<p> Natural peatlands are an important component of the global carbon cycle representing a net long-term sink of atmospheric carbon dioxide (CO2). The natural carbon storage function of these ecosystems can be severely impacted due to peatland drainage and peat extraction leading to large and persistent sources of atmospheric CO2 following peat extraction abandonment. Moreover, the cutover peatland has a low and variable water table position and high soil-water tension at the surface which creates harsh ecological and microclimatic conditions for vegetation reestablishment, particularly peat-forming Sphagnum moss. Standard restoration techniques aim to restore the peatland to a carbon accumulating system through various water management techniques to improve hydrological conditions and by reintroducing Sphagnum at the surface. However, restoring the hydrology of peatlands can be expensive due to the cost of implementing the various restoration techniques. The goal of this study is to examine a new extraction-restoration technique where the acrotelm is preserved and replaced on the cutover surface. More specifically, this thesis examines the effects of an acrotelm transplant experiment on the hydrology (i.e. water table, soil moisture and soil-water tension) and peatland-atmosphere CO2 exchange at a cutover peatland.</p> <p> The experimental acrotelm restoration technique maintained both high water table and moisture conditions providing sufficient water at the surface for Sphagnum moss. Furthermore, the high moisture conditions and low soil-water tensions compared to an adjacent natural site were maintained well above the measured critical Sphagnum threshold of 33% (-100 mb) VMC further providing favourable conditions for Sphagnum moss survival and growth.</p> <p> Peat respiration at the experimental restored acrotelm (110.5 g C m-2) was considerably lower than the natural peatland (144.8 and 203.7 g C m-2). However, gross ecosystem production (GEP) at the experimental site (-54.0 and -34.4 g C m-2) was significantly reduced compared to the natural site (-179.2 and -162.0 g C m-2). Consequently this resulted in a shift towards a net source of CO2 to the atmosphere over the season at the experimental site (78.5 and 56.5 g C m-2) and a sink of CO2 at the natural site (-17.6 and -22.8 g C m-2).</p> <p> Light response curves indicated that maximum GEP was considerably lower at the experimental site; however it is likely that the percentage of living and dead vegetation at the plots post restoration had a large control on this lower productivity as plots with more living vegetation had higher overall productivity (GEP). Despite wetter conditions at the experimental site, large diurnal variations in moisture (~30%) were observed suggesting disturbance to the peat structure. Although soil-water retention analysis and physical peat properties indicated that no apparent structural change in peat structure occurred, it is theorized that a change in volume in the capitula may enhance the wetting and drying cycles in moisture. Lateral expansion/contraction within the peat matrix may occur due to spaces (gaps/fissures) left between the replaced acrotelm blocks from the extraction-restoration process promoting large changes in moisture which consequently can affect the gas exchange process at the surface. Large changes in peat and capitual moisture have been shown to affect productivity leading to variable GEP and enhanced respiration, making it important to limit the moisture variability at the surface from a carbon cycling perspective. Therefore it is likely that a combination of both physiological health of the vegetation and wetting/drying cycles contributed to lower GEP, suggesting the importance of limiting disturbance at the surface during the extraction and restoration process.</p> <p> The new extraction-restoration technique has potential to return a peatland to both near-natural hydrological conditions and towards a net sink of atmospheric CO2. The replaced acrotelm on the cutover surface aided in maintaining adequate moisture conditions thereby provided adequate conditions for Sphagnum survival and reestablishment. However, the ability of the system to remain a net sink of CO2 as like the natural site was not observed post-disturbance due to differences in productivity. Nevertheless, the experimental site did maintain limited productivity post-extraction indicating that the carbon dynamics of the system was maintained due to this acrotelm restoration process potentially returning the ecosystem towards a natural sink of atmospheric CO2 over a longer period time.</p> / Thesis / Master of Science (MSc)

All species on Earth occupy limited geographic space. More than a century of observational, experimental, and theoretical work investigating the factors that drive species distributions have demonstrated the importance of the interactions between abiotic, biotic, and demographic factors in determining why species are found where they are. However, it is still unclear when and where these factors interact to set species range limits. Filling the existing knowledge gaps is imperative for the accurate predictions of how species will respond to global change, and particularly for invasive species, many of which are expected to benefit from global change. Here, I sought to investigate the mechanisms that enable, as well as limit, the range expansion of the globally invasive plant Sorghum halepense (L.) Pers. (Johnsongrass). I performed a series of field and laboratory experiments to study population and range dynamics throughout Johnsongrass's North American distribution, and test for the effects of climate, local habitat, and competition on multiple functional traits. I found Johnsongrass consistently demonstrated impressive performance across varying environments, often growing more than 3 m tall, producing hundreds of flowering culms within a single growing season, and maintaining positive population growth rates, even under intense competition with resident weeds. I also found evidence that seed germination has adapted to varying climates encountered during Johnsongrass's range expansion resulting in a shift in the germination temperature niche from warmer to cooler as Johnsongrass spread from warmer climates in the south to more temperate climates in higher latitudes. This shift in the germination temperature niche may have been an important contributing factor in the range expansion of Johnsongrass by enabling the optimization of seed germination in varying climates. On the other hand, results from a field study suggested a possible trade-off between flowering time and growth in populations originating from the range periphery (i.e., range boundary) which may be limiting, or slowing, continued range expansion of Johnsongrass. Together, the outcomes of this work contribute to our understanding of the factors involved in the distribution of species, which is a fundamental goal of Ecology, and essential to accurately predict how invasive species will respond to global change. / Doctor of Philosophy / Invasive species threaten our natural ecosystems, our agricultural systems, and even our infrastructure, and we spend billions of dollars each year attempting to control them and reduce their negative impacts. Climate change, habitat destruction, and other forms of global change, will benefit many of these species, magnifying their impacts and promoting their invasion into new territories. Because of the damaging effects of invasive species, and the costs to control them, it is imperative that we are able to predict how they will respond to global change so that we can improve plans to reduce their impact and spread. First, we need to understand the processes that promote their invasion across large swaths of land. Just as importantly, we must study the processes that prevent their invasion of certain areas. Here, I investigated some of the processes that have facilitated, as well as hampered, the spread of the invasive plant Johnsongrass. For this work, I used Johnsongrass plants originating from different habitats, including regions where Johnsongrass is highly invasive and those where Johnsongrass is very rare. I found Johnsongrass originating from regions where it is highly invasive were able to grow very large and produce thousands of seeds that were able to germinate under a range of conditions. These traits may have contributed to the invasion success of this species. However, I found a different pattern for plants that originated from regions where Johnsongrass is rare. These plants reached reproductive age earlier and grew smaller across all environmental conditions, potentially due to the less hospitable climates of these range edges. These findings allow us to project into future climate change scenarios, because it is likely that, as temperatures warm, invasive species will be able to invade new regions, where they will impact the work of conservationists, natural resource professionals, agricultural produces, and other land managers.

Arabidopsis arenosa represents a promising model for studying the mechanisms underlying the adaptation to serpentine soil. Genetic basis of serpentine adaptation is still poorly known and A. arenosa possesses many advantages as a tool to complete that knowledge. The first step of this study was to reveal the presence of a local adaptation to serpentine soil in a population of A. arenosa. To do so, I used the data from a reciprocal transplant experiment realized between a Czech pair of serpentine - non-serpentine populations and I explored the phenotypes associated with the adaptation. Subsequently, I produced the F2 hybrids coming from crosses between serpentine - non-serpentine parents and I studied the expression of fitness traits in F2 plants growing in serpentine in order to estimate the number of loci underlying the adaptation which I compared with other studies. I confirmed the presence of a local adaptation, with the population of serpentine origin performing better than the non-serpentine population in the serpentine substrate of origin, associated with accumulation of heavy metals in the leaves. Analyses of the soil composition revealed differences in heavy metals and nutrients contents, Ca/Mg ratio and pH between the two localities. Those results fitted with the function of the candidate...

Phenotypic plasticity and local adaptation via genetic change are two major mechanisms of response to dynamic environmental conditions. These mechanisms are not mutually exclusive, since genetic change can establish similar phenotypes to plasticity. This connection between both mechanisms raises the question of how much of the variation observed between species or populations is plastic and how much of it is genetic. In this study, we used a structured population of fire salamanders (Salamandra salamandra), in which two subpopulations differ in terms of physiology, genetics, mate-, and habitat preferences. Our goal was to identify candidate genes for differential habitat adaptation in this system, and to explore the degree of plasticity compared to local adaptation. We therefore performed a reciprocal transfer experiment of stream- and pond-originated salamander larvae and analyzed changes in morphology and transcriptomic profile (using species-specific microarrays). We observed that stream- and pond-originated individuals diverge in morphology and gene expression. For instance, pond-originated larvae have larger gills, likely to cope with oxygen-poor ponds. When transferred to streams, pond-originated larvae showed a high degree of plasticity, resembling the morphology and gene expression of stream-originated larvae (reversion); however the same was not found for stream-originated larvae when transferred to ponds, where the expression of genes related to reduction-oxidation processes was increased, possibly to cope with environmental stress. The lack of symmetrical responses between transplanted animals highlights the fact that the adaptations are not fully plastic and that some level of local adaptation has already occurred in this population. This study illuminates the process by which phenotypic plasticity allows local adaptation to new environments and its potential role in the pathway of incipient speciation.

No description available.

The tropical rainforests of the Peruvian Andes are some of the most biodiverse and most vulnerable to climate warming in the world. The Andes are predicted to experience substantial increases in warming of between +2 °C to +5 °C by the end of the century, in addition to an increases in the frequency of high temperature extremes, drought and flood events. The response of these forests to climate change over the next century has global relevance, due to the high levels of endemic species present and the potential role these areas will play as refugia for lowland species. Despite this, the response of tropical montane forests (TMCFs) to climate change remains under-studied. Our current understanding of how Andean species will respond to climate change is based on studies of past compositional changes. Upslope shifts in plant communities of approximately 1.2 - 2.0 m·y-1 have been observed along elevational gradients within Central and South America over the last decade. Based on these migration rates, it has been estimated that the majority of communities will lag behind increases in temperature by 5.5 °C by the end of the century. The implications of this for populations at the trailing range edge is unclear, due to a lack of mechanistic data concerning the acclimatory limits of rainforest species. When faced with rapid warming plant species will need to rapidly adapt, acclimate or migrate in order to survive. In the case of Andean species, migration rates may not be sufficient for a species to remain within its optimal thermal niche and adaptive responses will likely be too slow to be effective, hence individuals will have to acclimate in situ to prevent a decline in performance. The acclimatory ability of species can be quantified by measuring changes in performance, leaf physiology and anatomy in response to experimental manipulations of climate, however such studies are rare within the tropics. Here we carried out a seedling transplant experiment, utilising an extensive 400-3500 m asl elevational gradient in the Peruvian Andes, to simulate climate warming and upslope migration of tree seedlings under real-world conditions. To provide context for the transplant study, natural variation in leaf anatomical traits and physiological stress were explored for twelve species belonging to lowland (LF), mid-elevation (LMF) and tropical montane cloud forest communities. Adults and seedlings from the centre and furthest-most extent of each species' elevational range were studied and compared. Seedlings of each elevational forest community were transplanted downslope and upslope of their local elevational range by the equivalent of ±2 °C and ±4 °C in mean annual temperature. The experiment followed the transplanted seedlings of eleven species over a one year period, monitoring survival, growth and physiological stress (Fv/Fm) of individuals. The acclimatory ability of a subset of these species was quantified by measuring changes in photosynthetic capacity (Vcmax and Jmax), respiratory capacity (Rd) and anatomical traits (Na, Pa, LMA, LDMC) in response to transplantation. The results showed that within the natural population there was little evidence of leaf trait acclimation to elevational shifts in climate, but also little evidence of physiological stress at the trailing range edge. There were however differences in the leaf trait strategies employed by each elevational community, increasing in abiotic stress-tolerance with elevation. Physiological stress was greatest in the seedling population and, unlike the adult population, increased slightly at the trailing edge. This indicated that seedlings were more vulnerable to warming than their adult counterparts and at mid-elevations TMCF seedlings were more vulnerable than LMF seedlings. Seedling survival and growth declined in response to transplantation away from the home elevation for the majority of species, with upslope declines as a result of abiotic limitations, and downslope declines due to biotic limitations. All seedlings were found to be able to acclimate their respiratory capacity in response to transplantation, however this was not the case for photosynthetic capacity. LMF species performed significantly better than TMCF seedlings with transplantation, demonstrating a greater acclimatory capacity for photosynthesis. LMF species were able to adjust Jmax in order to maintain rates at ambient temperatures, but were not able to upregulate Vcmax upslope, whereas TMCF species were not able to respond in either transplant direction. Overall, these findings suggest that under moderate warming scenarios LMF species will have a competitive advantage over TMCF species at mid-elevations, gradually expanding their range into TMCF species' habitat over the next century. As a result of this and due to the slow pace of upslope migration, we predict that TMCF species will undergo range retractions and possible extinctions. The speed of this response will be determined by the trajectory of future warming and the frequency of extreme climatic events.

Models of climate change predict that temperature will increase during the 21th century and the largest warming will take place at high northern latitudes. In addition to warming, predictions for northern Europe include increased annual precipitation and a higher proportion of the precipitation during winter falling as rain instead of snow. These changes will substantially alter the hydrology of rivers and streams and change the conditions for riverine communities. The warming is also expected to result in species adjusting their geographic ranges to stay within their climatic tolerances. Riparian zones and wetlands are areas where excess water determines the community composition. It is therefore likely that these systems will be highly responsive to alterations in precipitation and temperature patterns. In this thesis we have tested the predicted responses of riparian vegetation to climate-driven hydrologic change with a six year long transplant experiment (I). Turfs of vegetation were moved to a new elevation with shorter or longer flood durations. The results demonstrate that riparian species will respond to hydrologic changes, and that without rare events such as unusually large floods or droughts, full adjustment to the new hydrological regime may take at least 10 years. Moreover, we quantified potential effects of a changed hydrology on riparian plant species richness (II) and individual species responses (III) under different climate scenarios along the Vindel River in northern Sweden. Despite relatively small changes in hydrology, the results imply that many species will become less frequent than today, with stochastic extinctions along some reaches. Climate change may threaten riparian vegetation along some of the last pristine or near-natural river ecosystems in Europe. More extensive loss of species than predicted for the Vindel River is expected along rivers in the southern boreal zone, where snow-melt fed hydrographs are expected to be largely replaced by rain-fed ones. With a seed sowing experiment, we tested the differences in invasibility between open wetlands, forested wetlands and riparian zones (IV). All six species introduced were able to germinate and survive in all habitats and disturbance levels, indicating that the tested wetlands are generally invisible. Germination was highest in open wetlands and riparian zones. Increasing seed sowing density increased invasion success, but the disturbance treatments had little effect. The fact that seeds germinated and survived for 2 to 3 years in all wetland habitats indicates that wetland species with sufficiently high dispersal capacity and propagule pressure would be able to germinate and establish here in their respective wetland type. Our results clearly demonstrate that a changed climate will result in substantial changes to functioning, structure and diversity of boreal wetland and riparian ecosystems. To preserve species rich habitats still unaffected by dams and other human stressors, additional protection and management actions may have to be considered.

This thesis is about the demography of the tunicate Styela clava, a species of some notoriety because of its invasiveness and impacts in many parts of the world. Species assemblages have continuously changed throughout evolutionary history, but the rate of today’s anthropogenically facilitated dispersal is unparalleled in history. Non-indigenous species (NIS) are now considered one of the most important risks to native biodiversity. NIS become invasive by becoming both widespread and locally dominant. This requires that a species becomes established, spreads locally, and increases in abundance. In the early stages of invasion, its demography and life history characteristics are of crucial importance. In New Zealand, Styela has established populations in several places, but none of these populations has yet reached the high densities found in other countries. In Lyttelton Port, where this study was located, Styela was first noticed in 2005. It therefore presented an ideal situation to study an invasive species in its early stages of establishment and provided a potentially good model for understanding how invasive species get local traction and spread from initial infestation points. Therefore, I set out to determine demographic features of Styela to understand the numbers game of population dynamics. This study used empirical data on growth rates, size-frequencies through time, and size and age to maturity to test several models, including von Bertalanffy, Logistic dose-response, Ricker and power models of individual growth. The most useful proved to be the von Bertalanffy model. Styela individuals shrink frequently, so average growth rates were often quite low, even though some individuals reached 160 mm or more in total length. Mortality was greatest in summer, presumably after reproduction, and lowest in winter. Fewer than 5% of individuals survived 12 months, and most or all of these died soon afterwards. Populations were, therefore, essentially annual. Recruitment was difficult to determine because of the cryptic nature of small juveniles. However, size-frequency, abundance and mortality data indicated that recruitment most likely occurred in early spring (late-October), and then again in late summer, with growth to maturity (at c. 50 mm total length) within < 5 months. Several manipulative experiments showed that Styela did not readily capitalise on provision of free space but the other non-native ascidian, Ciona intestinalis, rapidly recruited. Transplants of Styela were greatly affected by C. intestinalis, which overgrew them, similar to a localised replacement of Styela by Ciona seen overseas. Lefkovitch modelling was used to test whether Styela had an “Achilles heel” in its life history, whereby managed removal could impact future populations. This showed that under several scenarios intervention would most likely be ineffectual. Overall, this study showed that the original populations in Lyttelton Port are either static or in decline, somewhat contrary to original expectations. Nevertheless, it appears that these small populations may be acting as stepping stones for spread of this species outside of the port.

Abstract Local adaptation is important evolutionary process leading to adaptive population differentiation. Currently, examining its genetic basis is a major goal of evolutionary and ecological genetics. In my thesis I studied local adaptation and its genetic basis in populations of a perennial outcrossing model plant Arabidopsis lyrata by combining common garden experiments at the native field sites and in controlled conditions with quantitative trait locus mapping. Estimates of fitness in the field – both at the level of multiple components as well as hierarchical total fitness – showed that populations of A. lyrata were locally adapted. The studied populations were also phenotypically differentiated in ecologically relevant traits. Different components of fitness were important for the advantage of the locals depending on the environment. Local alleles were associated with high fitness in the field, suggesting that differing directional selection pressures have been involved in phenotypic differentiation. Mostly different genomic regions governed local adaptation in different environments, but the results also suggested that some of these regions could involve rarely documented fitness tradeoffs (antagonistic pleiotropy). Loci governing flowering time differentiation differed between the studied environments, highlighting the need to conduct experiments both in the wild and in controlled conditions. In contrast to most existing studies, F2 hybrids in general had surprisingly high fitness at one study site, largely due to beneficial dominance effects at loci governing survival in that environment. In addition to nuclear genes, cytoplasmic genomes also were found to have a role in local adaptation. / Tiivistelmä Luonnonvalinta saa aikaan paikallista sopeutumista ja adaptiivista erilaistumista. Paikallisen sopeutumisen perinnöllisen taustan selvittäminen on tällä hetkellä yksi tärkeimpiä evolutiivisen ja ekologisen genetiikan tavoitteita. Tässä väitöskirjatyössä tutkin paikallista sopeutumista ja sen geneettistä taustaa monivuotisella, ristipölytteisellä mallikasvilla, idänpitkäpalolla (Arabidopsis lyrata). Käytin työssäni geenikartoitusta kasveilla joita kasvatettiin yhdenmukaisissa oloissa sekä populaatioiden luontaisilla kasvupaikoilla että kontrolloiduissa olosuhteissa. Kenttäolosuhteissa arvioitu kelpoisuus osoitti idänpitkäpalkopopulaatioiden olevan paikallisesti sopeutuneita sekä yksittäisten kelpoisuuteen vaikuttavien ominaisuuksien että hierarkkisen kokonaiskelpoisuuden tasolla. Tutkitut populaatiot olivat myös erilaistuneita ekologisesti tärkeissä ominaisuuksissa. Kelpoisuuteen vaikuttavat ominaisuudet myös poikkesivat ympäristöjen välillä. Paikalliset alleelit olivat yhteydessä korkeaan kelpoisuuteen luonnossa, minkä perusteella voitiin päätellä erisuuntaisen luonnonvalinnan vaikuttaneen populaatioden erilaistumiseen. Kromosomiston eri alueet olivat tärkeitä sopeutumisessa eri ympäristöihin, mutta myös joidenkin samojen genomin alueiden havaittiin mahdollisesti vaikuttavan vastakkaisesti kelpoisuuteen eri ympäristöissä. Myös kukkimisajan erilaistumiseen vaikuttavat genomin alueet poikkesivat eri ympäristöjen välillä erityisesti verrattaessa kenttäkokeita kasvatushuone- ja kasvihuonekokeisiin. Toisin kuin useimmissa tutkimuksissa on havaittu, F2-sukupolven jälkeläistön kelpoisuus oli yllättävän korkea yhdessä kenttäkoeympäristössä. Tähän vaikuttivat kelpoisuuden kannalta suotuisat dominoivat geenivaikutukset, jotka paransivat kasvien selviytymistä kyseisessä ympäristössä. Tumassa sijaitsevien geenien lisäksi myös soluelimien perimällä havaittiin olevan yhteys paikalliseen sopeutumiseen.

La survie et la croissance des plantes sont essentielles afin d’assurer l’efficacité des protocoles de phytoremédiation et la décontamination des friches contaminées. La survie des saules et leur adaptation aux contaminants dépendent de la nature et de la concentration des contaminants. L’objectif de l’étude est d’identifier les cultivars ayant les meilleurs rendements, mais aussi de déterminer si la provenance des boutures (milieu contaminé ou milieu non contaminé) pourrait influencer la survie, la croissance et la phytoextraction (Cd, Cr, Cu, Ni, Pb, Zn) des saules. Nous avons comparé ces différents paramètres pour des boutures de dix cultivars de saules dans un milieu industriel fortement contaminé par les composés organiques et dans un milieu non-contaminé. Les variations dans la réponse des cultivars selon la provenance des boutures (milieu contaminé ou milieu non-contaminé) ont aussi été analysées dans chacun des sites d’étude. Selon nos résultats, le cultivar ˈ5005ˈ (Salix alba) est très productif en milieu extrêmement contaminé. Le cultivar ˈS25ˈ (Salix eriocephala) est aussi un choix très intéressant en phytoremédiation, puisqu’il produit près de deux fois plus de biomasse racinaire comparativement aux autres cultivars. La provenance des boutures n’a pas d’impact significatif sur la survie, la croissance et la phytoextraction pour la majorité des cultivars sauf pour le cultivar ‘Millbrook’, où les individus provenant du milieu contaminé ont produit significativement plus de biomasse aérienne lorsqu’ils poussaient en sol contaminé comparativement aux individus qui n’ont jamais été en contact avec les contaminants. Ces résultats pourraient aider à planifier des protocoles de phytoremédiation plus efficaces, en sélectionnant les cultivars de saule les plus adéquats et en élaborant l’échantillonnage des boutures utilisées dans les sites appropriés. / Plant survival and growth are essential parameters to monitor the effectiveness of phytoremediation protocols and the eventual decontamination of brownfields. The ability of different willow cultivars to survive and adapt to contaminants in polluted soils depends on the nature and concentration of the contaminants. The objective of the study was to identify the cultivars with the highest yields, but also to determine whether the origin of the cuttings (contaminated site or not) might influence survival, growth and phytoextraction of willow cultivars. We compared survival, growth and phytoextraction (Cd, Cr, Cu, Ni, Pb, Zn) of cuttings of ten willow cultivars in a highly organic-contaminated industrial environment and in an uncontaminated soil. Variations in the response of the cultivars according to the origin of the cuttings were also analyzed for each sites. According to our results, cultivar ˈ5005ˈ (Salix alba) was very productive in an extremely contaminated environment. Cultivar ˈS25ˈ (Salix eriocephala) was also a relevant choice, as it produced nearly twice more root biomass compare to other cultivars. The origin of the cuttings did not have significant influence on survival, growth and phytoextraction for almost all cultivar except the ˈMillbrookˈ cultivar: individuals originating from the contaminated environment produced significantly more aboveground biomass when growing in the contaminated environment compared to individuals who had never been in contact with contaminants. These results could help build more effective phytoremediation protocols in highly contaminated environments by selecting adequate willow cultivars and sampling cuttings in an appropriate environment.