Staff

Ole Seehausen

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Prof. Dr. Ole Seehausen

Department Fish Ecology & Evolution

About Me

Department Head, Eawag Fish Ecology and Evolution, Eawag Center for Ecology, Evolution & Biogeochemistry (CEEB)

Director, Institute of Ecology & Evolution (IEE), University of Bern

Division Head, Aquatic Ecology & Evolution, IEE, University of Bern

 

Academic & research interests

I am an evolutionary ecologist. I am keen to understand the evolutionary processes and ecological mechanisms by which biological diversity arises, those by which it is maintained and those by which it is lost. I am studying natural and sexual selection, gene flow and interspecific hybridisation, species interactions, evolutionary constraints and historical contingency. I want to know how these affect variation within populations and between populations, phenotypic polymorphisms, speciation, adaptive radiation, species assemblages and macro-ecological patterns. I also want to know how better understanding these processes can benefit nature conservancy.

I have studied the large adaptive radiations of cichlid fish in African lakes for more than 25 years,  especially the radiations in Lake Victoria and smaller lakes in Tanzania and Uganda, and in the Zambezi region of southern Africa. More than 1000 species have emerged in these radiations in the past 3 or 4 million years, and more than 500 in Lake Victoria alone within the last 100'000 years or less. These are the largest and fastest adaptive radiations known in the animal kingdom and understanding them will be important for understanding the origin of species diversity in general. But cichlid fish are also well suited for experimental work in laboratory aquaria. Unfortunately , cichlids also experienced the fastest large scale extinction event ever observed by humans. Due to eutrophication of Lake Victoria, and the arrival of a non-­native predator and competitor, perhaps as many as 200 endemic cichlid species disappeared in the past 30 years. Taken together, these three facts make cichlids perhaps the best vertebrate model organism for studying the origins, maintenance and loss of species diversity. It is also a great system to study the effects of species diversity and its loss on ecosystems because in each of the large African lakes, entire multi-trophic fish communities have evolved from scratch through adaptive radiation, including three or four different trophic levels. This is unparalleled in other recent fish radiations.

After moving to Switzerland in 2004, I established a second research program - parallel to the African cichlids - to investigate adaptive radiations of fish in the postglacial subalpine lake system of the European Alps. Switzerland alone has an impressive radiation of more than 30 endemic species of whitefish (Coregonus spp) most of which originated in the past 15,000 years. Like in the African cichlids, it appears that most larger lakes gave rise to their own endemic radiations, allowing for comparative analysis of speciation and adaptation between replicate radiations. Sadly, the whitefish radiations - much like Lake Victoria cichlids - are also an example of rapid recent mass extinction. My students and I showed that more than 30% of the endemic whitefish diversity of Switzerland has been lost in the past few decades. Our comparative analysis of extinction revealed that eutrophication of lakes is to blame. It reduced the diversity of reproductive and ecological niches and made distinct species collapse into hybrid populations. Most recently I have extended this research program to Alpine char (Salvelinus spp) that have diversified and gone extinct again in parallel with the whitefish in the same lakes.

In Switzerland I also started working on Threespined stickleback (Gasterosteus spp), a fish that fascinates me since my youth. A little indigenous population around Basel aside, stickleback only arrived in Switzerland in the 1870s. Yet, my students and I documented phenotypically and genetically very diverse types of stickleback in and around all larger midland lakes and some smaller lakes. We reconstructed the invasion history which involved three invasion fronts that met and mixed in the middle west of Switzerland. We now use this system to study the contemporary evolution of invasive species.

Using cichlid fish, stickleback, salmon-like fish and other species, students and Postdoctoral researchers in my research group address conceptual issues of broader relevance to the understanding of causes of variation in biodiversity. Such issues include the manifold interactions between historical contingency and ecological determinism that make biology so different from physics and chemistry, the role of interspecific hybridization, and the effects of speciation and adaptive radiation on ecosystems. To address these issues we combine methods from ecology, behavioral biology, experimental genetics, molecular population genetics and population genomics , phylogenomics and comparative methods.

Students and Postdoctoral researchers who come with their own ideas, questions and study systems are always welcome in my group.

 

Publications

Eawag Publications

all publications (1997-2015)

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Projects

We investigate the mechanisms of speciation and adaptive radiation

Speciation and adaptive radiation
Genome evolution and genomic divergence across the Swiss Alpine whitefish radiation

Speciation Genomics of Alpine Whitefish
Genome evolution and genomic divergence across five lake river pairs of three-spined sticklebacks

Modelling speciation and radiation
We investigate the ecological and genetic basis of adaptation to elevational variation in rivers and depth variation in lakes

Adaptation to thermal gradients
Almost two-thirds of the native fish species of Switzerland are threatened by extinction. To preserve or specifically enhance aquatic biodiversity and habitats ...

Projet Lac - on track of the fish in our lakes
Assessing biodiversity from genes to communities in Swiss river fish

Progetto Fiumi
We study causes of variation in diversity of fish assemblages and we wish to understand how variation in diversity affects the lake ecosystems

Community Ecology
We work to combat what we consider the largest stumbling block on the way to successful biodiversity management and conservation in aquatic ecosystems: the lack of quantitative baseline data

Conservation Biology

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Curriculum Vitae

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Publications

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Urea hydrolysis and precipitation dynamics in a urine-collecting system

Blockages caused by inorganic precipitates are a major problem of urine-collecting systems. The trigger of precipitation is the hydrolysis of urea by bacterial urease. While the maximum amount of precipitates, i.e. the precipitation potential, can be estimated with equilibrium calculations, little is known about the dynamics of ureolysis and precipitation. To gain insight in these processes, we performed batch experiments with precipitated solids and stored urine from a urine-collecting system and later simulated the results with a computer model. We found that urease-active bacteria mainly grow in the pipes and are flushed into the collection tank. Both, bacteria and free urease, hydrolyse urea. Only few days are necessary for complete urea depletion in the collection tank. Two experiments with precipitated solids from the pipes showed that precipitation sets in soon after ureolysis has started. At the end of the experiments, 11% and 24% of urea was hydrolysed while the mass concentration of newly formed precipitates already corresponded to 87% and 97% of the precipitation potential, respectively. We could simulate ureolysis and precipitation with a computer model based on the surface dislocation approach. The simulations showed that struvite and octacalcium phosphate (OCP) are the precipitating minerals. While struvite precipitates already at low supersaturation, OCP precipitation starts not until a high level of supersaturation is reached. Since measurements and computer simulations show that hydroxyapatite (HAP) is the final calcium phosphate mineral in urine solutions, OCP is only a precursor phase which slowly transforms into HAP.
Udert, K. M.; Larsen, T. A.; Biebow, M.; Gujer, W. (2003) Urea hydrolysis and precipitation dynamics in a urine-collecting system, Water Research, 37(11), 2571-2582, doi:10.1016/S0043-1354(03)00065-4, Institutional Repository

Genomics and the origin of species

Speciation is a fundamental evolutionary process, the knowledge of which is crucial for understanding the origins of biodiversity. Genomic approaches are an increasingly important aspect of this research field. We review current understanding of genome-wide effects of accumulating reproductive isolation and of genomic properties that influence the process of speciation. Building on this work, we identify emergent trends and gaps in our understanding, propose new approaches to more fully integrate genomics into speciation research, translate speciation theory into hypotheses that are testable using genomic tools and provide an integrative definition of the field of speciation genomics.
Seehausen, O.; Butlin, R. K.; Keller, I.; Wagner, C. E.; Boughman, J. W.; Hohenlohe, P. A.; Peichel, C. L.; Saetre, G.-P.; Bank, C.; Brännström, Å.; Brelsford, A.; Clarkson, C. S.; Eroukhmanoff, F.; Feder, J. L.; Fischer, M. C.; Foote, A. D.; Franchini, P.; Jiggins, C. D.; Jones, F. C.; Lindholm, A. K.; Lucek, K.; Maan, M. E.; Marques, D. A.; Martin, S. H.; Matthews, B.; Meier, J. I.; Möst, M.; Nachman, M. W.; Nonaka, E.; Rennison, D. J.; Schwarzer, J.; Watson, E. T.; Westram, A. M.; Widmer, A. (2014) Genomics and the origin of species, Nature Reviews Genetics, 15, 176-192, doi:10.1038/nrg3644, Institutional Repository

Speciation in freshwater fishes

The extraordinary species richness of freshwater fishes has attracted much research on mechanisms and modes of speciation. We here review research on speciation in freshwater fishes in light of speciation theory, and place this in a context of broad-scale diversity patterns in freshwater fishes. We discuss several major repeated themes in freshwater fish speciation and the speciation mechanisms they are frequently associated with. These include transitions between marine and freshwater habitats, transitions between discrete freshwater habitats, and ecological transitions within habitats, as well as speciation without distinct niche shifts. Major research directions in the years to come include understanding the transition from extrinsic environment-dependent to intrinsic reproductive isolation and its influences on species persistence and understanding the extrinsic and intrinsic constraints to speciation and how these relate to broad-scale diversification patterns through time.
Seehausen, O.; Wagner, C. E. (2014) Speciation in freshwater fishes, Annual Review of Ecology, Evolution, and Systematics, 45, 621-651, doi:10.1146/annurev-ecolsys-120213-091818, Institutional Repository

Cichlid species-area relationships are shaped by adaptive radiations that scale with area

A positive relationship between species richness and island size is thought to emerge from an equilibrium between immigration and extinction rates, but the influence of species diversification on the form of this relationship is poorly understood. Here, we show that within-lake adaptive radiation strongly modifies the species-area relationship for African cichlid fishes. The total number of species derived from in situ speciation increases with lake size, resulting in faunas orders of magnitude higher in species richness than faunas assembled by immigration alone. Multivariate models provide evidence for added influence of lake depth on the species-area relationship. Diversity of clades representing within-lake radiations show responses to lake area, depth and energy consistent with limitation by these factors, suggesting that ecological factors influence the species richness of radiating clades within these ecosystems. Together, these processes produce lake fish faunas with highly variable composition, but with diversities that are well predicted by environmental variables.
Wagner, C. E.; Harmon, L. J.; Seehausen, O. (2014) Cichlid species-area relationships are shaped by adaptive radiations that scale with area, Ecology Letters, 17(1), 583-592, doi:10.1111/ele.12260, Institutional Repository

Eutrophication causes speciation reversal in whitefish adaptive radiations

Species diversity can be lost through two different but potentially interacting extinction processes: demographic decline and speciation reversal through introgressive hybridization. To investigate the relative contribution of these processes, we analysed historical and contemporary data of replicate whitefish radiations from 17 pre-alpine European lakes and reconstructed changes in genetic species differentiation through time using historical samples. Here we provide evidence that species diversity evolved in response to ecological opportunity, and that eutrophication, by diminishing this opportunity, has driven extinctions through speciation reversal and demographic decline. Across the radiations, the magnitude of eutrophication explains the pattern of species loss and levels of genetic and functional distinctiveness among remaining species. We argue that extinction by speciation reversal may be more widespread than currently appreciated. Preventing such extinctions will require that conservation efforts not only target existing species but identify and protect the ecological and evolutionary processes that generate and maintain species.
Vonlanthen, P.; Bittner, D.; Hudson, A. G.; Young, K. A.; Müller, R.; Lundsgaard-Hansen, B.; Roy, D.; Di Piazza, S.; Largiader, C. R.; Seehausen, O. (2012) Eutrophication causes speciation reversal in whitefish adaptive radiations, Nature, 482(7385), 357-362, doi:10.1038/nature10824, Institutional Repository

Ecological opportunity and sexual selection together predict adaptive radiation

A fundamental challenge to our understanding of biodiversity is to explain why some groups of species undergo adaptive radiations, diversifying extensively into many and varied species, whereas others do not1,2. Both extrinsic environmental factors (for example, resource availability, climate) and intrinsic lineage-specific traits (for example, behavioural or morphological traits, genetic architecture) influence diversification, but few studies have addressed how such factors interact. Radiations of cichlid fishes in the African Great Lakes provide some of the most dramatic cases of species diversification. However, most cichlid lineages in African lakes have not undergone adaptive radiations. Here we compile data on cichlid colonization and diversification in 46 African lakes, along with lake environmental features and information about the traits of colonizing cichlid lineages, to investigate why adaptive radiation does and does not occur. We find that extrinsic environmental factors related to ecological opportunity and intrinsic lineage-specific traits related to sexual selection both strongly influence whether cichlids radiate. Cichlids are more likely to radiate in deep lakes, in regions with more incident solar radiation and in lakes where there has been more time for diversification. Weak or negative associations between diversification and lake surface area indicate that cichlid speciation is not constrained by area, in contrast to diversification in many terrestrial taxa3. Among the suite of intrinsic traits that we investigate, sexual dichromatism, a surrogate for the intensity of sexual selection, is consistently positively associated with diversification. Thus, for cichlids, it is the coincidence between ecological opportunity and sexual selection that best predicts whether adaptive radiation will occur. These findings suggest that adaptive radiation is predictable, but only when species traits and environmental factors are jointly considered.
Wagner, C. E.; Harmon, L. J.; Seehausen, O. (2012) Ecological opportunity and sexual selection together predict adaptive radiation, Nature, 487(7407), 366-369, doi:10.1038/nature11144, Institutional Repository

Ecology, sexual selection and speciation

The spectacular diversity in sexually selected traits among animal taxa has inspired the hypothesis that divergent sexual selection can drive speciation. Unfortunately, speciation biologists often consider sexual selection in isolation from natural selection, even though sexually selected traits evolve in an ecological context: both preferences and traits are often subject to natural selection. Conversely, while behavioural ecologists may address ecological effects on sexual communication, they rarely measure the consequences for population divergence. Herein, we review the empirical literature addressing the mechanisms by which natural selection and sexual selection can interact during speciation. We find that convincing evidence for any of these scenarios is thin. However, the available data strongly support various diversifying effects that emerge from interactions between sexual selection and environmental heterogeneity. We suggest that evaluating the evolutionary consequences of these effects requires a better integration of behavioural, ecological and evolutionary research.
Maan, M. E.; Seehausen, O. (2011) Ecology, sexual selection and speciation, Ecology Letters, 14(6), 591-602, doi:10.1111/j.1461-0248.2011.01606.x, Institutional Repository

Ecology: Speciation affects ecosystems

Evidence that speciation and adaptive radiation can change the properties of an ecosystem is a reminder of the pressing need to integrate ecosystems science and evolutionary biology.
Seehausen, O. (2009) Ecology: Speciation affects ecosystems, Nature, 458(7242), 1122-1123, doi:10.1038/4581122a, Institutional Repository

Speciation through sensory drive in cichlid fish

Theoretically, divergent selection on sensory systems can cause speciation through sensory drive. However, empirical evidence is rare and incomplete. Here we demonstrate sensory drive speciation within island populations of cichlid fish. We identify the ecological and molecular basis of divergent evolution in the cichlid visual system, demonstrate associated divergence in male colouration and female preferences, and show subsequent differentiation at neutral loci, indicating reproductive isolation. Evidence is replicated in several pairs of sympatric populations and species. Variation in the slope of the environmental gradients explains variation in the progress towards speciation: speciation occurs on all but the steepest gradients. This is the most complete demonstration so far of speciation through sensory drive without geographical isolation. Our results also provide a mechanistic explanation for the collapse of cichlid fish species diversity during the anthropogenic eutrophication of Lake Victoria.
Seehausen, O.; Terai, Y.; Magalhaes, I. S.; Carleton, K. L.; Mrosso, H. D. J.; Miyagi, R.; van der Sluijs, I.; Schneider, M. V.; Maan, M. E.; Tachida, H.; Imai, H.; Okada, N. (2008) Speciation through sensory drive in cichlid fish, Nature, 455(7285), 620-626, doi:10.1038/nature07285, Institutional Repository

An extant cichlid fish radiation emerged in an extinct Pleistocene lake

The haplochromine cichlid fish of the East African Great Lakes represent some of the fastest and most species-rich adaptive radiations known1, but rivers in most of Africa accommodate only a few morphologically similar species of haplochromine cichlid fish. This has been explained by the wealth of ecological opportunity in large lakes compared with rivers. It is therefore surprising that the rivers of southern Africa harbour many, ecologically diverse haplochromines. Here we present genetic, morphological and biogeographical evidence suggesting that these riverine cichlids are products of a recent adaptive radiation in a large lake that dried up in the Holocene. Haplochromine species richness peaks steeply in an area for which geological data reveal the historical existence of Lake palaeo-Makgadikgadi2,3. The centre of this extinct lake is now a saltpan north of the Kalahari Desert, but it once hosted a rapidly evolving fish species radiation, comparable in morphological diversity to that in the extant African Great Lakes. Importantly, this lake seeded all major river systems of southern Africa with ecologically diverse cichlids. This discovery reveals how local evolutionary processes operating during a short window of ecological opportunity can have a major and lasting effect on biodiversity on a continental scale.
Joyce, D. A.; Lunt, D. H.; Bills, R.; Turner, G. F.; Katongo, C.; Duftner, N.; Sturmbauer, C.; Seehausen, O. (2005) An extant cichlid fish radiation emerged in an extinct Pleistocene lake, Nature, 435(7038), 90-95, doi:10.1038/nature03489, Institutional Repository

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Address

E-Mail: ole.seehausen@eawag.ch
Phone: +41 58 765 2121
Fax: +41 58 765 2168
Address: Eawag
Seestrasse 79
6047 Kastanienbaum
Office: SL B16
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Expert on

fish, genetics, ecology, evolution

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Research Group

 Evolutionary Biodiversity Dynamics

Aquatic Ecology & Evolution @ University of Bern

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Focalpoints

evolution

speciation

adaptive radiation

biological invasion 

extinction

biodiversity

conservation

population genomics 

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