Browsing by department "Biovetenskapliga institutionen"

Northern aapa mires are important carbon sinks. Their CO2 exchange with the atmosphere is based on plant photosynthesis and respiration, and the decomposition of peat and other dead organic matter by microbial activity. The photosynthetic efficiency of plants depends on environmental factors and the amount and development of plant leaf area and biomass. There is not much research on the leaf area index and biomass of plants on aapa mires which makes them an interesting and important subject of research. This study investigated plant community composition, development and their effect on CO2 exchange at a northern aapa mire in Finland. The purpose of this study was to survey the biomass and leaf area index of plants within mire types and determine how they, together with water level and microbial activity, and explain the CO2 exchange between the mire and atmosphere. Another aim of this study was to construct regression models for predicting biomass and leaf area index using the plants height and coverage data. The study was conducted in summer 2014 at Halssiaapa, an aapa mire in Sodankylä. The mire was divided into oligotrophic, mesotrophic and eutrophic hummocks, lawns and hollows. The plant community species, their height and coverage were determined in early June, mid-July and mid-August. Moreover, the growth of plant groups was monitored weekly at 16 inventory squares between 6th June and 18th August. Biomass and leaf area samples were collected from different mire types in mid-July, and by the use of regression analysis, two equations were modelled for each plant group, one for predicting biomass and another for predicting leaf area index. The equations were used for predicting biomass and leaf area index for plant groups and mire types based on early June and mid-August data, and the weekly inventory squares. CO2 exchange, and factors controlling it, were measured via an eddy covariance method (measures exchange at ecosystem scale), and a closed chamber method (measures exchange from 1m2). Biomass, leaf area index, species composition, water level and soil factors (indicators of decomposer activity) were used to explain CO2 fluxes. The activity of decomposers in peat was measured via a decomposition test where litter bags containing tea or straw were placed at sampling sites on the mire. The regression models based on plant sample data explained well the biomass and leaf area indices of plant groups. The mire s overall and maximum biomass and leaf area indices were 147 g m-2 and 0,73 m2 m-2 respectively for vascular plants, and 351 g m-2 and 5,5 m2 m-2 respectively for mosses. Hollows displayed the lowest leaf area index and biomass values, whilst hummocks showed the highest values. Mesotrophic hummocks had the highest values for vascular plants and eutrophic lawns showed the highest values for mosses. Despite having a considerably higher level of biomass and leaf area index than vascular plants, Sphagnum mosses had a much lower gross photosynthetic capacity. Plant communities on lawns and hummocks with an abundancy of sedges (Cyperaceae) had a higher gross photosynthetic capacity and respiration level than plant communities in hollows. Factors leading to increased respiration were increasing vascular leaf area index, release of carbon from straw (indicating decomposer activity), decreasing water level (drier peat) and carbon content in surface peat. Factors leading to increased gross photosynthetic capacity were increasing vascular leaf area index, decreasing water level and decreased straw mass in surface peat (indicating decomposer activity). Temperature and PAR (Photosynthetically Active Radiation) explained 25 % of the variation in gross primary production and 39 % in respiration. The other environmental factors explained 55 % of the residual variation in gross primary production and 78 % in respiration. The mire s gross primary production showed highest increase rate in June and reached its maximum level in early August. Mean plant biomass and leaf area index had the same growth pattern as gross primary production, reaching peak levels at the end of July. The plants Menyanthes trifoliata , Potentilla palustris, Andromeda polifolia and the functional group containing sedges and Scheuchzeria palustris, had a similar growth pattern, but no change in biomass and leaf area index of Betula nana and Vaccinium oxycoccos was detected during the growing season. The models constructed in this study for predicting biomass and leaf area index can be used at Halssiaapa and other nearby aapa mires. Plant surveying and CO2 exchange measurements will be continued at the site in future. Longterm changes in plant community species and CO2 exchange can be researched by comparing results from year 2014 with in coming summers.

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease with poorly understood pathogenesis. It is characterized by abnormal remodelling of pulmonary vasculature due to uncontrolled apoptosis and proliferation of endothelial (ECs) and smooth muscle cells (SMCs) in vascular wall. In severe PAH pulmonary ECs exhibit hyperproliferative and apoptosis resistant phenotype contributing to the formation of neointima and development of plexiformic lesions. Structural changes promote occlusion of vascular lumen, and thus, increase in pulmonary vascular resistance. To date we lack efficient therapy to prevent vascular remodelling and restore normal vascular function in PAH. Purinergic signalling is potential modulator of pulmonary vascular homeostasis. It comprises of extracellular nucleotides, such as ATP, which signal through their receptors on cell membrane. Ectoenzymes with nucleotide hydrolyzing activity have an essential part in controlling homeostasis and physiologic concentration of extracellular nucleotides. Ectoenzyme CD39 plays a crucial role in dephosphorylating ATP, which is a known mediator of inflammation, angiogenesis, thrombosis and vasoconstriction according to previous research. Aims of this project were to study the role of extracellular ATP in pulmonary endothelial dysfunction during PAH pathogenesis. The goal was to evaluate the significance of ATPases, such as CD39, in the disease process and to identify significant ATP receptors on pulmonary ECs. We utilized a previously unused strategy to monitor ATPase activity in vivo in pulmonary endothelium of rats with PAH. With this strategy we could identify changes in a time-line manner. Our results indicate that ATPase activity is significantly attenuated in ECs during disease process. Similar finding was also observed in human pulmonary EC isolated from PAH patients suggesting that loss of ATPase activity mediated increase of extracellular ATP could play a role in disease pathogenesis. Our in vitro experiments reveal that loss-of CD39 in human pulmonary ECs leads to an apoptosis resistant and hyperproliferative phenotype. We also identify that purinergic receptor P2Y11 is a critical mediator of ATP responses in these ECs. Suppression of ATP mediated P2Y11 response in apoptosis resistant PAH patient ECs restores normal EC phenotype and thus, suggests a novel therapeutic strategy for pulmonary occlusive vasculopathy.

Viime vuosikymmeninä tiedonalakohtaista oppimista on tutkittu paljon käsitteellisen muutoksen näkökulmasta. Käsitteellinen muutos tarkoittaa oppijan tietorakenteiden muuttumista tai jäsentymistä virheellisistä kohti tieteellistä mallia. Käsitteellisen muutoksen teorioiden mukaan oppijoiden aikaisempien virhekäsitysten tunteminen ja huomioiminen on keskeistä oppimisen ja opetuksen onnistumisen kannalta. Tässä tutkimuksessa selvitettiin biologian yliopisto-opiskelijoiden fotosynteesiin liittyviä virhekäsityksiä, niiden muuttumista opetustekstin lukemisen seurauksena sekä biologian pääaineopiskelijoiden ja sivuaineopiskelijoiden virhekäsitysten eroja. Suomalaisten opiskelijoiden virhekäsityksiä on aiemmin tutkittu niukasti. Tämän tutkimuksen tavoitteena oli selvittää virhekäsityksiä suomalaisten opetussuunnitelmien mukaan opiskelleilta opiskelijoilta sekä selvittää virhekäsitysten yksityiskohtaista muuttumista käsitteellisen muutoksen näkökulmasta. Tutkimuksen aineistona oli yliopiston biologian peruskurssin opiskelijoiden (n=171) vastaukset fotosynteesiä ja sen ekologista merkitystä koskeviin avoimiin kysymyksiin. Opiskelijat vastasivat kysymyksiin ennen opetustekstin lukemista, heti opetustekstin lukemisen jälkeen sekä kaksi viikkoa lukemisen jälkeen. Aineisto analysoitiin laadullisin menetelmin kuvaamalla, tyypittelemällä ja tulkitsemalla havaittuja virhekäsityksiä. Virhekäsitysten tulkinnassa hyödynnettiin tiedon ja ajattelutaitojen tasojen luokittelua. Opiskelijoilla havaittiin yhteensä 58 fotosynteesiä koskevaa selkeästi virheellistä käsitystä ja 14 puutteellista tai epämääräistä käsitystä. Virhekäsitykset liittyivät fotosynteesireaktioon, kasvien rakenteisiin, kasvin energiatalouteen ja fotosynteesin ekologiseen merkitykseen. Lähes kaikki virhekäsitykset ja puutteelliset käsitykset olivat yleisempiä biologian sivuaineopiskelijoilla kuin pääaineopiskelijoilla. Virhekäsitykset vähenivät opetustekstin lukemisen seurauksena, ja monimutkaisempia tiedon ja ajattelutaitojen tasoja ilmentävät virhekäsitykset vähenivät vähintään yhtä paljon kuin muutkin. Lukuisia virhekäsityksiä kuitenkin säilyi oikeat vastaukset antaneesta opetustekstistä huolimatta. Kaksi viikkoa opetustekstin lukemisen jälkeen osa jo virhekäsityksensä korjanneista opiskelijoista vastasi jälleen virheellisesti. Tutkimus osoittaa, että suomalaisen peruskoulun ja lukion fotosynteesin oppimista koskevat tavoitteet eivät täyty edes monen biologian yliopisto-opiskelijan kohdalla. Suomalaisilla opiskelijoilla on pitkälti samoja virhekäsityksiä kuin kansainvälisesti tehdyssä tutkimuksessa on havaittu. Fotosynteesin oppimisen kannalta keskeisin tutkimuksessa havaittu ymmärryksen puute on vaikeus ymmärtää fotosynteesin merkitys Auringon valoenergian ja ravintoketjujen energian välisenä linkkinä. Opiskelijoiden vaikeudet korjata virhekäsityksiään selittyvät käsitteellisen muutoksen prosessin haastavuudella ja hitaudella. Fotosynteesiä koskevan oppimisen edistämiseksi opetuksessa tulisi aiempaa paremmin huomioida käsitteellisen muutoksen haasteet kognitiivisesta, sosiaalisesta ja motivaatioon liittyvistä näkökulmista. Tämä tutkimus tarjoaa tietoa niistä fotosynteesin oppimista koskevista erityispiirteistä, joita ilmiön tehokkaaseen oppimiseen pyrkivän opetuksen tulee huomioida.

Lymphangiogenesis is the process that leads to the formation of lymphatic vessels from pre-existing vessels. Vascular endothelial growth factor C (VEGF-C), the ma- jor lymphangiogenic growth factor, is produced as an inactive precursor and needs to be proteolytically processed into a mature form in order to activate its receptors VEGFR-3 and VEGFR-2. A deficiency of VEGF-C during embryonic lymphangiogenesis results in embryonic lethality due to the lack of lymphatic vasculature. Hennekam lymphangiectasia-lymphedema syndrome (OMIM 235510) is in a subset of patients associated with mutations in the collagen- and calcium-binding EGF domains 1 (CCBE1 ) gene. CCBE1 and VEGF-C act at the same stage during embryonic lymphangiogenesis and their deficiency results in similar lymphatic defects. The mechanism behind the lymphatic phenotype caused by CCBE1 mutations is un- known. The aim of this study was to investigate the potential link between VEGF-C and CCBE1 that could contribute to the lymphatic phenotype. In this study, 293T cells were used to observe the effect of CCBE1 on VEGF-C pro- cessing. The co-transfection of constructs coding for CCBE1 and VEGF-C showed processing of the inactive pro-VEGF-C into the active, mature form. However, this processing was efficient only in 293T cells. When CCBE1 from 293T supernatant was purified, A disintegrin and metalloproteinase with thrombospondin type 1 motif 3 (ADAMTS3) co-purified with CCBE1. The levels of pro-VEGF-C and active VEGF-C were monitored by immunoblotting or immunoprecipitating metabolically labeled supernatant with specific antibodies or receptors followed by autoradiography. The activity of the processed VEGF-C was verified by proliferation of Ba/F3 cells stably expressing VEGFR-3/EpoR or VEGFR-2/EpoR chimeras. Furthermore, a VEGFR-3 phosphorylation assay was performed in PAE (Porcine Aortic Endotheial) cells to study details of the CCBE1-mediated regulation of VEGF-C. We found that CCBE1 increases the proteolytic processing of pro-VEGF-C, thereby resulting in increased activity of VEGF-C. CCBE1 itself has no effect on VEGF-C activity but regulates VEGF-C by modulating the activity of the ADAMTS3 protease. We also found that both pro- and mature- VEGF-C can bind to VEGFR-3 but only mature form is able to induce VEGFR-3-mediated signaling. In addition to cleaving VEGF-C, ADAMTS3 was found to directly or indirectly mediate CCBE1 cleavage. The N-terminal amino acid sequence of the ADAMTS3-processed VEGF-C confirmed that ADAMTS3 is the protease responsible for the activation of VEGF-C by 293 cells. Hence, we have identified a mechanism that regulates VEGF-C activity. This mechanism suggests the possible use of CCBE1 as a therapeutic means to treat diseases that involve the lymphatic system.

Genome wide linkage and association methods are used to map genes affecting traits with genetic predisposition. In this thesis, I compare the methods suitable for quantitative trait mapping in complex, extended pedigrees. As a case study, gene-mapping study of musical aptitude is performed with these methods. Linkage analysis methods are developed for family studies. However, only a few methods are suitable for extended families with a quantitative trait. Three linkage programs were successfully applied for such data in this study. These programs are the SOLAR, JPSGCS and KELVIN. All of these three programs are based on different methods and thus, the same calculations are not repeated. SOLAR is based on the variance components method, JPSGCS on a graphical method and KELVIN on the Bayesian method. Association analysis is also difficult to implement for large pedigrees, because it is best suited for case-control data. Fortunately, methods are extended also for family-based studies. Here, a genomic control method was used to correct for the familial relationships. The method evaluates the relatedness from the whole genome data and the association tests are corrected for the relatedness rates. This method was implemented from the GenAbel program. As a case study, these methods were applied to a musical aptitude study. The musical aptitude is here understood as an ability to perceive the melody, harmony and rhythm of music, and to recognize structures in set of sounds. These abilities were tested with Carl Seashore s tests for pitch and time and Kai Karma's test for auditory structuring. The data consists of 107 pedigrees and 93 sporadic subjects, comprising in total of 915 individuals. Each family includes 2 - 50 individuals. These individuals were genotyped with a SNP chip for over 700,00 SNPs. The linkage analyses revealed several promising loci for the musical aptitude. The best result was located in 4q12 and it was found with all of the three linkage programs. Most of the other results could also be identified with multiple programs, but some differences also occurred. However, none of the findings could be discovered with association analysis, probably due to a too small sample size.

Trichoderma reesei, an anamorph of Hypocrea jecorina, is a filamentous fungus widely used for producing industrial enzymes. T. reesei is used for both endogenous and heterogenous protein production. The optimization of the production conditions and the effects of extracellular agents to T. reesei s production and secretion capacity are crucial for economically sustainable biotechnical production. The available carbon sources, most commonly different types of sugars, have a significant effect on the production and secretion of enzymes by T. reesei. Genetic modification of the pathways through which the fungi recognizes extracellular signals could bring advancements to industrial enzyme production. Because of T. reesei s potential and use as a production strain, the species is an interesting platform for genetic modifications that would enhance the production capacities. With the current methods the genome editing of T. reesei is however slow, and introducing multiple mutations to a single strain can take years. The aim of this study is to optimize the fairly new CRISPR/Cas9 genome editing system for use in T. reesei. In the CRISPR/Cas9 method, a catalytically active Cas9 enzyme is bound to a specific locus of the genome, guided by a guide RNA and the Watson-Crick base pairing principle. Once in the RNA-guided locus, Cas9 introduces a double stranded break in the DNA, which can be repaired by the cells endogenous non-homologous end joining pathways. This repair is error prone and produces mutations to site of the double stranded break. A donor DNA is often introduced together with the Cas9 and guide RNA. This donor DNA includes sequence homology to the site of interest and allows for the use of the cells homologous repair pathways. In this case, the mutation can be better controlled, and for example the risk of chromosomal mutations is reduced. Currently the CRISPR/Cas9 system is widely used in mammalian cell studies and up to 100% mutation frequencies have been reported in yeast cells. In this study the method is optimized for use in T. reesei. To our best knowledge, the research community has not found an organism in which CRISPR/Cas9 would not function. The question mainly lies on what type of set up and component introduction is suitable for each cell type and research purpose. In this thesis, three putative and one already published genes believed to be involved in hexose sugar sensing will be deleted from a T. reesei production strain with the help of CRISPR/Cas9. The effect of these deletions will be assessed through studying the secretion and activity of endogenous cellulases with enzymatic assays. One sugar transporter that may play a part in glucose sensing was identified in this study. The deletion of this transporter caused a decrease in cellulase production and/or secretion. The three other transporters or sensors did not have a significant effect on cellulase production in spent grain extract and lactose or glucose media. It s possible that these genes are involved in the uptake and use of other carbon sources. The continuous expression of the CRISPR/Cas9 system in T. reesei proved difficult. In the continuous expression method at least one of the CRISPR/Cas9 components, the Cas9 protein or the guide RNA, is produced in the cells in vivo. Neither was achieved in this study. Instead, a fully synthetic method in which the Cas9 is transformed into the cells as a protein along with an in vitro produced guide RNA was set up and produced up to 1000 × higher mutation frequencies when compared to the traditional transformation method used for T. reesei. This study also demonstrates a simultaneous deletion of two genes in T. reesei. To the best of our knowledge, multiple simultaneous gene modifications have never been achieved in T. reesei.

The purpose of this thesis was to examine the diversity and species composition of dung beetle (Scarabaeinae) communities in degraded rainforest landscapes in southeastern Madagascar. Several studies elsewhere in the world have revealed that forest-dwelling dung beetle communities and especially large species suffer from forest degradation and fragmentation by decreased species diversity. The most important factors affecting community structure of forest-dwelling dung beetles are habitat area, connectivity and vegetation quality i.e. microclimate. The hypothesis of this study was that the situation is the same in Madagascar. As dung beetles provide several important ecosystem services, like nutrient cycling and bioturbation, loss of dung beetle diversity imposes a secondary threat to the extraordinary nature of Madagascar by decreasing the regeneration ability of vegetation. Material for the study was collected in forest fragments of different size and quality between two areas of primary tropical rainforest – Ranomafana National Park and Vatovavy mountain – in November and December 2011 and January 2012. The sampling was conducted by transects of 30–60 fish- or carrion-baited pitfall traps which were set up in 55 localities in the study area. In each locality, several variables were measured to describe the vegetation and microclimatic conditions. The variables included temperature, humidity, estimate of vegetation quality by 6 observation-based classes, vegetation density, hights of three clearly visible vegetation layers, altitude and slope steepness. In addition, connectivities were measured for the localities using GIS and a satellite image –based vegetation classification. In order to demonstrate the differences between certain localities the study sites were divided into seven zones in terms of their distance from the Ranomafana National Park, average connectivity of the transects and elevation. Altogether 4,199 individuals belonging to 24 species were collected. Six of the species are currently under identification process in the Paris Museum of Natural History. According to the preliminary results they include two species new to science. Largest numbers of species were collected from good quality fragments between Ranomafana and Vatovavy. Also, a clear transition zone in species composition was detected a few kilometers west from Vatovavy, where altitude changes sharply. The study reveals that the species assemblages in the forest fragments and degraded forest areas are surprisingly species rich. This may, however, be partly because of extinction debt, and many of the still surviving species may soon die out due to restricted dispersal possibilities. Connectivity and vegetation quality were shown to have an effect on Canthonini species richness, with less species in less connected areas and lower vegetation quality. Vegetation quality was also shown to have an impact on the proportions of species with different body length: more small and medium-sized (< 8 mm) species were found in fragments where vegetation was more degraded. In addition to revealing how rainforest fragmentation and degradation affect local communities, the study gives interesting information about the distribution of certain species of Epilissus (Scarabaeinae: Canthonini). It has been known before that four species of Epilissus show elevational differentiation in their occurrence in Ranomafana. In this study, two more species of the same genus, E. prasinus and E. emmae obscurpennis, were shown to continue this pattern in lower elevations near Vatovavy mountain, about 50 kilometers east of Ranomafana.

Genetic variation is vital for both contemporary and long-term wellbeing of populations. Whereas heterozygosity (Ho) and allelic richness (A) are commonly used to measure the level of genetic diversity in a population, effective population size (Ne) describes the speed of loss of genetic variation. Various effective population sizes are proposed as standards for safe retention of genetic variation in a Minimum Viable Population (MVP). Since the 1940s, several types of effective population size estimators have been developed. Earlier estimators relied on demographic parameters, whereas genetic estimators are based on the analysis of either one or two genetic samples from a population. All Ne estimators have their unique sensitivities and limiting assumptions, which complicate the choice of estimator, comparison of results of different studies and the assessment of the reliability of the results. Ne estimators have recently been used e.g. in the monitoring of many aquatic populations, but their reliability and comparability has not often been tested with extensive ecological and genetic data, and it is not well established how much added value they bring to the conservation of easily observable species. I tested this with an extensive dataset on the Siberian jays (Perisoreus infaustus) living in Suupohja, Finland (62°22'N, 21°30'E). The Suupohja Siberian jays form one of the few isolates of Siberian jays in Southern Finland. I utilised three demographic and three genetic Ne estimators to estimate the Ne and the Ne/N ratio in the Suupohja Siberian jays, and compared the findings to the Ho and A estimates calculated with the same data, and to various suggested MVP standards. The results showed that the ratio of effective and census population sizes (Ne/N) is close to 0.6 in the Suupohja Siberian jays. Uneven survival of offspring and population size fluctuations are the main factors in the formation of this ratio. The average genetic Ne estimate would, then, suggest a census population size of 44 % higher than the average N in the Suupohja study area. This result is probably connected to the high proportion of breeding immigrants in the data, which would cause the Ne estimates to reflect a larger genetic neighbourhood than the study area. The genetic Ne estimates also suggest that the Suupohja Siberian jays might not be able to maintain their genetic diversity in the long term if gene flow would cease due to further isolation, especially if isolation would also cause a faster demographic decline. Conservation attempts should aim at ensuring gene flow to the remaining Siberian jay isolates in Southern Finland, in order to protect them from increasing genetic uniformity and inbreeding. It is possible that while the average dispersal distances in the Siberian jay are short, occasional long-distance dispersal events have an important role in the pretention of genetic structuring in a Siberian jay population. Ne estimation based on demographic data was laborious in the case of the Suupohja Siberian jays, whereas the genetic Ne estimates showed large variation depending on year and estimation method used. Reliable estimation of Ne with genetic methods would have required information on the large-scale genetic structure of the population. In any case, Ne estimates gave a clearer picture on the genetic viability of the Suupohja Siberian jays than the Ho and A estimates, which did not indicate any decrease of genetic diversity during the study period.

Adaptive radiation is an important mechanism of evolution, which can lead to emergence of sympatric species or morphotypes. Among other biological interactions, parasitic pressure can have significant evolutionary implications for host populations by reducing the fitness of the host individuals. Parasite community structure of fishes is typically strongly dependent on both host ecology (e.g. habitat and feeding behaviour) and environmental factors (e.g. water quality and temperature). However, the relative importance of these factors for parasite-mediated speciation is not known. Also, host gender-specific differences in parasite communities can have an effect on the differentiation of host morphs. In this Master's thesis, I focused on differences in parasite communities of sympatric morphs of three-spine stickleback (Gasterosteus aculeatus) in two large Icelandic lakes, Thingvallavatn and Mývatn. In these lakes, the habitats of sympatric mud and lava morphs are the same (soft/hard bottom), but the habitat water temperatures are opposite between the lakes. In this unique system, it is thus possible to compare between the effects of host ecology and water temperature on parasite community structure and strength of parasite-mediated selection. Additionally, I studied the effect of host sex on the parasitic pressure. There is also a third stickleback morph, Nitella morph, inhabiting the cold limnetic habitats in Lake Thingvallavatn. I sampled the stickleback morphs from both lakes and identified their parasite species. I discovered a total of five parasite genera: trematodes Apatemon and Diplostomum, and cestodes Diphyllobothrium, Proteocephalus and Schistocephalus. Most of the observed parasites have negative effects on health and fitness of the host. I found more parasites in sticklebacks living in higher temperature in both lakes regardless of the morph. When comparing the cold water morphs in Thingvallavatn, parasite abundance was higher in the limnetic Nitella morph than in the shallow water lava morph. Fish gender had an effect on parasitism only in Thingvallavatn as males of both lava and Nitella morphs were more heavily infected with cestodes. Similarities in parasite communities with water temperature indicate that water temperature mainly determines parasite infections in this system instead of host ecology. As similar fish morphotypes exist in different lakes under opposite parasitic pressure, parasitism has unlikely initiated host differentiation, but differences in infection probably have emerged secondary to the ecological specialization of the morphs to different habitats. These results are among the first to tackle the key question in parasite-mediated divergent selection: at which point of the speciation process parasite communities become differentiated and thus can have an effect on speciation. However, the comparison between the cold water morphs (lava and Nitella) indicates that although water temperature seems to be the main factor controlling infections in this system, its effect may still be over ridden by host ecology. Sex-depended differences in parasitic pressure, on the other hand, are likely to reflect specific characteristics of each fish population and lake. These results suggest complex interactions between host ecology and abiotic environment, such as water temperature, in determining the parasite community structure. Hence both factors have to take into consideration when studying the role of parasites in speciation processes. In future, it is necessary to pinpoint the stage of the host speciation process when parasite infections become differentiated in replicated systems to gain comprehensive understanding of the role of parasites in adaptive radiations.

Epidermolysis bullosa (EB) is a group of hereditary skin disorders caused by mutations in the genes that code for adhesion molecules in keratinocytes. The symptoms of the disease include blisters and erosions in the skin as well as abnormalities in the mucosal membranes, nails and tooth enamel. Depending on the causative mutation the severity of the disease ranges from mild to lethal. This master s thesis was carried out in professor Hannes Lohi s canine genetics research group. It is a case study aiming to identify the genetic cause of EB present in Central Asian shepherd dogs. Furthermore, the mode of inheritance, frequency of the mutation in the breed and the effect of the mutation on the tissue were also examined. Primary research material included blood and tissue samples from a family of Central Asian shepherd dogs. Additional samples were obtained from other Central Asian shepherd dogs as well as from dogs of closely related breeds. All dogs included in this study are owned by private persons, and participation in this study was voluntary. The research methods used in this study included both wet laboratory experiments and bioinformatic in silico procedures. The genome of one affected dog was sequenced in order to identify the gene causing EB, and data from the sequencing was filtered with multiple programs according to recessive model. The model was decided after analyzing the pedigree of the affected dogs. After finding the likely causative gene the mutation was validated in a larger cohort with Sanger sequencing. Protein expression in the tissue of affected dogs was also studied using immunofluorescence staining. As a result of this study, a new mutation causing recessive dystrophic EB was identified. The mutation is specific to Central Asian shepherd dogs. Affected dogs have a homozygous mutation in the COL7A1 gene, which codes for collagen VII α1 protein. The mutation causes a premature stop codon in the mRNA sequence, which results in abnormal protein production and separation of skin layers. The frequency of the mutation allele in the sample is approximately 18 % and more than a fourth of the dogs in the sample are carriers. Based on the pedigree analysis, the mutation is relatively new and it is only found in a small population. The disease can be prevented from becoming more common in the breed with the help of a gene test, and the test will be available in the commercial MyDogDNA gene test panel.