Browsing by Subject "ecology and evolutionary biology"

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  • Lehikoinen, Petteri (Helsingin yliopisto, 2020)
    Human induced climate change will affect global biodiversity considerably. One of the most studied consequences is climate driven redistributions of species. Simultaneously, increasing land development resulting in habitat loss will add difficulties for species to adapt and redistribute under changing climate. Failing to move or adapt, species face a risk of extinction. The high latitude and high altitude species are facing increased risk of extinction because these species have limited possibilities to retreat and the warming has been faster in northern high latitudes than other regions Protected areas are likely to aid species in adapting to the changing climate by preserving high quality natural habitats where species can thrive. However, due to extensive land use and habitat degradation protection cannot always cover a sufficient amount of high quality habitat. In this case, habitat restoration can be the solution to improve habitat quality and availability, which can have positive effects on the ability of species to move and persist under climate change. The aim of this thesis is to shed light on how protected areas have been able to mitigate the negative effects of the current climate change. In addition, it studies the role of habitat quality in the processes of redistribution events. Lastly, the thesis evaluates how habitat enhancement by restoration affects the abundances of species threatened by wide-scale habitat loss and degradation. The focal species of the thesis are birds, owing to the extensive, long-term Finnish monitoring data which are unique even in a global perspective. In the first chapter, I study changes in abundance of the past five decades on the trailing range edge of northern and leading range edge of southern bird species. This study shows that protected areas help northern bird species maintain their abundances on the southern boundary of their current area of distribution, while aiding certain southern bird species spread to new territories on the northern boundary of their distribution area. This suggests that protected areas are able to slow down the northbound retreat of species, but also facilitate northward range expansions of southern species. The second chapter studies if the effect of conservation in mitigating climate driven changes observed in the first chapter increases with increasing coverage of the protected area network. The results show that in northern and central Finland the increasing protected area coverage in the landscape is indeed associated with communities that are more stable and less affected by climate driven changes. However, such effect was not found in southern Finland, where the protected area coverage was very low, and in fact could be too low to support detectable levels of community resilience against climate change. Populations and communities are shown to be more resilient to environmental changes when higher proportions of suitable high-quality habitat is available. Thus habitat quality could certainly explain the results gained in chapters I & II. The chapter III studies the effect of habitat quality on the occurrence of the white-backed woodpecker. Woodpeckers occupied more frequently the high-quality habitat patches than lower quality patches suggesting that colonization events are more and local extinctions less frequent on these sites. Thus, high-quality habitats seem to enhance the ability of species to move and persist and therefore, protection of these sites should be a priority under the redistributing outcome of climate change. Chapter IV shows that habitat quality can be further improved through restoration. Counteracting the overgrowth of wetlands rapidly increased the number of staging and breeding birds. Many waterbird species are threatened and declining due to eutrophication and overgrowth and the results show that wetland management can mitigate these negative developments. The thesis concludes that protecting high-quality habitats can mitigate climate change driven range and community changes. However, current trajectories of conservation seem to be inadequate to preserve the current biodiversity. Therefore, to meet the aims to prevent further biodiversity loss, extensive and rapid efforts to increase protected area coverage and connectivity are direly needed. The main conclusion of this thesis support these acts and the benefits this will have for preserving biodiversity in the future.
  • Meller, Laura (Helsingin yliopisto, 2015)
    Anthropogenic pressures have pushed both climate and ecosystems to the point that their stability and functioning is at risk. Halting the loss of biodiversity by 2020 is one of the goals of the European Union. Climate change has been identified as one of the key challenges for biodiversity conservation in the EU. Empirical observations of climate change impacts, predictive tools and approaches, and appropriate policy responses are developed in separate fields of research with different methodologies and cultures. My thesis aims at bringing these three aspects together to explore responses to climate change from the perspective of biodiversity in the European Union. The thesis consists of a summary and five chapters. Chapter I looks into EU biodiversity policy in light of needs arising from climate change, with a focus on bridges between climate change impacts to appropriate conservation responses and further to policy. Chapter II evaluates approaches to reducing uncertainty in conservation prioritization based on ensemble modelling of species distributions. Chapter III builds methodologically on the findings of chapter II to explore the balance between various aims of biodiversity funding in the EU and how allocations of the funds reflect those aims. Chapters IV and V explore the balance between mitigation benefits and adaptation drawbacks of bioenergy as regards biodiversity conservation. The existing EU biodiversity policy has more potential to support effective adaptation than what its current interpretation and practice allows, although there seem to be gaps that cannot be addressed with the existing policies. The numerous scientific recommendations for conservation responses to climate change mainly address species range shifts. There is a mismatch between future conservation needs and the current practice of allocating funds for biodiversity conservation in the EU. For birds of European conservation concern, climate change drives larger changes in range size than land use for short-rotation woody bioenergy. However, bioenergy was predicted to have a negative impact on a larger proportion of the species than climate. Three policy recommendations arise from my thesis. First, compliance with strategic environmental assessment and green infrastructure guidance should be ensured for biodiversity projects receiving funds from the EU Structural and Cohesion funds. Second, biodiversity project funding from the SCF funds needs to be explicitly linked to the biodiversity strategy goals and assessed from the perspective of biodiversity needs. Indicators of project success should include an indicator relevant for biodiversity. Third, mitigation of climate change is a key strategy for biodiversity conservation, as it makes effective adaptation more feasible.
  • Kvist, Jouni (Helsingin yliopisto, 2014)
    The glanville fritillary butterfly is an important ecological model species for habitat fragmentation, whose genetics was poorly understood. In order to expand the research of this butterfly species into the realm of functional genomics a lot genetic tools were developed. These tools were used to investigate the genetic basis of phenotypic traits that are important in the wild. Gene expression microarrays based on de novo assembled transcriptome were used to study expression differences between adult butterflies from newly established colonies and older colonies as well as gene expression variation among larval families reared in three thermal regimens during final larval instar. Colonization and larval development are crucially important in maintaining the metapopulation structure of glanville fritillary butterfly in the Åland. We identified gene expression differences than can explain the observed variation in the phenotypes in the natural population. We sequenced the full genome of the glanville fritillary butterfly and used this to do additional gene expression and allelic variation analysis variation from multiple populations around the baltic sea using rna sequencing (rna-seq). Flight induced gene expression changes were analyzed using butterflies from Åland islands and the small isolated Pieni Tytärsaari ("daughter island") populations in a forced flight experiment. Fragmented populations (Åland islands and Uppland) were compared to continuous populations (saaremaa and öland) in order to find common signatures of selection caused by habitat fragmentation. Together these four full-genome studies have revealed that habitat fragmentation causes selection pressure on an intricately connected set of genes and pathways that leads to a so called life history syndrome , where the butterflies that colonize new habitat patches have a distinct set of traits and associated expression differences in these traits that make them more successful in establishing new colonies.
  • Ramiadantsoa, Tanjona (Helsingin yliopisto, 2015)
    Habitat loss and fragmentation is the main culprit behind the current decline in biodiversity. The estimated current rate of extinction is two or three orders of magnitude higher than the background extinction rate. This thesis analyzes existing data and develops models to improve our understanding of the role of spatial processes in the dynamics of populations and communities. This work is focused on the features of habitat destruction that causes decline of biodiversity as well as the traits that make species vulnerable to habitat loss. First, I attempt to infer relationships between spatial heterogeneity, rate of diversification (speciation and extinction), and the dynamics of geographical ranges from a reconstructed phylogeny. I build a flexible comparative method to analyze adaptive radiation and range dynamics that extends the current models in two directions by allowing more than two regions and by assuming diversity-dependent diversification rates. In a five-region system stimulated by the biogeography of Madagascar, processes that increase and decrease diversity are strongly correlated. Therefore, it is not possible to estimate independently region-specific speciation and extinction rates, though their ratios can be successfully estimated. When applied to Malagasy dung beetles, we found that diversification rate is highest in the northern (very heterogeneous) and lowest in the southern (most homogeneous) parts of Madagascar. Thus it appears that landscape heterogeneity promotes diversification and thus biodiversity. The two other chapters investigate the consequences of habitat loss and fragmentation for generalist and specialist species. We aim to understand how generalist and specialist species respond to habitat loss and fragmentation. In particular, we ask why generalist species often increase in abundance following an intermediate level of habitat destruction. I develop a modular modeling approach that allows one to switch on and off various mechanisms as needed. This approach one to assess the marginal and joint effects of different mechanisms by comparing model outcomes. Our analyses confirm that a high level of specialization leads to high sensitivity to habitat loss and fragmentation. When landscape quality is high, specialists are competitively superior, but when landscape degrades, generalists gradually become superior. In previous models, competitive hierarchy is usually thought to be an intrinsic property of species, but we show that a shift in competitive capacity is caused by extrinsic factors. Comparing deterministic versus stochastic models, we find that a key extrinsic factor is increase in demographic stochasticity in degraded landscapes that affects specialists more than generalists. In the third chapter, I ask about the role of large- scale habitat corridor for biodiversity conservation. We analyzed a community of 300 species belonging to 6 taxonomic groups inhabiting more than 2000 km2 forest, composed of two large national parks in Madagascar, Ranomafana and Andringitra, and connected by a corridor. We found that in 2000 the corridor was still functional, but since then it has degraded substantially and may lose its corridor function in the coming decades. Our spatially realistic simulations show that species with passive mode of dispersal suffer the most from corridor destruction. This thesis emphasizes the role of different mechanisms that should be considered while analyzing species responses to changes in habitat structure. The most important ones are the mode of dispersal, ecological specialization, temporal and spatial stochasticity, and competition. As such, tropical regions, like Madagascar, are in double trouble due to high ecological specialization of most species and high rates of habitat destruction. Effective measures need to be enforced to ameliorate the conditions within and outside protected areas so they can truly enhance biodiversity protection.