The aim of the Arctic charr and salmonid group at the University of Iceland, led by professor Sigurður S. Snorrason, is to investigate the genetic and developmental mechanisms underlying the rapid and repeated evolution of diverse ecological adaptations in Arctic charr (Salvelinus alpinus) and the phenotypic and genetic diversity among Brown trout (Salmo trutta) populations in Iceland.
The focal questions are:
- How flexible are the ecologically important traits of colonizing species?
- What is the role of isolation, adaptation and gene flow for diversification in novel habitats?
- What are the molecular underpinnings of parallel evolution?
- Do the same pathways, genes or even alleles contribute to divergence in multiple isolated populations within a species?
Since the end of the last ice age, about ten thousand years ago, Arctic charr and Brown trout have invaded and colonized multiple habitats in Iceland. Ecological studies on Arctic charr have shown extensive polymorphism in trophic morphology and life history. In some cases distinct morphs are found in sympatry, such as in Lake Thingvallavatn. Population genetic analyses and ecological studies indicate parallel evolution were ecologically processes have led to morphological divergence which may reflect the initial steps of adaptive speciation.
Pictured are the four charr morphs of lake Thingvallavatn, drawn by Eggert Petursson. PI: piscivorous, LB: large benthic, PL: planktivorous and SB: small benthic charr.
The overall aim of the arctic charr studies: To understand how diverse arctic charr populations have evolved in Iceland since the last Ice Age and to investigate mechanisms leading to morph formation and speciation.
Examples of specific research questions or objectives. We want to
- cast light on the development of key craniofacial elements in the charr
- study the structure of anadromous charr populations in Icelandic waters
- map the population genomics of small benthic diversity in older and recent habitats
- interrogate expression divergence which correlates with craniofacial divergence,
- detect genetic separation among morphs in genes or alleles that associate with specific phenotypes or ecological specializations
- understand the evolution of developmental mechanisms that produce the trophic differences among different charr morphs.
The group is also investigating Brown trout, with the the principal objective being to map the phenotypic variation in Icelandic Brown trout with respect to key ecological correlates and to employ population genomics to cast light on the processes of diversification.The specific aims are to:
- To survey phenotypic variation (e.g. in morphology, life history characteristics) in populations from a wide variety habitats and communities
To employ next generation sequencing techniques (RAD-seq) to survey genetic variation within and among populations which will enable the student to
- assess the genetic connectedness among populations and probe the history of colonization
- implicate loci that associate with morphological and ecological characteristics and assess if and how variation at these loci correlates with ecological specializations across multiple populations.
The group involves several researchers: Sigurður S. Snorrason (ecology/development), Zophonías O. Jónsson (molecular genetics), Arnar Pálsson (evolutionary genetics), Sigríður Rut Franzdóttir (development/molecular biology), Kalina H. Kapralova (morphometrics and molecular biology) and Valerie H. Maier (molecular biology/immunology) which are responsible for distinct aspects of the project.
Three Ph.D. students Johannes Gudbrandsson, Han Xiao and Marcos Lagunas and several bachelor students and interns are working on the project.
The picture is from Ahi et al 2014, demonstrating spatial expression of 3 genes in early charr development.
Charr group alumni
Ehsan Pashay Ahi - Ph.D. 2016.
Lieke Ponsioen - internship 2017.
Jovita Navikaitė - internship 2016.
Sebastina Matloz - internship 2016.
Freya M. O'Sullivan - B.Sc. 2016.
Jeremy Jaegers - internship 2015.
Sophie S. Steinhauser - B.Sc. 2014.
Isak M. Johannesson - summer project 2014.
Baldur Kristjansson - B.Sc. 2012.
Vanessa C. Baltanas - B.Sc. 2011.
Christina B. Santos - B.Sc. 2010.
Javier N. Escudero - B.Sc. 2011.