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Active dispersal is driven by extrinsic and intrinsic factors at the three stages of departure, transfer and settlement. Most empirical studies capture only one stage of this complex process, and knowledge of how much can be generalized from one stage to another remains unknown. Here we use genetic assignment tests to reconstruct dispersal across 5 years and 232 habitat patches of a Glanville fritillary butterfly ( Melitaea cinxia ) metapopulation. We link individual dispersal events to weather, landscape structure, size and quality of habitat patches, and individual genotype to identify the factors that influence the three stages of dispersal and post-settlement survival. We found that nearly all tested factors strongly affected departure probabilities, but that the same factors explained very little variation in realized dispersal distances. Surprisingly, we found no effect of dispersal distance on post-settlement survival. Rather, survival was influenced by weather conditions, quality of the natal habitat patch, and a strong interaction between genotype and occupancy status of the settled habitat patch, with more mobile genotypes having higher survival as colonists rather than as immigrants. Our work highlights the multi-causality of dispersal and that some dispersal costs can only be understood by considering extrinsic and intrinsic factors and their interaction across the entire dispersal process.

Background Microbes play a role in their host's fundamental ecological, chemical, and physiological processes. Host life-history traits from defence to growth are therefore determined not only by the abiotic environment and genotype but also by microbiota composition. However, the relative importance and interactive effects of these factors may vary between organisms. Such connections remain particularly elusive in Lepidoptera, which have been argued to lack a permanent microbiome and have microbiota primarily determined by their diet and environment. We tested the microbiome specificity and its influence on life-history traits of two colour genotypes of the wood tiger moth (Arctia plantaginis) that differ in several traits, including growth. All individuals were grown in the laboratory for several generations with standardized conditions. We analyzed the bacterial community of the genotypes before and after a reciprocal frass (i.e., larval faeces) transplantation and followed growth rate, pupal mass, and the production of defensive secretion. Results After transplantation, the fast-growing genotype grew significantly slower compared to the controls, but the slow-growing genotype did not change its growth rate. The frass transplant also increased the volume of defensive secretions in the fast-growing genotype but did not affect pupal mass. Overall, the fast-growing genotype appeared more susceptible to the transplantation than the slow-growing genotype. Microbiome differences between the genotypes strongly suggest genotype-based selective filtering of bacteria from the diet and environment. A novel cluster of insect-associated Erysipelotrichaceae was exclusive to the fast-growing genotype, and specific Enterococcaceae were characteristic to the slow-growing genotype. These Enterococcaceae became more prevalent in the fast-growing genotype after the transplant, which suggests that a slower growth rate is potentially related to their presence. Conclusions We show that reciprocal frass transplantation can reverse some genotype-specific life-history traits in a lepidopteran host. The results indicate that genotype-specific selective filtering can fine-tune the bacterial community at specific life stages and tissues like the larval frass, even against a background of a highly variable community with stochastic assembly. Altogether, our findings suggest that the host's genotype can influence its susceptibility to being colonized by microbiota, impacting key life-history traits.

Childhood fractures are common injuries, but the underlying risk factors arising from the prenatal environment or genetics are not well studied. It is not clear why certain children, without bone-affecting diseases, suffer a larger number of fractures than others. The external reasons, such as hobbies and nutritional issues, explain only part of the difference, particularly among young children. Maternal smoking and alcohol consumption during pregnancy are known to cause detrimental effects to the developing fetus. The purpose of this study is to investigate the possible association of these habits with childhood fractures. In addition, the birth weight and birth length of a child have also been shown to reflect the intrauterine conditions; therefore, the association of these parameters to the pediatric fractures was evaluated in this thesis. We also aimed to examine whether there would be genetic loci associated with fractures in children before school age by using a genome-wide association study. The study material included the Northern Finland Birth Cohort 1986, which is a comprehensive pregnancy-birth cohort that includes all women with the expected date of delivery between July 1985 and June 1986, and their live-born offspring from the two northernmost provinces of Finland. The fracture data was acquired from the National Hospital Discharge Register. We found that maternal smoking during pregnancy was associated with 1.83-fold (95% CI 1.06–3.02) increase and the prenatal alcohol consumption was associated with 2.22-fold (CI 1.09–4.12) increase in the offspring’s risk of suffering an inpatient treated bone fracture before school age. We did not find a significant association between the fracture risk and birth weight or birth length. The genome-wide association study (GWAS) revealed one genetic locus (SNP rs112635931) with significant association (p = 7.28x10-9) to fractures and six loci with suggestive association. Tiivistelmä Murtumat ovat yleisiä vammoja lapsuudessa, mutta niiden genetiikasta tai raskaudenaikaisista olosuhteista johtuvat taustatekijät ovat huonosti tunnettuja. On epäselvää, miksi osa luustoltaan terveistä lapsista murtaa luunsa useammin kuin toiset. Vaikka lapsuuden murtumariskiin vaikuttavat mm. ravitsemus ja harrastukset, eivät ulkoiset tekijät kuitenkaan täysin selitä eroa etenkään pienillä lapsilla. Äidin raskaudenaikaisen tupakoinnin ja alkoholin käytön tiedetään aiheuttavan kehittyvälle sikiölle vakavia haittoja. Tämän tutkimuksen tavoitteena oli selvittää, onko äidin raskaudenaikaisella tupakoinnilla tai alkoholin käytöllä yhteyttä lapsuusajan murtumiin. Syntymäpainon ja -pituuden on myös havaittu heijastavan kohdunsisäisiä olosuhteita, joten myös näiden parametrien yhteyttä lapsuusajan murtumiin tutkittiin. Halusimme myös selvittää genomin laajuisella assosiaatioanalyysilla, löytyykö aineistosta lapsuusajan murtumiin assosioituvia geneettisiä lokuksia. Tutkimuksen aineistona käytettiin Pohjois-Suomen syntymäkohortti 1986:sta, joka sisältää kaikki Oulun ja Lapin läänin alueella asuneet naiset, joiden laskettu aika oli heinäkuun 1985 ja kesäkuun 1986 välillä, sekä heidän elävänä syntyneet jälkeläisensä. Murtumatiedot saatiin terveydenhuollon hoitoilmoitusrekisteristä. Tutkimustemme tulosten valossa äidin raskaudenaikainen tupakointi assosioitui 1.83-kertaiseen (95% CI 1.06–3.02) murtumariskiin ja alkoholinkäyttö 2.22-kertaiseen (CI 1.09–4.12) murtumariskiin alle kouluikäisillä lapsilla. Lapsen syntymäpainolla ja -pituudella ei havaittu tilastollisesti merkitsevää yhteyttä murtumiin. Genomin assosiaatioanalyysi paljasti yhden geneettisen lokuksen (SNP rs112635931), joka assosioitui merkitsevästi (p = 7.28x10-9) lapsuuden murtumiin ja kuusi lokusta, jotka eivät yltäneet tilastolliseen merkitsevyyteen, mutta viittasivat mahdolliseen yhteyteen.

The study of polymorphic immune genes in host populations is critical for understanding genetic variation in susceptibility to pathogens. Controlled infection experiments are necessary to separate variation in the probability of exposure from genetic variation in susceptibility to infection, but such experiments are rare for wild vertebrate reservoir hosts and their zoonotic pathogens. The bank vole (Myodes glareolus) is an important reservoir host of Borrelia afzelii, a tick-borne spirochete that causes Lyme disease. Bank vole populations are polymorphic for Toll-like receptor 2 (TLR2), an innate immune receptor that recognizes bacterial lipoproteins. To test whether the TLR2 polymorphism influences variation in the susceptibility to infection with B. afzelii, we challenged pathogen-free, lab-born individuals of known TLR2 genotype with B. afzelii-infected ticks. We measured the spirochete load in tissues of the bank voles. The susceptibility to infection with B. afzelii following an infected tick bite was very high (95%) and did not differ between TLR2 genotypes. The TLR2 polymorphism also had no effect on the spirochete abundance in the tissues of the bank voles. Under the laboratory conditions of our study, we did not find that the TLR2 polymorphism in bank voles influenced variation in the susceptibility to B. afzelii infection.

Gene expression is highly plastic, which can help organisms to both acclimate and adapt to changing environments. Possible variation in gene expression among individuals with the same genotype (among clones) is not widely considered, even though it could impact the results of studies that focus on gene expression phenotypes, for example studies using clonal lines. We examined the extent of within and between clone variation in gene expression in the earthworm Dendrobaena octaedra, which reproduces through apomictic parthenogenesis. Five microsatellite markers were developed and used to confirm that offspring are genetic clones of their parent. After that, expression of 12 genes was measured from five individuals each from six clonal lines after exposure to copper contaminated soil. Variation in gene expression was higher over all genotypes than within genotypes, as initially assumed. A subset of the genes was also examined in the offspring of exposed individuals in two of the clonal lines. In this case, variation in gene expression within genotypes was as high as that observed over all genotypes. One gene in particular (chymotrypsin inhibitor) also showed significant differences in the expression levels among genetically identical individuals. Gene expression can vary considerably, and the extent of variation may depend on the genotypes and genes studied. Ensuring a large sample, with many different genotypes, is critical in studies comparing gene expression phenotypes. Researchers should be especially cautious inferring gene expression phenotypes when using only a single clonal or inbred line, since the results might be specific to only certain genotypes. peerReviewed

Independent of genotype, increased spacing results in increased branch diameter of Scots pine (Pinus sylvestris L.), but on different levels for different genotypes. Frequency of defects like spike knots and crooked stems are under stronger genetic than silvicultural control. Simultaneous improvement of rate of growth and timber properties is feasible. Deteriorating of both factors can happen rapidly at a negative selection. This needs consideration when selecting seed trees for natural regeneration. A defect like stem cracking of Norway spruce (Picea abies (L.) Karst.) only manifests itself under drought stress when certain genetic and environmental prerequisites are present, like high fertility and wide spacing. This emphasize the fact that new silvicultural methods may reveal genetic weaknesses.

The paper discusses the theoretical basis of quantitative analysis of the effect of genotype and environment in forest trees. Perhaps the main problem in the understanding of the laws of intrapopulation variability of the species of woody forest plants is the study of the structure of their populations. It may be characterized by a number of parameters. The intrapopulation variability of quantitative characteristics appears as a result of environmental and genetic factors, but to determine the relative weight of these factors in a concrete case is not easy. The study of the structure of a population by its quantitative characteristics has a wider task: to establish the relevance of the hereditary differences of the individuals of a population. Also, the differences caused by diverse growth conditions and how they are reflected in the level of general phenotypic variability of the quantitative characteristics in a given population has to be identified. The author gives examples of assessment of heritability in forest trees. The PDF includes a summary in Finnish.

Background In nature, organisms are commonly coinfected by two or more parasite strains, which has been shown to influence disease virulence. Yet, the effects of coinfections of environmental opportunistic pathogens on disease outcome are still poorly known, although as host-generalists they are highly likely to participate in coinfections. We asked whether coinfection with conspecific opportunistic strains leads to changes in virulence, and if these changes are associated with bacterial growth or interference competition. We infected zebra fish (Danio rerio) with three geographically and/or temporally distant environmental opportunist Flavobacterium columnare strains in single and in coinfection. Growth of the strains was studied in single and in co-cultures in liquid medium, and interference competition (growth-inhibiting ability) on agar. Results The individual strains differed in their virulence, growth and ability for interference competition. Number of coinfecting strains significantly influenced the virulence of infection, with three-strain coinfection differing from the two-strain and single infections. Differences in virulence seemed to associate with the identity of the coinfecting bacterial strains, and their pairwise interactions. This indicates that benefits of competitive ability (production of growth-inhibiting compounds) for virulence are highest when multiple strains co-occur, whereas the high virulence in coinfection may be independent from in vitro bacterial growth. Conclusions Intraspecific competition can lead to plastic increase in virulence, likely caused by faster utilization of host resources stimulated by the competitive interactions between the strains. However, disease outcome depends both on the characteristics of individual strains and their interactions. Our results highlight the importance of strain interactions in disease dynamics in environments where various pathogen genotypes co-occur. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-0922-2) contains supplementary material, which is available to authorized users.