umu.sePublications
Change search
Refine search result
12 51 - 81 of 81
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51. Ostman, Carina
    et al.
    Roat Kultima, Jens
    Roat, Carsten
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rundblom, Karl
    Acontia and mesentery nematocysts of the sea anemone Metridium senile (Linnaeus, 1761) (Cnidaria: Anthozoa)2010In: Scientia Marina, ISSN 0214-8358, E-ISSN 1886-8134, Vol. 74, no 3, p. 483-497Article in journal (Refereed)
    Abstract [en]

    Acontia and mesentery nematocysts of Metridium senile (Linnaeus, 1761) are described from interference-contrast light micrographs (LMs) and scanning electron micrographs (SEMs). The acontia have 2 nematocyst categories grouped into small, medium and large size-classes, including 5 types: of these, large b-mastigophores and large p-amastigophores are the largest and most abundant. Mesenterial tissues, characterised by small p-mastigophores and medium p-amastigophores, have 3 nematocyst categories grouped as small and medium, including 6 types. Attention is given to nematocyst maturation, especially to the differentiation of the shaft into proximal and main regions as helical folding of the shaft wall proceeds. Groups of differentiating nematoblasts occur along acontia, and near the junction between acontia and mesenterial filaments. Nematoblasts are sparsely found throughout mesenterial tissues.

  • 52.
    Persson, Jens
    et al.
    Inst. för skoglig zooekologi, SLU Umeå.
    Zachrisson, Anna
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Sandström, Camilla
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Ericsson, Göran
    Inst. för skoglig zooekologi, SLU Umeå.
    Lokal förvaltning av stora rovdjur: en kunskapssammanställning2004Report (Other academic)
    Abstract [sv]

    Hur våra gemensamma resurser bäst kan och ska förvaltas är både en komplicerad och ofta konfliktfylld fråga. Det framgår inte minst av debatten kring hur och på vilken nivå våra storarovdjur ska förvaltas. Eftersom rovdjuren vanligtvis lever i glesa populationer, spridda över mycket stora områden, men också är förknippade med såväl ekonomiska som sociala konflikter harden centrala nivån ansetts bäst lämpad att förvalta rovdjuren.Det har bland annat medfört att de som lever nära rovdjuren och riskerar att drabbas av rovdjuren upplever att de har småmöjligheter att påverka politikens och förvaltningens utformning.Det har i sin tur skapat konflikter kring hur och på vilketsätt rovdjuren bäst förvaltas (SOU 1999:146).

    I en strävan att öka förtroendet för den svenska rovdjurspolitikenoch överbrygga den klyfta mellan centralmakt och lokalnivå eller mellan stad och land som uppstått har riksdagenbeslutat att lokala aktörer på olika sätt ska involveras i förvaltningen.Inom ramen för en sammanhållen rovdjurspolitik harbland annat regionala rovdjursgrupper, sammansatta av olikaberörda intressen, bildats. Den svenska decentraliseringen avrovdjurspolitiken, följer den av FN fastslagna andra Malawi-principensom slår fast att förvaltning av ekosystem ska decentraliserastill lägsta ändamålsenliga nivå (UNEP/CBD/COP/4/inf.9).

    Att decentralisera förvaltningen av gemensamma resurser,i det här fallet stora rovdjur, är förknippat med en rad specifikaproblem. Förutom att det krävs biologisk kunskap om rovdjuren,är det nödvändigt att reda ut vilka sociala, ekonomiska och kulturellaaspekter som bör beaktas vid förvaltningen. Det är ocksånödvändigt att finna en acceptabel balans mellan decentraliseringoch centralisering av beslutsprocessen. Lokal förvaltningav rovdjur är relativt nytt även internationellt sett. Det är fortfarandetill stora delar okänt vad som egentligen krävs för attlokal förvaltning av rovdjur ska fungera. Det är emellertid möjligtatt vi kan lära något av de försök som redan genomförts. Syfte med den här rapporten är därför dels att sammanställakunskap om lokal eller decentraliserad förvaltning av stora rovdjur, främst utifrån biologiska, socioekonomiska och förvaltningspolitiskaförutsättningar, dels att skapa ett underlag för fortsattforskning inom ramen för forskningsprogrammet FjällMistra.

  • 53.
    Persson, L
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Claessen, D
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    De Roos,, A M
    Byström, P
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sjögren, S
    Svanbäck, Richard
    Wahlström, E
    Westman, E
    Cannibalism in a size-structured population: energy extraction and control2004In: Ecological Monographs, Vol. 74, p. 135-157Article in journal (Refereed)
  • 54.
    Persson, Lennart
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    De Roos, Andre M.
    Mixed competition-predation: potential vs. realized interactions2012In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 81, no 2, p. 483-493Article in journal (Refereed)
    Abstract [en]

    1. Life-history omnivory or size-induced mixed competitionpredation systems have under many conditions theoretically been shown to be fragile, whereas at the same time existing empirical data suggest such systems to be common in nature. 2. In a whole lake experiment covering 17 years, we analysed the effects of the introduction of the intraguild prey roach (Rutilus rutilus) on the population size and individual performance of the intraguild predator perch (Perca fluviatilis) and on resource levels in two low productivity systems. 3. A strong long-term effect of roach on the zooplankton resource but not on the macroinvertebrate resource was present. Competitive effects of roach on perch were observed in one of the lakes the first years after the introduction, but at the end of the study no competitive effect of roach on either size class of perch was observed in any of the two lakes. In contrast, a positive predatory effect reflected in improved growth rates of older perch was present. 4. The lack of a support for a competitive effect of roach on small perch raises the question of the importance of mixed competition-predation interactions in life-history omnivorous systems and the problem of comparing descriptive data on feeding relationships with theoretical predictions based on interaction modules.

  • 55. Pratt, Stephen C
    et al.
    Sumpter, David JT
    Umeå University, Faculty of Science and Technology, Department of mathematics.
    Mallon, Eamonn B
    Franks, Nigel R
    An agent-based model of collective nest choice by the ant Temnothorax albipennis2005In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 70, no 5, p. 1023-1036Article in journal (Refereed)
    Abstract [en]

    Colonies of the ant Temnothorax (formerly Leptothorax) albipennis can collectively choose the best of several nest sites, even when many of the active ants who organize the move visit only one site. Previous studies have suggested that this ability stems from the ants' strategy of graded commitment to a potential home. On finding a site, an ant proceeds from independent assessment, to recruiting fellow active ants via slow tandem runs, to bringing the passive bulk of the colony via rapid transports. Assessment duration varies inversely with site quality, and the switch from tandem runs to transports requires that a quorum of ants first be summoned to the site. These rules may generate a collective decision, by creating and amplifying differential population growth rates among sites. We test the importance of these and other known behavioural rules by incorporating them into an agent-based model. All parameters governing individual behaviour were estimated from videotaped emigrations of individually marked ants given a single nest option of either good or mediocre quality. The time course of simulated emigrations and the distribution of behaviour across ants largely matched these observations, except for the speed with which the final transport phase was completed, and the overall emigration speed of one particularly large colony. The model also predicted the prevalence of splitting between sites when colonies had to choose between two sites of different quality, although it correctly predicted the degree of splitting in only four of six cases. It did not fully capture variance in colony performance, but it did predict the emergence of variation in individual behaviour, despite the use of identical parameter values for all ants. The model shows how, with adequate empirical data, the algorithmic form of a collective decision-making mechanism can be captured.

  • 56.
    Razzak, Abdur
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå SE-901 87, Sweden.
    Ranade, Sonali Sachin
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå SE-901 87, Sweden.
    Strand, Åsa
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Garcia-Gil, M. R.
    Differential response of Scots pine seedlings to variable intensity and ratio of red and far-red light2017In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 40, no 8, p. 1332-1340Article in journal (Refereed)
    Abstract [en]

    We investigated the response to increasing intensity of red (R) and far-R (FR) light and to a decrease in R: FR ratio in Pinus sylvestris L. (Scots pine) seedling. The results showed that FR high-irradiance response for hypocotyl elongation may be present in Scots pine and that this response is enhanced by increasing light intensity. However, both hypocotyl inhibition and pigment accumulation were more strongly affected by the R light compared with FR light. This is in contrast to previous reports in Arabidopsis thaliana (L.) Heynh. In the angio-sperm, A. thaliana R light shows an overall milder effect on inhibition of hypocotyl elongation and on pigment biosynthesis compared with FR suggesting conifers and angiosperms respond very differently to the different light regimes. Scots pine shade avoidance syndrome with longer hypocotyls, shorter cotyledons and lower chlorophyll content in response to shade conditions resembles the response observed in A. thaliana. However, anthocyanin accumulation increased with shade in Scots pine, which again differs from what is known in angiosperms. Overall, the response of seedling development and physiology to R and FR light in Scots pine indicates that the regulatory mechanism for light response may differ between gymnosperms and angiosperms.

  • 57.
    Reidy Liermann, Catherine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Robertson, James
    Ng, Rebecca
    Implications of dam obstruction for global freshwater fish diversity2012In: BioScience, ISSN 0006-3568, E-ISSN 1525-3244, Vol. 62, no 6, p. 539-548Article in journal (Refereed)
    Abstract [en]

    Dams are obstructing rivers worldwide, impairing habitat and migration opportunities for many freshwater fish species; however, global data linking dam and fish distributions have been limited. Here, we quantify dam obstruction at the biogeographic scale of freshwater ecoregion, which provides the spatial framework necessary to assess the risk of fish species loss due to dams and allows us to identify both ecoregions and genera at risk. Nearly 50% of the 397 assessed freshwater ecoregions are obstructed by large- and medium-size dams, and approximately 27% face additional downstream obstruction. A synthesis of obstruction data and fish traits indicates that taxa such as lampreys (Lampetra spp.), eels (Anguilla spp.), and shads (Alosa spp.) are at particular risk of species loss. Threatened ecoregions with heavy dam obstruction and above-average counts of total, diadromous, or endemic species are found on all continents and include the Murray-Darling Province, Southern Italy, the Lower and Middle Indus Basin, West Korea, the South Atlantic region of the United States, the Upper Parana, and Mobile Bay ecoregions.

  • 58. Safholm, Moa
    et al.
    Jansson, Erika
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Berg, Cecilia
    Molecular and histological endpoints for developmental reproductive toxicity in Xenopus tropicalis: Levonorgestrel perturbs anti-Mullerian hormone and progesterone receptor expression2016In: Comparative Biochemistry and Physiology - Part C: Toxicology & Pharmacology, ISSN 1532-0456, E-ISSN 1878-1659, Vol. 181, p. 9-18Article in journal (Refereed)
    Abstract [en]

    There is an increasing concern regarding the risks associated with developmental exposure to endocrine disrupting chemicals and the consequences for reproductive capability. The present study aimed to refine the Xenopus (Silurana) tropicalis test system for developmental reproductive toxicity by characterising molecular and histological features of sexual development, and to explore effects of exposure to the progestagen levonorgestrel (LNG). Larvae were exposed to LNG (0, 3, 30, 300 ng/L) over the first three weeks of development, encompassing the beginning of gonadal differentiation. mRNA levels of amh (anti-Mullerian hormone), amhr2 (amh receptor 2), ipgr (intracellular progesterone receptor), mpgr beta (membrane progesterone receptor beta), and cyp19a1 (cytochrome p450 19a1) were quantified in larvae and juveniles (4 weeks post-metamorphosis). Relative cyp19a1 and amh expression was used as a molecular marker for phenotypic sex of larvae. Gonadal and Mullerian duct development were characterised histologically in juveniles. Compared to controls, LNG exposure increased the expression of amh and ipgr in male larvae. In juveniles, mpgr beta expression was increased in both sexes and amhr2 expression was decreased in males, implying persistent effects of developmental progestagen exposure on amh and pgr expression signalling. No effects of LNG on the gonadal or Mullerian duct development were found, implying that the exposure window was not critical with regard to these endpoints. In juveniles, folliculogenesis had initiated and the Mullerian ducts were larger in females than in males. This new knowledge on sexual development in X. tropicalis is useful in the development of early life-stage endpoints for developmental reproductive toxicity.

  • 59.
    Samuelsson, Emma
    et al.
    Umeå University, Faculty of Social Sciences, Department of Economics.
    Stage, Jesper
    Umeå University, Faculty of Social Sciences, Department of Economics.
    The size and distribution of the economic impacts of Namibian hunting tourism2007In: South African Journal of Wildlife Research, ISSN 0379-4369, E-ISSN 1996-8477, Vol. 37, no 1, p. 41-52Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to analyse the economic impacts of hunting tourism in Namibia. The economic impacts of hunting that takes place in communal land conservancies and on private lands, respectively, are studied, as well as the distribution of these impacts between different sectors and groups in the country. The study is based on data from a survey of hunters who visited Namibia during a five-year period. The income generated by hunting tourism, and the distribution of this income, are analysed using a recently developed Social Accounting Matrix (SAM). In aggregate, an extra N$ in spending by survey respondents translates into approximately one extra N$ in national income, and an average survey respondent's spending raised overall national income by an amount corresponding to two to three years' income for an average Namibian. The additional income generated by hunting tourism and associated tourism benefits rural households and urban wage earners to a greater extent, and capital owners to a lesser extent, than the average income distribution in the economy.

  • 60.
    Sandberg, Lisa
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Grodsamhällen längs vattendrag på Borneo: En identifiering av habitatkaraktärer viktiga för diversitet och abundans av grodor i tropisk regnskog2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The stretch from the riparian zone of a major river, through the mouth and upstream in tributaries forms a range of differing habitats. The aim of this study was to investigate the effect of these different habitats on the riparian frog community in primary rain forest in Borneo; i.e. examine whether any gradients could be demonstrated in terms of species composition, diversity and density of frogs, as well as which environmental characteristics that seem to be of most importance in forming habitats of high conservational value. A major river, Segama, and three of its tributaries were investigated. The surveys were carried out at night by searching for frogs visually and acoustically along the streams, from the shore of the Segama river and 400 metres upstream in the tributaries. In all transects 10 habitat variables were also measured. The results from the study show a significantly lower diversity and abundance of frogs along the shores of Segama and close to the mouths of the tributaries compared to further upstream, and a significant difference in species assemblage. Most species exhibited a negative correlation with the downstream transects or were not found there at all. The habitat characteristics waterfalls and boulders were found to be of most importance for the diversity and abundance of frogs, making these characteristics key components of habitats with high conservational value. Major rivers could also potentially form dispersal corridors for invasive species, which findings of the introduced species Fejervarya limnocharis along the shores of Segama shows.

  • 61.
    Sandström, Olof
    Umeå University, Faculty of Science and Technology.
    The ecology of the plankton fauna in the Gulf of Bothnia1980Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The geographical distribution of the Gulf of Bothnia zooplankton species is presented together with observations of abundancies and vertical distributions. The historical development of this plankton community in the last 70 years is discussed.Spring and summer development of the plankton fauna was studiedin the Bothnian Bay. Compared to in southern parts of the Balticit could be shown that the start of development in spring formany species was only moderately later in the Bothnian Bay. Theperiod of maximal biomass was in late summer and autumn.In a study of horizontal distribution large between-station variations were found. These variations were not random as close stations formed homogenous groups. Several cases of patchiness were established. Systematically appearing differences in age-distributions were proposed as a factor in the formation of patchiness.The selective prédation on zooplankton by Baltic herring was studied in the Bothnian Bay. Besides chosing certain species herring selects the older and larger stages of these species. Egg-bearing Eurytemora females were more heavily preyed upon than the males.From literature information and own observations it was proposed that in sence of production the Bothnian Bay and the Bothnian Sea are two very different systems. Climatic effects cause a delay of primary production in spring enabling the pelagic consumers to develop in phase with the producers in the Bothnian Bay. Contrary to systems with a spring peak in phytoplankton growth this situation will lead to high pelagial efficiency leaving little to feed the benthic communities.

  • 62.
    Schmid, Martin Rudolf
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Adult honeybees (Apis mellifera L.) abandon hemocytic, but not phenoloxidase-based immunity2008In: Journal of insect physiology, ISSN 0022-1910, E-ISSN 1879-1611, Vol. 54, no 2, p. 439-444Article in journal (Refereed)
  • 63.
    Serrano Gonzalez, Ignacio
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Larsson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Eriksson, L-O
    Migration performance of wild and hatchery sea trout (Salmo trutta L.) smolts: implications for compensatory hatchery programs2009In: Fisheries Research, ISSN 0165-7836, E-ISSN 1872-6763, Vol. 9, no 3, p. 210-215Article in journal (Refereed)
    Abstract [en]

    Migration success of hatchery-reared and wild sea trout smolts through the lower stretches and the estuary of a Baltic Sea river were studied. During 3 years, wild and hatchery trout smolts were implanted with acoustic transmitters and released 14 km upstream from the river mouth. In order to monitor their out-migration pattern, acoustic receivers were deployed along the migratory route. Data on number of fish detected and date and time of detections were analysed and the migratory performance of wild and hatchery-reared fish was compared. A significantly higher proportion of wild fish (80%) successfully migrated to the coast compared to fish of hatchery origin (27.5%) and migration was faster in wild smolts. Hatchery fish were larger and had a higher condition factor and lipid concentrations, which are proposed as possible reasons for the poorer migratory performance of the hatchery-reared fish.

  • 64.
    Serrano Gonzalez, Ignacio
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Rivinoja, P
    Karlsson, L
    Larsson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Riverine and early marine survival of stocked salmon smolts, Salmo salar L., descending the Testebo River, Sweden2009In: Fisheries Management and Ecology, ISSN 0969-997X, E-ISSN 1365-2400, Vol. 16, no 5, p. 386-394Article in journal (Refereed)
    Abstract [en]

    A combination of radio and acoustic telemetry was used to monitor the out-migration of hatchery-reared Atlantic salmon, Salmo salar L., in the River Testebo, its estuary and coastal system. As with many other Baltic rivers, the hydropower regulated River Testebo once had a self-sustaining salmon population that is now extinct. Substantial losses of smolts in the river (48-69%) and inner part of the estuary (43-47%) were found, but after leaving the estuary, the success of post-smolts moving out of the Bay was sufficiently high (83-89%) to conclude that habitat within the bay is not a factor limiting initial marine survival. The results suggest that hatchery-based recovery of a wild salmon population in the river will not be successful unless other actions, such as habitat improvement, are included.

  • 65.
    Sjöberg, Göran
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nesting and migration in the introduced Canada goose in Sweden1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of the thesis was to document patterns in breeding and migration in Swedish Canada geese Branta canadensis, to explain these against the genetic and historical background of the population, and to test predictions of hypotheses pertaining to parental investment.

    The Canada goose population in Sweden was founded by the introduction of a few individuals in the 1930's. DNA fingerprint similarity between geese breeding in Sweden was on average at the same level as between inbred close relatives in other wild bird species. The genetic variability of the population appeared to be considerably reduced in comparison to that of Canada geese breeding in North America.

    Dispersal and migration patterns were studied using plastic neck-bands that could be identified at long distance. Most Canada goose females nested at the lake where they grew up. Males were more prone to disperse than females, although most of them still returned to breed close to their area of origin.

    Geese from three breeding areas in Sweden had different winter distributions, although wintering areas overlapped considerably. Individual geese tended to return to the same wintering area as they had used in previous years.

    The females' investment in the egg clutch was related to the migration distance from spring foraging areas to the nesting area, suggesting an energetic cost of migration for egg production. Within breeding seasons, clutch size decreased with later initiation of nesting, but only in years with early breeding. A probable reason for this decrease was that body reserves available for egg production were larger in early layers. In years with late breeding, clutch size did not decrease, most likely because late-nesting females could supplement their body reserves by foraging on fresh vegetation.

    Nest defence intensity was studied by recording the behaviour of the female geese when a human approached the nest. The results largely confirmed predictions for nest defence intensity extracted from parental investment theory.

  • 66.
    Sjöberg, Kjell
    Department of Wildlife, Fish, and Environmental Studies at the Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Fishing Gear Used for River Lamprey Lampetra fluviatilis (L.) Catches: Documenting Rivers that Flow into the Baltic Sea. Part II, Finland, Latvia and Estonia2013In: Journal of Northern Studies, ISSN 1654-5915, Vol. 7, no 2, p. 7-74Article in journal (Refereed)
    Abstract [en]

    The river lamprey (Lampetra fluviatilis (L.)) is an anadromous fish that has a growth phase in the sea, then migrates up rivers mainly during autumn for spawning next spring. It is during this spawning migration the lampreys are caught in rivers. Lamprey fishing has been documented in the Baltic Sea region at least since the fifteenth century, and some of the fishing gear used has remained largely unchanged for hundreds of years. In recent decades however, new material has replaced wood, although the design of the gear is still often the same as before. In this study lamprey rivers in Sweden, Finland, Latvia and Estonia were visited and the lamprey fishing gear was documented. There are differences in the use of fishing gear both within countries and among countries as regards gear type and the ways in which the fishermen use different fishing techniques to suit the conditions found in various rivers.

  • 67.
    Sjöberg, Kjell
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Temporal relationships between fish-eating birds and their prey in a north Swedish river1987Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The seasonal and diel feeding habits of the goosander, Mergus merganser, the red-breasted merganser, M. serrator, gulls (Larus canus, L. argentatus and L. fuscusj and terns, Sterna hirundo/paradisaea were studied at 64V05'N. Birds' activity patterns were influenced by the nocturnal spawning of the river lamprey (Lampetra fluviatilis). Food selection and food consumption by hand-raised mergansers together with aquarium studies of the diel activity patterns of their most important prey supplemented the field data. River lamprey dominated the diet of the goosander by weight and the sculpin Cottus gobio by number. The fish consumption of the goosanders was found to be about 12% of the available river lamprey biomass and about 17% of the sculpin biomass during the breeding season.

    In experimental situations the river lamprey was a low- pritority species compared with salmon , Salmo salar, brown trout, 53. trutta, and minnow, Phoxinus phoxinus, when presented to satiated birds of both Mergus species. When hungry, however, the birds caught the available prey irrespective of species, but they selected larger prey when two size classes were present. Experimental results were compared with field data on availability, consumption and the escape behaviour of the various fish species.

    The rivers emptying in the Bothnian Bay are regarded as important feeding areas for birds breeding along the coast. In early spring they get access to abundant and reliable food resources, e.g the river lamprey. Later on the three-spined stickleback, Gasterosteus aculeatus, supply both Mergus species with food in the river and also along the coast. From the middle of June potential food supply available to birds decreases in the rivers and becomes more abundant in the coastal area.

  • 68.
    Sjödin, Tord
    et al.
    Umeå University, Faculty of Science and Technology, Mathematics and Mathematical Statistics.
    Løvtrup, Søren
    Umeå University, Faculty of Science and Technology, Studies in Biology and Environmental Sciences.
    Biomathematics and the fate map of the amphibian blastula1990In: Rivista di Biologia - Biology forum, ISSN 0035-6050, Vol. 83, no 1, p. 81-92Article in journal (Refereed)
    Abstract [en]

    A fate map of the amphibian embryo has been drawn by a computer on the basis of two simple and well-known processes of the cell differentiation. The two processes are related in so far as they both consist of the formation of a new type of cells, here called f-cells. The first process is the spontaneous formation of the Ruffini cells along the marginal edge around the circumference of the embryo, slightly below the equator. When this occurs, they will induce the neighbouring cells located towards the animal pole to undergo the same differentiation, and the induction, which seems to be rather an activation, spreads from cell to cell. The actual shape of the map is due to the fact that the formation of the Ruffine cells occurs along a temporal gradient from the dorsal to the ventral side.

  • 69. Sniegula, Szymon
    et al.
    Johansson, Frank
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Photoperiod affects compensating developmental rate across latitudes in the damselfly Lestes sponsa2010In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 35, no 2, p. 149-157Article in journal (Refereed)
    Abstract [en]

    1. Although there is a great deal of theoretical and empirical data about the life history responses of time constraints in organisms, little is known about the latitude-compensating mechanism that enables northern populations' developmental rates to compensate for latitude. To investigate the importance of photoperiod on development, offspring of the obligatory univoltine damselfly Lestes sponsa from two populations at different latitudes (53°N and 63°N) were raised in a common laboratory environment at both northern and southern photoperiods that corresponded to the sites of collection.

    2. Egg development time was shorter under northern photoperiod regimes for both populations. However, the northern latitude population showed a higher phenotypic plasticity response to photoperiod compared with the southern latitude population, suggesting a genetic difference in egg development time in response to photoperiod.

    3. Larvae from both latitudes expressed shorter larval development time and faster growth rates under northern photoperiod regimes. There was no difference in phenotypic plastic response between northern and southern latitude populations with regard to development time.

    4. Data on field collected adults showed that adult sizes decreased with an increase in latitude. This adult size difference was a genetically fixed trait, as the same size difference between populations was also found when larvae were reared in the laboratory.

    5. The results suggest phenotypic plasticity responses in life history traits to photoperiod, but also genetic differences between north and south latitude populations in response to photoperiod, which indicates the presence of a latitudinal compensating mechanism that is triggered by a photoperiod.

  • 70.
    Stenberg, Per
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Lundmark, Magnus
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine). Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Distribution, mechanisms and evolutionary significance of clonality and polyploidy in weevils2004In: Agricultural and Forest Entomology, ISSN 1461-9555, E-ISSN 1461-9563, Vol. 6, no 4, p. 259-266Article in journal (Refereed)
    Abstract [en]

    1 Genetical mtDNA relationships of 41 taxa of weevils were examined using cladistics. Ingroup taxa belong to Otiorhynchus scaber and O. nodosus and outgroup comparison was made with O. singularis. All three species are minor forest pests.

    2 Otiorhynchus scaber specimens are either diploid sexuals or diploid, triploid and tetraploid clones, from two different populations (Slovenia and Austria) that belong to two different evolutionary lineages. Otiorhynchus nodosus specimens are tetraploid clones. Both species show geographical parthenogenesis, as do many other Otiorhynchus species.

    3 Mitochondrial data indicate that O. nodosus clones are more closely related to Slovenian sexuals of O. scaber than these are to sexuals from Austria. It also shows that almost all clones of O. scaber collected in one of the two regions where sexuals are found are more closely related to sexuals from the other region.

    4 Three different hypotheses that may explain the distribution of O. scaber, mechanisms important for the evolution of the clones and implications of the presence of Wolbachia are discussed.

    5 We conclude that parthenogenesis is likely to be linked to hybridization in O. scaber and that hybridization events between ancestors of O. nodosus and O. scaber are the probable cause of the presence of O. nodosus in the ingroup. We also find that polyploid clones are superior colonizers compared to sexuals and diploid clones, in O. scaber.

    6 The results suggest that systems where both sexuals and clones exist are more complex than previously suggested. The mapping of genetic variation in clonal complexes and the tracing of clonal origins may be useful in pest management.

  • 71.
    Stenberg, Per
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Saura, Anssi
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Cytology of Asexual Animals2009In: Lost Sex: The Evolutionary Biology of Parthenogenesis / [ed] Isa Schön, Koen Martens, Peter Dijk, Dordrecht: Springer Netherlands, 2009, p. 63-74Chapter in book (Other academic)
    Abstract [en]

    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.

  • 72.
    Svanbäck, Richard
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bolnick, DI
    Intraspecific competition affects the strength of individual specialization: an optimal diet theory method2005In: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 7, no 7, p. 993-1012Article in journal (Refereed)
    Abstract [en]

    Question: Why would individuals that inhabit the same environment choose to feed on different subsets of the available resources?

    Mathematical method: We outline a flexible model that combines phenotypic variation with optimal diet theory and population dynamics. We then apply this model to investigate the role of different types of trade-offs. phenotype diversity and level of competition in determining the degree of individual specialization.

    Key assumptions: The foragers in the model are omniscient and maximize energy intake per time unit.

    Conclusion: Numerical simulations match empirical observations that changes in population density can alter the degree of individual specialization. Forager density and phenotypic variation affected prey densities. which in turn affected forager diet breadth and fitness (energy income). We propose that this feedback can explain the empirical relationship between forager density and the degree of individual specialization in the forager population.

  • 73.
    Svanbäck, Richard
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Eklöv, Peter
    Genetic variation and phenotypic plasticity: Causes of morphological and dietary variation in Eurasian perch2006In: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 8, no 1, p. 37-49Article in journal (Refereed)
  • 74.
    Svanbäck, Richard
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Individual diet specialization, niche width and population dynamics: implications for trophic polymorphisms2004In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 73, no 5, p. 973-982Article in journal (Refereed)
    Abstract [en]

    1. We studied a perch Perca fluviatilis L. population that during a 9-year period switched between a phase of dominance of adult perch and a phase dominated by juvenile perch driven by cannibalism and intercohort competition. We investigated the effects of these population fluctuations on individual diet specialization and the mechanisms behind this specialization.

    2. Due to cannibalism, the survival of young-of-the-year (YOY) perch was much lower when adult perch density was high than when adult perch density was low.

    3. Both the individual niche breadth (if weighed for resource encounter) and the population niche breadth were highest when adult population density was high and, consequently, individual specialization was highest at high adult perch densities.

    4. When adult perch density was low, the abundances of benthic invertebrate and YOY perch were high and dominated the diet of adult perch, whereas the density of zoo-plankton was low due to predation from YOY perch. At high perch densities, benthic invertebrate abundance was lower and zooplankton level was higher and some perch switched to feed on zooplankton.

    5. Our results show that individual specialization may fluctuate with population density through feedback mechanisms via resource levels. Such fluctuations may have profound implications on the evolution of resource polymorphisms.

  • 75. Svensson, Ola
    et al.
    Lissåker, Maria
    Mobley, Kenyon B
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Offspring recognition and the influence of clutch size on nest fostering among male sand gobies2010In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 64, no 8, p. 1325-1331Article in journal (Refereed)
    Abstract [en]

    When parental care is costly, parents should avoid caring for unrelated young. Therefore, it is an advantage to discriminate between related and unrelated offspring so that parents can make informed decisions about parental care. In the present study, we test the hypothesis that male sand gobies (Pomatoschistus minutus) recognize and differentially care for their own offspring when given a choice between a nest with sired eggs and a second nest with eggs sired by an unrelated male. The sand goby is a species with exclusive and costly paternal care. Male parasitic spawnings (e.g., sneaking) as well as nest takeovers by other males are common. Our results show that nests containing sired eggs were preferred and received significantly more care, as measured by nest building and nest occupancy, than nests with foreign eggs even when males cared for both nests. These findings suggest that males respond to paternity cues and recognize their own clutches. Relative clutch size also had a significant effect on male parental care. When sired clutches were larger than foreign clutches, males preferred to care for their own nest. In the few cases where males chose to take care of foreign nests, the foreign clutch was larger than their own clutch. Taken together, our results provide evidence that both paternity cues and clutch size influence parenting decisions among male sand gobies.

  • 76.
    Thorlacius, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hellström, Gustav
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brodin, Tomas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Behavioral dependent dispersal in the invasive round goby Neogobius melanostomus depends on population age2015In: Current Zoology, ISSN 1674-5507, Vol. 61, no 3, p. 529-542Article in journal (Refereed)
    Abstract [en]

    Biological invasions cause major ecological and economic costs in invaded habitats. The round goby Neogobius melanostomus is a successful invasive species and a major threat to the biodiversity and ecological function of the Baltic Sea. It is native to the Ponto-Caspian region and has, via ballast water transport of ships, invaded the Gulf of Gdansk in Poland. Since 1990, it has spread as far north as Raahe in Northern Finland (64 degrees 41'04"N, 24 degrees 28'44"E). Over the past decade, consistent individual differences of behavioral expressions have been shown to explain various ecological processes such as dispersal, survival or reproduction. We have previously shown that new and old populations differ in personality trait expression. Individuals in new populations are bolder, less sociable and more active than in old populations. Here we investigate if the behavioral differentiation can be explained by phenotype-dependent dispersal. This was investigated by measuring activity, boldness and sociability of individually marked gobies, and subsequently allowing them to disperse in a system composed of five consecutive tanks connected by tubes. Individual dispersal tendency and distance was measured. Our results revealed that in newly established populations, more active individuals disperse sooner and that latency of a group to disperse depends on the mean sociability of the group. This indicates the presence of personality dependent dispersal in this species and that it is maintained at the invasion front but lost as the populations get older.

  • 77. van den Brink, Valentijn
    et al.
    Bokma, Folmer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Morphometric shape analysis using learning vector quantization neural networks: an example distinguishing two microtine vole species2011In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 48, no 6, p. 359-364Article in journal (Refereed)
    Abstract [en]

    Closely related species may be very difficult to distinguish morphologically, yet sometimes morphology is the only reasonable possibility for taxonomic classification. Here we present learning-vector-quantization artificial neural networks as a powerful tool to classify specimens on the basis of geometric morphometric shape measurements. As an example, we trained a neural network to distinguish between field and root voles from Procrustes transformed landmark coordinates on the dorsal side of the skull, which is so similar in these two species that the human eye cannot make this distinction. Properly trained neural networks misclassified only 3% of specimens. Therefore, we conclude that the capacity of learning vector quantization neural networks to analyse spatial coordinates is a powerful tool among the range of pattern recognition procedures that is available to employ the information content of geometric morphometrics.

  • 78.
    Vickers, Kim
    et al.
    Department of Archaeology, University of Sheffield, UK.
    Buckland, Philip I
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Predicting island beetle faunas by their climate ranges: the tabula rasa/refugia theory in the North Atlantic2015In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 42, no 11, p. 2031-2048Article in journal (Refereed)
    Abstract [en]

    Aim: This paper addresses two opposing theories put forward for the origins of the beetle fauna of the North Atlantic islands. The first is that the biota of the isolated oceanic islands of the Faroes, Iceland and Greenland immigrated across a Palaeogene–Neogene land bridge from Europe, and survived Pleistocene glaciations in ameliorated refugia. The second argues for a tabula rasa in which the biota of the islands was exterminated during glaciations and is Holocene in origin. The crux of these theories lies in the ability of the flora and fauna to survive in a range of environmental extremes. This paper sets out to assess the viability of the refugia hypothesis using the climatic tolerances of one aspect of the biota: the beetle fauna. Location: The paper focuses on Iceland, the Faroe Islands and Greenland. Methods: The known temperature requirements of the recorded beetle faunas of the North Atlantic islands were compared with published proxy climate reconstructions for successive climate periods since the severing of a North Atlantic land bridge. We used the MCR (mutual climatic range) method available in the open access BugsCEP database software. Results: We show that most of the MCR faunas of the North Atlantic islands could not have survived in situ since the Palaeogene–Neogene, and are likely to have been exterminated by the Pleistocene glaciations. Main conclusions: The discrepancy between the climatic tolerances of the North Atlantic beetle fauna and the estimated climatic regimes since the severing of a land bridge strongly support the tabula rasa theory and suggests that the North Atlantic coleopteran fauna is Holocene in origin.

  • 79. Vrede, Tobias
    et al.
    Drakare, Stina
    Eklöv, Peter
    Hein, Arne
    Liess, Antonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olsson, Jens
    Persson, Jonas
    Quevedo, Mario
    Ragnarsson Stabo, Henrik
    Svanbäck, Richard
    Ecological stoichiometry of Eurasian perch: intraspecific variation due to size, habitat and diet2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 6, p. 886-896Article in journal (Refereed)
    Abstract [en]

    The turnover and distribution of energy and nutrients in food webs is influenced by consumer stoichiometry. Although the stoichiometry of heterotrophs is generally considered to vary only little, there may be intraspecific variation due to factors such as habitat, resources, ontogeny and size. We examined intraspecific variation in Eurasian perch Perca fluviatilis stoichiometry, a common species that exhibits habitat and resource specialization, ontogenetic niche shifts and a large size range. This study investigated the elemental stoichiometry of a wide size range of perch from littoral and pelagic habitats. The mean C:N:P stoichiometry of whole perch was 37:9:1 (molar ratios). However, %C, %P, C:N, C:P and N:P varied with size, morphology, habitat and diet category. These factors together explained 24–40% of the variation in C:N:P stoichiometry. In contrast, perch stoichiometry was not related to diet stoichiometry, suggesting that the former is homeostatically regulated. The results suggest that the high P content of perch may result in stoichiometric constraints on the growth of non-piscivorous perch, and that piscivory is an efficient strategy for acquiring P. Resource polymorphism, individual diet specialization and intraspecific size variation are widespread among animals. Thus changes in stoichiometry with size, habitat, morphology and resource use, and therefore also stoichiometric demands, are probably common.

  • 80. Williams, John W.
    et al.
    Grimm, Eric C.
    Blois, Jessica L.
    Charles, Donald F.
    Davis, Edward B.
    Goring, Simon J.
    Graham, Russell W.
    Smith, Alison J.
    Anderson, Michael
    Arroyo-Cabrales, Joaquin
    Ashworth, Allan C.
    Betancourt, Julio L.
    Bills, Brian W.
    Booth, Robert K.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Curry, B. Brandon
    Giesecke, Thomas
    Jackson, Stephen T.
    Latorre, Claudio
    Nichols, Jonathan
    Purdum, Timshel
    Roth, Robert E.
    Stryker, Michael
    Takahara, Hikaru
    The neotoma paleoecology database, a multiproxy, international, community-curated data resource2018In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 89, no 1, p. 156-177Article in journal (Refereed)
    Abstract [en]

    The Neotoma Paleoecology Database is a community-curated data resource that supports interdisciplinary global change research by enabling broad-scale studies of taxon and community diversity, distributions, and dynamics during the large environmental changes of the past. By consolidating many kinds of data into a common repository, Neotoma lowers costs of paleodata management, makes paleoecological data openly available, and offers a high-quality, curated resource. Neotoma’s distributed scientific governance model is flexible and scalable, with many open pathways for participation by new members, data contributors, stewards, and research communities. The Neotoma data model supports, or can be extended to support, any kind of paleoecological or paleoenvironmental data from sedimentary archives. Data additions to Neotoma are growing and now include >3.8 million observations, >17,000 datasets, and >9200 sites. Dataset types currently include fossil pollen, vertebrates, diatoms, ostracodes, macroinvertebrates, plant macrofossils, insects, testate amoebae, geochronological data, and the recently added organic biomarkers, stable isotopes, and specimen-level data. Multiple avenues exist to obtain Neotoma data, including the Explorer map-based interface, an application programming interface, the neotoma R package, and digital object identifiers. As the volume and variety of scientific data grow, community-curated data resources such as Neotoma have become foundational infrastructure for big data science.

  • 81. Young, Amanda B.
    et al.
    Cairns, David M.
    Lafon, Charles W.
    Moen, Jon
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Martin, Laura E.
    Dendroclimatic relationships and possible implications for mountain birch and Scots pine at treeline in northern Sweden through the 21st century2011In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 41, no 3, p. 450-459Article in journal (Refereed)
    Abstract [en]

    Changing climate in the Arctic is expected to have significant effects on the pattern and distribution of terrestrial vegetation. Species characteristic of specific zones in the mountains of northern Sweden have been shown to migrate up- and down-slope with changes in climate over the Holocene. This study evaluates the potential for Scots pine (Pinus sylvestris L.) to become a treeline dominant at Fennoscandian treelines, replacing mountain birch (Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti). Data from paired mountain birch and Scots pine tree-ring chronologies for eight locations in northern Sweden are used to develop climate – tree ring width index (RWI) relationships. Modeled climate–RWI relationships are then used to predict the relative RWI values of the two species under a suite of climate-forcing scenarios using an ensemble of three global climate models. Results indicate that mountain birch and Scots pine RWI are both correlated with summer temperatures, but Scots pine is more likely than mountain birch to be influenced by moisture conditions. Predictions of RWI under future climate conditions indicate that mountain birch is unlikely to be replaced by Scots pine within the next century.

12 51 - 81 of 81
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf