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Phenotypic Processes Triggered by Biological Invasions
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Individuals within a single population can vary widely in their phenotype e.g. in their body shape. These differences are an important source of biodiversity and they can precede evolutionary divergence within a population.

In this thesis we use the biological invasion of the zebra mussels into Swedish lakes to investigate which processes create or maintain phenotypic diversity within populations of the two native fish species perch and roach and the mussel itself. Both fishes have specially adapted body shapes that depend on whether they feed in the near-shore or open-water habitat of lakes. This habitat-specific divergence was more pronounced in lakes with zebra mussels, probably because resources in both habitats were in higher supply due to the mussels’ effects on the lakes. Divergence in perch body shapes between habitats was also higher in lakes with a higher water clarity, suggesting that visual conditions can affect the resource use and thus also the expression of a habitat-specific body shape.

When investigating the diversity of body shapes in the mussel itself we found that mussels from one lake changed their shell shape when exposed to different predators: fish predators induced a more elongated shell shape while crayfish predators induced a rounder shell. These specific shell shapes probably serve as two alternative predator defenses protecting the mussel from predation.

We conclude that the availability and use of distinct resources is an important source of diversity within populations. Abiotic conditions can play a previously underappreciated role by promoting or impairing the use of the distinct resources thus affecting the divergence. The diversity of shell shapes we found in the zebra mussels complements our study by demonstrating that not only consumer responses to resources but also resources’ responses to predators can generate phenotypic diversity.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2011. , 44 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 853
Keyword [en]
Resource polymorphism, phenotypic plasticity, phenotypic divergence, anti-predator responses, Perca fluviatilis, Rutilus rutilus, Dreissena polymorpha
National Category
Biological Sciences
Research subject
Biology with specialization in Limnology
Identifiers
URN: urn:nbn:se:uu:diva-158697ISBN: 978-91-554-8157-5 (print)OAI: oai:DiVA.org:uu-158697DiVA: diva2:440802
Public defence
2011-10-28, Ekmansalen, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2011-10-06 Created: 2011-09-13 Last updated: 2012-05-31
List of papers
1. Different venues, different menus: causes and consequences of disruptive selection in natural populations
Open this publication in new window or tab >>Different venues, different menus: causes and consequences of disruptive selection in natural populations
2011 (English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:uu:diva-158670 (URN)
Available from: 2011-09-13 Created: 2011-09-13 Last updated: 2013-06-12
2. Indirect trophic interactions with an invasive species affect phenotypic divergence in a top consumer
Open this publication in new window or tab >>Indirect trophic interactions with an invasive species affect phenotypic divergence in a top consumer
2013 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 172, no 1, 245-256 p.Article in journal (Refereed) Published
Abstract [en]

While phenotypic responses to direct species interactions are well studied, we know little about the consequences of indirect interactions for phenotypic divergence.In this study we used lakes with and without the zebra mussel to investigate effects ofindirect trophic interactions on phenotypic divergence between littoral and pelagic perch. We found a greater phenotypic divergence between littoral and pelagic individuals inlakes with zebra mussels and propose a mussel-mediated increase in pelagic and benthic resource availability as a major factor underlying this divergence. Lakes withzebra mussels contained higher densities of large plankton taxa and large invertebrates. We suggest that this augmented resource availability improved perch foraging opportunities in both the littoral and pelagic zones. Perch in both habitats could hence express a more specialized foraging morphology, leading to an increased divergence of perch forms in lakes with zebra mussels. As perch do not prey on mussels directly, we conclude that the increased divergence results from indirect interactions with the mussels. Our results hence suggest that species at lower food web levels can indirectlyaffect phenotypic divergence in species at the top of the food chain.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-158687 (URN)10.1007/s00442-013-2611-1 (DOI)000317686800022 ()
Available from: 2011-09-13 Created: 2011-09-13 Last updated: 2017-12-08Bibliographically approved
3. Replicated divergence in two consumer species affected by resource availability
Open this publication in new window or tab >>Replicated divergence in two consumer species affected by resource availability
Show others...
(English)Manuscript (preprint) (Other academic)
Keyword
food web, resource polymorphisms, adaptive foraging, morphological divergence, Rutilus rutilus, Perca fluviatilis
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-158685 (URN)
Available from: 2011-09-13 Created: 2011-09-13 Last updated: 2013-02-11
4. Water transparency drives intra-population divergence in Eurasian perch (Perca fluviatilis)
Open this publication in new window or tab >>Water transparency drives intra-population divergence in Eurasian perch (Perca fluviatilis)
2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 8, e43641- p.Article in journal (Refereed) Published
Abstract [en]

Trait combinations that lead to a higher efficiency in resource utilization are important drivers of divergent natural selection and adaptive radiation. However, variation in environmental features might constrain foraging in complex ways and therefore impede the exploitation of critical resources. We tested the effect of water transparency on intra-population divergence in morphology of Eurasian perch (Perca fluviatilis) across seven lakes in central Sweden. Morphological divergence between near-shore littoral and open-water pelagic perch substantially increased with increasing water transparency. Reliance on littoral resources increased strongly with increasing water transparency in littoral populations, whereas littoral reliance was not affected by water transparency in pelagic populations. Despite the similar reliance on pelagic resources in pelagic populations along the water transparency gradient, the utilization of particular pelagic prey items differed with variation in water transparency in pelagic populations. Pelagic perch utilized cladocerans in lakes with high water transparency and copepods in lakes with low water transparency. We suggest that under impaired visual conditions low utilization of littoral resources by littoral perch and utilization of evasive copepods by pelagic perch may lead to changes in morphology. Our findings indicate that visual conditions can affect population divergence in predator populations through their effects on resource utilization.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-158689 (URN)10.1371/journal.pone.0043641 (DOI)000308063700123 ()
Available from: 2011-09-13 Created: 2011-09-13 Last updated: 2017-12-08Bibliographically approved
5. Plastic Responses of a Sessile Prey to Multiple Predators: A Field and Experimental Study
Open this publication in new window or tab >>Plastic Responses of a Sessile Prey to Multiple Predators: A Field and Experimental Study
2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 12, e115192- p.Article in journal (Refereed) Published
Abstract [en]

Background: Theory predicts that prey facing a combination of predators with different feeding modes have two options: to express a response against the feeding mode of the most dangerous predator, or to express an intermediate response. Intermediate phenotypes protect equally well against several feeding modes, rather than providing specific protection against a single predator. Anti-predator traits that protect against a common feeding mode displayed by all predators should be expressed regardless of predator combination, as there is no need for trade-offs. Principal Findings: We studied phenotypic anti-predator responses of zebra mussels to predation threat from a handling-time-limited (crayfish) and a gape-size-limited (roach) predator. Both predators dislodge mussels from the substrate but diverge in their further feeding modes. Mussels increased expression of a nonspecific defense trait (attachment strength) against all combinations of predators relative to a control. In response to roach alone, mussels showed a tendency to develop a weaker and more elongated shell. In response to crayfish, mussels developed a harder and rounder shell. When exposed to either a combination of predators or no predator, mussels developed an intermediate phenotype. Mussel growth rate was positively correlated with an elongated weaker shell and negatively correlated with a round strong shell, indicating a trade-off between anti-predator responses. Field observations of prey phenotypes revealed the presence of both anti-predator phenotypes and the trade-off with growth, but intra-specific population density and bottom substrate had a greater influence than predator density. Conclusions: Our results show that two different predators can exert both functionally equivalent and inverse selection pressures on a single prey. Our field study suggests that abiotic factors and prey population density should be considered when attempting to explain phenotypic diversity in the wild.

Keyword
trade-off, multiple predators, inducible defenses, Dreissena polymorpha, Rutilus rutilus, Pacifastacus leniusculus
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-158690 (URN)10.1371/journal.pone.0115192 (DOI)000347215600054 ()
Available from: 2011-09-13 Created: 2011-09-13 Last updated: 2017-12-08Bibliographically approved

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