Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Biologiska vetenskaper) hsv:(Evolutionsbiologi) "

Sökning: hsv:(NATURVETENSKAP) hsv:(Biologiska vetenskaper) hsv:(Evolutionsbiologi)

Sortera/gruppera träfflistan
  • Caputo, Andrea, 1988- (författare)
  • Genomic and morphological diversity of marine planktonic diatom-diazotroph associations : a continuum of integration and diversification through geological time
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Symbioses between eukaryotes and nitrogen (N2)-fixing cyanobacteria (or diazotrophs) are quite common in the plankton community. A few genera of diatoms (Bacillariophyceae) such as Rhizosolenia, Hemiaulus and Chaetoceros are well known to form symbioses with the heterocystous diazotrophic cyanobacteria Richelia intracellularis and Calothrix rhizosoleniae. The latter are also called diatom-diazotroph associations, or DDAs. Up to now, the prokaryotic partners have been morphologically and genetically characterized, and the phylogenetic reconstruction of the well conserved nifH gene (encodes for the nitrogenase enzyme) placed the symbionts in 3 clusters based on their host-specificity, i.e. het-1 (Rhizosolenia-R. intracellularis), het-2 (Hemiaulus-R. intracellularis), and het-3 (Chaetoceros-C- rhizosoleniae). Conversely, the diatom-hosts, major representative of the phytoplankton community and crucial contributors to the carbon (C) biogeochemical cycle, have been understudied.The first aim of this thesis was to genetically and morphologically characterize the diatom-hosts, and to reconstruct the evolutionary background of the partnerships and the symbiont integration in the host. The molecular-clock analysis reconstruction showed the ancient appearance of the DDAs, and the traits characterizing the ancestors. In addition, diatom-hosts bearing internal symbionts (with more eroded draft genomes) appeared earlier than diatom-hosts with external symbionts. Finally a blast survey highlighted a broader distribution of the DDAs than expected.The second aim of this thesis was to compare genetic and physiological characteristics of the DDAs symbionts with the other eukaryote-diazotroph symbiosis, i.e. prymnesiophyte-UCYN-A (or Candidatus Atelocyanobacterium thalassa). The genome comparison highlighted more genes for transporters in het-3 (external symbiont) and in the UCYN-A based symbiosis, suggesting that symbiont location might be relevant also for metabolic exchanges and interactions with the host and/or environment. Moreover, a summary of methodological biases that brought to an underestimation of the DDAs is reported.The third aim of this thesis was to determine the distribution of the DDAs in the South Pacific Ocean using a quantitative polymerase chain reaction (qPCR) approach and to outline the environmental drivers of such distribution. Among the het-groups, het-1 was the most abundant/detected and co-occurred with the other 2 symbiotic strains, all responding similarly to the influence of abiotic factors, such as temperature and salinity (positive and negative correlation, respectively). Globally, Trichodesmium dominated the qPCR detections, followed by UCYN-B. UCYN-A phylotypes (A-1, A-2) were detected without their proposed hosts, for which new oligonucleotides were designed. The latter suggested a facultative symbiosis. Finally, microscopy observations of the het-groups highlighted a discrepancy with the qPCR counts (i.e. the former were several order of magnitudes lower), leading to the idea of developing a new approach to quantify the DDAs.  The fourth aim of this thesis was to develop highly specific in situ hybridization assays (CARD-FISH) to determine the presence of alternative life-stages and/or free-living partners. The new assays were applied to samples collected in the South China Sea and compared with abundance estimates from qPCR assays for the 3 symbiotic strains. Free-living cells were indeed detected along the transect, mainly at deeper depths. Free-living symbionts had two morphotypes: trichomes and single-cells. The latter were interpreted as temporary life-stages. Consistent co-occurrence of the 3 het-groups was also found in the SCS and application of a SEM model predicted positive interactions between the het groups. We interpreted the positive interaction as absence of intra-specific competition, and consistent with the previous study, temperature and salinity were predicted as major drivers of the DDAs distribution.
  • Bonnot, N. C., et al. (författare)
  • Who’s afraid of the big bad wolf? : Variation in the stress response among personalities and populations in a large wild herbivore
  • 2018
  • Ingår i: Oecologia. - Amsterdam : Springer. - 0029-8549 .- 1432-1939. ; 188:1, s. 85-95
  • Tidskriftsartikel (refereegranskat)abstract
    • Faced with rapid environmental changes, individuals may express different magnitude and plasticity in their response to a given stressor. However, little is known about the causes of variation in phenotypic plasticity of the stress response in wild populations. In the present study, we repeatedly captured individual roe deer (Capreolus capreolus) from two wild populations in Sweden exposed to differing levels of predation pressure and measured plasma concentrations of stress-induced cortisol and behavioral docility. While controlling for the marked effects of habituation, we found clear between-population differences in the stress-induced cortisol response. Roe deer living in the area that was recently recolonized by lynx (Lynx lynx) and wolves (Canis lupus) expressed cortisol levels that were around 30% higher than roe deer in the human-dominated landscape free of large carnivores. In addition, for the first time to our knowledge, we investigated the stress-induced cortisol response in free-ranging newborn fawns and found no evidence for hypo-responsiveness during early life in this species. Indeed, stress-induced cortisol levels were of similar magnitude and differed between populations to a similar extent in both neonates and adults. Finally, at an individual level, we found that both cortisol and docility levels were strongly repeatable, and weakly negatively inter-correlated, suggesting that individuals differed consistently in how they respond to a stressor, and supporting the existence of a stress-management syndrome in roe deer. © 2018, The Author(s).
  • Hurtado, P., et al. (författare)
  • Disentangling functional trait variation and covariation in epiphytic lichens along a continent-wide latitudinal gradient
  • 2020
  • Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8452 .- 1471-2954. ; 287:1922
  • Tidskriftsartikel (refereegranskat)abstract
    • Characterizing functional trait variation and covariation, and its drivers, is critical to understand the response of species to changing environmental conditions. Evolutionary and environmental factors determine how traits vary among and within species at multiple scales. However, disentangling their relative contribution is challenging and a comprehensive trait-environment framework addressing such questions is missing in lichens. We investigated the variation in nine traits related to photosynthetic performance, water use and nutrient acquisition applying phylogenetic comparative analyses in lichen epiphytic communities on beech across Europe. These poikilohydric organisms offer a valuable model owing to their inherent limitations to buffer contrasting environmental conditions. Photobiont type and growth form captured differences in certain physiological traits whose variation was largely determined by evolutionary processes (i.e. phylogenetic history), although the intraspecific component was non-negligible. Seasonal temperature fluctuations also had an impact on trait variation, while nitrogen content depended on photobiont type rather than nitrogen deposition. The inconsistency of trait covariation among and within species prevented establishing major resource use strategies in lichens. However, we did identify a general pattern related to the water-use strategy. Thus, to robustly unveil lichen responses under different climatic scenarios, it is necessary to incorporate both among and within-species trait variation and covariation.
  • Koch, Kamilla, et al. (författare)
  • Morphological differences in the ovary of Libellulidae (Odonata)
  • 2009
  • Ingår i: International Journal of Odonatology. - Oxford : Taylor & Francis. - 1388-7890. ; 12:1, s. 147-156
  • Tidskriftsartikel (refereegranskat)abstract
    • All female Odonata have been assumed to produce oocytes continuously during their mature life span. However, a recent study of ovariole orientation and development led to the suggestion that Libellulidae are divided into two groups of species, one with continuous, the other with stepwise oocyte production. To find more evidence of this division, we compared the size variation and growth within the vitellarium of the ovary, studying oocytes, and follicle cells. We found that morphological characters discriminate between the two ovary types in eight of the 10 investigated species. In both types we found an increase in all measurements from the anterior to the posterior end of the vitellarium. The increase in oocyte width and follicle cell length was significantly higher in species with a continuous oocyte production. We also noted that follicle cells may have more than one nucleus and that their number can vary during vitellogenesis. Our study confirmed the hypotheses that two different ovary types exist in Libellulidae. The two species not fitting into this grouping could be an artefact of small samp le size due to intraspecific phenotypic plasticity, or else there might be more than two ovary groups, or even a continuum. We could not offer an explanation as to how the process of stepwise oocyte production differs from continuous based production on morphological characters.
  • Spagopoulou, Foteini, et al. (författare)
  • Shifts in Reproductive Investment in Response to Competitors Lower Male Reproductive Success
  • 2020
  • Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 196:3, s. 355-368
  • Tidskriftsartikel (refereegranskat)abstract
    • In many species, males exhibit phenotypic plasticity in sexually selected traits when exposed to social cues about the intensity of sexual competition. To date, however, few studies have tested how this plasticity affects male reproductive success. We initially tested whether male mosquitofish,Gambusia holbrooki(Poeciliidae), change their investment in traits under pre- and postcopulatory sexual selection depending on the social environment. For a full spermatogenesis cycle, focal males were exposed to visual and chemical cues of rivals that were either present (competitive treatment) or absent (control). Males from the competitive treatment had significantly slower-swimming sperm but did not differ in sperm count from control males. When two males competed for a female, competitive treatment males also made significantly fewer copulation attempts and courtship displays than control males. Further, paternity analysis of 708 offspring from 148 potential sires, testing whether these changes in reproductive traits affected male reproductive success, showed that males previously exposed to cues about the presence of rivals sired significantly fewer offspring when competing with a control male. We discuss several possible explanations for these unusual findings.
  • Rest, Joshua S, et al. (författare)
  • Molecular systematics of primary reptilian lineages and the tuatara mitochondrial genome.
  • 2003
  • Ingår i: Molecular Phylogenetics and Evolution. - 1055-7903 .- 1095-9513. ; 29:2, s. 289-97
  • Tidskriftsartikel (refereegranskat)abstract
    • We provide phylogenetic analyses for primary Reptilia lineages including, for the first time, Sphenodon punctatus (tuatara) using data from whole mitochondrial genomes. Our analyses firmly support a sister relationship between Sphenodon and Squamata, which includes lizards and snakes. Using Sphenodon as an outgroup for select squamates, we found evidence indicating a sister relationship, among our study taxa, between Serpentes (represented by Dinodon) and Varanidae. Our analyses support monophyly of Archosauria, and a sister relationship between turtles and archosaurs. This latter relationship is congruent with a growing set of morphological and molecular analyses placing turtles within crown Diapsida and recognizing them as secondarily anapsid (lacking a skull fenestration). Inclusion of Sphenodon, as the only surviving member of Sphenodontia (with fossils from the mid-Triassic), helps to fill a sampling gap within previous analyses of reptilian phylogeny. We also report a unique configuration for the mitochondrial genome of Sphenodon, including two tRNA(Lys) copies and an absence of ND5, tRNA(His), and tRNA(Thr) genes.
  • Fallahshahroudi, Amir, 1981- (författare)
  • Domestication Effects on the Stress Response in Chickens : Genetics, Physiology, and Behaviour
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Animal domestication, the process where animals become adapted to living in proximity to humans, is associated with the alteration of multiple traits, including decreased fearfulness and stress response. With an estimated population of 50 billion, the domesticated chicken is the most populous avian species in the world. Hundreds of chicken breeds have been developed for meat and egg production, hobby or research purposes. Multidirectional selection and the relaxation of natural selection in captivity have created immense phenotypic diversity amongst domesticates in a relatively short evolutionary time. The extensive phenotypic diversity, existence of the wild ancestor, and feasibility of intercrossing various breeds makes the chicken a suitable model animal for deciphering genetic determinants of complex traits such as stress response. We used chicken domestication as a model to gain insights about the mechanisms that regulate stress response in an avian species. We studied behavioural and physiological stress response in the ancestral Red Junglefowl and one of its domesticated progenies, White Leghorn. An advanced intercross between the aforementioned breeds was later used to map genetic loci underlying modification of stress response. The general pattern of the stress response in chickens was comparable with that reported in mammals, however we identified distinctive differences in the stress modulatory pathways in chickens. We showed that changes in the expression levels of several stress modulatory genes in the brain, the pituitary and the adrenal glands underlie the observed modified stress response in domesticated chickens. Using quantitative trait loci (QTL) mapping, several QTL underlying stress induced corticosterone, aldosterone and baseline dehydroepiandrosterone (DHEA) levels were detected. As a next step, we combined QTL mapping with gene expression (eQTL) mapping and narrowed two QTL down to the putative causal genes, SERPINA10 and PDE1C. Both of these genes were differentially expressed in the adrenal glands of White Leghorn and the Red Junglefowl, had overlapping eQTL with hormonal QTL, and their expression levels in the adrenal glands were correlated with plasma levels of corticosterone and al-dosterone. These two genes thus serve as strong candidates for further functional investigation concerning modification of the stress response during domestication. This dissertation increase the knowledge about genetics and physiology of the stress response in an avian species and its modification during domestication. Our findings expand the basic knowledge about the stress response in chicken, which can potentially be used to improve welfare through appropriate genetic selection.
  • Stenberg, Per, et al. (författare)
  • Cytology of Asexual Animals
  • 2009
  • Ingår i: Lost Sex. - Dordrecht : Springer Netherlands. - 9789048127696 - 9789048127702 ; , s. 63-74
  • Bokkapitel (övrigt vetenskapligt)abstract
    • We review the cytological mechanisms underlying asexual reproduction, i.e. reproduction without fertilization, in animals. Asexuality or parthenogenesis has evolved many times and the cytological mechanisms to restore the parental chromosome number can vary between and even within species. In automictic or meiotic parthenogenesis, meiosis takes place but the chromosomal constitution of the mother is restored through one or several different mechanisms. Some of these mechanisms enforce homozygosity at all loci while some other mechanisms pass the genome of the mother intact to the offspring. In apomictic or mitotic parthenogenesis the eggs are formed through what is essentially a set of mitoses. Polyploidy, is in general incompatible with chromosomal sex determination and is a rare condition in animals. However, many asexual and hermaphroditic forms are polyploid to various degrees. Polyploidy is divided into allo- and autopolyploidy. In the former mode the chromosome sets are derived from two or more different species while in autopolyploidy the multiplication has taken place within one species. We discuss the evolutionary consequences of the different cytological mechanisms involved in asexual reproduction.
  • Sundman, Ann-Sofie, 1982- (författare)
  • Dog behaviour : Intricate picture of genetics, epigenetics, and human-dog relations
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Dogs, Canis familiaris, share the lives of humans all over the world. That dogs, and the behavior of dogs, are of interest to many is therefore no surprise. In this thesis, the main aim has been to identify factors that affect dogs’ behaviours.The dog, Canis familiaris, is our first domesticated animal. Since domestication, various types of dogs have developed through adaptation to an environment shared with humans and through our selective breeding, resulting in a unique variation in morphology and behaviour. Although there is an individual variation in the behaviour of dogs, there is also a difference between breeds. Moreover, selection during the last decades has split some breeds into divergent types. Labrador and golden retrievers are divided into a common type, for show and companionship, and a field type, for hunting. By comparing the breed types, we can study the effects of recent selection. In Paper I, we investigate differences in general behavioural traits between Labrador and golden retriever and between common and field type within the two breeds by using results from the standardized behaviour test Dog Mentality Assessment. There were differences between breeds and types for all behavioural traits. However, there was also an interaction between breed and type. Thus, a common/field-type Labrador does not behave like a common/field-type golden retriever. Even though they have been selected for similar traits, the selection has affected the general behavioural traits differently in the two breeds.In paper II, we were interested in dogs’ human-directed social skills. Dogs have a high social competence when it comes to humans. Two experiments commonly used to study these skills are the problem-solving test, where dogs’ human-directed behaviours when faced with a problem are measured, and the pointing test, where dogs are tested on how well they understand human gestures. We compared the social skills of German shepherds and Labrador retrievers, and of common- and field-type Labradors. Labradors were more successful in the pointing test and German shepherds stayed closer to their owners during the problem solving. Among Labrador types, the field type had more human eye contact than the common type. Importantly, when comparing the two experiments, we found no positive correlations between the problem-solving test and the pointing test, suggesting that the two tests measure different aspects of human-directed social behaviour in dogs.A previous study has identified two suggestive genetic regions for human-directed social behaviours during the problem-solving test in beagles. In paper III, we show that these SNPs are also associated to social behaviours in Labrador and golden retrievers. Moreover, the Labrador breed types differed significantly in allele frequencies. This indicates that the two SNPs have been affected by recent selection and may have a part in the differences in sociability between common and field type.The behaviour of dogs cannot simply be explained by genetics, there is also an environmental component. In paper IV, we study which factors that affect long-term stress in dogs. Long-term cortisol can be measured by hair samples. We found a clear synchronization in hair cortisol concentrations between dogs and their owners. Neither dogs’ activity levels nor their behavioural traits affected the cortisol, however, the personality of the owners did. Therefore, we suggest that dogs mirror the stress level of their owners.The mediator between genes and the environment is epigenetics, and one epigenetic factor is DNA methylation. In paper V, we compared methylation patterns of wolves and dogs as well as dog breeds. Between both wolves and dogs and among dogs there were substantial differences in methylated DNA regions, suggesting that DNA methylation is likely to contribute to the vast variation among canines. We hypothesize that epigenetic factors have been important during domestication and in breed formation.In this thesis, I cover several aspects on how dogs’ behaviours can be affected, and paint an intricate picture on how genetics, epigenetics, and human-dog relations forms dog behaviour.
Skapa referenser, mejla, bekava och länka
Typ av publikation
tidskriftsartikel (1736)
annan publikation (203)
doktorsavhandling (127)
forskningsöversikt (72)
konferensbidrag (61)
bokkapitel (41)
visa fler...
rapport (10)
recension (9)
bok (7)
licentiatavhandling (5)
visa färre...
Typ av innehåll
refereegranskat (1789)
övrigt vetenskapligt (443)
populärvet., debatt m.m. (35)
Ellegren, Hans (57)
Dalen, Love (53)
Björklund, Mats (51)
Jakobsson, Mattias (47)
Suh, Alexander (47)
Lascoux, Martin (44)
visa fler...
Arnqvist, Göran, 196 ... (42)
Johannesson, Hanna (36)
Sanchez, Sophie (35)
Berger, David (31)
Ettema, Thijs J. G. (29)
Qvarnström, Anna (29)
Höglund, Jacob (29)
Burri, Reto (28)
Wolf, Jochen B. W. (27)
Ericson, Per G P, 19 ... (27)
Friberg, Urban (27)
Johansson, Frank (26)
Günther, Torsten (26)
Hintze, Arend, Profe ... (24)
Ahlberg, Per, 1963- (23)
Ågren, Jon (22)
Laurila, Anssi (22)
Immler, Simone (21)
Maklakov, Alexei A. (21)
Kolm, Niclas (21)
Gustafsson, Lars (20)
Gilbert, M. Thomas P ... (20)
Glemin, Sylvain (20)
Andersson, Dan I. (19)
Friberg, Magne (19)
Ahlberg, Per (18)
Forsman, Anders (18)
Immonen, Elina (18)
Mugal, Carina F (18)
Wheat, Christopher W ... (17)
Zhang, Guojie (17)
Svensson, P. Andreas ... (17)
Lagercrantz, Ulf (16)
Skoglund, Pontus (16)
Adami, C. (15)
Werdelin, Lars (15)
Nylin, Sören (15)
Gustafsson, Lars, Pr ... (15)
Wiklund, Christer (15)
Andersson, Siv (15)
Doligez, Blandine (15)
Backström, Niclas (15)
Chen, Jun (15)
Schlebusch, Carina, ... (15)
visa färre...
Uppsala universitet (1538)
Stockholms universitet (297)
Umeå universitet (187)
Naturhistoriska riksmuseet (175)
Linnéuniversitetet (108)
Lunds universitet (94)
visa fler...
Linköpings universitet (93)
Högskolan Dalarna (33)
Kungliga Tekniska Högskolan (22)
Södertörns högskola (19)
Göteborgs universitet (18)
Karolinska Institutet (16)
Örebro universitet (13)
Karlstads universitet (10)
Sveriges Lantbruksuniversitet (9)
Mälardalens universitet (8)
Jönköping University (6)
Högskolan i Halmstad (6)
RISE (6)
Högskolan i Skövde (5)
Chalmers tekniska högskola (5)
Mittuniversitetet (3)
Luleå tekniska universitet (2)
Högskolan Väst (2)
Högskolan i Gävle (2)
VTI - Statens väg- och transportforskningsinstitut (2)
Högskolan Kristianstad (1)
Högskolan i Borås (1)
visa färre...
Engelska (2239)
Svenska (28)
Franska (2)
Spanska (1)
Finska (1)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (2271)
Medicin och hälsovetenskap (31)
Humaniora (31)
Samhällsvetenskap (23)
Lantbruksvetenskap (14)
Teknik (2)


Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy