Evolutionary Ecology

The overriding aim of evolutionary ecology research is to enhance our knowledge and understanding of the dynamics of genetic, functional, ecological and evolutionary mechanisms that interactively determine past, present and future patterns of biodiversity.

The research group is a part of Linnaeus University Centre for Ecology and Evolution in Micobial model Systems.

Our research

We live in a changing world. Today, anthropogenic activities influence ecosystems and climate worldwide, and extant species face environmental changes that probably occur faster than ever before in the history of life. Evolutionary theory predicts an interactive process, whereby environmental characteristics influence patterns of genetic and phenotypic variation in natural populations, while genetic and phenotypic diversity buffer populations against stress and allow for adaptive evolution in changing environments.

Our research questions are diverse and cover different levels of biological organisation, from the influence of genetic and environmental cues on phenotypic variation among individuals, via ecological consequences of colour polymorphism, and the role of dispersal and habitat choice for population divergence, to factors influencing geographic range distributions of species. As study organisms we mainly use insects (grasshoppers, butterflies and moths) but also fish, frogs, lizards, snakes and voles.

We use a combination of field studies, experiments, genetic markers, comparative analyses, modelling and literature reviews to answer our questions. We hope that our research will contribute to an increased understanding of life, to a better protection of biodiversity, and suggest routes to increased sustainable productivity in natural and managed biological systems.

Why use animal colour patterns as a model system?

The variability of colour patterns among and within species of plants and animals provide an unusually apparent example of biological diversity. Colour pattern is a functionally important trait and there are many ways by which it can contribute to variation among individuals in lifetime reproductive success. As model systems in studies of ecology and evolution colour patterns also have generated important insights, ranging from Darwin's and Wallace's idea of evolution by natural selection, Mendel's laws of genetic inheritance, McClintock's discovery of transposable elements, Kettlewell's textbook example of selection and micro-evolution in the peppered moth, recent work on 'evo-devo', to the vast number of studies of sexually dichromatic and aposematic (i.e., warningly coloured) species illustrating the roles of sexual selection and animal communication.

Among- and within-population divergence in colour polymorphic pygmy grasshoppers

Pygmy grasshoppers (Orthoptera, Tetrigidae) provide a classic example of colour polymorphism (i.e., the occurrence together within a single population of two or more distinct colour variants, or morphs). For almost a century, intra-specific variation has been documented and genetically analyzed. Their ground colours range from black, via various shades of brown to light grey, and some morphs are monochrome while others have patterning consisting of stripes, or specks or spots of variable colours and widths. Alternative colour variants of Tetrix differ in morphology, physiology, behaviour and life-history traits. We have previously shown that morph frequencies vary among populations as well as over time within populations. The colour polymorphism in pygmy grasshoppers provides a proxy of adaptive genetic variability of the population that is directly visible to the human eye. We combine information on colour morph frequencies in natural and experimentally manipulated populations with estimates of selectively neutral genetic diversity (microsatellites and AFLPs) to clarify how environmental change, population dynamics and gene flow jointly influence patterns of intra-specific variation and the evolution of local adaptation.

Ecological and evolutionary consequences of colour polymorphism

The existence of genetic colour polymorphisms have long puzzled evolutionary biologists, because theory posits that such polymorphisms can be maintained only under a very restricted set of conditions. We use colour polymorphism also as a model system for studying evolution of adaptations, intra-population divergence and multi-trait co-evolution (phenotypic integration). Another line of investigation concerns the influence of colour polymorphism on ecological and evolutionary processes at and above the population level. Does colour polymorphism enhance colonization and establishment success, range expansions, population persistence and perhaps even speciation? Phenotypic differences among individuals within a population may reflect an underlying genetic polymorphism, developmental plasticity, or randomized phenotype switching (bet-hedging). To what extent does the underlying mechanism(s) that cause phenotypic variation affect the consequences of that same variation for population processes? The results may contribute to our understanding of evolution and retention of biological diversity at various levels of organization, and may have implications for conservation biology.

Fire melanism - effects of changing environments on genetic polymorphisms

Environmental perturbations such as forest-fires constitute natural experiments that provide excellent opportunities for investigating the ecological and genetic consequences of environmental change. Understanding the effects of such perturbations on genetic polymorphisms in natural populations is important for several reasons. (i) There is no consensus with regard to predictions from theory; some models predict that environmental fluctuations will erode the genetic variability of populations, whereas other models propose that temporal variation in selection will promote the maintenance of polymorphisms. (ii) Knowing how environmental disturbances influence the genetic composition of natural populations, in a variety of organisms, is crucial for the development of successful plans for conservation and protection of biodiversity. (iii) The study of evolution in heterogeneous environments is rich in theoretical models, but there is a scarcity of data suitable for empirical evaluation of theory. (iv) Studies of how natural populations respond to environmental disturbances are thus of interest from theoretical and evolutionary viewpoints, as well as from an applied conservation perspective.

We use colour polymorphism and fire melanism in pygmy grasshoppers as a model system to explore the influence of environmental change on genetic composition of populations and the complex interplay between population dynamics and population genetics. Questions under investigation are: How do disturbance events and environmental change influence temporal dynamics of adaptive and neutral genetic variation of populations? Is the level of genetic diversity greater in populations that inhabit disturbed and changing environments, as compared with populations in relatively stable environments? Do founder events and bottlenecks differently influence adaptive and neutral genetic diversity? What is the importance of founder group diversity for population dynamics and persistence? What is the contribution of gene flow and phenotypic plasticity to the spatiotemporal dynamics of the polymorphism?

Function and evolution of protective coloration

Animal colour patterns may offer protection from predators in different ways. Disruptive coloration may distract the observer's eye from the outline of the animal whereas cryptic resemblance may enable an animal to avoid detection by blending into the visual background of the habitat. A Conspicuous colour pattern that distinctly contrasts with the habitat may instead serve as an avoidance inducing signal or warning device. Aposematic animals use defence mechanisms such as distastefulness coupled with distinctive odours, sounds, or colour patterns to signal their unprofitable nature to potential predators. Consequently, for both cryptic and warning coloration, one would expect selection imposed by visually oriented predators to act not on colour pattern per se, but on the combination of colour pattern and other traits, such as body size and behaviour. We explore the role of such correlational selection for the function and evolution of protective coloration, using a combination of staged predator prey encounter experiments, CMR-studies in the field and phylogenetic comparative analyses. We also investigate the protective value of colour pattern polymorphism from the viewpoint of single prey individuals and from the viewpoint of groups of individuals.

Ecology and evolution of body size and population divergence in Northern pike Esox lucius

In collaboration with members of the fish ecology group we seek to: (1) quantify and describe patterns of phenotypic and genetic variation in body size and growth rate of the northern pike; (2) identify which environmental factors and mechanisms have caused the differentiation among populations; and (3) investigate the implications of local divergence for future protection, management and utilization of populations. We use populations in lakes and the Baltic Sea as a model system and combine observational and experimental approaches to address the following general questions. What is the pattern of variation in body size and growth rate within and among natural population? Are there morphological traits that can be used as reliable predictors of growth rate and age-specific body size? What is the contribution of local adaptation, gene flow and developmental plasticity to population divergence? Does admixture due to dispersal or human caused translocation of fish improve or impair population fitness and productivity? How is the size and characteristics of the Baltic Sea pike influenced by spawning migration and recruitment from freshwater streams? In view of our results, how could management strategies become modified to improve protection, recreational and commercial fishing and aquaculture?