This page and also my projects are under construction
—but here is a list of a few projects.
Current projects:
Ecology and Evolution of Adaptive Phenotypic Variation in Perch
Divergent natural selection between and within populations exploiting different resources is hypothesized to be a primary cause of trophic polymorphism and adaptive radiation. In this project I have focused on questions regarding foraging performance and trade-offs between foraging on different resources in the littoral and pelagic habitat of lakes using Eurasian perch (Perca fluviatilis) as a model organism. The main findings of this project are; (i) the pattern between morphology and habitat choice in perch where deeper bodied individuals are found in the littoral habitat whereas the more streamlined are found in the pelagic habitat of lakes (Svanbäck and Eklöv 2002, 2003), (ii) there is a trade-offs that in foraging efficiency between the littoral and pelagic habitats that is connected to the morphological variation (Svanbäck and Eklöv 2003, 2004), (iii) perch habitat choice is density dependent where at low densities all perch are found in the littoral habitat (Svanbäck and Persson 2004, 2009), and (iv) the morphological variation in perch is mainly due to phenotypic plasticity but there is also a small genetic component to the morphological variation (Svanbäck and Eklöv 2006). More information will follow...
Svanbäck, R. and Eklöv, P. (2002) Effects of habitat and food resources on morphology and ontogenetic growth trajectories in perch. Oecologia 131: 61-70.
Svanbäck, R. and Eklöv, P. (2003) Morphology dependent foraging efficiency in perch: a trade-off for ecological specialization? Oikos 102: 273-284.
Svanbäck, R. and Eklöv, P. (2004) Morphology in perch affects habitat specific feeding efficiency. Functional Ecology 18: 503-510.
Svanbäck, R. and Persson, L. (2004) Individual specialization, niche width and population dynamics: implications for trophic polymorphisms. Journal of Animal Ecology 73: 973-982.
Svanbäck, R. and Eklöv, P. (2006) Genetic variation and phenotypic plasticity: causes of morphological variation in Eurasian perch. Evolutionary Ecology Research 8: 37-49
Svanbäck, R., and Persson, L. (2009). Population density fluctuations change the selection gradient in Eurasian perch. American Naturalist 173: 507-516.
Individual Diet Specialization
Most empirical and theoretical studies of resource-use and population dynamics treat conspecific individuals as ecological equivalent. This simplification is only justified if inter-individual niche variation is rare, weak, or has a trivial effect on ecological processes. However, I have found that there exist lots of examples of varying degree of individual specialization in populations across a broad range of taxonomic groups suggesting that individual specialization is a widespread phenomenon (Bolnick et al. 2003). The variation in individual specialization among species and among populations reflects a diverse array of physiological, behavioural, and ecological mechanisms that can generate intra-population variation. The mechanisms behind intra-population variation is poorly investigated and in this project I am investigating the ecological mechanisms involved in individual specialization, especially effects of competition but also predation (Svanbäck and Persson 2004, Svanbäck and Bolnick 2005, 2007, Eklöv and Svanbäck 2006, Bolnick et al. 2007).
Bolnick, D.I., Yang, L.H., Fordyce, J.A., Davis, J.M. and Svanbäck, R. (2002) Measuring individual-level trophic specialization. Ecology 83: 2936-2941.
Bolnick, D.I., Svanbäck, R., Fordyce, J.A., Yang, L.H., Davis, J.M., Hulsey, C.D. and Forister, M.L. (2003) The ecology of individuals: incidence and implications of individual specialization. American Naturalist 161: 1-28.
Svanbäck, R. and Persson, L. (2004) Individual specialization, niche width and population dynamics: implications for trophic polymorphisms. Journal of Animal Ecology 73: 973-982.
Svanbäck, R., and Bolnick, D.I. (2005) Intraspecific competition affects the strength of individual specialization: an optimal diet theory method. Evolutionary Ecology Research 7: 993-1012.
Eklöv, P. and Svanbäck, R. (2006) Predation favors phenotypic divergence in sympatric perch populations. American Naturalist 167: 440-452.
Svanbäck, R., and Bolnick, D.I. (2007) Intraspecific competition drives increased resource use diversity within a natural population. Proceedings of the Royal Society, Biological sciences 274: 839-844.
Bolnick, D.I., Svanbäck, R., Araújo, M.S., and Persson, L. (2007). More generalized populations are also more heterogeneous: comparative support for the niche variation hypothesis. Proceedings of the National Academy of Science, USA 104: 10075-10079.
Predator or competitor driven morphological evolution in Asellus
Most studies of ecological speciation have concentrated on morphological specialization of diet related traits and this has lead to a neglect of other important ecological factors for the adaptive divergence of species, such as the presence of predators. As predation and competition works in concert I will in this application investigate the combined effects of predation and competition on the evolution of morphological variation and investigate the influence of predator-prey numerical dynamics on the evolution of morphological- and genetic variation. In experiments I will look at the trade off in anti-predator traits between environments but also the trade-off in foraging/growth between the environments. In another experiment I will look at the combined effects of predation and competition in driving habitat choice. In two field studies I will investigate the suggested mechanisms from the experiments for the evolution of morphological variation, investigate if the morphological variation has evolved one time and then spread to all populations or if it have evolved independently in all populations and investigate the effects of predator-prey numerical dynamics on the evolution of morphological variation.
This is a rather new project and more information will follow...
Ecology and Evolution of phenotypic plasticity
If environmental fluctuations and changes in the environment are more long-term, then plastic individuals will have a fitness advantage. Phenotypic plasticity is the ability of a genotype to produce alternative phenotypes according to the environment that it experiences and it might be an adaptive response to environmental variability. During the last two decades, empirical evidence that phenotypic plasticity meets all the conditions required for being selected for has accumulated: (i) phenotypic plastic genotypes can have fitness advantages relative to non-plastic ones; (ii) plasticity may be genetically controlled; and (iii) additive genetic variation exists for phenotypic plasticity. Appreciating that phenotypic plasticity can be selected for raises questions about the genetic and ecological conditions that promote or prevent its evolutionary emergence. For example, are populations that experience fluctuating environments more plastic than populations in stable environments, or are specialized populations/species less plastic than generalist populations/species? In this project I have found that due to fluctuations in perch population density the fitness landscape fluctuates between directional and stabilizing at low density to being disruptive at high density (Svanbäck and Persson 2009). These fluctuations in population density and fitness landscape are probably the reason for why perch morphology is mainly determined by phenotypic plasticity (Svanbäck and Eklöv 2006). This hypothesis has also been confirmed in an adaptive dynamics model where populations that undergo high amplitude cycling evolve phenotypic plasticity whereas populations with more stable numerical dynamics loose their plasticity and branch into two species (Svanbäck, Pineda-Krch and Doebeli 2009). Furthermore, it seems like the expression of phenotypic plasticity is dependent on the energy income from foraging acticvities (Olsson et al. 2006, 2007). More information will follow...
Svanbäck, R. and Eklöv, P. (2006) Genetic variation and phenotypic plasticity: causes of morphological variation in Eurasian perch. Evolutionary Ecology Research 8: 37-49.
Olsson, J., Svanbäck, R., and Eklöv, P.(2006) Growth rate constrain morphological divergence when driven by competition. Oikos 115: 15-22.
Olsson, J., Svanbäck, R., and Eklöv, P. (2007) Variation in resource levels overrides the effects of habitat type on trait plasticity in a fish. Oecologia 152: 48-56.
Svanbäck, R., and Persson, L. (2009). Population density fluctuations change the selection gradient in Eurasian perch. American Naturalist 173: 507-516.
Svanbäck, R., Pineda-Krch, M., and Doebeli, M. (2009). Fluctuating population dynamics promotes the evolution of phenotypic plasticity. American Naturalist, 174: 176-189.
Evolutionary effects of invasive species
This is a project that is carried out by my graduate student Philipp Hirsch.
Philipp's research revolves around the evolutionary processes triggered by biological invasions. Using both native and invasive fish, crayfish and a mussel as model species Philipp study how invaders express different phenotypes to adapt to the invasion process and, on the other hand, how native species change the expression of phenotypes in response to a new species in the system..
Past projects:
Suction feeding in fishes
The magnitude of buccal pressure in suction feeding is thought to be correlated with the rate of buccal expansion. The produced subambient pressure then creates a flow of water that carries the prey into the mouth of the predator. This project was carried out while I was a visiting researcher in Peter Wainwright’s lab at UC Davis. In this project we investigated the effect of suction pressure on the prey by simultaneously measuring pressure changes in the buccal cavity of largemouth bass (Micropterus salmoides) and prey movement, based on high-speed video recordings (Svanbäck et al. 2002). Furthermore, we also investigated the suggested kinematic mechanisms hypothesised to affect the pressure change in the buccal cavity.
Svanbäck, R., Wainwright, P.C. and Ferry-Graham, L.A. (2002) Linking cranial kinematics and buccal pressure to suction feeding performance in largemouth bass. Physiological and Biochemical Zoology 75: 532-543.