Roger Butlin

Principal Investigator

Animal and Plant Sciences, University of Sheffield, UK (70%)

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden (30%)


My research is concerned primarily with the origin of barriers to gene exchange, especially the evolutionary genetics of reproductive isolation. I have used insect acoustic and chemical signals as model systems to investigate the controversial process of reinforcement and genomic approaches to investigate barriers to gene flow. Currently, my research is focused on contact zones in Littorina to study local adaptation and the transition to speciation through the acquisition of new barriers, and the coupling of existing barriers to gene flow.

Other speciation projects include experimental evolution in monogonont rotifers to test impacts of gene flow and recombination on speciation and collaborations in projects on postmating, prezygotic isolation in Drosophila, host race formation in aphids, Howea palms and Formica ants. I also collaborate on the genetics and evolution of the parasitic plant Striga, the evolution of asexual reproduction using ostracods and lizards, and evolution at range margins.

Kerstin Johannesson

Principal Investigator

Professor in Marine Ecology and Director of Tjärnö Marine Laboratory, Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


My interest in Littorina started with a master project 40 years ago. These snails are fascinating and they have prompted me to ask a number of questions about evolution and ecology over the years. Such as, what genetic and ecological mechanisms are involved when a species diverges into locally adapted populations (ecotypes)? What is the role of gene flow, drift and selection in maintaining a specific population genetic structure? Why do females mate multiple males, and what is the reason for high and variable rates of abortion? In recent years increasingly powerful genomic resources have opened up ways to address fascinating questions, such as: Why does a species have chromosomal inversions? Do inversions play a role in local adaptation and speciation? What is going on in the hybrid zones between ecotypes?

João Carvalho

PhD Student

cE3c – Centre for Ecology, Evolution and Environmental Changes, Universidade de Lisboa, Lisboa, Portugal


I’m currently doing a PhD in Biodiversity, Genetics & Evolution at the University of Lisbon within the Evolutionary Genetics group of cE3c. During my PhD project I aim to develop and test new tools to infer past demographic events in populations. I’m particularly interested in the development of statistical tools, using approximate Bayesian computation (ABC) methods, that would allow us to leverage the power of pooled sequencing to perform demographic inferences. I plan to apply those methods to a large Littorina saxatilis dataset and contribute to our understanding of the evolutionary origins of populations adapted to particular features of the environment.

Aurélien De Jode

Postdoctoral Research Fellow

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden[at]

I am interested in biodiversity patterns and how they are influenced by environmental factors, in particular in the marine environment. During my PhD, my research covered two levels of biodiversity: the diversity of species in communities and the genetic diversity within species. Therefore, I used population genetic/genomics and community ecology based on genetic tools (metabarcoding). My study system was the coralligenous habitat, a benthic biogenic habitat constituting a biodiversity hotspots in the Mediterraenan Sea. My past research also brought me to work on species delimitation using genetic data, discovery of cryptic species and on speciation. I worked with a wide variety of organisms from marine invertebrate to macroalgae and phytoplankton. I am currently working on speciation genomics in Littorina saxatilis, looking at the build-up of barriers to gene flow at the genomic level between the ecotypes. In all my research, I use bioinformatic tools and programming in several languages to analyze dataset obtained from different New Generation Sequencing technologies.

Martin Eriksson

PhD student

Department of Marine Science, University of Gothenburg, Sweden


I work with computer models of range expansions. In particular, I am interested in the role of phenotypic plasticity during and after range expansions. How does phenotypic plasticity affect the range expansion capacity of a population and what are the effects on the local genetic adaptation?

The models will be connected to empirical data from organisms that have colonised the Baltic Sea since it opened to the ocean after the last glacial period.


Rui Faria


CIBIO – Research Center in Biodiversity and genetic Resources, Porto, Portugal

Associate member of Animal and Plant Sciences, University of Sheffield, UK

Visiting researcher at CIIMAR – Interdisciplinary Center in Marine and Environmental Research, University of Porto, Portugal


I am an evolutionary biologist primarily focused on the study of adaptation and speciation. In particular, I’m interested in understanding the role of chromosomal rearrangements in adaptation and reproductive isolation mainly using Littorina species as model systems. Among these, I started by investigating the genomic architecture of parallel evolution of ecotypes within L. fabalis and of divergence between this species and L. obtusata, covering the whole speciation continuum. In 2016, I joined Roger Butlin’s lab, where we identified multiple inversions in and assessed their role in parallel ecotype divergence, which opened new avenues of research with relevant implications in the field. I am now back to Portugal where I have been investigating, the evolution of chromosomal inversions in L. saxatilis together with Roger Butlin and other researchers in this group and the genetic basis of colour polymorphism in L. fabalis with Miguel Carneiro at CIBIO/InBIO. My ultimate goal is to contribute to an open and creative environment while searching for answers to a diverse array of problems within the field of evolutionary biology.

Katie Hearn

PhD student

Animal and Plant Sciences, University of Sheffield, UK


The origin of species via adaptive divergence in the face of gene flow is a controversial process, but may be aided by processes that restrict recombination in the genome. Suppression of recombination combats the homogenising effect of gene flow by maintaining coadapted complexes of alleles at locally adaptive loci and can enable the build-up of reproductive isolation. Putative chromosomal inversions discovered in Littorina saxatilis may contribute to differentiation between locally adapted populations. My work looks at understanding the role of genomic architecture (including the inversions), habitat choice and divergent selection on local adaptation between populations and on the speciation process. Further, a main focus of my work is how these processes interact with sex determination and the early evolution of sex chromosomes. One linkage group in L. saxatilis shows genetic differences (signals of inversions) between the sexes as well as between ecotypes. Due to a comparable role of recombination suppression in sex chromosome evolution to adaptive divergence – by linking sexually antagonistic loci to sex-determining loci to maintain favourable combinations – there is potential for inversions on this linkage group to play a role in both evolutionary processes. I aim to characterise the sex-genotype-environment associations of this putative young sex chromosome and determine how it contributes to (and is affected by) local adaptation and reproductive isolation.

Eva Koch


Animal and Plant Sciences, University of Sheffield, UK


I’m an evolutionary biologist and postdoc in Roger Butlin’s group in Sheffield. A main focus of my work is local adaptation and its underlying mechanisms. During my PhD I used quantitative genetics, whole transcriptomes, and experimental evolution to study adaptations to new environments in flour beetles. In Littorina my research focuses on the effects of chromosomal inversions on phenotypes and their contribution to ecotype formation.

Jenny Larsson

PhD student

Animal and Plant Sciences, University of Sheffield, UK


I am a final year PhD student in Roger Butlin’s group at the University of Sheffield. My background is in mathematics, where my main interests are in the areas of shape and geometry, and I am now applying my mathematical knowledge to biology by analysing the shell shape variability in Littorina saxatilis.

My research includes developing a method for quantifying shape and describing the growth pattern of mollusc shells, and constructing 3D models, from 2D images. This developmentally-informative description can then be used to analyse shape variation of large sample sets, not only for L. saxatilis but within and between a wide variety of species, and is hoped to improve our ability to understand the genetic basis of shell shape.

I am currently also working on fluid dynamics analysis of various shapes and sizes of L. saxatilis shells to better understand their different hydrodynamic properties, which relates to their fitness in wave swept environments.

Erica Leder

Senior Lecturer

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


I am an evolutionary biologist with a particular interest in understanding the molecular mechanisms of phenotypic evolution. Using genome-wide approaches (e.g. proteomics, transcriptomics, whole genome sequencing), I aim to identify the molecular mechanisms responsible for variation in traits under selection. In Littorina, I am investigating gene regulatory networks responsible for phenotypic variation of snail ecotypes, particularly shell morphology. 

Alan Le Moan


Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


I am generally interested in how the process of speciation is achieved, how new species evolved and what is the contribution of the environment to this process of speciation. To answer these questions, I am using mostly population genomics and comparatives approaches. I have been working on different marine species (tunicates and fishes) that have the particularity to show extreme value of population size and/or dispersal capacity, limiting the effect of genetic drift on the process of divergence, which makes them good model species to study the processes linked to natural selection. I am now working with the periwinkle Littorina fabalis to study further the process of speciation. This species of snail shows two ecotypes, a dwarf and a large ecotype, which live in sympatry along the seashore of Europe. I am trying to dissect their genome in order to characterize the regions that create barriers to reproduction between ecotypes.

Hernan Morales

Research Fellow

Evogenomics, Globe Institute, University of Copenhagen


I am an evolutionary biologist primarily focused on the study of adaptation, speciation and conservation. My main research interest revolves around how genetic diversity is generated, maintained and lost.  I was involved in the population genomics analyses of hundreds of genomes to shed light on how Littorina adapted multiple times to replicated heterogenous environments. As I continue to collaborate with the Littorina team I am currently a Research Fellow at the Evogenomics section of Copenhagen University trying to figure out how endangered birds species have lost genetic diversity in the last few hundred years using historical and modern genomes.

Olga Ortega-Martinez


Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


I work in Professor Johannesson’s research group where I am involved in the optimisation of diverse nucleotide protocols and development of DNA libraries for different organisms under the evolutionary scope, including Littorina saxatilis and L. fabalis and Fucus vesiculosus.

I am also working with the brittle star Amphiura filiformis. I have been part of developing all basic expression analysis techniques in this organism and I am now the coordinator of the genome sequencing initiative for A. filiformis as part of CeMEB at Göteborgs Universitet.

Marina Panova


Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


I started to work with Littorina snails already during my BSc and MSc studies at St. Petersburg State University, looking at the behaviour and ecology of the snails. In my PhD at the University of Gothenburg I used population genetics approaches to study evolution of the Swedish Crab and Wave ecotypes, after which I gradually moved to phylogeography, gene expression, population genomics and finally, the de novo genome project for Littorina saxatilis. My main research focus is on how genes and genomes change in the process of adaptation and speciation, and what genomic features may facilitate those processes. At the gene level, I am looking at the evolution of a few candidate genes that are probably under strong divergent selection in the snails, such as aspartate aminotransferase in L. saxatilis and arginine kinase in L. fabalis. At the genome scale, I am working with the whole genome annotation and annotation of genes that show sequence-level and/or expression-level variation between the ecotypes. Recently, I became interested in metabarcoding, metagenomics and eDNA approaches. In connection to Littorina, I am conducting a project on microbiomes associated with the snail ecotypes.

Samuel Perini

PhD student

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


In my opinion, nature is the ultimate puzzle and there is a part of this puzzle that more than the others has drawn my attention. This is where evolutionary processes such as population history, natural and sexual selection interact and potentially drive the origin of new species, an area of research called speciation. In order to collect and (re)arrange these pieces of evolution, I am using statistical and genetic tools on large datasets which can only be produced by a team of great researchers like the one formed by the Littorina people. As a member of this stimulating group, my aim is to investigate the mating behaviour and fertilisation in the intertidal snail, Littorina saxatilis, an excellent case study to understand the role of sexual reproduction during adaptation to different habitats and speciation. I am also looking into the genetics of this organism to assess whether small changes of the DNA sequence can be diagnostic to explain the evolution of this species.

Marina Rafajlovic

Assistant Professor

Department of Marine Science, University of Gothenburg, Sweden


I am mostly interested in the mechanisms of speciation, evolution of species’ ranges and the evolutionary (dis)advantages of sexual reproduction. I do not list these as three separate topics in evolution – simply because they are all highly entangled. In connection to this, I’ve been asked several times: “Which of these three topics is your favorite?”, and I would usually reply with: “Which three topics? I mentioned only one.” Having a background in Physics, my research method involves mathematical modelling and individual-based computer simulations informed by, and/or tested by empirical genetic data. The models I use are either general and conceptual, or specifically tailored to account for life-history characteristics of a species of interest. The particular species for which I have been developing models so far include, among others, the marine snail, Littorina saxatilis, brown macroalgae Fucus radicans and Fucus vesiculosus, isopod Idotea balthica, as well as humans. An important component of my research is tight collaboration with many excellent empiricists, bioinformaticians and theoretical biologists (not least within the “Littorina group”). Many of the collaborations I have today were established through the Centre of Marine Evolutionary Biology (CeMEB;

Photo: Hasselblad Foundation.

Francesca Raffini

Postdoctoral researcher

Animal and Plant Sciences, University of Sheffield, UK


I am broadly interested in natural sciences, particularly biology and understanding the amazing diversity we can observe in Nature. My research experience has revolved around understanding how biological and environmental processes within and among populations or species produce biodiversity and adaptations, and how to preserve them.

Adaptation and speciation are key processes that determine biological diversity and its distribution in space and time. Speciation requires the evolution of barriers to gene flow between diverging populations. The mechanisms underlying these processes are often unclear, particularly when they occur under gene flow. I am currently focusing on Littorina saxatilis, an ideal study system to address this conundrum. This marine snail shows repeated adaptive divergence between two ecotypes associated with different rocky shore habitats: “crab”, inhabiting boulder fields exposed to crab predation, and “wave”, living on cliffs subjected to dislocation by wave. They are morphologically and behaviourally distinct and adapted to their specific micro-environment (crab/wave exposure), but hybridize where the two habitats overlap. Hybrid zones are particularly useful to identify genomic loci under selection, clarify the relationship between phenotype, genotype, environment and fitness, and the mechanisms underlying (adaptive) divergence. These findings shed light on the factors and interactions that promote speciation-with-gene-flow in nature.

Suda Parimala Ravindran

Postdoctoral Researcher

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden

I am interested in understanding how snails adapt to contrasting habitats on the Swedish coast. For this, I use population genomics approaches to identify candidate genes that shape local adaptation at both regulatory and sequence level.

James Reeve

PhD student

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


I am researching the inversions we find in Littorina saxatilis to shed more light on their origins and function. My research is divided into three main projects; 1) determining the phenotypic effects of genetic candidates for local adaptation inside the inversions, 2) determining the age and origin of the inversions, and 3) developing a theoretical model that explains why inversions remain polymorphic in populations.

Sean R Stankowski

Postdoctoral Research Associate

IST Austria, Klosterneuburg, Austria


I am broadly interested in speciation—the evolution of reproductive isolation between populations. Reproductive isolation (RI) is critical to the origin and maintenance of biodiversity because it allows organisms to adapt to different ecological niches while living together in the same areas. Despite being a major focus of research since Darwin, there is still much to learn about how and why speciation happens. Some key questions that I address include: (i) what are the environmental and genetic conditions that promote speciation, (ii) what is the genetic and genomic basis of barriers to gene flow, and (iii) how does geography contribute to the speciation process? I address these questions using a range of tools including classical genetics, cutting edge genomics and field and laboratory experiments.

Anja M Westram

Postdoctoral fellow / Guest professor

IST Austria, Klosterneuburg, Austria; Nord University, Bodø, Norway


I am an evolutionary biologist studying processes generating biological diversity – adaptation and speciation – and particularly their genomic basis and spatial patterns. For that, I combine field surveys, morphological and behavioural phenotyping, analyses of various genomic data sets, and computer simulations. I use Littorina saxatilis ecotypes as a model system. In particular, I am interested in parallel evolution – a process where the same trait evolves repeatedly in the same direction in independent populations. L. saxatilis is ideal for studying this process, as numerous parallel hybrid zones exist across Europe. Studying parallel evolution is important as it allows for insights into the predictability and repeatability of evolution. I am currently particularly focusing on the role of chromosomal inversions in parallel evolution.

I am also working on a theoretical study aiming to understand parallel evolution in greater detail. In particular, I am interested in the origin of genomic variation that makes parallel evolution possible – does it emerge from new mutation, gene flow, or variation that has long been segregating within populations? To answer this question, I am combining mathematical and simulation approaches with empirical genomic data.

Meghan L Wharton

Research Technician

Animal and Plant Sciences, University of Sheffield, UK


I am broadly interested in evolutionary theory and behavioural ecology of marine animals, in particular sensory ecology and its links to behaviour. As a research technician in the Butlin group, I have been largely involved in fieldwork carried out on the rocky shore on the Galician coast. This work is aimed at testing hypotheses about how local adaptation and habitat choice contribute to speciation between the crab and wave ecotypes of the rough periwinkle Littorina saxatilis. These ecotypes are associated with distinct micro-environments in the intertidal zone and are thought to hybridise within the middle shore. I am currently involved in analysing data from mark-recapture experiments to characterise patterns of movement after relocation (i.e. up-shore, down-shore), and to test if habitat choice may contribute to reproductive isolation.

Zuzanna B Zagrodzka

Research Technician

Animal and Plant Sciences, University of Sheffield, UK


I have been part of the Littorina group since 2015 – at the beginning working as a Research Technician for several months at the Tjärnö Marine Research Station and now for the last 3 years in Sheffield. Most of my time I am responsible for planning and organising laboratory work and fieldwork. Recently I have started to analyse RNAseq data to identify female reproductive genes or differentially expressed regions which contribute to reproductive isolation between Littorina saxatilis and Littorina arcana. I am always keen to learn and try new protocols and learn new skills.

Former members

Andrea Cabrera

Research assistant

Department of Marine Science at Tjärnö, University of Gothenburg, Sweden


As part of the Littorina team, I work with marine snails of the genus Littorina as models for studies of local adaptation, hybrid zones and speciation. Currently a big emphasis is on ecotype formation and the evolution of barriers to gene exchange in L. saxatilis. Since this species occurs in various ecotypes it is of interest to investigate the different adaptations to crab predation and wave action found across their distribution. I assist on experiments investigating natural selection, dispersal and mating of these marine snails. Some of my duties include field collection, manipulation and dissection of snails, behavioural observations, image analysis as well as DNA extraction.