| 1. |
- Lubin, Yael, et al.
(author)
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Limited male dispersal in a social spider with extreme inbreeding
- 2009
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In: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 97:2, s. 227-234
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Journal article (peer-reviewed)abstract
- Cooperatively breeding animals commonly avoid incestuous mating through pre-mating dispersal. However, a few group-living organisms, including the social spiders, have low pre-mating dispersal, intra-colony mating, and inbreeding. This results in limited gene flow among colonies and sub-structured populations. The social spiders also exhibit female-biased sex ratios because survival benefits to large colonies favour high group productivity, which selects against 1 : 1 sex ratios. Although propagule dispersal of mated females may occasionally bring about limited gene flow, little is known about the role of male dispersal. We assessed the extent of male movement between colonies in natural populations both experimentally and by studying colony sex ratios over the mating season. We show that males frequently move to neighbouring colonies, whereas only 4% of incipient nests were visited by dispersing males. Neighbouring colonies are genetically similar and movement within colony clusters does not contribute to gene flow. Post-mating sex ratio bias was high early in the mating season due to protandry, and also in colonies at the end of the season, suggesting that males remain in the colony when mated females have dispersed. Thus, male dispersal is unlikely to facilitate gene flow between different matrilineages. This is consistent with models of non-Fisherian group-level selection for the maintenance of female biased sex ratios, which predict the elimination of male dispersal.
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| 2. |
- Söderlund, Hedvig, et al.
(author)
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Cerebral changes on MRI and cognitive function: The CASCADE Study.
- 2006
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In: Neurobiology of Aging. - : Elsevier BV. - 0197-4580. ; 27:1, s. 16-23
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Journal article (peer-reviewed)abstract
- The aging, non-demented brain undergoes several physiological changes, some of which may and some of which may not affect cognitive function. The goal of the present study was to examine the effects of subcortical and periventricular white matter hyperintensities (WMHs), and cortical and subcortical atrophy on cognitive function (episodic and semantic memory, attention, and perceptual, cognitive, and motor speed). This was done within a European collaborative study, CASCADE (Cardiovascular Determinants of Dementia), in which Magnetic Resonance Imaging (MRI) was performed on community-dwelling individuals. The study includes 1,254 persons from eight European study centers, ranging between 64 and 76 years of age (M 69.4 + 3.3; 55% men). When demographics (age, education, and sex), study center, and concurrent brain changes had been adjusted for, periventricular WHMS predicted lower performance in motor speed and Stroop (errors). The findings are consistent with findings from lesion and functional neuroimaging studies.
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