The molecular mechanisms and evolutionary significance of plumage colour variation in pied flycatchers (Ficedula hypoleuca)

A common feature of natural populations is that individuals differ in morphology, physiologyand behavior (i.e .phenotype). A thorough understanding of the molecular mechanisms and evolutionary forces behind this phenotypic variation is a prerequisite for understanding evolution.This thesis examines the molecular mechanism and the roles of the different evolutionary forces in plumage colour variation in pied flycatchers (Ficedulahypoleuca). Malepied flycatchers exhibit marked variation in both pigmentary and structural plumage colourand the trait has repeatedly been suggested to be of adaptive significance. An examination of plumage colour variation on reproductive output trevealed that structural colouration, and more specifically the degree of ultraviolet (UV) reflectance had an effect on number of young sired. Paternity analyses of breeding males revealed that males that had been cuckolded by their social mate tended to be less UV reflectant than males that had not been cuckolded.Neither pigment-based norstructural colouration was found to affect the probability of siring young in other nests. Phenotypic differentiation was found to be markedly greater than differentiation at neutralgenetic markers across the pied flycatcher breeding range. Furthermore patterns of differentiationin phenotypes and selectively neutral genes were not uniform. Outlier tests searching for genomic footprints of selection revealed elevated levels of genetic divergence in a gene associated with feather development (and thus potentially structural colouration) and ultraviolet vision. Th eobserved differentiation in allelic frequencies was particularly pronounced in the Spanish piedflycatcher populations. Examining gene expression during feather development indicated that the TYRP1 gene (known to be involved in the production of black pigment) may be relevant in generating phenotypic variation in pied flycatcher plumage. Also, energy homeostasis related genesfeatured prominently among the genes found to be expressed in one extreme phenotype but not the other. This is of particular interest in light of what is known about the pleiotropy ofthe melanocortin system which underlies brown-black pigment production. The melanocortinsystem is also associated with energy homeostasis (among a number of other physiological functions) and thus the results could be pointing to the signalling function of brown-blackplumage. Plumage colour variation in pied flycatchers, both structural and pigmentary, can thus beconcluded to be exhibiting signals of non-neutral evolution. Structural colouration was found to play a role in sexual selection and putative signals of selection were further detected in acandidate gene for this trait. Evidence for non-neutral evolution of pigmentary colouration was also detected. These findings, together with the fact that preliminary evidence for an energy balance associated signalling function for plumage was found, present good starting points for further investigations into the meaning and mechanisms of plumage colour variation in piedflycatchers.

A Diagnostic view of the Genetics of CASADIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL, OMIM #125310) is an inherited vascular disease. The main symptoms include migraineous headache, recurrent strokes and progressive cognitive impairment. CADASIL is caused by mutations in the NOTCH3 gene which result in degeneration of vascular smooth muscle cells, arteriolar stenosis and impaired cerebral blood flow. The aims of this study were assessment of the genetic background of Finnish and Swedish CADASIL patients, analysis of genetic and environmental factors that may influence the phenotype, and identification of the optimal diagnostic strategy. The majority of Finnish CADASIL patients carry the p.Arg133Cys mutation. Haplotype analysis of 18 families revealed a region of linkage disequilibrium around the NOTCH3 locus, which is evidence for a founder effect and a common ancestral mutation. Despite the same mutational background, the clinical course of CADASIL is highly variable between and even within families. The association of several genetic factors with the phenotypic variation was investigated in 120 CADASIL patients. Apolipoprotein E allele 4 was associated with earlier occurrence of strokes, especially in younger patients. Study of a pair of monozygotic twins with CADASIL revealed environmental factors which may influence the phenotype, i.e. smoking, statin medication and physical activity. Knowledge of these factors is useful, since life-style choices may influence the disease progression. The clinical CADASIL diagnosis can be confirmed by detection of either the NOTCH3 mutation or granular osmiophilic material by electron microscopy in skin biopsy, although the sensitivity estimates have been contradictory. Comparison of these two methods in a group of 131 diagnostic cases from Finland, Sweden and France demonstrated that both methods are highly sensitive and reliable.

Spatial and temporal variation in fish populations and assemblages in coastal waters of the northern Baltic Proper

The distribution and traits of fish are of interest both ecologically and socio-economically. In this thesis, phenotypic and structural variation in fish populations and assemblages was studied on multiple spatial and temporal scales in shallow coastal areas in the archipelago of the northern Baltic Proper. In Lumparn basin in Åland Islands, the fish assemblage displayed significant seasonal variation in depth zone distribution. The results indicate that investigating both spatial and temporal variation in small scale is crucial for understanding patterns in fish distribution and community structure in large scale. The local population of Eurasian perch Perca fluviatilis L displayed habitat-specific morphological and dietary variation. Perch in the pelagic zone were on average deeper in their body shape than the littoral ones and fed on fish and benthic invertebrates. The results differ from previous studies conducted in freshwater habitats, where the pelagic perch typically are streamlined in body shape and zooplanktivorous. Stable isotopes of carbon and nitrogen differed between perch with different stomach contents, suggesting differentiation of individual diet preferences. In the study areas Lumparn and Ivarskärsfjärden in Åland Islands and Galtfjärden in Swedish east coast, the development in fish assemblages during the 2000’s indicated a general shift towards higher abundances of small-bodied lower-order consumers, especially cyprinids. For European pikeperch Sander lucioperca L., recent declines in adult fish abundances and high mortalities (Z = 1.06–1.16) were observed, which suggests unsustainably high fishing pressure on pikeperch. Based on the results it can be hypothesized that fishing has reduced the abundances of large predatory fish, which together with bottom-up forcing by eutrophication has allowed the lower-order consumer species to increase in abundances. This thesis contributes to the scientific understanding of aquatic ecosystems with new descriptions on morphological and dietary adaptations in perch in brackish water, and on the seasonal variation in small-scale spatial fish distribution. The results also demonstrate anthropogenic effects on coastal fish communities and underline the urgency of further reducing nutrient inputs and regulating fisheries in the Baltic Sea region.

Genetic diversity and phenotypic variability of phytoplankton populations in the Baltic Sea

En av naturens mest grundläggande aspekter är den enorma mängd av variation som existerar mellan arter. Denna variation har lett oss till att klassificera olika organismer på basis av morfologiska skillnader och på senare tid till att jämföra genetiska skillnader på individens nivå. Den marina kiselalgen Skeletonema marinoi är en av de vanligaste växtplanktonarter i Östersjön under vårblomningen och anses viktig för den årliga produktionen. En av mina främsta målsättningar var att beskriva den intra-specifika diversiteten hos denna art längs med miljögradienter i Östersjön. Ett annat mål var att klargöra de faktorer som eventuellt är involverade i konfigurationen av genetisk diversitet och differentiering. Med hjälp av genetiska markörer visade jag att den genetiska diversiteten hos S. marinoi populationer i Östersjön är lägre jämfört med populationer i östra delen av Nordsjön. Arten är genetiskt uppdelad så att en utpräglad population förekommer i Östersjön och en annan, genetiskt åtskild population förekommer norr om de Danska sunden. Resultaten visar att de genetiskt åtskilda populationerna är anpassade till lokala salinitetsförhållanden. Genflödet mellan populationerna korrelerade kraftigt med havströmmar i området. Mina studier avslöjade även omfattande variation av fenotypiska, ekologiskt vikitga särdrag hos olika kloner. Djurplankton som äter kiselalger kunde modifiera den klonala mångfalden av fenotypiskt variabla S. marinoi populationer. En ökad klonal mångfald ledde till högre prestationsförmåga i fråga om primär produktion och stabiliserade ekofysiologiska funktioner. Som visas i denna avhandling består en art allt som oftast av åtskilliga genetiska varianter med fenotypiska skillnader. Kunskap om sådana intra-specifika skillnader är en förutsättning för att vi skall kunna förstå var och varför arter förekommer. Denna kunskap utgör även en grund för prognoser som siktar på att förutspå huruvida arter kan anpassa sig till framtida miljöförhållanden. ------------------------------------------------------ Suunnaton määrä variaatioita eliölajien välillä on perustavanlaatuinen ominaisuus luonnossa. Perinteisesti tätä monimuotoisuutta on käytetty organismien luokittelemiseen eri lajeihin niiden morfologisten eroavaisuuksien perusteella. Hiljattain myös geneettisten erojen huomioimista yksilötasolla on hyödynnetty lajien luokittelemisessa. Merialueilla esiintyvä piilevä, Skeletonema marinoi on yksi Itämeren tavallisimmista kasviplanktonlajeista kevätkukinnan aikana. Tavoitteenani oli selventää geneettistä ja fenotyyppistä monimuotoisuutta pitkin Itämeren ympäristögradienttejä. Geneettisen monimuotoisuuteen ja erkaantumiseen vaikuttavien tekijöiden selvittäminen oli tärkeä aspekti väitöstutkimuksessani. Geneettisiä markkereita käyttämällä pystyin toteamaan, että S. marinoi levän geneettinen monimuotoisuus on Itämeressä merkittävästi alhaisempi kuin läheisessä Pohjanmeren itäosassa. Tutkittu laji jakautuu geneettisesti yhteen erilliseen populaatioon Itämeressä ja toiseen selvästi erottuvaan populaatioon Tanskan salmien pohjoispuolella. Kokeellisten tulosten perusteella nämä geneettisesti erilaistuneet populaatiot ovat kumpikin sopeutuneet paikalliseen veden suolapitoisuuteen. Populaatioiden välisen geenivirran ja merivirtojen luoman yhteyden välillä havaittiin vahva korrelaatio. Tutkimukseni paljastivat myös laajaa vaihtelua Skeletonema-kloonien ekologisesti tärkeissä ominaisuuksissa. Kokeellisten tutkimusteni perusteella laiduntajat pystyivät muuttamaan geneettisten kloonien lukumäärää monimuotoisissa S. marinoi populaatioissa. Lisääntynyt kloonien lukumäärä paransi perustuotantokykyä ja vakautti ekofysiologisia toimintoja. Kuten tässä väitöstutkimuksessa osoitetaan, lajit koostuvat useimmiten lukuisista geneettisistä muunnelmista, jotka eroavat usein fenotyypeiltään. Ymmärtääksemme missä tietyt lajit esiintyvät ja miksi, tarvitsemme tietoa lajien sisäisistä vaihteluista. Tämä tieto on tarpeellista, jotta voimme ennustaa lajien sopeutumista tuleviin ympäristönmuutoksiin.