ole seehausen

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Papers by ole seehausen

Genetics of male nuptial colour divergence between sympatric sister species of a Lake Victoria cichlid fish

Journal of Evolutionary Biology, May 1, 2010

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Variation in parasite infection between replicates of speciation in Lake Victoria cichlid fish

Evolution, May 18, 2023

Because of potentially strong eco-evolutionary interactions with their hosts, parasites may initi... more Because of potentially strong eco-evolutionary interactions with their hosts, parasites may initiate or enhance host diversification. The adaptive radiation of cichlid fish in Lake Victoria provides a good system to study the role of parasites at different stages of host speciation. We analyzed the macroparasite infection of four replicates of sympatric blue and red Pundamilia species pairs that vary in their age and extent of differentiation. Sympatric host species differed in parasite community composition and in the infection levels of some of these parasite taxa. Most infection differences were consistent between sampling years, indicating temporal consistency in parasite-mediated divergent selection between species. Infection differentiation increased linearly with genetic differentiation. However, significant infection differences between sympatric species were only found in the oldest, most strongly differentiated Pundamilia species pair. This is inconsistent with parasite-driven speciation. Next, we identified five distinct species of Cichlidogyrus, a genus of highly specific gill parasites that has radiated elsewhere in Africa. Infection profiles of species of Cichlidogyrus differed between sympatric cichlid species only in the oldest and most differentiated pair, again inconsistent with parasite-mediated speciation. To conclude, parasites may contribute to host differentiation after speciation, but do not initiate host speciation.

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Allopatric and sympatric diversification within roach (<i>Rutilus rutilus</i>) of large pre‐alpine lakes

Journal of Evolutionary Biology, Sep 19, 2019

Allopatric and sympatric diversification within roach (Rutilus rutilus) of large prealpine lakes ... more Allopatric and sympatric diversification within roach (Rutilus rutilus) of large prealpine lakes Abstract 5 Intraspecific differentiation in response to divergent natural selection between environments is a common phenomenon in some lineages of northern 7 freshwater fishes, especially salmonids and stickleback. Understanding why 8 these taxa diversify and undergo adaptive radiations while most other fish 9 species in the same environments do not, remains an open question. The possibility for intraspecific diversification has rarely been evaluated for most northern freshwater fish species. Here, we assess the potential for intraspecific differentiation between and within lake populations of roach (Rutilus rutilus)-a widespread and abundant cyprinid species-in lakes in which salmonids have evolved endemic adaptive radiations. Based on more than 3,000 polymorphic RADseq markers, we detected low but significant genetic differentiation between roach populations of two ultraoligotrophic lakes and between these and populations from other lakes. This, together with differentiation in head morphology and stable isotope signatures, suggests evolutionary and ecological differentiation among some of our studied populations. Next, we tested for intralacustrine diversification of roach within Lake Brienz, the most pristine lake surveyed in this study. We found significant phenotypic evidence for ecological intralacustrine differentiation between roach caught over a muddy substrate and those caught over a rocky substrate. However, evidence for intralacustrine genetic differentiation is at best subtle and phenotypic changes may therefore be mostly plastic. Overall, our findings suggest roach can differ between ecologically distinct lakes, but the extent of intralacustrine ecological differentiation is weak, which contrasts with the strong differentiation among endemic species of whitefish in the same lakes.

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Appendix, Figure S1, Supplementary Tables 1-5 from Genetic architecture of a key reproductive isolation trait differs between sympatric and non-sympatric sister species of Lake Victoria cichlids

We normalized DNA concentration for all samples in one library prior to restriction enzyme digest... more We normalized DNA concentration for all samples in one library prior to restriction enzyme digestion. 4-48 individuals carrying TruSeq P1-adaptors and different custom 5bp-8bp barcodes were pooled into one library (see Table S5). For shearing we used a Covaris M220 Focusedultrasonicator. Sheared fragments between 300-700bp were selected on a SageELF machine. After ligation of the TruSeq P2-adaptors each library was amplified in four aliquots of 50 μl.

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A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae)

ZooKeys, Feb 2, 2023

The taxonomy of the endemic whitefish of the lakes of the Reuss River system (Lucerne, Sarnen, Zu... more The taxonomy of the endemic whitefish of the lakes of the Reuss River system (Lucerne, Sarnen, Zug) and Lake Sempach, Switzerland, is reviewed and revised. Lake Lucerne harbours five species. Coregonus intermundia sp. nov. and C. suspensus sp. nov., are described. Coregonus nobilis Haack, 1882, C. suidteri Fatio, 1885, and C. zugensis Nüsslin, 1882, are redescribed. Genetic studies have shown that C. suidteri and C. zugensis are composed of several distinct species endemic to different lakes. The names C. suidteri and C. zugensis are restricted to the species of lakes Sempach and Zug, respectively. The whitefish populations previously referred to as C. suidteri and C. zugensis from Lake Lucerne are described as C. litoralis sp. nov. and C. muelleri sp. nov., respectively. Furthermore, the whitefish from Lake Zug that were previously referred to as C. suidteri are described as C. supersum sp. nov. A holotype is designated for C. supersum that was previously one of two syntypes of C. zugensis. The other syntype is retained for C. zugensis. Coregonus obliterus sp. nov. is described from Lake Zug, and C. obliterus and C. zugensis from Lake Zug are extinct. Finally, we describe C. sarnensis sp. nov. from lakes Sarnen and Alpnach. Coregonus suidteri from Lake Sempach shows strong signals of introgression from deliberately translocated non-native whitefish species, which questions if the extant population still carries a genetic legacy from the original species and thus may need to be considered extinct. Coregonus suspensus is genetically partially of allochthonous origin, closely related to the radiation of

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Evolutionary divergence in replicate pairs of ecotypes of Lake Victoria cichlid fish

Evolutionary Ecology Research, 2012

Questions: (1) Do replicate pairs of ecotypes of cichlid fish represent different stages of ecolo... more Questions: (1) Do replicate pairs of ecotypes of cichlid fish represent different stages of ecological speciation? (2) Are phenotypic and genetic divergence correlated with each other and with the steepness of the habitat gradients? Study system: Three replicate pairs of putative ecotypes of cichlid fish in the genus Neochromis from three islands in Lake Victoria. The three pairs present similar trophic polymorphisms. The three islands differ in steepness of the benthic habitat gradients mediated by variation in water clarity, shore slopes, and depths of the rock-sand interface. Analytical methods: We quantified fish body morphology and dentition, typed population samples at nine microsatellite loci, and analysed how phenotypic and neutral genetic variation were distributed among ecotypes and along the habitat gradients. Results: Despite weak or absent genetic differentiation at neutral markers, ecotypes were divergent in phenotypes in a replicated manner, involving from one to many different traits in a nested series. Variation in eco-morphological traits and allelic variation at neutral marker loci were associated with depth of habitat at some islands.

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Visual adaptation and microhabitat choice in two closely related cichlid species from Lake Victoria

Model species Material and methods When different genotypes choose different habitats to better m... more Model species Material and methods When different genotypes choose different habitats to better match their phenotypes, adaptive differentiation and reproductive isolation may be promoted. In cichlid fish, visual adaptation to alternative visual environments is hypothesised to contribute to speciation. Here, we investigated whether variation in visual sensitivity causes variation in visual habitat preference, in the context of the sensory drive hypothesis (Endler 1992, Boughman 2002). We use two closely related cichlid species that occur at different water depths in Lake Victoria, experiencing different light conditions and showing genetic differences in visual perception (Pundamilia pundamilia-inhabiting shallow waters; and Pundamilia nyererei-found in deeper waters, Seehausen et al 2008; Figure 1). We also explore potential effects of visual plasticity, taking advantage of captive fish artificially reared in two different light conditions, mimicking either shallow-water or deep-water light environments.

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Visual adaptation and microhabitat choice in Lake Victoria cichlid fish

Royal Society Open Science, Mar 1, 2019

When different genotypes choose different habitats to better match their phenotypes, genetic diff... more When different genotypes choose different habitats to better match their phenotypes, genetic differentiation within a population may be promoted. Mating within those habitats may subsequently contribute to reproductive isolation. In cichlid fish, visual adaptation to alternative visual environments is hypothesized to contribute to speciation. Here, we investigated whether variation in visual sensitivity causes different visual habitat preferences, using two closely related cichlid species that occur at different but overlapping water depths in Lake Victoria and that differ in visual perception (Pundamilia spp.). In addition to species differences, we explored potential effects of visual plasticity, by rearing fish in two different light conditions: broad-spectrum (mimicking shallow water) and red-shifted (mimicking deeper waters). Contrary to expectations, fish did not prefer the light environment that mimicked their typical natural habitat. Instead, we found an overall preference for the broad-spectrum environment. We also found a transient influence of the rearing condition, indicating that the assessment of microhabitat preference requires repeated testing to control for familiarity effects. Together, our results show that cichlid fish exert visual habitat preference but do not support straightforward visual habitat matching.

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Relaxed trait covariance in interspecific cichlid hybrids predicts morphological diversity in adaptive radiations

Journal of Evolutionary Biology, Dec 16, 2013

The process of adaptive radiation involves multiple events of speciation in short succession, ass... more The process of adaptive radiation involves multiple events of speciation in short succession, associated with ecological diversification. Understanding this process requires identifying the origins of heritable phenotypic variation that allows adaptive radiation to progress. Hybridisation is one source of genetic and morphological variation that may spur adaptive radiation. We experimentally explored the potential role of hybridisation in facilitating the onset of adaptive radiation. We generated first-and second-generation hybrids of four species of African cichlid fish, extant relatives of the putative ancestors of the adaptive radiations of Lakes Victoria and Malawi. We compared patterns in hybrid morphological variation with the variation in the lake radiations. We show that significant fractions of the interspecific morphological variation and the major trajectories in morphospace that characterize whole radiations can be generated in second-generation hybrids. Furthermore we show that covariation among traits is relaxed in second-generation hybrids, which may facilitate adaptive diversification. These results support the idea that

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Divergent selection and phenotypic plasticity during incipient speciation in Lake Victoria cichlid fish

Journal of Evolutionary Biology, Nov 18, 2008

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

Ecology Letters, Mar 6, 2014

A positive relationship between species richness and island size is thought to emerge from an equ... more 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.

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Speciation in Freshwater Fishes

Annual Review of Ecology, Evolution, and Systematics, Nov 23, 2014

The extraordinary species richness of freshwater fishes has attracted much research on mechanisms... more 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.

Chapter Fourteen. Geographical Mode and Evolutionary Mechanism of Ecological Speciation in Cichlid Fish

Princeton University Press eBooks, Dec 31, 2011

Signals of predation-induced directional and disruptive selection in the threespine stickleback

Evolutionary Ecology Research, Dec 1, 2012

Background: Different predation regimes may exert divergent selection pressure on phenotypes and ... more Background: Different predation regimes may exert divergent selection pressure on phenotypes and their associated genotypes. Threespine stickleback Gasterosteus aculeatus have a suite of bony structures, which have been shown to be an effective defence against predation and have a well-known genetic basis. Question: Do different predator regimes induce different selective pressures on growth rates and defence phenotypes in threespine stickleback between different habitats across distinct age classes? Hypothesis: In the presence of predation-induced selection, we expect diverging morphological responses between populations experiencing either low or high predation pressure. Study system: Threespine stickleback were sampled from two natural but recently established populations in an invasive range. One site has a high density of fish and insect predators, while at the other site predation pressure is low. Methods: We inferred predator-induced selection on defence traits by comparing the distribution of size classes, defence phenotypes, and an armour-related genotype between different age classes in a high and a low predation regime. Results: Under high predation, there are indications of directional selection for faster growth, whereas lateral plate phenotypes and associated genotypes show indications for disruptive selection. Heterozygotes at the Eda-gene have a lower survival rate than either homozygote. Neither pattern is evident in the low predation regime. Conclusion: Potential evolutionary responses to divergent predation pressures between sites are apparent in a recently established system.

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Geographical Mode and Evolutionary Mechanism of Ecological Speciation in Cichlid Fish

Princeton University Press eBooks, Jul 13, 2021

Effects of interspecific gene flow on the phenotypic variance–covariance matrix in Lake Victoria Cichlids

Hydrobiologia, Jun 2, 2016

Quantitative genetics theory predicts adaptive evolution to be constrained along evolutionary lin... more Quantitative genetics theory predicts adaptive evolution to be constrained along evolutionary lines of least resistance. In theory, hybridization and subsequent interspecific gene flow may however rapidly change the evolutionary constraints of a population and eventually change its evolutionary potential, but empirical evidence is still scarce. Using closely related species pairs of Lake Victoria cichlids sampled from four different islands with different levels of interspecific gene flow, we tested for potential effects of introgressive hybridization on phenotypic evolution in wild populations. We found that these effects differed among our study species. Constraints measured as the eccentricity of phenotypic variance-covariance matrices declined significantly with increasing gene flow in the less abundant species for matrices that have a diverged line of least resistance. In contrast we find no such decline for the more abundant species. Overall our results suggest that hybridization can change the underlying

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The association of feeding behaviour with the resistance and tolerance to parasites in recently diverged sticklebacks

Journal of Evolutionary Biology, Jul 23, 2016

This article has been accepted for publication and undergone full peer review but has not been th... more

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Interspecific hybridization can generate functional novelty in cichlid fish

Proceedings of The Royal Society B: Biological Sciences, Oct 23, 2019

The role of interspecific hybridization in evolution is still being debated. Interspecific hybrid... more The role of interspecific hybridization in evolution is still being debated. Interspecific hybridization has been suggested to facilitate the evolution of ecological novelty, and hence the invasion of new niches and adaptive radiation when ecological opportunity is present beyond the parental species niches. On the other hand, hybrids between two ecologically divergent species may perform less well than parental species in their respective niches because hybrids would be intermediate in performance in both niches. The evolutionary consequences of hybridization may hence be context-dependent, depending on whether ecological opportunities, beyond those of the parental species, do or do not exist. Surprisingly, these complementary predictions may never have been tested in the same experiment in animals. To do so, we investigate if hybrids between ecologically distinct cichlid species perform less well than the parental species when feeding on food either parent is adapted to, and if the same hybrids perform better than their parents when feeding on food none of the species are adapted to. We generated two first-generation hybrid crosses between species of African cichlids. In feeding efficiency experiments we measured the performance of hybrids and parental species on food types representing both parental species niches and additional 'novel' niches, not used by either of the parental species but by other species in the African cichlid radiations. We found that hybrids can have higher feeding efficiencies on the 'novel' food types but typically have lower efficiencies on parental food types when compared to parental species. This suggests that hybridization can generate functional variation that can be of ecological relevance allowing the access to resources outside of either parental species niche. Hence, we provide support for the hypothesis of ecological context-dependency of the evolutionary impact of interspecific hybridization.

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Geographic variation in opsin expression does not align with opsin genotype in Lake Victoria cichlid populations

Ecology and Evolution, Jul 9, 2019

This is an open access article under the terms of the Creat ive Commo ns Attri bution License, wh... more

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Sympatric colour polymorphisms associated with nonrandom gene flow in cichlid fish of Lake Victoria

Molecular Ecology, Jul 23, 2010

Colour polymorphisms have fascinated evolutionary ecologists for a long time. Yet, knowledge on t... more Colour polymorphisms have fascinated evolutionary ecologists for a long time. Yet, knowledge on the mechanisms that allow their persistence is restricted to a handful of well-studied cases. We studied two species of Lake Victoria cichlid fish, Neochromis omnicaeruleus and Neochromis greenwoodi, exhibiting very similar sex-linked colour polymorphisms. The ecology and behaviour of one of these species is well studied, with colour-based mating and aggression preferences. Here, we ask whether the selection potentially resulting from female and male mating preferences and aggression biases reduces gene flow between the colour morphs and permits differentiation in traits other than colour. Over the past 14 years, the frequencies of colour morphs have somewhat oscillated, but there is no evidence for directional change, suggesting the colour polymorphism is persistent on an ecological timescale. We find limited evidence of ecomorphological differentiation between sympatric ancestral (plain) and derived (blotched) colour morphs. We also find significantly nonrandom genotypic assignment and an excess of linkage disequilibrium in the plain morph, which together with previous information on mating preferences suggests nonrandom mating between colour morphs. This, together with negative frequency-dependent sexual selection, found in previous studies, may facilitate maintenance of these polymorphisms in sympatry.

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Genetics of male nuptial colour divergence between sympatric sister species of a Lake Victoria cichlid fish

Journal of Evolutionary Biology, May 1, 2010

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Variation in parasite infection between replicates of speciation in Lake Victoria cichlid fish

Evolution, May 18, 2023

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Allopatric and sympatric diversification within roach (<i>Rutilus rutilus</i>) of large pre‐alpine lakes

Journal of Evolutionary Biology, Sep 19, 2019

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Appendix, Figure S1, Supplementary Tables 1-5 from Genetic architecture of a key reproductive isolation trait differs between sympatric and non-sympatric sister species of Lake Victoria cichlids

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