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Browsing by study line "Palaeontology and Global Change"

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  • Sandell, Mia (2023)
    Evolution can lead to changes in body size among mammals and when that occurs, organs usually scale along. Teeth are an organ that scale along with body size and therefore, investigating how the teeth are getting along when a mammal is subjected to a rapid reduction of body size is of value. During human evolution, body size has generally increased but jaw and teeth size has decreased. As of recent, human evolution witness a potential decrease of body size, due to the discovery of island-living hominins; Homo floresiensis and Homo luzonensis. The phenomenon of decreasing body size among large animals and increasing body size among small animals in an insular setting is so well-known that it has its own ecological rule, called the island rule or Foster’s rule. However, this phenomenon has not really been studied from the perspective of teeth. In this thesis I focus on the effects of body size decrease on teeth in the context of relatively rapid body size reduction. Researching the effect that a reduction of body size has on teeth is relevant for understanding morphological changes related to island dwarfism and the origins of island forms among humans. Dogs (Canis familiaris) provide an extreme example of rapid and large reduction of both body- and teeth size. Comparing dog molars to molars of their closest ancestor, the wolf (Canis lupus), can shed light on how the teeth behave when scaling down in size. This reduction in body size may be comparable to insular dwarfing as selective breeding of pure breed dogs is limiting the availability of mating partners in a similar way that a secluded island limits the availability of mating partners for insular animals. To answer my research questions, I measure and photograph dog molars and compare the results with data of wolf molars. Furthermore, if any patterns emerge, data of human molar is compared to the canid data to investigate if any similarities can be found. The results show that dog molars are overall smaller in size than wolf molars and that both species follow a pattern where m1 > m2 > m3. Furthermore, small dogs are more likely to have an absent m3 than big dogs and wolves. Moreover, the results show that the size relation between dog m1-m2 is a continuum of wolf m1-m2 relation. However, dogs have enlarged their m3 and therefore the m2-m3 size relation is not a continuum of wolf molar relation. When comparing the human data to the results of dog/wolf m1-m2 and m2-m3 size relation, the results show that Homo floresiensis molars are on the same trajectory as Homo erectus molars. This implies that dogs have done adjustments to their molars that diverge from their ancestors’ molars and that the change has happened during a short period of time. Therefore, dog molars cannot be seen as simply scaled down version of wolf molars, as far as size is concerned. The information gained from this thesis can be used to further investigate if molars of other rapidly dwarfed species may have behaved in a similar manner. It is however too early to say if dogs can be seen as an island rule simulation or if they can shed light on the origins of hominin island forms. More research, such as comparing the number of cusps between dog and wolf molars or investigating the upper carnassial and the following molars, needs to be done to be able to draw any further conclusions.
  • Douglas, Regan (2024)
    Mesowear, a method that scores the wear of teeth to determine the amount of abrasive material in the diet, has long been used to understand palaeoecology though the diet of herbivores. Until recently, proboscidean teeth could not be used for these studies. The method of mesowear angle analysis introduced by Saarinen et al. in 2015 has made this possible by measuring the relative angle between the enamel ridges and dentine valleys of the lophs of proboscidean teeth to account for wear. This study compares the average mesowear angles of 428 specimens of Pleistocene Mammuthus to determine geospatial variation across the genus as well as within the species M. primigenius. These results are then corroborated with previous studies of other palaeoecological proxies to ensure they truly reflect a means to determine palaeoecology through proboscidean mesowear. Overall, this study finds that significant geospatial variation and little interspecific variation of Mammuthus proves that mammoths were highly adaptable herbivores capable of surviving in a wide array of the harshest habitats and browsing or grazing habits were not determined by species morphologies, but the environments they inhabited.
  • Redmond Roche, Benjamin Heikki (2019)
    Significant changes in sea-ice variability have occurred in the northern North Atlantic since the last deglaciation, resulting in global scale shifts in climate. By inferring the dynamic changes of palaeo seaice to past changes in climate, it is possible to predict future changes in response to anthropogenic climate change. Diatoms allow for detailed reconstructions of palaeoceanographic and sea-ice conditions, both qualitatively, using information of species ecologies and quantitatively, via a transfer function based upon diatom species optima and tolerances of the variable to be reconstructed. Three diatom species comprising a large portion of the training set are proxies for the presence of sea ice: Fragilariopsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica, have currently been grouped into one species – F. oceanica – in the large diatom training set of the northern North Atlantic region. The clustering of the species may result in an imprecise reconstruction of sea ice that does not take into account all the available ecological information. The proportions of the three species were recounted from the original surface sediment slides alongside the additional chrysophyte cyst Archaeomonas sp. and statistically analysed using Canoco and the R software package eHOF. A core from Kangerlussuaq Trough comprising the Late Holocene (~690–1498 Common Era) was also recounted and analysed using C2. The separated diatom species and chrysophyte cyst Archaeomonas sp. exhibited different relationships to both sea-ice concentration (aSIC) and sea surface temperature (aSST). The separated F. oceanica is a ‘cold-mixed’ water species occurring at cold aSST and both low and high aSIC. High abundances occur in the marginal ice zone (MIZ) where surficial meltwater is high during the spring bloom, with additional inputs from glacial meltwaters nearshore. F. reginae-jahniae is a sea-ice associated species related to cold aSST and high aSIC. High abundances occur in the low salinity Arctic Water dominated MIZ which experiences significant aSIC. F. arctica is a sea-ice associated species related to cold aSST and high aSIC. High abundances occur in the low salinity Arctic Water dominated MIZ which experiences high aSIC, particularly in polynya conditions. F. arctica can be considered a characteristic polynya species at high abundances. Archaeomonas sp. is a ‘cold-mixed’ water species related to both cold and relatively warm aSST and low and high aSIC. High abundances occur in both relatively warm ice-free Atlantic Water and also in cold high aSIC Arctic Water conditions rendering it a more complex indicator for aSST or aSIC proxy. However, the aversion to MIZ conditions indicates that Archaeomonas sp. is associated with a relatively saline unstratified water column. This is the first time that the distribution and ecology of Archaeomonas sp. has been presented. As such, the ecology described here can be used in future studies. The separation of the three diatom species is crucial for the ecological interpretation of downcore assemblage changes. It is also crucial for the application of transfer functions in order to have greater precision in reconstructing aSIC and assessing the influence of Arctic Water or Atlantic Water, even at low abundances.
  • Railo, Sohvi (2023)
    Ongoing climate change alters Northern marine ecosystems, where annual sea-ice cover has a significant role. Changes caused by climate change, such as sea surface temperature and sea-ice season, affect the composition of the community of primary producers. Primary producers have an important role in the ecosystems and biological and geological cycle, and a slight change in their community can have a significant impact on the marine system. Past environments provide important information on the effects of future changes in the environment and climate as well as tools to control them. Diatoms are commonly used in micropaleontology and paleoecology as an indicator for past environmental conditions and are therefore important proxies for paleoenvironments and climates. To better understand the past and future changes in the environment and climate, it is important to study not only microfossils in the sediments but also the relationship of modern diatoms to environmental factors. In the Baltic Sea, seasons strongly regulate the environmental conditions, which are reflected in the diatom community. Different seasons are represented by diatoms adapted to different conditions, which could lead to misrepresentation of environmental conditions if seasonal patterns are not recognized. In this master’s thesis, modern diatom seasonal succession is studied, as well as the role of environmental factors on diatom species over one year period. A sediment trap was used to monitor seasonal diatom succession and sediment vertical flux in Tvärminne Storfjärden, Gulf of Finland between 2012–2013. New information was discovered on the ecology and succession of common diatom species in the Baltic Sea. Data shows a clear succession according to the season as diatom community evolved to represent winter and early spring community, late spring community and autumn community. In winter the diatom community consists mainly of sea-ice species such as Pauliella taeniata and cold-water species Thalassiosira levanderi. The role of Pauliella taeniata was smaller than expected, possibly due to long-term decreasing trend associated with changing environment. Other central species were sea-ice related Stauroneis radissonii and a species belonging to Chaetoceros group. Sea-ice species formed a bloom around sea-ice melt and again during the spring bloom. In contrast to sea-ice species Thalassiosira levanderi formed a bloom only in the early spring, although it was present throughout the year. The bloom was probably initiated by optimal environmental conditions and lack of competition. Dominant species during spring bloom were common spring species in the Baltic Sea Skeletonema marinoi and Diatoma moniliformis. The latter occurs in benthic and planktic environments that were discovered blooming in planktic on spring blooms in May of 2013. In summer diatoms were relatively scarce, but a group of small centric species (including Cyclotella Choctawhatcheeana, Cyclotella atomus, Minidiscus proschkinae) formed massive autumn blooms as turbidity and nutrient concentrations increased in September and August.
  • Stark, Piritta (2022)
    In this study, single-grain rutile techniques (rutile U-Pb geochronology, Zr-in rutile thermometry, rutile Nb-Cr systematics and trace element composition) are applied on Red Clay samples from Lingtai, central-southern Chinese Loess Plateau (CLP), to reveal more detailed information on provenance of the Red Clay and wind regimes responsible for transporting the particles from source to sink between 7 Ma and 2.6 Ma. The new rutile data are combined with previous zircon U-Pb data from Lingtai and nearby Chaona to strengthen the interpretations with multi-proxy approach. The results suggest that from 7.05 Ma to 6.23 Ma the westerlies and the East Asian Winter Monsoon (EAWM) were relatively equally responsible for the sediment transportation to the CLP. At 5.55 Ma, the Red Clay was mostly derived from the westerly sources. At 3.88 Ma, contribution from northeastern Tibetan Plateau was most dominant suggesting enhanced East Asian Summer Monsoon (EASM) and surficial drainage from the source regions. At 3.20 Ma, the Red Clay was mainly sourced from proximal areas and fluctuation between EAWM and EASM had begun. This study demonstrates that single-grain rutile techniques have strong potential to aid a more precise distinction between individual primary and secondary sources for aeolian dust in the CLP region, especially when combined with zircon geochronology or other single-grain techniques. However, at present the applicability of rutile in provenance studies is hindered by scarcity of rutile data from the potential primary as well as secondary source regions, and lack of truly homogenous rutile standards for the analysis.
  • Suvorov, Alexander (2024)
    In this thesis, fossilized teeth of herbivores from four sites in Western Mongolia (Altanteel, Chono-Kharyakh, Oshin-Boro-Udzyur-Ula and Khrigis Nur) are examined for their stable carbon and oxygen isotope record. The fossils date to the Late Neogene period (ca. 10-3 Ma). The aim of the thesis is to reconstruct the palaeoclimate and palaeoenvironment of Western Mongolia during the Late Neogene using the isotopic records obtained from the fossilized teeth. The enamel of fourteen teeth from Rhinoceros, Equids, and a possible Giraffid was sampled and analyzed for δ13C and δ18O-values. The analyses were conducted using well-established methods with Isotope Ratio Mass Spectrometry. The stable carbon isotopes (13C and 12C) can be used to determine, the types of plants that these animals consume. Plants can be categorized into three groups based on their photosynthesis pathways. This study focuses on the C3 -plants, typically found in moister environments, and the C4-plants, which thrive in dry conditions. Specific δ13C-values have been established for these groups: –34‰ to –24‰ for C3-plants, and –20‰ to – 9‰ for C4. The δ13C-values obtained from the teeth of herbivores can be compared to these limits, allowing evaluation of the mammals’ diets (whether they consisted of C3 or C4-plants). If C3 plants dominate the die, this would indicate a moister climate, and likely a forested environment. Conversely, the presence of C4 plants would suggest grassland areas with more arid climatic conditions. The stable oxygen record in the teeth relates to the δ18O-composition of meteoric water in the area. Analysing δ18O-values facilitates the reconstruction of the mean temperatures of the habitats and allows for a comparison of climatic factors affecting precipitation and temperature over time. The stable carbon and oxygen records are compared to reconstruct the climate and environment of Western Mongolia during the Late Neogene. The results suggest an increase in the δ13C-values over time, which indicating a shift in the animals’ diets towards a more drought-stressed C3 and C4 plant-based one. The δ18O-values, on the other hand, remain stable and do not indicate a change in temperature during the Late Neogene. Comparing both the δ13C- and δ18O- values with studies conducted in China indicates a gradual aridification in Western Mongolia and China during the Late Neogene. However, the temperatures did not change significantly, although there were most likely alternating cooler and warmer periods during the time span of 10-3 Ma.
  • Laakkonen, Aliisa (2022)
    Peatlands are complex ecosystems that not only respond to external changes but also influence their environment. Permafrost peatlands have an important role in the global carbon (C) cycle as they store about 200 Pg of C. As permafrost thaws this C can be released either as methane (CH4) or carbon dioxide (CO2). In addition to these peatlands also emit nitrous oxide (N2O). Climate warming may change this sink-source balance of peatlands. Hydrological conditions are an important factor in peatland C dynamics. As permafrost thaws it can shift these ecosystems towards wetter or dryer conditions. Peat decomposition under dry conditions can have a strong positive feedback to climate change due CO2 emissions. Though wetter conditions can increase CH4 emissions. Through topography and hydrology, permafrost also affects vegetation dynamics. In this thesis I am examining peat profiles collected from two subarctic permafrost peatlands located in Kevo, Finland and Karlebotn, Norway. The profiles included an un-frozen active layer profile and a permafrost sample collected from inside a palsa mound. These samples were analysed for vegetation composition and peat properties (C and N content, C/N ratio and bulk density), they were also 14C dated and incubated. The purpose was to simulate a warmer climate to which these ecosystems will be exposed to in the future and observe how they will respond. The observations focused on the three most common GHGs of peatlands, CH4, CO2 and N2O. The permafrost samples showed potential for CH4 and CO2 emissions, whereas the active layer only emitted CO2. The CH4 emissions were interpreted to represent old CH4, whereas the CO2 was interpreted to be produced by the peat.