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9 novembre 2016

What determines direction of asymmetry : genes, environment or chance ? [Royal Society Open Science]

Keywords : left–right asymmetry, symmetry breaking, random asymmetry, evolution of development, handed behaviour, phenotypic plasticity

Conspicuous asymmetries seen in many animals and plants offer diverse opportunities to test how the development of a similar morphological feature has evolved in wildly different types of organisms. One key question is : do common rules govern how direction of asymmetry is determined (symmetry is broken) during ontogeny to yield an asymmetrical individual ? Examples from numerous organisms illustrate how diverse this process is. These examples also provide some surprising answers to related questions. Is direction of asymmetry in an individual determined by genes, environment or chance ? Is direction of asymmetry determined locally (structure by structure) or globally (at the level of the whole body) ? Does direction of asymmetry persist when an asymmetrical structure regenerates following autotomy ?(...)

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8 novembre 2016

Gene expression plasticity as a mechanism of coral adaptation to a variable environment [Nature Ecology & Evolution]

Keywords : evolutionary genetics, molecular ecology

Local adaptation is ubiquitous, but the molecular mechanisms that give rise to this ecological phenomenon remain largely unknown. A year-long reciprocal transplant of mustard hill coral (Porites astreoides) between a highly environmentally variable inshore habitat and a more stable offshore habitat demonstrated that populations exhibit phenotypic signatures that are consistent with local adaptation. We characterized the genomic basis of this adaptation in both coral hosts and their intracellular symbionts (Symbiodinium sp.) using genome-wide gene expression profiling. (...)

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8 novembre 2016

An invasive social insect overcomes genetic load at the sex locus [Nature Ecology & Evolution]

Keywords : ecological genetics, entomology, evolutionary genetics, invasive species, molecular ecology

Some invasive hymenopteran social insects found new populations with very few reproductive individuals. This is despite the high cost of founder effects for such insects, which generally require heterozygosity at a single locus—the complementary sex determiner, csd—to develop as females. Individuals that are homozygous at csd develop as either infertile or subfertile diploid males or not at all. Furthermore, diploid males replace the female workers that are essential for colony function. Here we document how the Asian honey bee (Apis cerana) overcame the diploid male problem during its invasion of Australia. Natural selection prevented the loss of rare csd alleles due to genetic drift and corrected the skew in allele frequencies caused by founder effects to restore high average heterozygosity. Thus, balancing selection can alleviate the genetic load at csd imposed by severe bottlenecks, and so facilitate invasiveness.(...)

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7 novembre 2016

The effect of colour producing mechanisms on plumage sexual dichromatism in passerines and parrots [Functional Ecology]

1.Sexual dichromatism (SD) often reflects intense sexual selection on males. It has been hypothesised that sexual selection should favour the elaboration of those male colours that honestly signal quality, and that such colours should therefore show higher SD. Costliness of colours is expected to vary according to their production mechanism (pigment type, feather microstructure, and combinations thereof). Carotenoid-based colours, due to their dietary origin and competing functions of carotenoid pigments, are the best documented costly colours, while endogenous pigments and structural colours are expected to be less costly. However, how SD varies with colour producing mechanism has not been systematically addressed.
2.Here we test the link between SD and mechanisms of colour production across nearly all Australian passerines (n=302) and parrots (n=48), using reflectance spectrometry and visual models.(...)

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4 novembre 2016

Migratory birds under threat [Science/Perspective/Conservation]

The populations of migratory bird species that breed in Europe and overwinter in sub-Saharan Africa are declining considerably faster than those of nonmigratory resident species or of migratory species that overwinter in Europe (1). Likely factors are habitat changes due to changes in land use, illegal killing and taking along the northern African coasts, and climate-induced changes in timing of migration and breeding. However, not only European trans-Saharan migrants are declining fast. This holds also for North American long-distance migrants wintering in Central and South America. To halt these declines, preservation of remaining habitats and restoration of habitats both at breeding and nonbreeding grounds is essential, as well as stopping illegal killing and taking of birds along their migration routes.

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