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The development of resource polymorphism – Effects of diet, predation risk and population dynamical feedbacks.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the evolution of individuals within a species adapted to utilize specific resources, i.e. resource polymorphism. Although a well-known phenomenon, the understanding of the mechanisms behind is not complete. Considering the ruling theories, resource polymorphism is suggested to depend on severe competition for resources, the presence of open niches to be occupied leading to a reduction in competition, and disruptive selection where generalist are out-competed due trade-offs in foraging efficiency for different prey. In order to study resource polymorphism, I have used fish as the animal group in focus and the methods I have used range over laboratory experiments, field experiments, literature surveys and theoretical modelling.

In my work, I have showed that different resource use induces different body shapes and that the rate of change is dependent of the encounter rate of different resources. The induced body changes partly led to increased foraging efficiency but surprisingly I did not find any trade-offs due to specialization. However, when studying predation risk in relation to resource polymorphism, my studies point towards that resource use and predation risk may act as balancing factors in such a way that disruptive selection can take place.

My work also shows that population feedbacks have to be explored when considering the evolution of resource polymorphism. In pond and field experiments, I found that changes in resource densities affected the actual resource use despite previous adaptations to certain resources. By performing a literature survey, I found that cannibalism indirectly by its effect on population dynamics seems to facilitate the evolution of resource polymorphism. Modelling a size-structured population, I found that resource dynamics were stabilized, and the relative availability of different resources was levelled out due to cannibalism.

Taken together, my studies strongly suggest that to understand the development of resource polymorphism in consumer populations, future studies have to include the effect of a dynamic environment both with respect to resources and predators.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap , 2005. , 21 p.
Keyword [en]
body shape, diet, geometric morphometrics, phenotypic plasticity, population dynamics, predation risk, resource polymorphism, size structured populations
Identifiers
URN: urn:nbn:se:umu:diva-639ISBN: 91-7305-867-X (print)OAI: oai:DiVA.org:umu-639DiVA: diva2:144097
Public defence
2005-12-09, 10:00
Supervisors
Available from: 2005-11-18 Created: 2005-11-18 Last updated: 2012-05-14Bibliographically approved
List of papers
1. Effects of diet-induced resource polymorphism on performance in Arctic charr (Salvelinus alpinus)
Open this publication in new window or tab >>Effects of diet-induced resource polymorphism on performance in Arctic charr (Salvelinus alpinus)
2003 In: Evolutionary Ecology Research, Vol. 5, 213-228 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-4840 (URN)
Available from: 2005-11-18 Created: 2005-11-18Bibliographically approved
2. Behavioural and morphological responses to cannibalism in Arctic charr (Salvelinus alpinus)
Open this publication in new window or tab >>Behavioural and morphological responses to cannibalism in Arctic charr (Salvelinus alpinus)
2005 (English)In: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 7, no 5, 767-778 p.Article in journal (Refereed) Published
Abstract [en]

Question: Does cannibalism lead to resource polymorphism in young Arctic charr (Salvelinusalpinus, Pisces)?

Hypothesis: Cannibals should evoke a low-activity morph that is well adapted to benthivorybut not planktivory, and which differs in morphology compared with a planktivorous morph.

Methods: We reared young-of-the-year charr in laboratory aquaria with and without largercannibalistic charr present. Thereafter, we measured foraging efficiency on pelagic and benthicresources, swimming speed when foraging, and morphology of the young charr.

Conclusions: Living among cannibals did not affect the morphology of the young charr. Italso did not affect the foraging efficiency of the young charr on the benthic resource. However,individuals from cannibal treatments swam closer and had lower foraging efficiency on thepelagic resource.

Place, publisher, year, edition, pages
Tucson: Evolutionary Ecology, 2005
Keyword
geometric morphometrics, phenotypic plasticity, predation risk, resource polymorphism
Identifiers
urn:nbn:se:umu:diva-4841 (URN)
Available from: 2005-11-18 Created: 2005-11-18 Last updated: 2017-12-14Bibliographically approved
3. Plastic reources polymorphism: effects or resource availability on Arctic char (Salvelinus alpinus) morphology
Open this publication in new window or tab >>Plastic reources polymorphism: effects or resource availability on Arctic char (Salvelinus alpinus) morphology
2005 (English)In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 85, no 3, 341-351 p.Article in journal (Refereed) Published
Abstract [en]

Resource polymorphism has been suggested to be a platform for speciation. In some cases resource polymorphism depends on phenotypic plasticity but in other cases on genetic differences between morphotypes, which in turn has been suggested to be the ongoing development of a species pair. Here we study environmentally induced morphological differences in two age classes of Arctic char (Salvelinus alpinus) influencing char performance and diet in relation to resource availability. We found that structurally complex habitats with relatively lower zooplankton densities gave rise to individuals with a deeper body, and a downward positioned tip of the snout compared with individuals from structurally simple habitats with relatively higher zooplankton densities for both age classes. Environment also had an effect on foraging efficiency on zooplankton, with fish from structurally simple habitats had a higher foraging rate than fish from structurally complex habitats. Diet analyses showed that resource use in char mainly depends on the relative abundance of different resources. Therefore, to gain further understanding of resource polymorphism we suggest that future studies must include population dynamic feedbacks by the resources on the consumers.

Place, publisher, year, edition, pages
London: Acad. P., 2005
Keyword
diet, foraging efficiency, geometric morphometrics, habitat, planktivory, resource densities
Identifiers
urn:nbn:se:umu:diva-4842 (URN)10.1111/j.1095-8312.2005.00501.x (DOI)
Available from: 2005-11-18 Created: 2005-11-18 Last updated: 2017-12-14Bibliographically approved
4. Interactions between predator- and diet-induced phenotypic changes in body shape of crucian carp
Open this publication in new window or tab >>Interactions between predator- and diet-induced phenotypic changes in body shape of crucian carp
2006 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 273, no 1585, 431-437 p.Article in journal (Refereed) Published
Abstract [en]

Predator cues and diet, when studied separately, have been shown to affect body shape of organisms. Previous studies show that the morphological responses to predator absence/presence and diet may be similar, and hence could confound the interpretation of the causes of morphological differences found between groups of individuals. In this study, we simultaneously examined the effect of these two factors on body shape and performance in crucian carp in a laboratory experiment. Crucian carp (Carassius carassius) developed a shallow body shape when feeding on zooplankton prey and a deep body shape when feeding on benthic chironomids. In addition, the presence of chemical cues from a pike predator affected body shape, where a shallow body shape was developed in the absence of pike and a deep body shape was developed in the presence of pike. Foraging activity was low in the presence of pike cues and when chironomids were given as prey. Our results thereby suggest that the change in body shape could be indirectly mediated through differences in foraging activity. Finally, the induced body shape changes affected the foraging efficiency, where crucians raised on a zooplankton diet or in the absence of pike cues had a higher foraging success on zooplankton compared to crucian raised on a chironomid diet or in the presence of pike. These results suggest that body changes in response to predators can be associated with a cost, in terms of competition for resources.

Place, publisher, year, edition, pages
The Royal Society, 2006
Keyword
morphology, induced defence, diet, behaviour, Carassius carassius, phenotypic plasticity
National Category
Biological Sciences
Identifiers
urn:nbn:se:umu:diva-6228 (URN)10.1098/rspb.2005.3343 (DOI)16615209 (PubMedID)
Available from: 2007-12-07 Created: 2007-12-07 Last updated: 2017-12-14Bibliographically approved
5. Resource polymorphism and population dynamical feedbacks in Fish
Open this publication in new window or tab >>Resource polymorphism and population dynamical feedbacks in Fish
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Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-4844 (URN)
Available from: 2005-11-18 Created: 2005-11-18 Last updated: 2010-01-13Bibliographically approved

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