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Saudarkrokur, Iceland

Parsons K.J.,University of Guelph | Skulason S.,Holar University College | Ferguson M.,University of Guelph
Evolution and Development | Year: 2010

Natural selection requires genetically based phenotypic variation to facilitate its action and cause adaptive evolution. It has become increasingly recognized that morphological development can become canalized likely as a result of selection. However, it is largely unknown how selection may influence canalization over ontogeny and differing environments. Changes in environments or colonization of a novel one is expected to result in adaptive divergence from the ancestral population when selection favors a new phenotypic optimum. In turn, a novel environment may also expose variation previously hidden from natural selection. We tested for changes in phenotypic variation over ontogeny and environments among ecomorphs of Arctic charr (Salvelinus alpinus) from two Icelandic lakes. Populations represented varying degrees of ecological specialization, with one lake population possessing highly specialized ecomorphs exhibiting a large degree of phenotypic divergence, whereas the other displayed more subtle divergence with more ecological overlap. Here we show that ecomorphs hypothesized to be the most specialized in each lake possess significant reductions in shape variation over ontogeny regardless of environmental treatment suggesting canalized development. However, environments did change the amount of shape variation expressed in these ecomorphs, with novel environments slowing the rate at which variation was reduced over ontogeny. Thus, environmental conditions may play an important role in determining the type and amount of genetically based phenotypic variation exposed to natural selection. © 2010 Wiley Periodicals, Inc. Source


Kotrschal A.,Uppsala University | Rasanen K.,ETH Zurich | Kristjansson B.K.,Holar University College | Senn M.,ETH Zurich | Kolm N.,Uppsala University
PLoS ONE | Year: 2012

Selection pressures that act differently on males and females produce numerous differences between the sexes in morphology and behaviour. However, apart from the controversial report that males have slightly heavier brains than females in humans, evidence for substantial sexual dimorphism in brain size is scarce. This apparent sexual uniformity is surprising given that sexually distinct selection pressures are ubiquitous and that brains are one of the most plastic vertebrate organs. Here we demonstrate the highest level of sexual brain size dimorphism ever reported in any vertebrate: male three-spined stickleback of two morphs in an Icelandic lake have 23% heavier brains than females. We suggest that this dramatic sexual size dimorphism is generated by the many cognitively demanding challenges that males are faced in this species, such as an elaborate courtship display, the construction of an ornate nest and a male-only parental care system. However, we consider also alternative explanations for smaller brains in females, such as life-history trade-offs. Our demonstration of unprecedented levels of sexual dimorphism in brain size in the three-spined stickleback implies that behavioural and life-history differences among the sexes can have strong effects also on neural development and proposes new fields of research for understanding brain evolution. © 2012 Kotrschal et al. Source


Ragnarsson S.,Holar University College | Lindberg J.E.,Swedish University of Agricultural Sciences
Livestock Science | Year: 2010

The influence of cutting time of mixed grass haylages on energy and nitrogen (N) metabolism, and the coefficients of total tract apparent digestibility (CTTAD) were studied in four mature Icelandic geldings by performing total collection of faeces and urine. The experiment was arranged as 4 × 4 balanced Latin square. The four haylages used were harvested at different times and were considered to be representative in botanical composition for mixed grass haylages in Iceland. The CTTAD of dry matter (DM), organic matter (OM), crude protein, neutral detergent fibre, acid detergent fibre (ADF) and energy were different (p < 0.05) in the haylage batches. The CTTAD of all dietary components and energy decreased with time of cutting. The content of ADF (% in DM) accounted for a major part of the difference in CTTAD of OM (r2 = 0.95) between haylage batches. The urinary nitrogen losses decreased with date of cutting, while the energy losses in urine (as % of digestible energy intake) were unaffected (p > 0.05). The digestible energy content of the haylages studied ranged from 13.4 to 10.8 MJ/kg DM. © 2010 Elsevier B.V. All rights reserved. Source


Ragnarsson S.,Holar University College | Jansson A.,Swedish University of Agricultural Sciences
Journal of Animal Physiology and Animal Nutrition | Year: 2011

The aim of the present study was to compare digestibility and metabolic response in Icelandic and Standardbred horses fed two grass haylages harvested at different stages of maturity. Six horses of each breed were used in a 24-day change-over design. A total collection of faeces was made on days 15-17 and 22-24. Blood samples were collected on day 24 of each period and analysed for total plasma protein (TPP), plasma urea, non-esterified fatty acids, cortisol and insulin concentration. There were no differences in digestibility coefficients of crude protein, neutral detergent fibre or energy between breeds but organic matter digestibility was higher in the Standardbred horses. On both haylages, the Icelandic horses gained weight whereas the Standardbred horses lost weight. The Icelandic horses had higher TPP, plasma insulin and lower plasma urea concentrations. Our results indicate that the Icelandic horse may be more prone to maintain positive energy balance in relation to the Standardbred horse, but there were no indication of a better digestive capacity in the Icelandic horses. © 2010 Blackwell Verlag GmbH. Source


MacQueen D.J.,University of St. Andrews | Kristjansson B.K.,Holar University College | Paxton C.G.M.,University of St. Andrews | Vieira V.L.A.,University of St. Andrews | Johnston I.A.,University of St. Andrews
Molecular Ecology | Year: 2011

Ecological factors have a major role in shaping natural variation in body size, although the underlying mechanisms are poorly understood. Icelandic Arctic charr (Salvelinus alpinus L.) populations represent an ideal model to understand body-size evolution, because adult dwarfism has arisen independently on multiple occasions in response to parallel environmental pressures. The mechanistic target of rapamycin (mTOR) pathway transmits signals from the environment to control cellular growth and is a primary candidate to be under selection for the dwarf phenotype. To test this hypothesis, we modified 'inputs' to this pathway in five dwarf and two generalist populations (with ancestral life history and body-size traits), using a standardized manipulation of food intake in a common environment. The skeletal muscle transcript levels of 21 mTOR-pathway genes were quantified in 274 individuals (∼6000 datapoints), and statistical modelling was used to elucidate sources of variation. Constitutive expression differences between populations were the main component of variation for around three-quarters of the studied genes, irrespective of nutritional-state and body-size phenotype. There was evidence for stabilizing selection acting among populations, conserving the nutritionally dependent regulation of pathway genes controlling muscle atrophy. There were three genes (mTOR, 4E-BP-1 and IGFBP4), where the expression variation between dwarf and generalist populations exceeded the between-population variation. Divergence in the expression of these candidate adaptive genes was most evident during a period of rapid growth following sustained fasting and was directionally consistent with their functions regulating growth and protein synthesis. We concluded that selection has operated efficiently to shape gene expression evolution in Icelandic charr populations and that the regulation of certain mTOR-pathway genes evolved adaptively in locations favouring dwarfism, resulting in reduced muscle protein accretion under growth-favouring conditions. © 2011 Blackwell Publishing Ltd. Source

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