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Publications (10 of 14) Show all publications
Öhlund, G., Bodin, M., Nilsson, K. A., Öhlund, S.-O., Mobley, K. B., Hudson, A. G., . . . Englund, G. (2020). Ecological speciation in European whitefish is driven by a large-gaped predator. Evolution Letters, 4(3), 243-256
Open this publication in new window or tab >>Ecological speciation in European whitefish is driven by a large-gaped predator
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2020 (English)In: Evolution Letters, E-ISSN 2056-3744, Vol. 4, no 3, p. 243-256Article in journal (Refereed) Published
Abstract [en]

Lake-dwelling fish that form species pairs/flocks characterized by body size divergence are important model systems for speciation research. Although several sources of divergent selection have been identified in these systems, their importance for driving the speciation process remains elusive. A major problem is that in retrospect, we cannot distinguish selection pressures that initiated divergence from those acting later in the process. To address this issue, we studied the initial stages of speciation in European whitefish (Coregonus lavaretus) using data from 358 populations of varying age (26-10,000 years). We find that whitefish speciation is driven by a large-growing predator, the northern pike (Esox lucius). Pike initiates divergence by causing a largely plastic differentiation into benthic giants and pelagic dwarfs: ecotypes that will subsequently develop partial reproductive isolation and heritable differences in gill raker number. Using an eco-evolutionary model, we demonstrate how pike's habitat specificity and large gape size are critical for imposing a between-habitat trade-off, causing prey to mature in a safer place or at a safer size. Thereby, we propose a novel mechanism for how predators may cause dwarf/giant speciation in lake-dwelling fish species.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
Body size, ecological speciation, gape size, predator, trade-off
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-171947 (URN)10.1002/evl3.167 (DOI)000533252100001 ()2-s2.0-85096179796 (Scopus ID)
Available from: 2020-06-18 Created: 2020-06-18 Last updated: 2023-03-23Bibliographically approved
Englund, G., Öhlund, G., Olajos, F., Finstad, A., Bellard, C. & Hugueny, B. (2020). Holocene extinctions of a top predator: effects of time, habitat area and habitat subdivision. Journal of Animal Ecology, 89(5), 1202-1215
Open this publication in new window or tab >>Holocene extinctions of a top predator: effects of time, habitat area and habitat subdivision
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2020 (English)In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 89, no 5, p. 1202-1215Article in journal (Refereed) Published
Abstract [en]

Loss of habitat and changes in the spatial configuration of habitats are major drivers of species extinctions, but the responses to these drivers differ between organisms. To advance theory on how extinction risk from different types of habitat alteration relates to species-specific traits, there is a need for studies of the long-term extinction dynamic of individual species. The goal of this study was to quantify how habitat area and the spatial configuration of habitats affect extinction rate of an aquatic top predator, the northern pike Esox lucius L. We recorded the presence/absence of northern pike in 398 isolated habitat fragments, each one consisting of a number of interconnected lakes. Time since isolation of the habitat fragments, caused by cut-off from the main dispersal source in the Baltic Sea, varied between 0 and 10,000 years. Using survival regression, we analysed how pike population survival was affected by time since isolation, habitat size and habitat subdivision. The approach builds on the assumptions that pike colonized all fragments before isolation and that current absences result from extinctions. We verified these assumptions by testing (a) if pike was present in the region throughout the entire time period when the lakes formed and (b) if pike typically colonize lakes that are formed today. We also addressed the likelihood that unrecorded anthropogenic introductions could bias our estimates of extinction rate. Our results supported the interpretation that current patterns of presence/absence in our study system are shaped by extinctions. Further, we found that time since isolation and fragment area had strong effects on pike population survival. In contrast, spatial habitat subdivision (i.e. if a fragment contained few large lakes or many small lakes) and other environmental covariates describing climate and productivity were unrelated to pike survival. Over all, extinction rate was high in young fragments and decreased sharply with increasing fragment age. Our study demonstrates how the link between extinction rate and habitat size and spatial structure can be quantified. More similar studies may help us find generalizations that can guide management of habitat size and connectivity.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
aquatic ecosystems, connectivity, extinction, fragmentation, habitat age, habitat area
National Category
Zoology Ecology Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-168983 (URN)10.1111/1365-2656.13174 (DOI)000512817300001 ()31943165 (PubMedID)2-s2.0-85079448005 (Scopus ID)
Available from: 2020-03-27 Created: 2020-03-27 Last updated: 2023-03-24Bibliographically approved
Skulason, S., Parsons, K. J., Svanback, R., Räsänen, K., Ferguson, M. M., Adams, C. E., . . . Snorrason, S. S. (2019). A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems. Biological Reviews, 94(5), 1786-1808
Open this publication in new window or tab >>A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems
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2019 (English)In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 94, no 5, p. 1786-1808Article, review/survey (Refereed) Published
Abstract [en]

A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
divergent evolution, epigenetics, genetics, niche construction, non-genetic inheritance, phenotype, phenotypic plasticity, natural selection, polymorphic fishes, speciation
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-164612 (URN)10.1111/brv.12534 (DOI)000485285900013 ()31215138 (PubMedID)2-s2.0-85067462518 (Scopus ID)
Available from: 2019-11-13 Created: 2019-11-13 Last updated: 2023-03-24Bibliographically approved
Olajos, F., Bokma, F., Bartels, P., Myrstener, E., Rydberg, J., Öhlund, G., . . . Englund, G. (2018). Estimating species colonization dates using DNA in lake sediment. Methods in Ecology and Evolution, 9(3), 535-543
Open this publication in new window or tab >>Estimating species colonization dates using DNA in lake sediment
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2018 (English)In: Methods in Ecology and Evolution, E-ISSN 2041-210X, Vol. 9, no 3, p. 535-543Article in journal (Refereed) Published
Abstract [en]
  1. Detection of DNA in lake sediments holds promise as a tool to study processes like extinction, colonization, adaptation and evolutionary divergence. However, low concentrations make sediment DNA difficult to detect, leading to high false negative rates. Additionally, contamination could potentially lead to high false positive rates. Careful laboratory procedures can reduce false positive and negative rates, but should not be assumed to completely eliminate them. Therefore, methods are needed that identify potential false positive and negative results, and use this information to judge the plausibility of different interpretations of DNA data from natural archives.
  2. We developed a Bayesian algorithm to infer the colonization history of a species using records of DNA from lake-sediment cores, explicitly labelling some observations as false positive or false negative. We illustrate the method by analysing DNA of whitefish (Coregonus lavaretus L.) from sediment cores covering the past 10,000 years from two central Swedish lakes. We provide the algorithm as an R-script, and the data from this study as example input files.
  3. In one lake, Stora Lögdasjön, where connectivity with the proto-Baltic Sea and the degree of whitefish ecotype differentiation suggested colonization immediately after deglaciation, DNA was indeed successfully recovered and amplified throughout the post-glacial sediment. For this lake, we found no loss of detection probability over time, but a high false negative rate. In the other lake, Hotagen, where connectivity and ecotype differentiation suggested colonization long after deglaciation, DNA was amplified only in the upper part of the sediment, and colonization was estimated at 2,200 bp based on the assumption that successful amplicons represent whitefish presence. Here the earliest amplification represents a false positive with a posterior probability of 41%, which increases the uncertainty in the estimated time of colonization.
  4. Complementing careful laboratory procedures aimed at preventing contamination, our method estimates contamination rates from the data. By combining these results with estimates of false negative rates, our models facilitate unbiased interpretation of data from natural DNA archives.
Place, publisher, year, edition, pages
British Ecological Society, 2018
Keywords
ancient DNA, colonization, Coregonus lavaretus, detection probability, divergence, environmental DNA, lake sediment, population age
National Category
Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-143248 (URN)10.1111/2041-210X.12890 (DOI)000426867600010 ()2-s2.0-85030156606 (Scopus ID)
Funder
Swedish Research Council, 2013-5110
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2024-05-20Bibliographically approved
Öhlund, G., Hedström, P., Norman, S., Hein, C. L. & Englund, G. (2015). Temperature dependence of predation depends on the relative performance of predators and prey. Proceedings of the Royal Society of London. Biological Sciences, 282(1799), Article ID 20142254.
Open this publication in new window or tab >>Temperature dependence of predation depends on the relative performance of predators and prey
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2015 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1799, article id 20142254Article in journal (Refereed) Published
Abstract [en]

The temperature dependence of predation rates is a key issue for understanding and predicting the responses of ecosystems to climate change. Using a simple mechanistic model, we demonstrate that differences in the relative performances of predator and prey can cause strong threshold effects in the temperature dependence of attack rates. Empirical data on the attack rate of northern pike (Esox lucius) feeding on brown trout (Salmo trutta) confirm this result. Attack rates fell sharply below a threshold temperature of +11 degrees C, which corresponded to a shift in relative performance of pike and brown trout with respect to maximum attack and escape swimming speeds. The average attack speed of pike was an order of magnitude lower than the escape speed of brown trout at 5 degrees C, but approximately equal at temperatures above 11 degrees C. Thresholds in the temperature dependence of ecological rates can create tipping points in the responses of ecosystems to increasing temperatures. Thus, identifying thresholds is crucial when predicting future effects of climate warming.

Keywords
predation, northern pike, brown trout, swimming speed, temperature, tipping points
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-98833 (URN)10.1098/rspb.2014.2254 (DOI)000345624600010 ()2-s2.0-84920996926 (Scopus ID)
Available from: 2015-03-16 Created: 2015-01-27 Last updated: 2023-03-23Bibliographically approved
Hein, C. L., Öhlund, G. & Englund, G. (2014). Fish introductions reveal the temperature dependence of species interactions. Proceedings of the Royal Society of London. Biological Sciences, 281(1775), 20132641
Open this publication in new window or tab >>Fish introductions reveal the temperature dependence of species interactions
2014 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, no 1775, p. 20132641-Article in journal (Refereed) Published
Abstract [en]

A major area of current research is to understand how climate change will impact species interactions and ultimately biodiversity. A variety of environmental conditions are rapidly changing owing to climate warming, and these conditions often affect both the strength and outcome of species interactions. We used fish distributions and replicated fish introductions to investigate environmental conditions influencing the coexistence of two fishes in Swedish lakes: brown trout (Salmo trutta) and pike (Esox lucius). A logistic regression model of brown trout and pike coexistence showed that these species coexist in large lakes (more than 4.5 km(2)), but not in small, warm lakes (annual air temperature more than 0.9-1.5 degrees C). We then explored how climate change will alter coexistence by substituting climate scenarios for 2091-2100 into our model. The model predicts that brown trout will be extirpated from approximately half of the lakes where they presently coexist with pike and from nearly all 9100 lakes where pike are predicted to invade. Context dependency was critical for understanding pike-brown trout interactions, and, given the widespread occurrence of context-dependent species interactions, this aspect will probably be critical for accurately predicting climate impacts on biodiversity.

Keywords
context dependency, coexistence, biotic interactions, climate change, species distribution models
National Category
Environmental Sciences Ecology Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-87657 (URN)10.1098/rspb.2013.2641 (DOI)000332380800015 ()2-s2.0-84902665819 (Scopus ID)
Available from: 2014-04-07 Created: 2014-04-07 Last updated: 2023-03-24Bibliographically approved
Öhlund, G. (2012). Ecological and evolutionary effects of predation in environmental gradients. (Doctoral dissertation). Umeå: Umeå universitet
Open this publication in new window or tab >>Ecological and evolutionary effects of predation in environmental gradients
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Understanding species interactions and how they affect densities and distributions of organisms is a central theme in ecological research. Studying such interactions in an ecosystem context is challenging as they often depend on species-specific characteristics and rates that not only change during the ontogeny of an organism, but also are affected by the surrounding environment. This thesis focuses on two separate questions and study systems that highlight different aspects of how effects of predation can depend on environmental conditions. In the first part of the thesis, we studied how temperature affects attack rate and handling time, two ecological rates with profound importance for predator-prey dynamics. Using a metaanalysis, we first show that the currently dominating model for temperature dependence in predator-prey interactions, i.e. the Arrhenius equation, has weak support in available empirical literature. This suggests that we need new rules for how and when we can generalize on the temperature-dependence of intake rates. We then use a simple model and a series of experiments to demonstrate that differences in the relative physiological capacity between predator and prey can impose strong non-linear effects on temperature-response curves of attack rate. In the second part of the thesis, we study the role of predation along a benthic-pelagic habitat gradient in promoting divergence and resource polymorphism among prey. We show that presence of a large piscivorous predator, the northern pike (Esox lucius), induces dwarfs, giants or divergence into both ecotypes in populations of European whitefish (Coregonus lavaretus) depending on lake characteristics. Using dated introductions of whitefish as controlled natural experiments, we show that pike presence induces rapid life history divergence between pelagic and littoral habitat use strategies, and that this divergence can translate into partial reproductive isolation in a matter of decades. Our results demonstrate the potential for thresholds in a crucial ecological rate, setting the stage for tipping points with potentially far reaching implications for effects of warming on predator prey dynamics and ecosystem stability. Moreover, they illustrate the potentially drastic consequences of such tipping points by demonstrating the importance of a single predator species as a driving force behind the creation and maintenance of biodiversity in a natural system.  

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2012. p. 23
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-59465 (URN)978-91-7459-464-5 (ISBN)
Public defence
2012-10-05, KBC-huset, Stora Hörsalen, 10:05
Opponent
Supervisors
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2018-06-08Bibliographically approved
Hein, C. L., Öhlund, G. & Englund, G. (2012). Future distribution of Arctic Char Salvelinus alpinus in Sweden under climate change: Effects of temperature, lake size and species interactions. Ambio, 41(3), 303-312
Open this publication in new window or tab >>Future distribution of Arctic Char Salvelinus alpinus in Sweden under climate change: Effects of temperature, lake size and species interactions
2012 (English)In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 3, p. 303-312Article in journal (Refereed) Published
Abstract [en]

Novel communities will be formed as species with a variety of dispersal abilities and environmental tolerances respond individually to climate change. Thus, models projecting future species distributions must account for species interactions and differential dispersal abilities. We developed a species distribution model for Arctic char Salvelinus alpinus, a freshwater fish that is sensitive both to warm temperatures and to species interactions. A logistic regression model using lake area, mean annual air temperature (1961-1990), pike Esox lucius and brown trout Salmo trutta occurrence correctly classified 95 % of 467 Swedish lakes. We predicted that Arctic char will lose 73 % of its range in Sweden by 2100. Predicted extinctions could be attributed both to simulated temperature increases and to projected pike invasions. The Swedish mountains will continue to provide refugia for Arctic char in the future and should be the focus of conservation efforts for this highly valued fish.

Place, publisher, year, edition, pages
Springer Netherlands, 2012
Keywords
Climate change, Freshwater fish, Species distribution models, Species interactions, Dispersal
National Category
Climate Research Ecology
Identifiers
urn:nbn:se:umu:diva-58916 (URN)10.1007/s13280-012-0308-z (DOI)000307285200013 ()2-s2.0-84867471216 (Scopus ID)
Available from: 2012-09-07 Created: 2012-09-06 Last updated: 2023-03-24Bibliographically approved
Hein, C. L., Öhlund, G. & Englund, G. (2011). Dispersal through stream networks: modelling climate-driven range expansions of fishes. Diversity & distributions: A journal of biological invasions and biodiversity, 17(4), 641-651
Open this publication in new window or tab >>Dispersal through stream networks: modelling climate-driven range expansions of fishes
2011 (English)In: Diversity & distributions: A journal of biological invasions and biodiversity, ISSN 1366-9516, E-ISSN 1472-4642, Vol. 17, no 4, p. 641-651Article in journal (Refereed) Published
Abstract [en]

Aim To incorporate dispersal through stream networks into models predicting the future distribution of a native, freshwater fish given climate change scenarios. Location Sweden. Methods We used logistic regression to fit climate and habitat data to observed pike (Esox lucius Linnaeus) distributions in 13,476 lakes. We used GIS to map dispersal pathways through streams. Lakes either (1) contained pike or were downstream from pike lakes, (2) were upstream from pike lakes, but downstream from natural dispersal barriers, or (3) were isolated from streams or were upstream from natural dispersal barriers. We then used climate projections to model future distributions of pike and compared our results with and without including dispersal. Results Given climate and habitat, pike were predicted present in all of 99,249 Swedish lakes by 2100. After accounting for dispersal barriers, we only predicted pike presence in 31,538 lakes. Dispersal barriers most strongly limited pike invasion in mountainous regions, but low connectivity also characterized some relatively flat regions. Main conclusions The dendritic network structure of streams and interconnected lakes makes a two-dimensional representation of the landscape unsuitable for predicting range shifts of many freshwater organisms. If dispersal through stream networks is not accounted for, predictions of future fish distributions in a warmer climate might grossly overestimate range expansions of warm and cool-water fishes and underestimate range contractions of cold-water fishes. Dispersal through stream networks can be modelled in any region for which a digital elevation model and species occurrence data are available.

Place, publisher, year, edition, pages
Wiley, 2011
Keywords
Bioclimate envelope models, climate change, connectivity, dispersal barriers, fish distributions, stream networks
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-48973 (URN)10.1111/j.1472-4642.2011.00776.x (DOI)000293138400006 ()2-s2.0-79958081501 (Scopus ID)
Available from: 2011-10-28 Created: 2011-10-28 Last updated: 2023-03-24Bibliographically approved
Englund, G., Öhlund, G., Hein, C. L. & Diehl, S. (2011). Temperature dependence of the functional response. Ecology Letters, 14(9), 914-21
Open this publication in new window or tab >>Temperature dependence of the functional response
2011 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 14, no 9, p. 914-21Article in journal (Refereed) Published
Abstract [en]

The Arrhenius equation has emerged as the favoured model for describing the temperature dependence of consumption in predator-prey models. To examine the relevance of this equation, we undertook a meta-analysis of published relationships between functional response parameters and temperature. We show that, when plotted in lin-log space, temperature dependence of both attack rate and maximal ingestion rate exhibits a hump-shaped relationship and not a linear one as predicted by the Arrhenius equation. The relationship remains significantly downward concave even when data from temperatures above the peak of the hump are discarded. Temperature dependence is stronger for attack rate than for maximal ingestion rate, but the thermal optima are not different. We conclude that the use of the Arrhenius equation to describe consumption in predator-prey models requires the assumption that temperatures above thermal optima are unimportant for population and community dynamics, an assumption that is untenable given the available data.

Place, publisher, year, edition, pages
Wiley, 2011
Keywords
Arrhenius, attack rate, functional response, handling time, optimum, parasitoid, predator, prey, response curve, temperature
National Category
Earth and Related Environmental Sciences Ecology
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-46321 (URN)10.1111/j.1461-0248.2011.01661.x (DOI)21752171 (PubMedID)2-s2.0-84931749017 (Scopus ID)
Available from: 2011-08-30 Created: 2011-08-30 Last updated: 2023-03-24Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1670-6254

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