Ilkka Hanski's research while affiliated with University of Helsinki and other places
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Publications (367)
It has been hypothesised that the 2‐year oscillations in abundance of Xestia moths are mediated by interactions with 1‐year Ophion parasitoid wasps. We tested this hypothesis by modelling a 35‐year time series of Xestia and Ophion from Northern Finland. Additionally, we used DNA barcoding to ascertain the species diversity of Ophion and targeted am...
Tropical forests, which harbor high levels of biodiversity, are being lost at an alarming speed. Madagascar, a biodiversity hotspot, has lost more than half of its original forest cover. Most of the remaining forests are small fragments of primary and secondary forest with differing degrees of human impact. These forests, as well as coffee and frui...
Inbreeding is common in nature, and many laboratory studies have documented that inbreeding depression can reduce the fitness of individuals. Demonstrating the consequences of inbreeding depression on the growth and persistence of populations is more challenging because populations are often regulated by density‐ or frequency‐dependent selection an...
Background:
Sufficient exposure to natural environments, in particular soil and its microbes, has been suggested to be protective against allergies.
Objective:
We aim at gaining more direct evidence of the environment-microbiota-health axis by studying the colonization of gut microbiota in mice after exposure to soil and by examining immune stat...
Empirical studies have shown that, unlike species with specialized resource requirements, generalist species may benefit from habitat destruction. We use a family of models to probe the causes of the contrasting responses of these two types of species to habitat destruction. Our approach allows a number of mechanisms to be switched on and off, ther...
Significance
Urban, Westernized populations suffer extensively from noncommunicable diseases such as allergies. However, the overlapping effects of living environment and lifestyle are difficult to separate. Intriguingly, also our fellow animals, dogs, suffer from analogous diseases. Therefore, we suggest that pet dogs, sharing their environment an...
In western societies, the majority of children are nurtured in daycares. About 80% of 3-5 year-old children attend formal child care in OECD-countries [1]. As children spend daily a large proportion of their time in daycares, their practices can have an important contribution to the overall exposure of children to natural environments. This can be...
Dispersal is important for determining both a species ecological processes, such as population viability, and its evolutionary processes, like gene flow and local adaptation. Yet obtaining accurate estimates in the wild through direct observation can be challenging or even impossible, particularly over large spatial and temporal scales. Genotyping...
The quality of the forest landscape was calculated in eight different forest areas in southern Finland. A nonlinear response of the fraction of the suitable habitat occupied is detected when the quality of the landscape decreases. There might therefore be critical threshold values for the persistence of the species in forest landscapes (see T. Pakk...
Number of male and female individuals genotyped for each population (Åland, Gotland, Öland, Saaremaa, and Uppland).
In the main experiment (2009) and the pilot experiment (2007), and number of individuals included in each PCA1 (larval and pupal traits only), PCAM (male adult traits only) and PCAF (female adult traits only).
Values of developmental PC1-2 for the different genotypes of the two SNPs c50_est:735A>G and c50_est:824A>G in the Hemolymph proteinase-5 gene.
Sample size for each category is given by the number at the top of the graph. Heavy horizontal lines represent median values, boxes give interquartile ranges, whiskers give minimum and maximum values, dots...
Values of developmental PC1-1 for the different genotypes of the SNP hsp_4:106G>A in the Heat shock protein 70kDa gene.
Sample size for each category is given by the number at the top of the graph. Heavy horizontal lines represent median values, boxes give interquartile ranges, whiskers give minimum and maximum values, dots represent outliers.
Pearson correlation matrices for the larval and pupal traits, the adult male traits and the adult females traits.
Values are Pearson correlative values (R) and asterisks denote significance at the 0.05 (*), 0.01 (**) and 0.001 (***) levels. The Bonferroni alpha values were corrected for 27, 15 and 91 correlations, respectively.
Eigen values, cumulative proportion of variance value and component loadings for the four first principal components of the principal component analysis performed on the larval and pupal traits.
Highest values from each PCA appear in bold for easier visualization of the results.
Details of statistical analyses showing significant results, including statistical models used for each trait, as well as the explanatory variables included in the models.
Models of inheritance are given within brackets as Dominant, Recessive or Additive. Both main effects and interactions are reported. “NS” stands for non-significant.
Minimum allele frequency (MAF), and minor allele for the 49 SNPs genotyped.
Each Pgi locus was genotyped twice. SNPs tagged with “(f)” failed our quality criteria, while SNPs tagged with “(*)” were genotyped for the 2007 pilot study. HWE, Hardy Weinberg Equilibrium; MAF, Minimum Allele Frequency; Gen, Genotyping; Homoz, Homozygote. Aland (AL) and U...
Details of the genotyping quality for the 49 SNPs genotyped. (f): SNPs that failed the quality criteria.
Each Pgi locus was genotyped twice. HW, Hardy Weinberg equilibrium; MAF, Minimum Allele Frequency; Gen, Genotyping; Homoz, Homozygote.
The 15 SNPs showing significant environment effect on allele frequency, with the type of substitution and allele frequencies.
The minimum allele frequency for each SNP is shown in bold to ease visualization of the results. Allele frequencies differences between environments were calculated using directed permutation tests (1e+6 random permutations)...
Values of male PCM1 for the different genotypes of the SNP c3917_est:386A>C in the Serine proteinase-like protein gene.
Sample size for each category is given by the number at the top of the graph. Heavy horizontal lines represent median values, boxes give interquartile ranges, whiskers give minimum and maximum values, dots represent outliers.
The five study populations and their monthly average temperatures.
(A) Map of the Baltic Sea region with five populations of the Glanville fritillary: the Uppland coastal region, and Öland, Gotland, Saaremaa and Åland Islands. (B) Average monthly temperatures (full lines) and average monthly maximum and minimum temperatures (dashed) from 1992 to 20...
Values of male PCM3 for the different genotypes of a SNP in either the Heat shock protein gene or the Hemolymph proteinase genes.
Sample size for each category is given by the number at the top of the graph. Heavy horizontal lines represent median values, boxes give interquartile ranges, whiskers give minimum and maximum values, dots represent outl...
Heatmap for allele count variation between individuals of the Glanville fritillary butterfly from four populations in the Baltic region.
Dendograms on the Y-axes show the hierarchical clustering of all samples used in the study, color coded by population of origin (ÅL, UP, ÖL and SA, in red, magenta, yellow and turquoise, respectively). The SNPs ap...
Larval development-related traits and genotypes of the SNP EU888473.1(Pgi):c.331A>C.
(A) The 5th instar larval weight (mg) for the different genotypes of samples collected in 2009. (B) The pupal weight (mg) for the different genotypes of samples collected in 2006. Sample size is given by the number above the bar. Heavy horizontal lines represent me...
Eigen values, cumulative proportion of variance value and component loadings for the three first principal components of the principal component analysis performed on the male adult traits.
Highest values from each PCA appear in bold for easier visualization of the results.
Eigen values, cumulative proportion of variance value and component loadings for the three first principal components of the principal component analysis performed on the female adult traits.
Highest values from each PCA appear in bold for easier visualization of the results.
Within the framework of adaptive dynamics we consider the evolution by natural selection of reproductive strategies in which individuals may adjust their reproductive behaviour in response to changing environmental conditions. As a specific example we considered a discrete-time model in which possible fluctuations in the environmental conditions ar...
Phylogeny can provide information about the processes that have shaped extant diversity. Here, we complement existing comparative phylogenetic methods by developing a model that couples diversity-dependent diversification rate and range dynamics. Unlike many models, we used Approximate Bayesian Computation to fit the model to the data. We validated...
Background. Adaptation to local habitat conditions may lead to the natural divergence of populations in life-history traits such as body size, time of reproduction, mate signaling or dispersal capacity. Given enough time and strong enough selection pressures, populations may experience local genetic differentiation. The genetic basis of many life-h...
Background. Adaptation to local habitat conditions may lead to the natural divergence of populations in life-history traits such as body size, time of reproduction, mate signaling or dispersal capacity. Given enough time and strong enough selection pressures, populations may experience local genetic differentiation. The genetic basis of many life-h...
Background.
Adaptation to local habitat conditions may lead to the natural divergence of populations in
life-history traits such as body size, time of reproduction, mate signaling or dispersal capacity. Given
enough time and strong enough selection pressures, populations may experience local genetic
differentiation. The genetic basis of many life-h...
The composition of human microbiota is affected by a multitude of factors. Understanding the dynamics of our microbial communities is important for promoting human health because microbiota has a crucial role in the development of inflammatory diseases, such as allergies. We have studied the skin microbiota of both arms in 275 Finnish children of f...
Supplementary Figures and Supplementary Tables
Ecologists are challenged to construct models of the biological consequences of habitat loss and fragmentation. Here, we use a metapopulation model to predict the distribution of the Glanville fritillary butterfly during 22 years across a large heterogeneous landscape with 4,415 small dry meadows. The majority (74%) of the 125 networks into which t...
Data for the 125 patch networks.
Background:
Atopic allergy has been more common among schoolchildren in Finland, as compared to Russian Karelia. These adjacent regions show one of the most contrasting socio-economically differences in the world.
Objective:
We explored changes in allergy from school age to young adulthood from 2003 to 2010/2012 in these two areas. The skin and...
The rapidly increasing body of literature on commensal microbiota has revealed a large phylotypic and functional diversity of microbes associated with vertebrates and invertebrates. In insects, the gut microbiota plays a role in digestion and metabolism of the host as well as protects the host against pathogens. In the study reported here, we sampl...
Flying insects have the highest known mass-specific demand for oxygen, which makes it likely that reduced availability of oxygen, as in hypoxia, may limit sustained flight instead of or in addition to the limitation due to metabolite resources. The Glanville fritillary butterfly (Melitaea cinxia) occurs as a large metapopulation in which adult butt...
Significance
Understanding how species respond to environmental changes is essential for comprehending their ecological and evolutionary dynamics. Changes in land use have led to widespread loss and fragmentation of many habitats, resulting in the extinction of innumerable populations and species. Here, using historical DNA samples from now extinct...
Supplementary Tables S1–S5.
Summary
1.Stable coexistence of ecologically identical species is not possible according to the established ecological theory. Many coexistence mechanisms have been proposed, but they all involve some form of ecological differentiation among the competing species.
2.The aggregation model of coexistence would predict coexistence of identical speci...
In the 1950s and the 1960s, when I was a boy, it was common in Finland for children to spend school holidays at the countryside, in one’s grandparents’ place. I was no exception. My father had left his small village on the coast of the Gulf of Finland following the war, to settle down, with my mother, in the town of Tampere some 300 km away. Starti...
Flight is essential for foraging, mate searching and dispersal in many insects, but flight metabolism in ectotherms is strongly constrained by temperature. Thermal conditions vary greatly in natural populations and may hence restrict fitness-related activities. Working on the Glanville fritillary butterfly (Melitaea cinxia), we studied the effects...
The body reserves of adult Lepidoptera are accumulated during larval development. In the Glanville fritillary butterfly, larger body size increases female fecundity, but in males fast larval development and early eclosion, rather than large body size, increase mating success and hence fitness. Larval growth rate is highly heritable, but genetic var...
The maternally transmitted bacterium Wolbachia pipientis is well known for spreading and persisting in insect populations through manipulation of the fitness of its host. Here, we identify three new Wolbachia pipientis strains, wHho, wHho2 and wHho3, infecting Hyposoter horticola, a specialist wasp parasitoid of the Glanville fritillary butterfly....
Insect flight is one of the most energetically demanding activities in the animal kingdom, yet for many insects flight is necessary for reproduction and foraging. Moreover, dispersal by flight is essential for the viability of species living in fragmented landscapes. Here, working on the Glanville fritillary butterfly (Melitaea cinxia), we use tran...
In biodiversity conservation, habitat corridors are assumed to increase landscape-level connectivity and to enhance the viability of otherwise isolated populations. While the role of corridors is supported by empirical evidence, studies have typically been conducted at small spatial scales. Here, we assess the quality and the functionality of a lar...
Climate change is known to shift species' geographical ranges, phenologies and abundances, but less is known about other population dynamic consequences. Here, we analyse spatio-temporal dynamics of the Glanville fritillary butterfly (Melitaea cinxia) in a network of 4000 dry meadows during 21 years. The results demonstrate two strong, related patt...
In a recent article in this journal, Fahrig (2013, Journal of Biogeography, 40, 1649–1663) concludes that variation in species richness among sampling sites can be explained by the amount of habitat in the ‘local landscape’ around the sites, while the spatial configuration of habitat within the landscape makes little difference. This conclusion may...
Urban living in built environments, combined with the use of processed water and food, may not provide the microbial stimulation necessary for a balanced development of immune function. Many chronic inflammatory disorders, including allergic, autoimmune, metabolic, and even some behavioural disorders, are linked to alteration in the human commensal...
1. The Glanville fritillary butterfly (Melitaea cinxia L.) has a small population (Ne ∼ 100) on the small island of Pikku Tytärsaari (PT) in the Gulf of Finland. The population has remained completely isolated for ∼100 generations, which has resulted in greatly reduced genetic variation and high genetic load (low fitness). In particular, females la...
The Finnish and Russian Karelia are adjacent areas in northern Europe, socio-economically distinct but geoclimatically similar. The Karelia Allergy Study was commenced in 1998 to characterize the allergy profiles in the two areas. Allergy prevalence had increased in Finland since the early 1960s, but the situation in Russia was unknown. The key fin...
Description of confounding factors used in Table S4.
Logistic regression model of the prevalence of atopy across the land-use gradient.
Association between atopy and the habitat gradient separately for specific IgE's to primarily indoor vs outdoor allergens.
Supplementary information on study methodology and legends for Supplementary Tables and Figures.
Distribution of atopic individuals across the land-use gradient in different data sets (study cohorts), for different ages.
Prevalence of atopy in three data sets for different IgE thresholds for defining atopy.
Environmental land-use remains a significant predictor of allergic sensitization (atopy) in the LUKAS data set after controlling for several confounding factors.
The atopy-land-use relationship and the allergy/asthma of parents, the consumption of farm milk at 1 year of age, the gender of the children, and dog ownership at 2mon of age.
Relative abundance of Proteobacteria increases along the land-use gradient for healthy individuals.
Evolution of the specific IgE antibodies to inhalant allergens with age.
Background
Western lifestyle is associated with high prevalence of allergy, asthma and other chronic inflammatory disorders. To explain this association we tested the ‘biodiversity hypothesis’, which posits that reduced contact of children with environmental biodiversity, including environmental microbiota in natural habitats, has adverse consequen...
The biodiversity hypothesis postulates that the rapid increase in the prevalence of allergies, asthma and other chronic inflammatory disorders in developed countries in the past few decades is caused by loss of biodiversity, which reduces human exposure to beneficial environmental microbes with essential immunoregulatory functions. The biodiversity...
Background:
The human commensal microbiota interacts in a complex manner with the immune system, and the outcome of these interactions might depend on the immune status of the subject.
Objective:
Previous studies have suggested a strong allergy-protective effect for Gammaproteobacteria. Here we analyze the skin microbiota, allergic sensitization...
Previous studies have reported that chromosome synteny in Lepidoptera has been well conserved, yet the number of haploid chromosomes varies widely from 5 to 223. Here we report the genome (393 Mb) of the Glanville fritillary butterfly (Melitaea cinxia; Nymphalidae), a widely recognized model species in metapopulation biology and eco-evolutionary re...
Background/Question/Methods
The role of rapid evolution in driving patterns of community structure is beginning to gain widespread acknowledgement from ecologists and evolutionary biologists alike. However, theoretical advances are now severely outpacing empirical demonstrations of such “eco-evolutionary” effects. Furthermore, these empirical dem...
We characterize allelic and gene expression variation between populations of the Glanville fritillary butterfly (Melitaea cinxia) from two fragmented and two continuous landscapes in northern Europe. The populations exhibit significant differences in their life history traits, e.g. butterflies from fragmented landscapes have higher flight metabolic...
Dispersal capacity is a key life-history trait especially in species inhabiting fragmented landscapes. Evolutionary models predict that, given sufficient heritable variation, dispersal rate responds to natural selection imposed by habitat loss and fragmentation. Here, we estimate phenotypic variance components and heritability of flight and resting...
Ambient temperature is an ubiquitous environmental factor affecting all organisms. Global climate change increases temperature variation and the frequency of extreme temperatures, which may pose challenges to ectotherms. Here, we examine phenotypic plasticity to temperature and genotypic effects on thermal tolerance in the Glanville fritillary butt...
Fitness-related life history traits often show substantial heritable genetic variation in natural populations, but knowledge of the genetic architecture of these traits is limited. In the Glanville fritillary butterfly, we measured the heritability of key life history traits in a large outdoor population cage during two years and generations, and c...
Habitat loss and climate change are rapidly converting natural habitats and thereby increasing the significance of dispersal capacity for vulnerable species. Flight is necessary for dispersal in many insects, and differences in dispersal capacity may reflect dissimilarities in flight muscle aerobic capacity. In a large metapopulation of the Glanvil...
Habitat loss and fragmentation threaten the long-term viability of innumerable species of plants and animals. At the same time, habitat fragmentation may impose strong natural selection and lead to evolution of life histories with possible consequences for demographic dynamics. The Baltic populations of the Glanville fritillary butterfly (Melitaea...
Background:
Evolutionary change in individual species has been hypothesized to have far-reaching consequences for entire ecological communities, and such coupling of ecological and evolutionary dynamics ("eco-evolutionary dynamics") has been demonstrated for a variety systems. However, the general importance of evolutionary dynamics for ecological...
Long-term observational studies conducted at large (regional) spatial scales contribute to better understanding of landscape effects on population and evolutionary dynamics, including the conditions that affect long-term viability of species, but large-scale studies are expensive and logistically challenging to keep running for a long time. Here, w...
