Traditionally, females have been considered to be strictly monogamous. Today, we know that females in the majority of species actively seek out and mate with several males. Trying to understand female preferences, including what benefits mate choice entails, has been the focus of intense research during the last decades. Females can gain both direct (e.g. access to better territories or paternal care) and indirect (i.e. genetic) benefits. The aim of this thesis is to further our understanding of the female reproductive strategies in the ruff, Philomachus pugnax (Aves, Scolopacidae). The ruff is a lekking wader, where males gather on leks to display to females that come there to mate. Males do not provide any paternal care to the offspring. Lekking systems are ideal for studying indirect benefits of female choice, as females do not gain any direct benefits from males. Females mated with several males and 50% of the broods were fathered by at least two males. The level of genetic similarity between two parents has previously been shown to be an important source of variation in offspring fitness. Males that were less closely related to the female fathered more offspring in broods with multiple paternity, such that females that mated multiply gained in terms of receiving more outbred offspring. There did not, however, appear to be an overall female preference for less closely related males. There are two genetically determined male reproductive strategies in the ruff, that differ in behaviour and morphology. There was no evidence for females taking male strategy into account when choosing a partner. Female post-fertilisation strategies may also influence fitness, e.g. through differential investment in eggs, gender of the offspring and choice of breeding habitat. Females allocated sex in a non-random manner dependent upon body condition, such that females in good condition had more daughters. Females were found to nest in higher than average vegetation and in areas with higher than average abundance of insects, factors likely to influence predation rates on both eggs and young, as well as foraging opportunities for the precocial young. Further, females were faithful to their previous breeding site and usually nested within meters of their previous nest. Hatching success did not, however, affect a female’s decision to return or not.

Much of current ecological theory stems from experimental studies. These studies have often been conducted in closed systems, at spatial scales that are much smaller than the systems of interest. It is known that the outcome of these experiments may be seriously affected by artefacts associated with the caging procedures, as well as by the actual difference in spatial scale between experimental and target system. Yet, quantitative methods for estimating and removing artefacts of enclosure and for extrapolating experimental results to the scales of natural systems are largely lacking. The aim of this thesis was to confront some of the problems encountered when scaling from experiments to nature in studies on predator-prey systems, with focus on effects of changes in spatial heterogeneity. Specifically, I examined mechanisms that may cause consumption rate estimates to depend on the size of the experimental arena. I also studied methods for scaling up these process rate estimates to natural predator-prey systems. The studies were performed on invertebrate predator-prey systems found in the northern Baltic Sea. Initially, a descriptive study of small-scale distribution patterns was performed, in order to get background information on how the behaviour of the organisms was manifested in the spatial structure of the community. Experimental studies of two predator-prey systems exposed an artefact that may be widespread in experiments aiming at quantifying biotic interactions. It is caused by predator and prey aggregating along the walls of the experimental containers. This behaviour affects the encounter rate between predator and prey, thereby causing consumption rates to be scale-dependent. Opposing the common belief that larger arenas always produce less biased results, this scale effect may instead be reduced by decreasing arena size. An alternative method for estimating the magnitude of, and subsequently removing, the artefact caused by aggregation along the arena wall was presented. Once unbiased estimates of process functions have been derived, the next step is to scale up the functions to natural systems. This extrapolation entails a considerable increase in spatial heterogeneity, which may have important implications for the dynamics of the system. Moment approximation provides a method of taking the heterogeneity of natural populations into account in the extrapolation process. In the last study of the thesis, the concepts of moment approximation and how to estimate relevant heterogeneity were explained, and it was shown how the method may be used for adding space as a component to a dynamic predator-prey model. It was concluded that moment approximation provides a simple and useful technique for dealing with effects of spatial variation, and that a major benefit of the method is that it provides a way of visualising how heterogeneity affects ecological processes.

In this thesis, I have studied long shoot performance in the monoecious, deciduous tree Betula pubescens ssp. czerepanovii. In field studies and a common garden experiment, I have a) studied how environmental variations affect the performance of long shoots in mountain birch, and b) described the relationship between long shoot performance and characteristics of the parent long shoot. I have shown that difference in long shoot performance to some extent can be explained by environmental variables such as temperature, precipitation and global radiation the current and previous summer, annual soil and air temperatures, and the length of growing season. For example, a low summer temperature the previous summer had a negative effect on a majority of long shoot characteristics. Variation in shoot characteristics was of the same magnitude along the regional east-western gradient as along the local altitudinal gradient. Variation among individual trees was of the same magnitude as variation among years. Further, long shoot performance was affected by the parent shoot characteristics and reflects that primordia of different organs are formed in the previous summer. On several occasions, freezing damage to mountain birch has been observed on Mt Njulla in northernmost Sweden. Following such damage, fewer but larger leaves emerge. Damages were compensated for with increased number of buds on long shoots produced the same year and one year after damage. Moreover, there were more new long shoots born on short shoots among damaged trees. Dormant buds and short shoots fulfil important functions in a fluctuating environment and as an adaptation to recurring damages of different origin and severity. Differences in the performance among mountain birch saplings grown in a common-garden at Abisko could to a large degree be explained by their origin. Further, saplings from Sweden and from Iceland responded differently to defoliation, and fertilization did not alter the responses to defoliation.

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No description available.

<p>Med kinesisk sammanfattning</p>

Den snabba förändringen av markanvändningen i Sverige har påverkat arter som är beroende av de minskande markanvändningsklasserna negativt, eftersom stora mängder habitat har förlorats. Genom att använda geografiska informationssystem för att studera kartmaterial, kan man dra slutsatser om förändring i habitattillgång och fragmenteringsgrad i området, baserat på undersökningsområdets historia. I denna studie undersöks kartmaterial över Julita gård i Södermanland, Sverige från åren 1798, 1850, 1900, 1950 och 2015 med avseende på förändring i markanvändning och fragmenteringsgrad. Resultaten visar att ängar och hagmarker har minskat betydligt i yta över åren, samtidigt som skogens yta har ökat kraftigt. Habitatförlusten av ängar och hagmarker är stor, men den förväntade fragmenteringseffekten uteblir. Habitatförlusten i Julitaområdet kan till stor del förklaras av ekonomiska och politiska tillstånd och åtgärder som har påverkat hela Sverige. Förlusten av habitat i undersökningsområdet har en förmodad stor negativ påverkan på diversiteten av arter som är knutna till ängar och hagmarker.

Sverige är fortfarande ett av världens mest våtmarksrika länder och har därför ett internationellt ansvar för bevarandearbetet. Däremot försvann huvuddelen av våtmarkerna i södra Sverige på grund av dikningar och sjösänkningar mellan 1800- och 1900-talen. Idag har en del våtmarker restaurerats och nyskapats, men det rör sig oftast om öppna vatten med strandzoner och arealmässigt långt mindre än det som trots allt finns kvar. De få kvarvarande kalkfuktängar har ett stort vetenskapligt och kulturellt värde. En rapport om Skånes rikkärr 2009 redogjorde för att 81 % av länets skyddade rikkärr är i behov av insatser i en eller annan form. Strax söder om Kristianstad sänktes Lyngsjön under början av 1800-talet och värdefulla rikkärr och kalkfuktängar bildades på den gamla sjöbottnen. Dessa marker är utnämnda Natura 2000-områden och kommer att bli skyddade som naturreservat. Floran är både art- och individrik och det är bland annat den rika förekomsten av orkidéer gör markerna skyddsvärda. För att bidra till kunskapsunderlaget för framtida skötsel- och bevarandeåtgärder studerades litteraturen och kärlväxterna undersöktes längs tre transekter. Resultatet visade att majoriteten av kärlväxterna som finns där är mer gynnade av bete än av slåtter. Många av arterna visade på en god hävd men det fanns inslag av bladvass Phragmites australis och andra konkurrensstarka växter som har möjlighet att ta över området på ett oönskat sätt. Målsättningen för markerna är att långsiktigt bevara och utveckla områdets naturvärden knutna till ett kulturpåverkat landskap. Här finns en lång tradition av odling och hävd med bete och slåtter. Betesupplägget behöver utvärderas för att ta hänsyn till floran och det finns behov av kompletterande skötsel när betesdjuren inte räcker till för att bevarandestatusen ska kunna upprätthållas.

No description available.

<p>An organism that is transferred from one place to another, causing major problems to the native species is termed invasive. Its natural dispersal across barriers may have been prevented but as man has turned able to rapidly travel all over the world organisms are brought to sites where they were never before observed. Adding the increasing global warming organisms may find it necessary to move around even further. This might cause major disturbance to the biological diversity, and hybridization and homogenization is one of many scenarios that could disturb the native diversity. In Sweden more that 2/3 of all alien plant species have been introduced to disturbed areas and the major introduction mechanism is gardening. The object of study in this presentation, <em>Pimpinella major</em> (Apiaceae) was introduced in Sweden alongside garden grasses during the 19^th century but has so far spread only marginally from the areas of introduction. The aim of the study was to quantify the appearance of <em>Pimpinella major</em> in different types of vegetation apart from road verges, where it has been noted systematically for over a decade. The investigation area covers most of the Tullgarn nature reserve. The result shows an astonishing tendency of P. major to remain growing only along the roads in the area. The very few findings besides next to roads are from deciduous and coniferous forests and fields. It seems that <em>Pimpinella major</em> almost without exception prefers heavily disturbed areas and access to large amounts of nitrogen fertilizer from exhaust fumes</p>