[This new 2024 homepage replaces my old Joensuu Molecular Ecology Group (JMEG) page, which became increasingly outdated after my move to NIBIO Svanhovd in 2018. The old page can be accessed via the link in the right margin, but it will eventually be taken offline.]

Ecological and evolutionary research using genomic tools

The overarching theme of my research is to use molecular-genetic methods for studying ecological and evolutionary questions. My research foci include, for example, estimation of community composition and trophic interactions, phylogeny-based inference of niche shifts, speciation–extinction dynamics, and biogeography, analyses of population structures, and inferences of genetic diversity at the level of individuals, populations, and species. Due to the diversity my of research questions, I have flexibly applied various genetic methods and markers, with an increased emphasis on approaches based on high-throughput sequencing technologies. All studies are done in collaboration with a wide international network of other researchers (see the People and Publications pages).

Most of my works have focused on the assembly and maintenance of species-rich multitrophic food webs — how do species interact with each other, how do these interactions change through time and space, and do changes in interactions lead to the origin of new species? For such questions, the species-rich food webs composed of northern plants, plant-feeding insects, and insect parasitoids offer almost unlimited opportunities for hypothesis-based research.

The other main line of my work focuses on conservation-genetic questions related to the maintenance and practical importance of genetic diversity — how is genetic variation lost in isolated populations, and does loss of genetic diversity in endangered species matter? In these investigations, I have mainly used northern seals and their parasites as model systems.

Evolution and ecology of multitrophic resource–consumer networks

Most of the biodiversity on Earth is embedded in food webs consisting of plants, plant-feeding insects, and insect parasitoids. Both plant–herbivore and herbivore–parasitoid networks are characterized by specialized trophic interactions. This means that most insect herbivores feed on only a subset of the plants that are available in their environment, and most parasitoids attack only some of the available herbivores. Specialized feeding is in fact typical of nearly all organisms with a parasitic lifestyle, including mammalian endo- and ectoparasites and insects associated with forest fungi. Because host–parasite associations change through time, host shifts could be a general driver of speciation in numerous taxa.

My focal questions include, for example:

(1) What determines how plant-feeding insects utilize plants that are available in their environment, and how do associations between insects and plants change through time and space?

(2) Is speciation in herbivorous insects spurred by shifts among host plants, and do macroevolutionary diversification rates differ between insect groups associated with different plant taxa?

(3) Can similar effects on short- and long-term diversification be found in other systems characterized by specialized parasitic interactions, such as herbivore–parasitoid networks or food webs consisting of mammals and their parasites?

Conservation genetics

Anthropogenic overexploitation, habitat loss, and climate change reduce biodiversity at an astonishing speed around the world. Before a species goes extinct, its lowered population size will lead to erosion of intraspecific genetic diversity through inbreeding and drift. One of the most pressing questions of today is whether low genetic diversity hastens the process of extinction.

My conservation-genetic research has focused on the endangered Saimaa ringed seal, a postglacial relict subspecies endemic to Lake Saimaa in southeastern Finland. With the Saimaa ringed seal research group of the University of Eastern Finland, we have used genetic data to investigate the origin, demographic history, and population structure of the Saimaa ringed seal.

Recently, we have expanded the conservation-genetic line of research to encompass also seal parasites. Theoretically, bottlenecking and fragmentation of endangered animal populations is expected to trigger loss of species and genetic diversity also in their specialist parasites. Although parasites constitute a sizeable fraction of overall global biodiversity, the field of multitrophic conservation genetics is still in its infancy. Because of their widely different population sizes and isolation histories, northern European seals constitute an excellent model system for studying cascading diversity loss. Seals support a multitude of parasite species with divergent life histories and levels of host specificity, which facilitates comparative studies on how parasite traits determine genetic responses to bottlenecks and fragmentation in the host populations.

Non-invasive monitoring of wild animal populations

Efficient protection and management of animal populations requires information on their size, demographic structure, dietary status, and health. Obtaining all these pieces of information using traditional observational methods is work-intensive and costly. Fortunately, these problems can now in many cases be circumvented by using genetic analyses of non-invasive samples such as hair or feces, which can be collected from the field without disturbing or even seeing the animals.

Previously, we developed a microsatellite-based method for assessing breeding-site fidelity in Saimaa ringed seal females based on DNA extracted from placentas collected from pupping sites after the breeding season. In the recently started RemoTnitor project, we develop molecular-genetic methods for monitoring brown bear, moose, and reindeer populations based on fecal samples collected from the field. Our aims are to develop cost-efficient GT-seq markers for identifying individuals in the three focal species, and to refine multiplexed metabarcoding and metagenomic approaches for assessing their diet, gut microbiomes, pathogens, and parasites.