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  • Viivi, Virtanen (Helsingin yliopisto, 2000)
  • Kekkonen, Mari (Helsingin yliopisto, 2014)
    Systematics, phylogenetics and taxonomy are the scientific fields of species discovery, delimitation, description, classification and evolutionary history. The major task of these fields is to form meaningful groups, such as species and higher taxa, based on certain rules and characters. Species and higher taxa create the units of the Linnean hierarchic classification system, which is needed as the basis of all knowledge on biodiversity. Indeed, there is a great need for a complete classification, covering every species on earth, because all subsequent studies and applications are hindered as long as species remain undescribed. However, the estimated count of nine million species on earth, of which ca. 86% are currently unknown to science, together with the numerous threats to biodiversity pose a real challenge to taxonomy, and efficient tools and procedures are strongly needed. In order to be both effective and high-quality, the taxonomic workflow needs to be divided into different steps in the correct sequence. A sampling scheme, the choice of characters and analytical tools are dependent on the phase performed along the workflow. The main aim of Mari Kekkonen s doctoral thesis is to study and conduct different steps along this taxonomic flowchart by using various gelechioid moths as focal species. Specifically, the thesis includes four chapters: a phylogenetic examination of the superfamily Gelechioidea based on combined data of multi-locus DNA and morphology, and three studies focusing on delineation of putative species (i.e., operational taxonomic units, OTUs) based on single-locus DNA barcodes. The delineation studies cover various topics, from testing different OTU delineation methods (BIN, TCS, ABGD, GMYC) with reference species, developing criteria for discordant results and a protocol for associating short sequences from type specimens to delineated groups, to employing the methods, criteria and protocols in practice. The first chapter presents a phylogenetic hypothesis for the Gelechioidea with the best support for families to date. This was achieved mainly due to the use of both molecular and morphological data. We also provide a new family-level classification with redefined 16 families. The three OTU delineation studies revealed taxon-dependent performance within the four datasets (Finnish Gelechiinae, Australian Elachistinae, Australian Hypertrophinae, European Elachista dispunctella complex), but otherwise rather congruent results between the methods. The third chapter provides 120 putative species for poorly-known hypertrophine moths and criteria for evaluating discordant delineation results. Finally, in the last chapter, the E. dispunctella group with a high number of poorly-defined species is re-examined based on DNA barcodes from both fresh non-type and old type specimens. This doctoral thesis is a part of a long-term study of the Hypertrophinae, aiming to provide well-supported phylogeny and species boundaries for the group. The results here not only enhance the study on hypertrophines, but also offer tools to benefit the taxonomic research in general. As a result of the great challenge of taxonomy to describe all species, every new innovation to speed up the workflows without compromising the quality is of crucial importance.
  • Sohrabi, Mohammad (Helsingin yliopisto, 2012)
    This dissertation is focused on the taxonomy, phylogeny, and ecology of the vagrant, erratic and allied terricolous and saxicolous species of the genera Aspicilia A. Massal. and Circinaria Link (Megasporaceae), particularly those traditionally referred to as manna lichens . The group has previously been defined on the basis of few morphological characters. The phylogeny of the family Megasporaceae is inferred from the combined dataset of nuLSU and mtSSU sequences. Five genera Aspicilia, Circinaria, Lobothallia, Megaspora, and Sagedia are recognized. Lobothallia is sister of the four other genera, while Aspicilia and Sagedia form the next clade. All these genera have small asci with eight spores. Circinaria is a sister genus of Megaspora, and these two have in common asci with (1 4) 6 8 large spores. Circinaria forms a monophyletic group and sphaerothallioid species form a monophyletic group within Circinaria. The presence of certain morphological characters such as pseudocyphellae, thickness of cortex and medulla layers, as well as ecological differences in sphaerothallioid species distinguish it from some other crustose species, especially those containing aspicilin and characterised by thin cortex and medulla layers, conidium length c. 6 12 µm and absence of pseudocyphellae. If sphaerothallioid species are accepted as a distinct genus, the rest of the Circinaria species would remain as a paraphyletic assemblage. Currently, the genus Circinaria includes all the sphaerothallioid species and its generic position is confirmed and accepted. Thus, it is proposed as a correct generic name also for the manna lichens described originally in other genera. Phylogeny at the species level was studied using nrITS sequence data. Traditionally, morphological characters have been used for the recognition of species. They were re-evaluated in the light of molecular data. Since characters such as vagrant, erratic and crustose growth forms proved to be misleading for the recognition of some species, a combination of several characters (including molecular data) is recommended. Vagrant growth form seems to have evolved several times among the distantly related lineages and even within a single population. The reasons behind the high plasticity in the external morphology of the sphaerothallioid Circinaria remain, however, unknown. Six new species are recognized: Aspicilia tibetica, Circinaria arida, C. digitata nom provis., C. gyrosa nom. provis., C. rogeri nom. provis., and C. rostamii nom. provis. Based on an analysis of nrITS dataset, three new erratic, vagrant and crustose species were also recognized, but these require additional study. The results also reveal that C. elmorei and C. hispida are not monophyletic as currently understood. In addition, 13 new combinations in the genus Circinaria are proposed.
  • Miettinen, Otto (Helsingin yliopisto, 2011)
    Tutkimus käsittelee kääpien sukulaisuussuhteita. Käävät ovat kantasienten (Basidiomycota) muotoryhmä, joiden itiöemien alapinta muodostuu yhteensulautuneista pilleistä. Muotoryhmänä kääpiä voi verrata vaikka puihin siinä mielessä, että käävät kuten puutkaan eivät ole samankaltaisuudestaan huolimatta kaikki sukua toisilleen. DNA:n käyttö sukulaisuussuhteiden selvittämisessä on aloittanut mullistuksen kääpien luokittelussa. Aiemmin käytetty, itiöemien ominaisuuksiin perustunut luokittelu on osoittautunut keinotekoiseksi sukulaisuussuhteiden kannalta. Tutkimuksessani syvennyttiin useamman kääpäsuvun polveutumishistoriaan hyödyntäen DNA:ta ja perinteisiä menetelmiä. Tutkimuksen keskeisimmät tulokset liittyvät sitkokääpien sukuun (Antrodiella). Tämä noin 70 lajia sisältävä suku osoittautui rikkonaiseksi - sitkokääpiin luetut lajit kuuluvat kahteen sienilahkoon ja oikesti vähintään 13 sukuun. Tutkimuksessa löytyi kaksi Suomelle uutta sitkokääpää, leppikääpä (A. ichnusana) ja nipukkakääpä (A. leucoxantha). Uudet suvut kuvattiin Suomessa esiintyville sirppikääville (Sidera) ja talikääville (Obba). Uusi kääpäsuku ja -laji kuvattiin myös Indonesiasta (Sebipora aquosa). Valtaosa sitkokääpiin luetuista lajeista kuuluu orakarakoiden heimoon (Steccherinaceae), joka rajattiin tässä tutkimuksessa uudelleen. Heimoon kuuluvat mm. karakäävät (Junghuhnia) ja orakasmaiset orakarakat (Steccherinum). Sen sisällä selvitettiin kääpien ja orakkaiden sukulaisuussuhteita. Perinteisesti käävät ja orakkaat on viety eri sukuihin riippumatta niiden mikroskooppisesta samankaltaisuudesta. Tulosten valossa orakarakoiden heimossa käävät ja orakkaat pysyvät pääosin erillisissä suvuissa, mutta tästä on myös poikkeuksia (Antrodiella, Metuloidea ja Steccherinum). Lähes kaikki DNA:n perusteella määriteltävissä olevat suvut ovat tunnistettavissa itiöemien ominaisuuksiensa perusteella. Tulokset antavat eväitä kääpien luokitteluun laajemminkin osoittamalla, mitkä ominaisuudet ovat luokittelun kannalta merkityksellisiä. Tarkentunut tieto lajimäärästä ja lajien sukulaisuussuhteista hyödyttää ekologista tutkimusta sekä arvioita lajien uhanalaisuudesta. Tutkimuksen aikana luotua DNA-kirjastoa käytetään lajien tunnistamiseen. Tuloksia voidaan hyödyntää myös etsittäessä bioteknologisia sovelluksia käävistä, sillä sovellusten kannalta kiinnostavat ominaisuudet seuraavat usein sienten sukupuuta.
  • Virtanen, Laura (Helsingin yliopisto, 2015)
    Water quality in streams usually changes fast, and sensitive biological indicators are essential for monitoring these changes. Diatoms are widely used in biological stream quality assessments. However, there are temporal and spatial variations in diatom communities that may result in unreliable quality assessments. Under different kinds of environmental stressors, diatoms can produce deformed frustules. Heavy metals are among the most common causes of these teratological forms. In addition to eutrophication and organic pollution, diatoms could potentially be used for indicators of heavy metal enrichment. The aim here was to examine the interannual and intra-annual turnover of stream diatom communities. The focus of this study was on whether specific species traits and species local abundance and regional distribution affected temporal occurrence of diatom species. The study also included an examination of how stable diatom inferred stream classifications are in time and if pure spatial variation in diatoms should be considered when assessing stream water quality based on diatoms. The final aspect of the study was to determine which heavy metals, and to what extent, trigger the occurrence of deformations in diatom Achnanthidium minutissimum. Our results imply that abundant and widely distributed species with larger niches and the ability to attach to the substratum sustain persistent populations in varying environmental conditions typical for streams. The most persistent species are thus perhaps the most reliable species to be used as indicators of water quality. The stream classification based on diatoms resulted in temporally stable and statistically distinct community types. Thus, the results suggest that sampling of diatoms in every three years seems to be a reliable procedure to assess biological water quality. The investigation also revealed that study regions differ in their diatom species composition more than in their environmental features indicating that diatoms are structured not only by the local environment but also by large-scale processes, possibly related to climate, dispersal and history. As diatom species composition varies between regions, future bioassessments would benefit from regional stratification. Finally, study results indicated that two metals, copper and zinc, and a metalloid, antimony, were the most likely triggers of A. minutissimum deformations. The definition of their morphological and quantitative characteristics, along with a better taxonomic circumscription of the affected species, should allow the use of deformations as a reliable indicator of heavy metal enrichment in freshwater habitats.
  • Nevalainen, Elisa (Helsingin yliopisto, 2009)
    The actin cytoskeleton is essential for many cellular processes, including motility, morphogenesis, endocytosis and signal transduction. Actin can exist in monomeric (G-actin) or filamentous (F-actin) form. Actin filaments are considered to be the functional form of actin, generating the protrusive forces characteristic for the actin cytoskeleton. The structure and dynamics of the actin filament and monomer pools are regulated by a large number of actin-binding proteins in eukaryotic cells. Twinfilin is an evolutionarily conserved small actin monomer binding protein. Twinfilin is composed of two ADF/cofilin-like domains, separated by a short linker and followed by a C-terminal tail. Twinfilin forms a stable, high affinity complex with ADP-G-actin, inhibits the nucleotide exchange on actin monomers, and prevents their assembly into filament ends. Twinfilin was originally identified from yeast and has since then been found from all organisms studied except plants. Not much was known about the role of twinfilin in the actin dynamics in mammalian cells before this study. We set out to unravel the mysteries still covering twinfilins functions using biochemistry, cell biology, and genetics. We identified and characterized two mouse isoforms for the previously identified mouse twinfilin-1. The new isoforms, twinfilin-2a and -2b, are generated from the same gene through alternative promoter usage. The three isoforms have distinctive expression patterns, but are similar biochemically. Twinfilin-1 is the major isoform during development and is expressed in high levels in almost all tissues examined. Twinfilin-2a is also expressed almost ubiquitously, but at lower levels. Twinfilin-2b turned out to be a muscle-specific isoform, with very high expression in heart and skeletal muscle. It seems all mouse tissues express at least two twinfilin isoforms, indicating that twinfilins are important regulators of actin dynamics in all cell and tissue types. A knockout mouse line was generated for twinfilin-2a. The mice homozygous for this knockout were viable and developed normally, indicating that twinfilin-2a is dispensable for mouse development. However, it is important to note that twinfilin-2a shows similar expression pattern to twinfilin-1, suggesting that these proteins play redundant roles in mice. All mouse isoforms were shown to be able to sequester actin filaments and have higher affinity for ADP-G-actin than ATP-G-actin. They are also able to directly interact with heterodimeric capping protein and PI(4,5)P2 similar to yeast twinfilin. In this study we also uncovered a novel function for mouse twinfilins; capping actin filament barbed ends. All mouse twinfilin isoforms were shown to possess this function, while yeast and Drosophila twinfilin were not able to cap filament barbed ends. Twinfilins localize to the cytoplasm but also to actin-rich regions in mammalian cells. The subcellular localizations of the isoforms are regulated differently, indicating that even though twinfilins biochemical functions in vitro are very similar, in vivo they can play different roles through different regulatory pathways. Together, this study show that twinfilins regulate actin filament assembly both by sequestering actin monomers and by capping filament barbed ends, and that mammals have three biochemically similar twinfilin isoforms with partially overlapping expression patterns.
  • Holmala, Katja (Helsingin yliopisto, 2009)
    The composition of the carnivore community influences the different forms of inter-specific interactions. Furthermore, inter-specific interactions of carnivores have important implications for intra-guild competition, epidemiology and strategies of species-specific population management. Zoonooses, such as rabies, are diseases that can be transmitted from wildlife to people. Knowing the ecological characteristics of the species helps us to choose the right preventive actions and to time them accurately. In this thesis, I have studied how raccoon dogs Nyctereutes procyonoides, European badgers Meles meles, red foxes Vulpes vulpes and domestic cats Felis silvestris catus act as members of carnivore community, and how these interactions relate to the transmission risk of rabies. In the study area, these species form a community of medium-sized and rather generalist predators. They live in the same areas, in spatially and temporally overlapping home ranges and use the same habitats and dens and even have similar diets. However, there is no direct evidence of competition. Shared dens point to good tolerance of other species. Numerous observations of animals moving in each other’s proximity give similar clues. However, overlapping home ranges and similar habitat preferences lead to frequent inter-specific contacts, which increase the risk of possible rabies transmission. Also, the new insight of habitat use gained by this study illustrates the similar favouring of deciduous forests and fields by these sympatric medium-sized carnivores, creating a basis for contact zones, i.e. risky habitats for rabies transmission and spread. This study is so far the only simultaneous radio tracking study of raccoon dogs, badgers, foxes and cats. These results give new insight of the interactions in the carnivore community, as well as of the behaviour of each individual species. Also, these results have significant implications for the planning of rabies control. In order to reach viable management decisions, not only one or two species should be taken into consideration, but the whole community. In particular, this changes the perspective to inter-specific contacts, animal densities, densities of individuals susceptible to diseases and the magnitude of preventive actions. Rabies should be considered as a multi-vector disease, at least in Finland and the Baltic states. It is of interest for disease management to be able to model an epizootic with local parameters to reflect the real situation and also to suite best the local management needs.
  • Meier, Christoph M (Helsingin yliopisto, 2012)
    A central goal in ecology is to identify and understand causal factors that lead to the expansion or contraction of species ranges. Spatio - temporal population dynamics depend on biotic and abiotic environmental conditions, local demography, dispersal behaviour, and phenotypic variation. In particular understanding dispersal behaviour turns out to be a tough problem, because complex feedback loops between dispersal, local demography, and individual variations can arise. Furthermore, previous attempts to understand dispersal by reducing the complexity either in space or time have often resulted in a disregard of these feedbacks. The aim of this thesis was to investigate the influence of dispersal on spatio-temporal population dynamics with models and experiments that explicitly consider the multi causality of dispersal. The thesis is composed of three different studies: Firstly, for an active dispersing species, a plausible factor affecting dispersal behaviour could be personal information. Birds, for example, might gather information on future nest sites and, as a result, individuals differ in the amount and quality of information they possess for use in reaching a dispersal decision. We manipulated the information available to flycatchers (Ficedula hypoleuca) in a field experiment and we found that individuals which were longer exposed to the information altered dispersal behaviour to a greater extent, but only at a local spatial extent. Secondly, models of sex-biased dispersal rarely take space into account. With a computer simulation model, we showed that acknowledging the spatial distribution of the sexes has consequences for the evolutionary outcome of the model leading to selection of more similar dispersal behaviour among the two sexes. Thirdly, models of invasion spread rate often ignore the dependency of dispersal on environmental heterogeneity. We expanded on a reaction-diffusion model to improve this deficit and show that the invasion dynamics of an ecto-parasite (deer ked, Lipoptena cervi) is dependent on the local density of its main host, moose (Alces alces), across its Finnish range. In conclusion, these studies point at the necessity to consider interactions between dispersal and environmental variability, feedbacks between causal factor of dispersal, and realistic assumptions about space and time in order to solve the conundrum of factors determining the spatio-temporal distribution of species.
  • Keränen, Soile V. E. (Helsingin yliopisto, 2000)
  • Wahlberg, Niklas (Helsingin yliopisto, 2000)
  • Raiskila, Sanni (Helsingfors universitet, 2008)
    Three different Norway spruce cutting clones growing in three environments with different soil and climatic conditions were studied. The purpose was to follow variation in the radial growth rate, wood properties and lignin content and to modify wood lignin with a natural monolignol, coniferyl alcohol, by making use of inherent wood peroxidases. In addition, the incorporation of chlorinated anilines into lignin was studied with synthetic model compounds and synthetic lignin preparations to show whether unnatural compounds originating from pesticides could be bound in the lignin polymer. The lignin content of heartwood, sapwood and earlywood was determined by applying Fourier transform infrared (FTIR) spectroscopy and a principal component regression (PCR) technique. Wood blocks were treated with coniferyl alcohol by using a vacuum impregnation method. The effect of impregnation was assessed by FTIR and by a fungal decay test. Trees from a fertile site showed the highest growth rate and sapwood lignin content and the lowest latewood proportion, weight density and modulus of rupture (MOR). Trees from a medium fertile site had the lowest growth rate and the highest latewood proportion, weight density, modulus of elasticity (MOE) and MOR. The most rapidly growing clone showed the lowest latewood proportion, weight density, MOE and MOR. The slowest growing clone had the lowest sapwood lignin content and the highest latewood proportion, weight density, MOE and MOR. Differences between the sites and clones were small, while fairly large variation was found between the individual trees and growing seasons. The cutting clones maintained clone-dependent wood properties in the different growing sites although variation between trees was high and climatic factors affected growth. The coniferyl alcohol impregnation increased the content of different lignin-type phenolic compounds in the wood as well as wood decay resistance against a white-rot fungus, Coriolus versicolor. During the synthetic lignin preparation 3,4-dichloroaniline became bound by a benzylamine bond to β-O-4 structures in the polymer and it could not be released by mild acid hydrolysis. The natural monolignol, coniferyl alcohol, and chlorinated anilines could be incorporated into the lignin polymer in vivo and in vitro, respectively.
  • Salonen, Maiju (Helsingin yliopisto, 2012)
    Organisms have environmental requirements in order to grow and reproduce. These restrictions concerning environmental requirements lead to the overall distribution of organisms. Alterations in the environment leads to acclimatisation, changes in distribution or even extinction of a species in the specific environment. Eutrophication, increase of nutrients and consequently the general productivity level, is a global phenomenon in the aquatic environment. In the Baltic Sea, the progress of eutrophication has been observed since the 1960s. The central issue in my thesis is the shift in an environmental condition, i.e. the increase of water turbidity due to increased primary production and the effects of turbidity on predatory fish, i.e. larval pike. In general, phytoplankton-induced turbidity deteriorates the visual environment by absorbing visible light. Depending on the fish species in question, this can have positive, negative or neutral effects on predator-prey interactions. In addition to effects of water turbidity, my thesis focuses on the ramifications of the quality and quantity of prey on first-feeding larval pike in the nursery grounds of the northern Baltic Sea archipelago areas. The amount of suitable prey is important for effective growth. Rapid growth is essential for larvae, as growing larvae becomes more aware of their surroundings, and are more able to avoid contact with predators and escape attacks. The quality of zooplankton as prey is affected by community species composition, phytoplankton community composition, temperature and eutrophication for example. The quality, in turn, has a direct impact on the growth and development of planktivorous fish. Pike populations have diminished in some coastal areas of the Baltic Sea since the 1970s, and the catches have collapsed in areas where environmental changes have been considerable. My thesis included two field studies, where environmental factors (salinity, turbidity, temperature, oxygen concentration, wave exposure) and important resources (zooplankton quantity and community structure) are related to the distribution and condition of pike larvae. I also conducted two sets of experiments that focused on the effects of turbidity and food quality on prey capture and larval growth. According to my results, phytoplankton-induced turbidity has a negative effect on larval pike condition and growth. Turbidity also impacts prey capture negatively by diminishing the number of copepods captured. In my experiment the quality of prey, measured as fatty acids, was higher in the outer site than in the inner site. Both increased water turbidity and food quality affected the growth of larval pike when food quantity was kept constant. However, more sites from both inner and outer archipelago zones should be surveyed in the future to find out whether this is a trend or an outcome of this experiment. There were also other factors that affected the larval pike populations in the two areas; the density of zooplankton is higher in the inner archipelago sites compared with the outer archipelago sites while the density and condition of larval pike were decreasing towards the outer archipelago sites simultaneously with increasing exposition to pelagic circumstances. The occurrence and density of important prey species help explain the distribution of larval pike in the archipelago areas, but as larval pike do not disperse much from the spawning grounds; this is also related to adult pike spawning behaviour. The countries surrounding the Baltic Sea have made actions to diminish the amount of allochtonous nutrients entering the sea. Even though many projects have led to a decrease of these substances, the nutrient load is still quite high as the internal loading of nutrients sustains the eutrophicated and turbid conditions of the sea for a long period of time.
  • Vlieger, Leon (Helsingin yliopisto, 2010)
    When organisms compete for mates and fertilisations, the process of sexual selection drives the evolution of traits that increase reproductive success. The traits targeted by selection, and the extent to which they change, are constrained by the local environment. Sexual selection due to female mate choice can be undermined by alternative reproductive tactics (ARTs), which refers to discontinuous variation in traits or behaviours used in reproduction. As human activities are rapidly changing our planet, this raises the question how ARTs will be affected. Fish show a bewildering diversity of ARTs, which make them good model organisms to answer these questions. One example of human-induced environmental change, which is affecting aquatic ecosystems around the world, is eutrophication, the over-enrichment of water bodies with nutrients. One of its effects is decreased underwater visibility due to increases in both turbidity and vegetation density. The aims of this thesis were to investigate the effects increased turbidity and vegetation density have on an ART in sticklebacks, a fish common to marine and fresh water bodies of the Northern hemisphere. I furthermore investigated how this affected sexual selection for male size, a trait commonly under selection. I used a combination of behavioural observations in microcosms, where I manipulated underwater visibility, with collection of genetic material to reconstruct parentage of broods, and thus identify sneak fertilisations. The results show that turbidity might have weak negative effects on the frequency of sneaking behaviour, although this behaviour was rather infrequent in these experiments, which complicates firm conclusions. In dense vegetation the number of sneak fertilisations decreased slightly, as fewer nesting males sneaked, while the number of non-nesting males sneaking remained constant. The paternity analyses revealed that a significantly smaller fraction of eggs was sneak fertilised under dense vegetation. Furthermore, amongst the nesting males that sneaked, the amount of eggs sneak fertilised correlated positively with courtship success. A reduction in sneaking by these males under dense vegetation equalised the distribution of fertilisation success, in turn contributing to a decrease in the opportunity for selection. Under dense vegetation significantly more males built nests, which has also been observed in previous field studies. In a separate experiment we addressed if such changes in the proportion of nesters and non-nesters, without changes in visibility, affected the incidence of sneak fertilisation. My results show this was not the case, likely because sneaking is an opportunistic tactic shown by both nesters and non-nesters. Non-nesters did sneak proportionately more when there were many of them, which could be due to changes in the cost-benefit ratio of sneaking. As nesters can only attack one intruder at a time, the costs and risks per sneaker will decrease as the number of sneakers increases. The defensive behaviours shown by the nesters before spawning shifted to a more aggressive form of nest defence. This could be because less aggressive behaviours lose their effectiveness when the number of intruders increases. It could also indicate that the risks associated with aggressive behaviours decrease when there are fewer fellow nesters, as other studies indicate nesters are competitive and aggressive individuals. Under turbid conditions I did not detect changes in the opportunity for selection, based on fertilisation success, nor was male size under significant selection under clear or turbid conditions. More thorough analyses under densely vegetated conditions across the nesting, courtship and fertilisation stages revealed a decrease in the opportunity for selection across all stages. A reduction in sneaking by nesters contributed to this. During the nesting stage, but not during later stages, body size was under significant directional selection under sparse, but not dense vegetation. This illustrates the importance of considering all selection stages to get a complete picture of how environmental changes affect sexual selection. Leaving out certain stages or subgroups can result in incomplete or misleading results.
  • Björklund, Heidi (Helsingin yliopisto, 2015)
    Human-caused habitat changes have led to declines of many species by impairing their occurrence, reproduction and interactions with other species. In Northern Europe, intensive forestry has transformed boreal forests and worsened conditions of species dependent on old forest, but the mechanisms by which habitat changes affect species are often unknown. In my dissertation, I examined habitat changes, their effects and habitat-associated breeding performances of three declining forest-dwelling hawks, the northern goshawk (Accipiter gentilis), the common buzzard (Buteo buteo) and the honey buzzard (Pernis apivorus). These species can compete for nest sites and goshawks can also predate the buzzards. Raptors may lack nest sites in managed forests which is why their nesting has been supported by constructing artificial nests. I analysed the breeding success of the hawks in artificial nests since their benefits as a conservation measure were not previously analysed. Finally, I studied the conditions when dominant species can exclude subordinate ones in competition for suitable nest sites. According to my results, old forests have decreased and young forests increased throughout southern Finland. These changes are adverse for the goshawk whose breeding success improves when old spruce forests are more abundant and young forests scarce around their nests. Breeding performances of the common buzzard and honey buzzard were not significantly associated with habitats. However, common buzzards were reluctant to re-occupy nests surrounded by a vastness of old forest. The breeding success of the goshawk and common buzzard was lower in artificial nests than in natural ones. Thus, this measure aimed at enabling hawk breeding in managed forests seems to conflict with its conservation objectives. I discuss the possible contributing factors and directions for further investigations. Interspecific interactions with other raptors proved to be important when a subordinate hawk decided on territory occupancy. Common buzzards prefer to occupy safe territories, where threats of goshawk predation and interference competition with other raptors are small. Thus, interspecific raptors that are predators or competitors may exclude subordinate raptors from their territories, and thereby contribute to their occurrence. Adverse interactions with other raptors may even impede a subordinate raptor from fully exploiting the periodic food peaks. My dissertation shows that for each species, it is crucial to identify the most relevant spatiotemporal scales in order to identify, how external disturbances affect them most. Long-term data is of paramount importance to detect these scales.
  • Hamberg, Leena (Helsingin yliopisto, 2009)
    Although changes in urban forest vegetation have been documented in previous Finnish studies, the reasons for these changes have not been studied explicitly. Especially, the consequences of forest fragmentation, i.e. the fact that forest edges receive more solar radiation, wind and air-borne nutrients than interiors have been ignored. In order to limit the change in urban forest vegetation we need to know why it occurs. Therefore, the effects of edges and recreational use of urban forests on vegetation were investigated together in this thesis to reveal the relative strengths of these effects and to provide recommendations for forest management. Data were collected in the greater Helsinki area (in the cities of Helsinki, Vantaa and Espoo, and in the municipalities of Sipoo and Tuusula) and in the Lahti region (in the city of Lahti and in the municipality of Hollola) by means of systematic and randomized vegetation and soil sampling and tree measurements. Sample plots were placed from the forest edges to the interiors to investigate the effects of forest edges, and on paths of different levels of wear and off these paths to investigate the effects of trampling. The natural vegetation of mesic and sub-xeric forest site types studied was sensitive both to the effects of the edge and to trampling. The abundances of dwarf shrubs and bryophytes decreased, while light- and nitrogen-demanding herbs and grasses - and especially Sorbus aucuparia – were favoured at the edges and next to the paths. Results indicated that typical forest site types at the edges are changing toward more nitrophilic vegetation communities. Covers of the most abundant forest species decreased considerably – even tens of percentages – from interiors to the edges indicating strong edge effects. These effects penetrated at least up to 50 m from the forest edges into the interiors, especially at south to west facing open edges. The effects of trampling were pronounced on paths and even low levels of trampling decreased the abundances of certain species considerably. The effects of trampling extended up to 8 m from path edges. Results showed that the fragmentation of urban forest remnants into small and narrow patches should be avoided in order to maintain natural forest understorey vegetation in the urban setting. Thus, urban forest fragments left within urban development should be at least 3 ha in size, and as circular as possible. Where the preservation of representative original forest interior vegetation is a management aim, closed edges with conifers can act as an effective barrier against solar radiation, wind and urban load, thereby restricting the effects of the edge. Tree volume at the edge should be at least 225-250 m3 ha-1 and the proportion of conifers (especially spruce) 80% or more of the tree species composition. Closed, spruce-dominated edges may also prevent the excessive growth of S. aucuparia saplings at urban forest edges. In addition, closed edges may guide people’s movements to the maintained paths, thus preventing the spontaneous creation of dense path networks. In urban areas the effects of edges and trampling on biodiversity may be considerable, and are important to consider when the aim of management is to prevent the development of homogeneous herb-grass dominated vegetation communities, as was observed at the investigated edges.
  • Alho, Jussi (Helsingin yliopisto, 2010)
    One of the main aims of evolutionary biology is to explain why organisms vary phenotypically as they do. Proximately, this variation arises from genetic differences and from environmental influences, the latter of which is referred to as phenotypic plasticity. Phenotypic plasticity is thus a central concept in evolutionary biology, and understanding its relative importance in causing the phenotypic variation and differentiation is important, for instance in anticipating the consequences of human induced environmental changes. The aim of this thesis was to study geographic variation and local adaptation, as well as sex ratios and environmental sex reversal, in the common frog (Rana temporaria). These themes cover three different aspects of phenotypic plasticity, which emerges as the central concept for the thesis. The first two chapters address geographic variation and local adaptation in two potentially thermally adaptive traits, namely the degree of melanism and the relative leg length. The results show that although there is an increasing latitudinal trend in the degree of melanism in wild populations across Scandinavian Peninsula, this cline has no direct genetic basis and is thus environmentally induced. The second chapter demonstrates that although there is no linear, latitudinally ordered phenotypic trend in relative leg length that would be expected under Allen s rule an ecogeographical rule linking extremity length to climatic conditions there seems to be such a trend at the genetic level, hidden under environmental effects. The first two chapters thus view phenotypic plasticity through its ecological role and evolution, and demonstrate that it can both give rise to phenotypic variation and hide evolutionary patterns in studies that focus solely on phenotypes. The last three chapters relate to phenotypic plasticity through its ecological and evolutionary role in sex determination, and consequent effects on population sex ratio, genetic recombination and the evolution of sex chromosomes. The results show that while sex ratios are strongly female biased and there is evidence of environmental sex reversals, these reversals are unlikely to have caused the sex ratio skew, at least directly. The results demonstrate that environmental sex reversal can have an effect on the evolution of sex chromosomes, as the recombination patterns between them seem to be controlled by phenotypic, rather than genetic, sex. This potentially allows Y chromosomes to recombine, lending support for the recent hypothesis suggesting that sex-reversal may play an important role on the rejuvenation of Y chromosomes.