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9 novembre 2016

A global analysis of bird plumage patterns reveals no association between habitat and camouflage [PeerJ]

Keywords : biodiversity, ecology, evolutionary studies, zoology

Evidence suggests that animal patterns (motifs) function in camouflage. Irregular mottled patterns can facilitate concealment when stationary in cluttered habitats, whereas regular patterns typically prevent capture during movement in open habitats. Bird plumage patterns have predominantly converged on just four types—mottled (irregular), scales, bars and spots (regular)—and habitat could be driving convergent evolution in avian patterning. Based on sensory ecology, we therefore predict that irregular patterns would be associated with visually noisy closed habitats and that regular patterns would be associated with open habitats. Regular patterns have also been shown to function in communication for sexually competing males to stand-out and attract females, so we predict that male breeding plumage patterns evolved in both open and closed habitats. Here, taking phylogenetic relatedness into account, we investigate ecological selection for bird plumage patterns across the class Aves.(...)

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9 novembre 2016

Assessment of pollen rewards by foraging bees [Functional Ecology]

Keywords : bees, behaviour, learning, pollen, pollination, sensory

1.The removal of pollen by flower-visiting insects is costly to plants, not only in terms of production, but also via lost reproductive potential. Modern angiosperms have evolved various reward strategies to limit these costs, yet many plant species still offer pollen as a sole or major reward for pollinating insects.
2.The benefits plants gain by offering pollen as a reward for pollinating are defined by the behaviour of their pollinators, some of which feed on the pollen at the flower, while others collect pollen to provision offspring.
3.We explore how pollen impacts on the behaviour and foraging decisions of pollen-collecting bees, drawing comparisons with what is known for nectar rewards. This question is of particular interest since foraging bees typically do not eat pollen during collection, meaning the sensory pathways involved in evaluating this resource are not immediately obvious.(...)

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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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