| 21. |
- Lindborg, Regina, 1966-
(författare)
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Land Use Change in Space and Time : implications for plant species conservation in semi-natural grasslands
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Land use change has during the last century altered the traditional rural landscape in Sweden, resulting in a major decline in species diversity. Traditional small-scale farming, with a remarkably high small-scale species richness, has changed in favour of rationalized agriculture, and many semi-natural grasslands, i.e. traditionally managed pastures and meadows, have become abandoned. In this thesis I examine how spatio-temporal processes affect plant species in Swedish semi-natural grasslands exposed to habitat degradation as well as recovery (restoration). I also discuss how to conserve plant species associated with semi-natural grasslands. In general, species responded slowly to habitat degradation, but quickly to improvement of habitat quality. Population viability analysis (PVA) of the grazing favoured herb Primula farinosa suggested, in contrast to historical records, that populations in abandoned grasslands performed better than populations in traditionally managed grasslands, a result questioning the accuracy of PVAs. Restoration of grasslands counteracted species richness decline and the number of species increased within seven years after restoration. It was possible to recruit grassland species in grazed former arable fields by artificial seed-sowing. This may help to speed up the natural recruitment, which often is low due to dispersal limitations in modern fragmented landscapes. Studies at larger regional scales showed century long time-lags in the response of plant species richness to land use change. Species richness was not related to present-day connectivity of grasslands, but positive effects appeared for grassland configuration in 1950s and 1900s. Thus, making conservation guidelines based solely on present-day data may be strongly misleading and under-estimate the actual risk of species loss. To secure long-term survival of species, it is important to focus on processes associated with larger spatial scales. This may benefit natural dynamics at longer time-scales, where abandoned and restored grasslands, together with species-rich semi-natural grasslands, could become natural parts of sustainable landscape management.
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| 22. |
- Ryberg, Eleonor Eva Stina, 1989-
(författare)
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Holocene species distributions in boreal peatlands : An exploration of factors driving change using Temporal Paleo-Species Distribution Models
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Northern peatlands are terrestrial ecosystems that provide specialized habitats in which biomass production exceeds decomposition, resulting in accumulation of organic matter. Understanding what factors drive species changes in future climate conditions in these systems is of high importance since this has the potential to affect ecosystem functioning and biodiversity, and by extension carbon sequestration. In ecology, a common method for investigating species’ relationships with climate variation, linked with spatial information, is species distribution modelling (SDM). This method typically uses information about current climate conditions tied to locations of species occurrences, forecasting the effects of change on future geographic distributions based on the implicit assumption that temporal variation can be substituted by contemporary spatial variation. This assumption might not be met for several reasons, namely (1) species changes often occur over much longer time-scales than the ones involved in contemporary ecology, and therefore (2) responses to climatic changes are time-lagged. Incorporating paleo-records of actual (past) changes in species distributions and climate conditions therefore provides a much more direct way to model species responses to climate change. In this project, a combination of methods from the fields of paleoecology and ecology were employed to create a novel approach to explore species distribution changes over time in boreal peatlands. This was done by first reconstructing the vegetation of two proximal peatlands (Store Mosse and Dala Mosse bogs; Paper I and III) in south-central Sweden, followed by statistical modeling of the species data and climatic parameters over time (obtained from independent paleoclimate data; Paper II and III), creating Temporal Paleo-Species Distribution Models (Temporal Paleo-SDMs). Paper I identifies factors driving species changes in Store Mosse bog based on internal (successional steps and biotic interactions) and external (climatic) processes. This study tests the assumption that climate has been the main driver of species change by producing a high-resolution postglacial vegetation reconstruction using macrofossil analysis, which is assessed against a set of independent proxy records representing changes in local and regional hydrology, nutrient input, and temperature. Paper II uses the same high-resolution plant macrofossil dataset from Store Mosse and pairs this with independent information about local and regional climate conditions, nutrient input and fire incidence during the same period to create the first Temporal Paleo-SDM and thereby assess the relationships between bog species and climate variability over time (reaching ~10 000 cal yr BP). Paper III tests the repeatability of the Temporal Paleo-SDM method by applying it to a new high-resolution species dataset from Dala Mosse, using the same climate parameters as in Paper II. This thesis bridges across paleoecology and ecology and shows the power of interdisciplinary collaborations and demonstrates the useful contributions they can make in future peatland research.
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| 23. |
- Sandring, Saskia, 1974-
(författare)
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Plant-Animal Interactions and Evolution of Floral Display and Flowering Phenology in Arabidopsis lyrata
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits, and population differentiation in the insect-pollinated, outcrossing, perennial herb Arabidopsis lyrata. More specifically, I (1) determined whether selection on flowering phenology and floral display can be attributed to interactions with pollinators and herbivores, (2) examined whether population differentiation in flowering phenology and floral display is correlated with current selection on these traits, and (3) tested for local adaptation from contrasting environments in Europe.A field experiment conducted in a Swedish population demonstrated, that interactions with pollinators may markedly affect selection on both floral display and phenology of flowering. In an alpine population in Norway, grazing damage to inflorescences strongly influenced selection on floral display. The results suggest that variation in the abundance of pollinators and herbivores should contribute to spatio-temporal variation in selection on flowering phenology and floral display in A. lyrata. A common-garden experiment showed that flowering phenology and floral display vary among Scandinavian populations of A. lyrata. For some traits patterns of population differentiation were consistent with differences in the direction and strength of phenotypic selection determined in comparisons (a) between an alpine population in Norway and a coastal population in Sweden, and (b) among coastal populations in Sweden. This suggests that current selection contributes to the maintenance of genetic differentiation in these traits.Adaptive differentiation among populations was examined in a reciprocal transplant experiment that included populations from three contrasting environments, alpine Norway, coastal Sweden and lowland, continental Germany. The experiment provided evidence for local adaptation, and indicated that populations have diverged in traits affecting plant establishment and early growth.
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| 24. |
- Toräng, Per, 1978-
(författare)
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Pollinators, Enemies, Drought, and the Evolution of Reproductive Traits in Primula farinosa
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits and population differentiation in the insect-pollinated, self-incompatible, perennial herb Primula farinosa. More specifically, I (1) determined whether the effects of floral display and interactions with pollinators and seed predators, and plant reproductive success were frequency-dependent and affected by surrounding vegetation context, (2) examined the consequences of intermittent drought years on population dynamics using numerical simulations based on demographic data collected over seven years, (3) analyzed among-population differentiation in flowering phenology and reproductive allocation, and its relationship to soil-depth at the site of origin.A field experiment suggested that conspicuous plants facilitate inconspicuous plants in terms of pollinator attraction, and that the facilitation effect is contingent on the height of the surrounding vegetation. Further experiments revealed that both mutualistic and antagonistic interactions can result in frequency-dependent selection on floral display. Among inconspicuous plants, both fruit initiation, and damage from seed predators increased with the proportion of the conspicuous morph. The relative strength of these effects, and therefore their net outcome on the relationship between morph ratio and seed production varied among years.I combined information on vital rates and their relation to environmental conditions in simulations to predict future population viability in changing environments. Simulated stochastic population growth rate decreased with increasing frequency of drought years.Reproductive allocation varied significantly among populations both in the field and in a common-garden experiment, but was correlated with soil depth at the site of origin only in the field. The results suggest that among-population variation in reproductive effort in the field mainly reflects plastic responses to environmental conditions, and that this plasticity may be adaptive. The common-garden experiment suggested that the study populations have diverged genetically in flowering time.
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