| 11. |
- Christiansen, Ditte Marie, 1990-
(författare)
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Responses of boreal forest understory plant communities to climate and forestry
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A warming climate is altering species distributions and community compositions. To understand and predict changes in species distributions to climate change, we often use species occurrences together with large-scale regional climate data. This can be problematic for several reasons. Species living near the ground experience small-scale spatial variation in temperatures, i.e., microclimate, that are influenced by topography and vegetation and can therefore deviate a lot from regional temperatures. Further, climate often affects species indirectly via species interactions, and such interactions can also change with climate. And last, species may respond slower than climate changes. Ignoring these aspects can complicate our understanding of species-climate relationships.In this thesis, I examined how microclimate and changes in microclimate due to forest management impact performances, interactions, and distributions of plant species in boreal forest understory communities. First, I quantified the importance of microclimate for species performances and distributions. Specifically, I compared the effects of spring temperatures measured on local and regional scales on the population dynamics of a southern forest herb (I). I also tested how small-scale spatial microclimate variation contributed to the regional co-existence of northern and southern understory plant species (II). Second, I examined the role of species interactions in driving abundance patterns of two moss species with different temperature niches across their Swedish ranges by transplanting them separately and together across a climate gradient (III). Lastly, I investigated how understory plant communities respond to changes in microclimate caused by forest management (IV), and how past microclimates influence current patterns of species occurrence, abundance, and reproduction (II).I found that local spring temperatures had a significant effect on the population dynamics of the southern forest herb that could not be detected using regional spring temperatures (I). Spatial variation in microclimate explained the regional co-existence of two northern and two southern species, where the northern species were favoured by cold microclimates and the southern species by warm microclimates (II). In the transplant experiment (III), I found that climate-mediated competition can override the direct effects of climate and limit abundances across ranges. Lastly, I found that microclimate changes caused by forest management activities had a large effect on understory communities (IV), and that current abundances of northern and southern species were partly explained by past microclimate (II).Overall, I demonstrated that, to understand how species (particularly understory plants) respond to climate, we need to replace the standard use of regional climate data with locally measured climate data or down-scaled gridded climate data that account for variation in topography as well as vegetation. To predict how species will respond to climate change, we also need to include species interactions and how these interactions change with a changing climate. Finally, changes in microclimate following changes in forest structure have large effects on understory species. The last finding is important to consider when studying changes in understory communities in a climate context and could be used to mitigate climate effects on forest biodiversity.
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| 12. |
- Karlsson, Konrad, 1983-
(författare)
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Local adaptation in life history traits and population size estimation of aquatic organisms
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human society is dependent on healthy aquatic ecosystems for our basic needs and well-being. Therefore, knowledge about how organisms respond and interact with their environments is pivotal. The Baltic Sea is highly affected by human activity and future populations living in its catchment area will have to respond to multiple set of changing abiotic and biotic predictors.The first two papers of this thesis focus on local adaptation, adaptive capacity, and the response to changing temperature, salinity, and food conditions of different Eurytemora affinis populations, a ubiquitous zooplankton species in the Baltic Sea. Development time of zooplankton is an important trait and relates to how fast a population can increase in number. Common garden experiments showed that E. affinis populations from warmer southern areas had shorter development time from nauplii to adult at high temperature compared to populations from colder areas, which indicates an adaptation to temperature. The adaptation was explained by a correlation in development time between higher temperatures, 17 and 22.5 °C, while development between a colder temperature, 12 °C, and the two higher temperatures was uncorrelated. This implies that adaption to short development time at high temperature is unlikely for populations originating from cold temperatures. Hence, global warming will be disadvantageous for northern, compared to southern populations. However, development time is heritable and may change under selection, and may improve the competitive advantage of northern populations. The population with the shortest development time had comparably lower survival at high temperature and low food quality. This represents a cost of fast development, and emphasizes the importance of including multiple stressors when investigating potential effects of climate change.E. affinis inhabits a broad range of habitats from an epi-benthic life in freshwater lakes and river mouths, to pelagic life in estuaries. Paper III aims to link the morphology of different populations to habitat and resource utilization. Results showed that the individuals of a pelagic population were smaller in size and more slender, compared to a littoral population of larger and more fecund individuals. In experimentally constructed benthic and pelagic algae communities, the littoral population produced less offspring than the pelagic population when filamentous benthic diatoms were included. This suggests that filaments disturb their feeding and that littoral populations of E. affinis stay epi-benthic. As pelagic fish typically select larger prey, living close to the bottom probably allows the littoral population to grow larger than the pelagic. These results link morphology to habitat specialization, and show contrasting ecological effects of two E. affinis populations.Paper IV focuses on the recreational angler’s potential role as a citizen scientist. The pike Esox lucius has a stabilizing role in ecosystems as a top consumer and is highly valued by recreational anglers in European lakes and estuaries. Results showed that recreational angling could be used to estimate population size and connectivity of E. lucius in spatial capture-recapture models. The only prerequisite is that anglers practice catch and release, retain spatial data, and take photos of their caught fish. These results show that data from recreational angling can be of potential use for fisheries managers and researchers.
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| 13. |
- König, Malin A. E., 1987-
(författare)
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Context dependency of plant – animal interactions
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The strength and direction of interactions between organisms vary spatially across the landscape. Traditionally, the focus has been on how trait variation affects the interactions between species. However, differences in abiotic and biotic environmental factors may also alter the distribution, phenology and behavior of the interacting species. To be able to understand why an interaction varies across the landscape, the effects of trait variation has to be separated from the effects of the environmental context. In this thesis, I try to separate the effects of context and trait differences on plant resistance against herbivory, through experimental and observational studies conducted with two cytotypes of the perennial herb Cardamine pratensis and its main herbivore, Anthocharis cardamines.The results show that differences in plant resistance against oviposition under controlled conditions were mainly mediated by flower size; larger flowers were more attractive to the female butterfly. However, among-populations differences in oviposition under natural conditions were not related to the resistance observed under controlled conditions, or to ploidy type, flowering phenology or plant size. Within populations under natural conditions the oviposition patterns by A. cardamines was affected by the plant traits plant size and flowering phenology.The result of this thesis shows that among-population differences in intensity of plant-herbivore interactions were caused by differences in environmental context rather than by herbivore preferences for any phenotypic plant traits, while host plant selection within population was based on plant traits. This suggests that biotic and biotic context can have important effects on the intensity of plant-herbivore interactions. Although genetic traits influenced the outcome of the interaction within populations, it was the environmental context of the populations that determined largely if the interaction took place or not.
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| 14. |
- Toftegaard, Tenna, 1982-
(författare)
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Temperature and the synchrony of plant-insect interactions
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increasing temperatures resulting from climate change have within recent years been shown to advance phenological events in a large number of species worldwide. Species can differ in their response to increasing temperatures, and understanding the mechanisms that determine the response is therefore of great importance in order to understand and predict how a warming climate can influence both individual species, but also their interactions with each other and the environment. Understanding the mechanisms behind responses to increasing temperatures are however largely unexplored.The selected study system consisting of host plant species of the Brassicaceae family and their herbivore Anthocharis cardamines, is assumed to be especially vulnerable to climatic variations. Through the use of this study system, the aim of this thesis is to study differences in the effect of temperature on development to start of flowering within host plant species from different latitudinal regions (study I), and among host plant species (study II). We also investigate whether different developmental phases leading up to flowering differ in sensitivity to temperature (study II), and if small-scale climatic variation in spring temperature influence flowering phenology and interactions with A. cardamines (study III). Finally, we investigate if differences in the timing of A. cardamines relative to its host plants influence host species use and the selection of host individuals differing in phenology within populations (study IV).Our results showed that thermal reaction norms differ among regions along a latitudinal gradient, with the host plant species showing a mixture of co-, counter- and mixed gradient patterns (study I). We also showed that observed differences in the host plant species order of flowering among regions and years might be caused by both differences in the distribution of warm days during development and differences in the sensitivity to temperature in different phases of development (study II). In addition, we showed that small-scale variations in temperature led to variation in flowering phenology among and within populations of C. pratensis, impacting the interactions with the butterfly herbivore A. cardamines. Another result was that the less the mean plant development stage of a given plant species in the field deviated from the stage preferred by the butterfly for oviposition, the more used was the species as a host by the butterfly (study IV). Finally, we showed that the later seasonal appearance of the butterflies relative to their host plants, the higher butterfly preference for host plant individuals with a later phenology, corresponding to a preference for host plants in earlier development stages (study IV).For our study system, this thesis suggest that climate change will lead to changes in the interactions between host plants and herbivore, but that differences in phenology among host plants combined with changes in host species use of the herbivore might buffer the herbivore against negative effects of climate change. Our work highlights the need to understand the mechanisms behind differences in the responses of developmental rates to temperature between interacting species, as well as the need to account for differences in temperature response for interacting organisms from different latitudinal origins and during different developmental phases in order to understand and predict the consequences of climate change.
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| 15. |
- Andersson, Petter, 1975-
(författare)
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The importance of search behavior and movements for spatial distributions of herbivorous insects
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Insect populations commonly show large spatial variation in density, and much variation have been shown to be explained by the search behavior applied by the insect when locating habitat patches. This thesis explores the importance of odor-mediated attraction for immigration rates of herbivorous insects in relation to the size of the patches and the density of host plants within the patches. By using electroantennogram and measuring moth antennal responses to sex pheromones and thereby estimating the relative odor-mediated attraction from odor patches in field experiments (Paper I, III), I show that the length of the odor plumes emanating from the patches increase proportional with the square-root of the number of odor sources. In laboratory and field experiments (with the weevils Cionus scrophulariae and C. tuberculosus and the host plant figwort Scrophularia nodosa; Paper II) and meta-analyses on multiple insect herbivores (Paper III), I examined whether the relative increase in plume length could also predict the immigration rates of olfactory searching insects in relation to patches with increasing area and increasing density of host plants. The experiments (Paper II) and meta-analyses (Paper III) showed that the observed immigration rates of olfactory searching insects was well predicted by the relative increase in plume length, as estimated from the electroantennogram measurements (Paper I, III). The importance of immigration rates, relative to the effect of emigration and local growth was also investigated for the Cionus weevils in natural S. nodosa patches (Paper IV). This study showed that the density-patch size relationships of the weevils during early season were predicted by the net scaling of emigration and immigration rates, and differences in density-patch size relationships between the two species could be explained by inter-specific differences in their emigration rates from small patches. In conclusion, this thesis shows that search behavior can be used to predict immigration rates and spatial distributions of insects, with implications for pest control, conservation ecology and general ecological theory.
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| 16. |
- Lönnell, Niklas, 1969-
(författare)
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Dispersal of bryophytes across landscapes
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dispersal, especially long-distance dispersal, is an important component in many disciplines within biology. Many species are passively dispersed by wind, not least spore-dispersed organisms.In this thesis I investigated the dispersal capacity of bryophytes by studying the colonization patterns from local scales (100 m) to landscape scales (20 km). The dispersal distances were measured from a known source (up to 600 m away) or inferred from a connectivity measure (1–20 km). I introduced acidic clay to measure the colonization rates over one season of a pioneer moss, Discelium nudum (I–III). I also investigated which vascular plants and bryophytes that had colonized limed mires approximately 20–30 years after the first disturbance (IV).Discelium effectively colonized new disturbed substrates over one season. Most spores were deposited up to 50 meters from a source but the relationship between local colonization rates and connectivity increased with distance up to 20 km (I–III). Also calcicolous wetland bryophyte species were good colonizers over similar distances, while vascular plants in the same environment colonized less frequently. Common bryophytes that produce spores frequently were more effective colonizers, while no effect of spore size was detected (IV). A mechanistic model that take into account meteorological parameters to simulate the trajectories for spores of Discelium nudum fitted rather well to the observed colonization pattern, especially if spore release thresholds in wind variation and humidity were accounted for (III).This thesis conclude that bryophytes in open habitats can disperse effectively across landscapes given that the regional spore source is large enough (i.e. are common in the region and produce spores abundantly). For spore-dispersed organisms in open landscapes I suggest that it is often the colonization phase and not the transport that is the main bottle-neck for maintaining populations across landscapes.
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| 17. |
- von Euler, Tove, 1976-
(författare)
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Environmental heterogeneity, population dynamics and life-history differentiation in Primula farinosa
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Allocation to reproduction is a key life-history trait. Optimal allocation to reproduction depends on environmental conditions because of their effects both on costs and benefits of reproduction and on patterns of growth, fecundity, and mortality. In this thesis, I studied 24 populations of the perennial herb Primula farinosa in the northern part of the Great Alvar on Öland, SE Sweden, and in an experimental garden at Stockholm University to investigate how plant allocation patterns and population dynamics vary along environmental gradients. In the first study, I performed experimental manipulations of reproduction to study costs of reproduction in relation to water availability. In the second study, I performed a demographic survey to investigate the effects of pre-dispersal seed predation on host-plant population dynamics in relation to environmental context. In the third study, I used a common garden experiment to investigate whether environmental variation among natural populations was correlated with genetic differentiation in reproductive effort, and in the fourth study, I performed reciprocal transplantations among four populations to investigate whether genetically based adaptive differentiation among local populations could be detected. The results showed that under natural conditions, plant reproductive costs, intensity of pre-dispersal seed predation, population growth rate and reproductive effort varied with water availability and vegetation height. Costs of reproduction were detected at high and low water availability but not under intermediate soil moisture conditions (paper I). Population dynamics of P. farinosa were affected by environmental conditions both directly, through effects on potential population growth rate (in the absence of seed predation) and indirectly, through effects on seed predation intensity and sensitivity to seed predation (paper II). Among-population genetic differentiation in reproductive allocation was documented in the common-garden experiment (paper III). However, reciprocal transplantations among populations separated by up to 6.2 km provided no evidence of local adaptation to current environmental conditions. Moreover, large differences in the performance of individuals transplanted to different study sites suggest that the study populations display considerable phenotypic plasticity (paper IV). Taken together, the results of these studies suggest that environmental variation has important direct and indirect effects on population dynamics and life history trade-offs in P. farinosa, and that differences in reproductive effort partly reflect genetic differentiation, but that phenotypic variation observed among natural populations does not reflect adaptations to current environmental conditions.
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| 18. |
- von Zeipel, Hugo, 1973-
(författare)
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The spatial and temporal dynamics of plant-animal interactions in the forest herb Actaea spicata
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Landscape effects on species performance currently receives much attention. Habitat loss and fragmentation are considered major threats to species diversity. Deciduous forests in southern Sweden are previous wooded pastures that have become species-rich communities appearing as islands in agricultural landscapes, varying in species composition. Actaea spicata is a long-lived plant occurring in these forests. In 150 populations in a 10-km2 area, I studied pre-dispersal seed predation, seed dispersal and pollination. I investigated spatio-temporal dynamics of a tritrophic system including Actaea, a specialist seed predator, Eupithecia immundata, and its parasitoids. In addition, effects of biotic context on rodent fruit dispersal and effects of flowering time and flower number on seed set, seed predation and parasitization were studied. Insect incidences of both trophic levels were related to resource population size and small Eupithecia populations were maintained by the rescue effect. There was a unimodal relationship between seed predation and plant population size. Seed predator populations frequently went extinct in small plant populations, resulting in low average seed predation. Parasitoids were present in large plant populations but did not affect seed predator density. Seed predators aggregated at edges, relaxing seed predation in patch interiors. Flowering phenology was unrelated to seed set and insect incidence. A higher flower number did not influence seed predation but was associated with higher seed set and a tendency for a higher parasitization rate. In the study on fruit dispersal more fruits were removed inside than outside populations. Within plant populations more fruits were removed from large aggregations. Overall, this thesis underlines the importance of plant-animal interactions during different phases of the life cycle. The spatial configuration of host plants plays an important role for the outcome of plant-animal interactions and trophic cascades.
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| 19. |
- Boalt, Elin, 1976-
(författare)
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Ecology and evolution of tolerance in two cruciferous species
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tolerance to herbivory is the ability of plants to maintain fitness in spite of damage. The goal of this thesis is to investigate the genetic variation and expression of tolerance within species, determine whether and in what conditions tolerance has negative side-effects, and how tolerance is affected by different ecological factors. Tolerance is investigated with special focus on the effects of different damage types, competitive regimes, history of herbivory, and polyploidization in plants. Studies are conducted as a literature review and three experiments on two cruciferous species Raphanus raphanistrum and Cardamine pratensis.In the tolerance experiments, plants are subjected to artificial damage solely, or in a combination with natural damage. A literature review was conducted in order to investigate the effects of damage method. We found that traits related to tolerance, such as growth and fitness were not as sensitive in regard to damage method as measures of induced chemical traits, or measures of secondary herbivory.Genetic variation of tolerance was demonstrated within populations of R. raphanistrum and between subspecies of C. pratensis. In R. raphanistrum, traits involved in floral display and male fitness were positively associated with plant tolerance to herbivore damage. A potential cost of tolerance was demonstrated as a negative correlation between levels of tolerance in high and low competitive regimes. I found no evidence of other proposed costs of tolerance in terms of highly tolerant plants suffering of reduced fitness in the absence of herbivores or trade-offs in terms of a negative association between tolerance to apical and leaf damage, or between tolerance and competitive ability. In C. pratensis, higher ploidy level in plants involved higher levels of tolerance measured as clonal reproduction. Furthermore, populations exposed to higher levels of herbivory had better tolerance than populations exposed to lower levels of herbivory. In this thesis, I demonstrate evidence of different components for the evolution of tolerance in plants: genotypic variation, selective factors in terms of costs and ploidization, and selective agents in terms of changing environment or herbivore pressure.
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| 20. |
- Isaeus, Martin, 1964-
(författare)
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Factors structuring Fucus communities at open and complex coastlines in the Baltic Sea
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with physical factors and biological interactions affecting the distribution of two fucoid species, Fucus vesiculosus and F. serratus, in the Baltic Sea. Studies have been carried out in two quite different environments: an archipelago, and an open rocky coast. The archipelago has an extremely long coastline with a heterogeneous submerged landscape of different substrate types, slopes, water qualities, and degrees of wave exposure. The factors influencing F. vesiculosus distribution, morphology and epiphyte composition were studied in the Stockholm archipelago using field surveys and spatial modelling in Geographic information systems (GIS). A GIS-method to estimate wave exposure was developed and validated by comparing the result to an index based on vertical zonation of lichens. Wave exposure was considered an important factor for predicting the distribution of F. vesiculosus by its ability to clean hard surfaces from silt, and a predictive model was constructed based on the information of wave exposure and slope of the shore. It is suggested that the lower distribution boundary of attached F. vesiculosus is set by sediment in sheltered parts of the archipelago, and by light availability in highly wave exposed parts. The morphology of F. vesiculosus was studied over a wave exposure gradient, and several characters responded in accordance with earlier studies. However, when separating effects of wave exposure from effects of other confounding water property parameters, only thallus width was significantly different. Several water property parameters were shown to be correlated with wave exposure in the Stockholm archipelago, and the mechanism responsible for the effects on F. vesiculosus morphology is discussed. The composition of epiphytes on F. vesiculosus varied over a wave exposure gradient with a positive correlation to Elachista fucicola, and a negative to Chorda filum. At an open coast the physical environment is much less heterogeneous compared to an archipelago. The distributions of F. vesiculosus, F. serratus, turf-forming algae, and the seafloor substrate, were surveyed along the open coasts of Öland and Gotland. Turf-forming algae dominated all hard substrates in the area, and Polysiphonia fucoides was most abundant. At the Gotland coast F. vesiculosus was less abundant than at the Öland coast, and F. serratus occurred only in the southern-most part. Fucus serratus was increasingly more common towards south which was interpreted as an effect mainly of the Baltic salinity gradient, or the variation of salinity that has occurred in the past. The effects of turf-forming algae and sediment on F. serratus recruitment at 7 m depth off the Öland east coast were studied in the field, and by laboratory experiments. Almost no recruits were found in the algal turf outside the F. serratus patches. More fine sediment was found in the turf than in the F. serratus patches, suggesting that the turf accumulates sediment by decreasing resuspension. Both filamentous algae and sediment decreased the attachment ability of F. serratus zygotes and survival of recruits, and sediment had the strongest effect. It is therefore suggested that F. serratus has difficulties recruiting outside its patches, and that these difficulties are enforced by the eutrophication of the Baltic Sea, which has favoured growth of filamentous algae and increased sedimentation. An overall conclusion is that Fucus distribution is affected by large-scale-factors, such as the eutrophication and salinity changes of the Baltic Sea, as well as by small-scale variation in wave exposure, substrate and slope, and by surface competition with neighbouring species.
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