Research Assessment Exercise 2007 University of Oulu
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3a.4 Year 2004Folmer Bokma (2004) Why most birds are small - a macro-ecological approach to the evolution of avian body size. Acta Universitatis Ouluensis A 411. University of Oulu, Department of Biology. http://herkules.oulu.fi/isbn9514273451/ There are more small-bodied species of birds than those having large bodies. Generally, and relative to occurrance in any one place, small-bodied species also contain more individuals than large-bodied species. The same patterns have been documented for several groups of higher organisms for example, snakes, flowering plants and mammals, which suggests that there exists a general reason "why", which applies to other groups of species as well as to birds. This thesis attempts to identify this reason. In the first place, it is possible that most species happened to become small-bodied by chance. Simulations of neutral body-size evolution indicate however that the observed bias towards small size is stronger than that accounted for by neutral evolution. Then, the most plausible explanation for why most species are small is that small-bodied species speciate faster. However, statistical analyses accounting for historical relatedness of present-day species indicate no relation between body size and the rate of speciation. Finally, instead of little by little, the dominance of small species may have arisen suddenly, when approximately 65 million years ago (presumably) a large meteorite hit the earth, causing mass extinctions. However, analysis of body sizes and genetic differences of extant species reveals that while avian species numbers were approximately halved, the catastrophe affected small and large species equally. Thus, the reason why most species are small does not seem to be due to differential rates of speciation or extinction. Instead, the cause appears to be in the tempo and mode of evolution. It was found by analysis of extant species' body size that probably most differences in body size between species arise at the moment of speciation. Differences between small-bodied species are smaller than between large-bodied species and probably this difference also has its origin at the moment of speciation. Consequently, groups of small species stay small whereas groups of large species are more variable in body size, so that in the end most species are small. Keywords: body size, extinction, macroevolution, punctuated equilibrium, speciation Kalle Hellström (2004) Variation in grazing tolerance and restoration of meadow plant communities. Acta Universitatis Ouluensis A 423. University of Oulu, Department of Biology. http://herkules.oulu.fi/isbn9514274938/ The area of traditionally managed semi-natural meadows is declining throughout Europe. Knowledge of how to restore their species richness is urgently needed. Community manipulations by means of grazing and mowing and, on the other hand, knowledge of species-level responses as well as the responses of functional plant groups to management may help in planning appropriate restoration tools. The restoration of species richness was studied in two community-level experiments: in a sheep grazing experiment and in a mowing experiment. Three species-level studies were conducted to test the compensatory capacity of monocarpic, herbaceous plants (Gentianella amarella, Erysimum strictum, Euphrasia stricta) to simulated herbivory (10–50% of stem being cut). The perennial Linaria vulgaris was used to study whether there is any benefit of clonal integration in the tolerance of simulated herbivory. This topic was studied in a growth experiment and a 13C tracer study. In both grazing and mowing experiments, small herbs gained more space, while the dominant tall herbs subsided. The species number increased by 30% on the grazed plots, but mowing did not affect species richness, probably indicating seed limitation. At sites of this kind, seed addition could be used to promote restoration. Functional plant groups appeared to be useful in predicting the effects of grazing on plant communities. Early season grazing and mowing seem to be proper management tools in overgrown/degraded meadows. In species-level studies, all the species had relatively good compensatory capacity to repair small damage. Overcompensation was observed in response to apical damage, especially when the growing conditions were favourable, supporting the compensatory continuum hypothesis. The studied monocarpic plant species may share a common unbranched growth form where incidental apical damage leads to activation of uninitialized meristems and slight overcompensation. These responses may represent consequences of adaptation to above-ground competition, rather than adaptation to predictable herbivory. In Linaria, damaged ramets were not supported, but the neighbouring ramets seemed to compete with each other for root resources. While growing in disturbed habitats, it is more profitable for this species to invest in new ramets. The present studies showed that, while the appearance and structure of a traditional grassland rich in small-growing herbs can be restored in five years, it is more difficult to increase species diversity by mere mowing or grazing. Knowledge of the tolerance of individual species for herbivory could provide useful information for planning management practices. More studies on the effects of different management tools on different meadow types are urgently needed for the maintenance of the diversity of these valuable environments. Keywords: compensatory continuum, functional plant groups, herbivory, management, monocarpic species, mowing, restoration, semi-natural meadows, species diversity Essi Keskinen (2004) Post-embryonic growth and fine-structural organization of arthropod photoreceptors. A study involving selected species of insects and crustaceans. Acta Universitatis Ouluensis A 424. University of Oulu, Department of Biology. http://herkules.oulu.fi/isbn9514275608/ Arthropod photoreceptors are versatile sense organs. Any investigation of these organs has to consider that their structure and functional limitations at the moment of fixation depend on many factors: species, sex, developmental and nutritional state of the animal, time of day and ambient light. The microscopic image of an arthropod photoreceptor is always a sample frozen in time and space. Quite often publications on arthropod photoreceptors only provide the name of the species studied, but nothing beyond that. At least the developmental status of the study animals ought to be noted, possibly even the sex and body size. Forty publications on insect and 54 on crustacean photoreceptors were checked for the information that was given about the investigated animals: Out of these papers 40% provide only information on the name of the studied species and nothing else. The aim of this thesis, thus, was to investigate, to what extent the developmental state and the sex of the animal as well as the ambient light conditions affect the structure of the eye of a given species. Five species of arthropods were chosen: (a) the semi-terrestrial isopod Ligia exotica and two aquatic Branchiuran fishlice, Argulus foliaceus and A. coregoni, to represent the Crustacea, and (b) the stick insect Carausius morosus and the spittle bug Philaenus spumarius, both terrestrial, to represent the Insecta. The addition of new ommatidia was studied in a paper on L. exotica, which also dealt with the site of newly added ommatidia. It was found that all of these species had two sessile, large compound eyes firmly positioned on their heads (but fishlouse compound eyes were bathed in haemocoelic liquid). In all species, the compound eye was found to be of the apposition type. The gross structural organization of the ommatidia stayed approximately the same during the whole post-embryonic development. Lateral ocelli of the A. coregoni nauplius eye changed from elongated to spherical between the metanauplius and the 8th stage pre-adult. The sex of the specimens was not found to affect the structure of the eye. In all species, it turned out that the larger the animal and hence the eye, the better its sensitivity. The addition of new ommatidia in the L. exotica compound eye was concluded to take place in the anterior and ventral marginal areas of the eye. Keywords: Compound eye, crustaceans, insects, nauplius eye, post-embryonic development Eero Niemelä (2004) Variation in the yearly and seasonal abundance of juvenile Atlantic salmon in a long-term monitoring programme. Methodology, status of stocks and reference points. Acta Universitatis Ouluensis A 415. University of Oulu, Department of Biology. http://herkules.oulu.fi/isbn9514273702/ The long-term monitoring programme for the River Teno Atlantic salmon (Salmo salar L.) stocks has covered the juvenile densities (25 yr) and the abundance and characteristics of the returning adults (31 yr). The feasibility of the programme was examined by studying the interrelationships between the yearly catches and juvenile salmon densities, performance and reliability of the electrofishing method, and the effects of fishing regulations on the salmon stocks. Finally, juvenile salmon abundances were related to the available fluvial habitat and reference levels were defined by using habitat models. Extensive seasonal variation in juvenile salmon density was apparent. The densities of fry and parr showed an increase from early summer towards late August and a subsequent decline towards the autumn. Long-term electrofishing monitoring is recommended to be carried out in as standardized a form as possible in order to reduce variations in catchability. Over the 25-year monitoring period, the abundance of parr (1+) increased in one sampling site cluster out of nine clusters and declined in one cluster. Fry densities increased in seven clusters. Juvenile densities exhibited considerable temporal and spatial variation. Similarly, the salmon catches varied extensively, and the numbers of 1-2SW salmon and previous spawners increased. The numbers of 1–2SW female salmon in the catches and the subsequent juvenile densities were significantly related, as regression models explained 19–44% of the variation in juvenile abundance. The juvenile monitoring allows evaluation of the relative spawner abundance in preceding years, confirming the information provided by catch statistics. Juvenile salmon densities explained 23–41% of the variation in subsequent 1–2SW salmon catches. Significant correlations were detected with a lag of one year between the subsequent sea-age groups of salmon in the catches. Thus, these relationships can be used for forecasting future salmon abundances. Large areas of high habitat quality in the River Teno system fail to meet their expected juvenile densities, and factors others than physical habitat characteristics, such as a lack of spawners, restrict the juvenile abundance. More than 50% of the permanent sampling sites where habitat would predict high densities (≥ 50 parr per 100 m2) had observed densities in the mid (10–49) or low density category (< 10). It was expected that the densities should increase after regulatory measures implemented in 1989–1990, but results indicate that the reference levels of parr densities have not been attained and the densities have not increased, whereas a general increase in salmon fry densities was detected. Nonetheless, the management measures have succeeded in maintaining the River Teno salmon stocks, which still today enable and support diversified fisheries. Keywords: density, electrofishing, long-term monitoring, Salmo salar, spatial and temporal variability, trends Jarmo Poikolainen (2004) Mosses, epiphytic lichens and tree bark as biomonitors for air pollutants - specifically for heavy metals in regional surveys. Acta Universitatis Ouluensis A 421. University of Oulu, Department of Biology. http://herkules.oulu.fi/isbn9514274792/ The thesis consists of regional forest condition studies, using different biomonitors. Heavy metal deposition was investigated in 1985–2000 on the basis of the heavy metal concentrations (As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, V, Zn) in mosses in Finland. A comparison on the suitability of mosses, epiphytic lichens and pine bark as biomonitors of heavy metals was also carried. Bark was also used to study the dispersal of emissions from the Kola Peninsula into northern Finland. The occurrence of green algae on conifers in Finland was investigated in 1985 and 1995. Regional and temporal differences were found in the heavy metal concentrations of mosses in Finland. The concentrations of most metals were the highest in southern Finland, and they decreased towards the north. Some of the major emission source had a noticeable effect on the Cu, Ni and Cr concentrations of mosses in the surroundings of the emission sources. The Pb, Cd and V concentrations decreased the most during the study period. Mosses, lichens and bark gave a relatively similar result for heavy metal deposition in Finland. However, the comparisons indicated that mosses are better suited as biomonitors for regional surveys than epiphytic lichens, because the regional differences in heavy metal deposition were more readily reflected by concentrations in mosses than in lichens. Bark is relatively unsuitable for regional surveys due to the small range of variation in the concentrations. Emissions from the Kola Peninsula had a clear effect on the sulphur and heavy metal concentrations of pine bark. The concentrations in bark were at very high levels close to the smelters, but they rapidly decreased on moving towards the west. The effects of emissions were still clearly visible in north-eastern Lapland. There was strong increase in the abundance of green algae on conifers in southern and central Finland during the period 1985–1995. The increase is probably due to following factors: climate warming, and an increase in nitrogen and a decrease in sulphur in their habitats. Half of each biomonitor sample collected in the surveys has been stored in the specimen bank at Paljakka. The storage of samples offers advantages for monitoring purposes. The availability of long-term sample series makes it possible to construct retrospective time series of the pollutants. The specimen bank is to be further developed in the future by establishing a reputation as a storage facility for samples related to forest ecosystems. Keywords: atmospheric deposition, biomonitors, heavy metals, nitrogen, regional surveys, sulphur Leena Uimaniemi (2004) Maintenance of genetic diversity in four taiga specialists. Acta Universitatis Ouluensis A 417. University of Oulu, Department of Biology. http://herkules.oulu.fi/isbn9514274105/ Genetic diversity in three taiga specialists - the Siberian tit (Parus cinctus), the Siberian jay (Perisoreus infaustus) and the Siberian flying squirrel (Pteromys volans) - was assessed by comparing DNA sequence variation across the mitochondrial control region and allele frequencies of microsatellites from samples collected from Fennoscandia and Siberia. Population sizes of these species have declined in association with fragmentation and loss of suitable forest habitat due to modern forestry practices in Fennoscandia. The red squirrel (Sciurus vulgaris) served as a reference for the flying squirrel. Genetic differentiation among species studied ranged from a panmictic population in the Siberian tit to that of the strong differentiation of populations (θST = 53%) in the flying squirrel in Finland. MtDNA and microsatellite data, together with assignment studies, showed the Siberian jay population to be significantly genetically structured and supported the existence of a metapopulation like structuring in Fennoscandia. Division of genetic variation among flying squirrel populations along the ancient shoreline of the Littorina Lymnea Sea stage of the Baltic Sea (7000 BP) and two geographically associated branches in the minimum spanning network supported a two-way colonisation history for the species. The Finnish inland appears to have been colonised from the east in association with the arrival of Norway spruce. At the same time, Coastal Finland was colonised from the south-east through the Karelian Isthmus. Gene flow of the species appeared female biased and restricted. Species exhibiting more restrictive dispersal characteristics and habitat requirements possessed stronger population genetic structure than those with opposite characteristics. Growth or contractions in population size leave characteristic signatures in mtDNA that can be studied by comparing different sequence diversity estimates among populations. I applied this method to the species studied. Significant differences in nucleotide diversities indicated restrictions in gene flow among populations in all species studied. Half of the Siberian jay populations gave a signal of population size bottleneck. All the species studied showed differences in their population genetic structures across their entire distribution ranges consistent with the multirefugia model, most likely to be attributable to differences in their ecological characteristics and Pleistocene histories. Keywords: conservation, microsatellites, mitochondrial DNA, phylogeography, taiga species |