Search results for: Ivar Folstad

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Flowers for bees, autumn colours for whom? An experimental test with autumn colouration in mountain birches (Betula pubescens ssp. czerepanovii) as a signal against the moth Epirrita autumnata

Trond Isaksen, Ivar Folstad

Entomologia Experimentalis et Applicata > 152 > 2 > 141 - 147

In 2001, Hamilton and Brown proposed a controversial hypothesis of handicap signalling to potential insect parasites as an adaptive explanation for autumn leaf colouration. In subsequent studies there has been little attention to the costs and benefits of early autumnal colour change. Yet, in an observational study by Hagen et al. (2003) it was demonstrated that birch trees [Betula pubescens ssp. czerepanovii ...

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Sperm velocity and its relation to social status in Arctic charr (Salvelinus alpinus)

Thomas Haugland, Geir Rudolfsen, Lars Figenschou, Ivar Folstad

Animal Reproduction Science > 2009 > 115 > 1-4 > 231-237

Sperm velocity has been shown to be a major determinant of fertilization success of external fertilizers. Yet, sperm velocity varies both within and between ejaculates and only a small number of fast sperm cells within an ejaculate are likely to have the potential of fertilizing the eggs. Having such fast cells should be of special importance during sperm competition, particularly for subordinate...

article

Factors predicting male fertilization success in an external fertilizer

Ståle Liljedal, Geir Rudolfsen, Ivar Folstad

Behavioral Ecology and Sociobiology > 2008 > 62 > 11 > 1805-1811

In postcopulatory sexual selection both sperm competition and cryptic female choice are considered to be important selective agents, but their relative importance for male fertilization success has received little attention. We tested whether sperm quality, male spawning coloration, male heterozygosity, and genetic overlap with the female explained a male’s fertilization success in controlled in vitro...

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White plumage reflects individual quality in female eiders

Sveinn Are Hanssen, Ivar Folstad, Kjell Einar Erikstad

Animal Behaviour > 2006 > 71 > 2 > 337-343

Sexual selection predicts that males should signal their viability and health and this is often achieved with elaborate ornaments. However, females' phenotypic and genotypic quality may also be related to ornamental expression. We investigated the association between a female ornamental trait (white wing plumage) and female quality in the common eider, Somateria mollissima. Only females incubate and...

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MHC and fertilization success in the Arctic charr (Salvelinus alpinus)

Frode Skarstein, Ivar Folstad, Ståle Liljedal, Mats Grahn

Behavioral Ecology and Sociobiology > 2005 > 57 > 4 > 374-380

Genes of the major histocompatibility complex (MHC) are remarkably polymorphic. Several selection mechanisms have been invoked to account for this diversity, including disassortative mating preferences. In addition, eggs may discriminate between sperm based on MHC. To investigate the effects of MHC-genotype on fertilization success, we obtained mature gametes from ripe Arctic charr (Salvelinus alpinus...

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Effects of ovarian fluid on sperm velocity in Arctic charr (Salvelinus alpinus)

Davnah Urbach, Ivar Folstad, Geir Rudolfsen

Behavioral Ecology and Sociobiology > 2005 > 57 > 5 > 438-444

Numbers of studies in externally fertilizing fish species provide evidence for an effect of ovarian fluid on sperm motility characteristics such as duration of forward mobility, velocity or percent motile sperm cells. Yet, because of variations among females in the quality of their ovarian fluid, such effects might differ between individuals. Additionally, ovarian fluid from different females could...

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Reduced immunocompetence and cost of reproduction in common eiders

Sveinn Are Hanssen, Ivar Folstad, Kjell Einar Erikstad

Oecologia > 2003 > 136 > 3 > 457-464

Immunocompetence may be especially important in long-lived species where infectious organisms may have detrimental effects upon future reproductive value of hosts. The resource demand for immunocompetence may reduce resource availability for reproduction and a trade-off between these traits has therefore been proposed. Capital breeders, such as the common eider (Somateria mollissima), rely upon accumulated...

article

Male dimorphism, sperm traits and immunology in the corkwing wrasse (Symphodus melops L.)

Ingebrigt Uglem, Falck Galloway, Gunilla Rosenqvist, Ivar Folstad

Behavioral Ecology and Sociobiology > 2001 > 50 > 6 > 511-518

Abstract.The evolution of alternative male mating phenotypes inevitably involves variation in risk or intensity of sperm competition. Males that typically mate in disfavoured roles (i.e. sneakers/parasitic males) are predicted to experience higher magnitudes of sperm competition than males mating in favoured roles (preferred by females/exhibiting mate monopolisation). Here, we investigated whether...

article

Antler asymmetry and immunity in reindeer

Kristin Lagesen, Ivar Folstad

Behavioral Ecology and Sociobiology > 1998 > 44 > 2 > 135-142

Abstract Fluctuating asymmetry (FA) measures an individuals ability to undergo identical development in bilaterally symmetrical characters and may indicate sensitivity to environmental stress. FA in ornamental characters is often positively related to parasite intensities, which are important environmental stressors. Parasites affect and are affected by several parts of the immune system, and the...

article

Reindeer antlers: visual indicators of individual quality?

Eystein Markusson, Ivar Folstad

Oecologia > 1997 > 110 > 4 > 501-507

Abstract Fluctuating asymmetry (FA) in ornamental characters may reflect developmental stability in the translation from genotype to phenotype. Antlers of reindeer show FA, are visually conspicuous ornaments and are important in intraspecific assessment. We show that there is a negative relationship between size and asymmetry in visual antler characteristics (i.e., antler length and number of tines)...

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