Change search
ReferencesLink to record
Permanent link

Direct link
Effects of warming and nutrient enrichment on feeding behavior, population stability and persistence of consumers and their resources
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Consumer-resource interactions are the basic building blocks of every food web. In spite of being a central research theme of longstanding interest in ecology, the mechanisms governing the stability and persistence of consumer-resource interactions are still not entirely understood. In particular, theoretical predictions on consumer-resource stability along gradients of temperature and nutrient enrichment diverge widely and are sometimes in conflict with empirical results. In this thesis I address these issues from the angle of the functional response, which describes a consumer’s feeding rate as a function of resource density. Specifically, I explore mechanistic, nutrient-based consumer-resource interaction models with respect to the influence of feeding behavior (the shape of the functional response), environmental temperature, nutrient enrichment, and resource quality on consumer-resource stability and persistence. In order to parameterize these models I performed extensive laboratory experiments with pairs of freshwater pelagic algae and grazers of the genus Daphnia, which are widespread, ecologically important model organisms.

I found a sigmoidal type III functional response in every studied Daphnia-algae species pair. The exact form of its shape is described by an exponent b which is determined by fitting functional response models to the experimental data. A high value of b can stabilize consumer-resource systems under the otherwise destabilizing influence of nutrient enrichment, as predicted by a novel stability criterion relating b to the consumer’s prey handling time, food conversion efficiency and mortality. Estimated parameter values and, consequently, stability predictions are sensitive to the method of parameter estimation, and I propose a new estimation procedure that minimizes parameter uncertainty. Because many consumers’ feeding rates depend on temperature, warming is expected to strongly affect food web stability. In functional response experiments over a broad temperature gradient, I found that the attack rate coefficient and the maximum ingestion rate of Daphnia are hump-shaped functions of temperature. Moreover, the functional response exponent increases with warming towards stronger type III responses. Plugging these findings into a nutrient-based consumer-resource model, I found that predator persistence is a U-shaped function of temperature in nutrient enrichment-temperature space. Enrichment easily turns the system unstable when the consumer has a type II response, whereas a type III response opens up a large region of stability at intermediate, for the consumer optimal, temperatures. These findings reconcile seemingly conflicting results of earlier studies of temperature effects on consumer-resource dynamics, which can be mapped as special cases onto the enrichment-temperature space. I finally demonstrate the utility of three key model ingredients - temperature dependence of rate parameters, a mechanistic description of the dynamics of algal resources, and a type III functional response in Daphnia - by successfully implementing them in the description and explanation of phytoplankton-Daphnia dynamics in a mesocosm experiment exploring effects of warming on the spring succession of the plankton.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2016. , 27 p.
Keyword [en]
consumer-resource, Daphnia, functional response, nutrient enrichment, parameter estimation, persistence, plankton, predator-prey, stability, temperature, type II, type III, warming
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-124876ISBN: 978-91-7601-544-5OAI: oai:DiVA.org:umu-124876DiVA: diva2:956201
Public defence
2016-09-20, Lilla Hörsalen (KB3A9), KBC, Umeå University, Umeå, 09:30 (English)
Opponent
Supervisors
Available from: 2016-08-30 Created: 2016-08-29 Last updated: 2016-08-30Bibliographically approved
List of papers
1. When is a type III functional response stabilizing?: theory and practice of predicting plankton dynamics under enrichment
Open this publication in new window or tab >>When is a type III functional response stabilizing?: theory and practice of predicting plankton dynamics under enrichment
Show others...
2015 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96, no 12, 3243-3256 p.Article in journal (Refereed) Published
Abstract [en]

The curvature of generalized Holling type functional response curves is controlled by a shape parameter b yielding hyperbolic type II (b = 1) to increasingly sigmoid type III (b > 1) responses. Empirical estimates of b vary considerably across taxa. Larger consumer-resource body mass ratios have been suggested to generate more pronounced type III responses and therefore to promote dynamic stability. The dependence of consumer-resource stability on b has, however, not been systematically explored, and the accurate empirical determination of b is challenging. Specifically, the shape of the functional response of the pelagic grazer Daphnia feeding on phytoplankton, and its consequences for stability, remain controversial. We derive a novel analytical condition relating b to local stability of consumer-resource interactions and use it to predict stability of empirically parameterized models of Daphnia and phytoplankton under enrichment. Functional response parameters were experimentally derived for two species of Daphnia feeding separately on single cultures of two different phytoplankton species. All experimentally studied Daphnia-algae systems exhibited type III responses. Parameterized type III responses are predicted to stabilize the modeled Daphnia-phytoplankton dynamics in some species pairs but not in others. Remarkably, stability predictions differ depending on whether functional response parameters are derived from clearance vs. ingestion rates. Accurate parameter estimation may therefore require fitting to both rates. In addition, our estimates of b for filter-feeding Daphnia are much smaller than predicted for actively hunting predators at similar consumer-resource body mass ratios. This suggests that the relationship between functional response shape and body mass ratios may vary with predation mode.

Place, publisher, year, edition, pages
John Wiley & Sons, 2015
Keyword
body size, clearance rate, consumer-resource dynamics, Daphnia, filter feeder, functional response, gestion rate, parameter estimation, phytoplankton-zooplankton dynamics, stability
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-114583 (URN)10.1890/15-0055.1 (DOI)000367287900012 ()
External cooperation:
Available from: 2016-02-16 Created: 2016-01-25 Last updated: 2016-08-29Bibliographically approved
2. Temperature dependence of the type III functional response in Daphnia
Open this publication in new window or tab >>Temperature dependence of the type III functional response in Daphnia
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-124872 (URN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29
3. Effects of warming on predator-prey interactions: a resource-based approach and a theoretical synthesis
Open this publication in new window or tab >>Effects of warming on predator-prey interactions: a resource-based approach and a theoretical synthesis
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-124873 (URN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29
4. Stoichiometric mismatch causes a warming-induced regime shift in experimental plankton communities
Open this publication in new window or tab >>Stoichiometric mismatch causes a warming-induced regime shift in experimental plankton communities
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-124874 (URN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29

Open Access in DiVA

fulltext(593 kB)54 downloads
File information
File name FULLTEXT01.pdfFile size 593 kBChecksum SHA-512
96dcbec96c5012f854a1cbcf7d986f0539b25be8dee1a25bbe98b9b77040d130402c0d375c9960957250526546c235ad114d99e296390a59db6d2d2532d71679
Type fulltextMimetype application/pdf
spikblad(177 kB)5 downloads
File information
File name SPIKBLAD01.pdfFile size 177 kBChecksum SHA-512
0d8da33b2fd2dab46fe151e9890d973db93d66d845d4e60a3fe8b2188235aacccc8f40d1bb4bd73da37860b2d1b4e73f8967311ce93cfd08e96fdc9e25022d0a
Type spikbladMimetype application/pdf

Search in DiVA

By author/editor
Uszko, Wojciech
By organisation
Department of Ecology and Environmental Sciences
Ecology

Search outside of DiVA

GoogleGoogle Scholar
Total: 54 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 481 hits
ReferencesLink to record
Permanent link

Direct link