends on the relationships between the per capita covariance and densities of predators and prey. Specifically, we establish that a positive relationship with prey density and a negative relationship with predator density tend to be stabilizing. On a more mechanistic level we show how these relationships are linked to the movement reaction norms of predators and prey. Numerical results show that these findings hold both for local and global movements, i.e., both when migration is biased towards neighbouring patches and when all patches are reached with equal probability.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Moment closure, Population dynamics, Spatial structure, Species coexistence, Stochastic processes
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-83171 (URN)10.1016/j.jtbi.2013.09.019 (DOI)
Funder
Swedish Research Council
Available from: 2013-11-20 Created: 2013-11-20 Last updated: 2017-12-06Bibliographically approved
2. Space race functional responses
Open this publication in new window or tab >>Space race functional responses
2015 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1801, 20142121Article in journal (Refereed) Published
Abstract [en]

We derive functional responses under the assumption that predators and prey are engaged in a space race in which prey avoid patches with many predators and predators avoid patches with few or no prey. The resulting functional response models have a simple structure and include functions describing how the emigration of prey and predators depend on interspecific densities. As such, they provide a link between dispersal behaviours and community dynamics. The derived functional response is general but is here modelled in accordance with empirically documented emigration responses. We find that the prey emigration response to predators has stabilizing effects similar to that of the DeAngelis-Beddington functional response, and that the predator emigration response to prey has destabilizing effects similar to that of the Holing type 11 response. A stability criterion describing the net effect of the two emigration responses on a Lotka-Volterra predator-prey system is presented. The winner of the space race (i.e. whether predators or prey are favoured) is determined by the relationship between the slopes of the species' emigration responses. It is predicted that predators win the space race in poor habitats, where predator and prey densities are low, and that prey are more successful in richer habitats.

Keyword
functional response, dispersal behaviours, space race, community dynamics
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-101395 (URN)10.1098/rspb.2014.2121 (DOI)000350077000006 ()
Note

Originally published in manuscript form.

Available from: 2015-07-03 Created: 2015-03-30 Last updated: 2017-12-04Bibliographically approved
3. Density dependence induced by the spatial covariance between predators and prey
Open this publication in new window or tab >>Density dependence induced by the spatial covariance between predators and prey
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-83173 (URN)
Available from: 2013-11-20 Created: 2013-11-20 Last updated: 2014-02-28Bibliographically approved
4. Contingent dispersal and the formation of cooperative groups
Open this publication in new window or tab >>Contingent dispersal and the formation of cooperative groups
(English)Manuscript (preprint) (Other academic)
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-83188 (URN)
Available from: 2013-11-20 Created: 2013-11-20 Last updated: 2013-11-21Bibliographically approved

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