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Environmental variability uncovers disruptive effects of species interactions on population dynamics
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
2015 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1812, 67-75 p.Article in journal (Refereed) Published
Abstract [en]

How species respond to changes in environmental variability has been shown for single species, but the question remains whether these results are transferable to species when incorporated in ecological communities. Here, we address this issue by analysing the same species exposed to a range of environmental variabilities when (i) isolated or (ii) embedded in a food web. We find that all species in food webs exposed to temporally uncorrelated environments (white noise) show the same type of dynamics as isolated species, whereas species in food webs exposed to positively autocorrelated environments (red noise) can respond completely differently compared with isolated species. This is owing to species following their equilibrium densities in a positively autocorrelated environment that in turn enables species species interactions to come into play. Our results give new insights into species response to environmental variation. They especially highlight the importance of considering both species interactions and environmental autocorrelation when studying population dynamics in a fluctuating environment.

Place, publisher, year, edition, pages
ROYAL SOC , 2015. Vol. 282, no 1812, 67-75 p.
Keyword [en]
environmental autocorrelation; environmental tracking; food webs; indirect effects; paradox of enrichment; population stability
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:liu:diva-122442DOI: 10.1098/rspb.2015.1126ISI: 000362305500008PubMedID: 26224705OAI: oai:DiVA.org:liu-122442DiVA: diva2:866734
Note

Funding Agencies|Linkoping University

Available from: 2015-11-03 Created: 2015-11-02 Last updated: 2017-12-01
In thesis
1. Species Responses to Environmental Fluctuations: impacts of food web interactions and noise color
Open this publication in new window or tab >>Species Responses to Environmental Fluctuations: impacts of food web interactions and noise color
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Species constantly experience changes in their environmental conditions owing to natural or human induces reasons. Understanding how species respond to these fluctuations are important for ecology, especially given the ongoing climate change. Empirical studies have shown that species respond differently to the same disturbance. However, our knowledge of what create these differences in the environmental response is limited and in most cases based on studies focusing on single species. In this thesis, I have taken a theoretical approach and used dynamical models to investigate how the population dynamics of species are affected by species-species interactions and environmental fluctuations.

 

In the first paper (Paper I) I investigated how a species respond to environmental fluctuations when isolated or embedded in a food web. The study showed that species-species interactions had an effect in temporally positively autocorrelated environments (red noise) but not in uncorrelated environments (white noise). This was owing to species following their equilibrium densities in red environments which in turn enabled species-species interactions to come into play. Red environmental variables are more prominent in nature than white. Thus, these results show the importance of using a food web approach when analyzing species response to environmental fluctuations.

 

The most commonly discussed effect of climate change is an elevated mean temperature. This shift is expected to affect the growth rate of many species. However, there is no robust theory of how we should expect species in food webs to respond to a rise in temperature. In the second paper (Paper II) I defined and studied the dynamic rate of food webs

(DR) acting analogously to single species growth rate. I found that the higher DR the easier for species population densities to follow their equilibrium over time. Both DR and noise color changed the temporal relationship between the population and the environmental noise. Thus, it is of major importance to take the scale of time into consideration when investigating species response to environmental fluctuations.

 

Another important factor which affect population dynamics is species spatial distributions. Dispersal between subpopulations enable individuals to rescue or prolong the time to extinction for the population seen as a whole. In the third paper (Paper III), I investigated how species in food webs respond to environments that varies both in time and space and compared the results with the one from single species. I found that single species were stabilized by an increased dispersal rate independent of the noise color. Species-species interactions had an effect for some of the species in these landscapes.

At red asynchronous noise, one resource species in each food web had a local minimum in stability at low dispersal rate. Here, dispersal decoupled local population dynamics and prevented species from tracking their equilibriums. At high dispersal rates, all resource species and their single species counterparts were stabilized by dispersal as local patch dynamics lost its importance. Environmental noise together with the spatial dimension does seem to explain much of the stability properties of species on our planet.

 

However, natural ecosystems are much more complex and species rich than the food web models I have used so far. Theoreticians have previously had a hard time describing stable complex systems that survive environmental fluctuations. Thus, in my fourth and last project (Paper

IV) I investigated how species population dynamics are affected by environmental fluctuations when embedded in larger food webs. These systems were built by connecting food web modules with periodic boundary conditions (PBC). The PBC method has previously helped physicists to understand the nature of waves and particles by removing the edges in systems. I found that food web size does not have to have a negative effect on food web stability. I showed that by removing the destabilizing effect of edges it is possible to describe large stable food webs, more similar to natural ecosystems.

 

Overall, the research presented here give new insights into species responses to environmental fluctuations. They especially highlight the importance of considering both species interactions and environmental noise color when studying population dynamics in a fluctuating environment. A food web approach is necessary when analyzing species population dynamics and planning for conservation actions, especially when studying the effects of climate change on biodiversity.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1839
National Category
Ecology
Identifiers
urn:nbn:se:liu:diva-136840 (URN)10.3384/diss.diva-136840 (DOI)978-91-7685-560-7 (ISBN)
Public defence
2017-06-13, Planck, Fysikhuset, Campus Valla, Linköping, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2017-05-15 Created: 2017-04-28 Last updated: 2017-05-17Bibliographically approved

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