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8 février 2018

Profound genetic divergence and asymmetric parental genome contributions as hallmarks of hybrid speciation in polyploid toads [Proceedings of the Royal Society B - Biological Sciences]

Keywords : polyploidy, hybridization, divergence, multi-locus phylogeny, directional asymmetry, Bufo viridis subgroup

The evolutionary causes and consequences of allopolyploidization, an exceptional pathway to instant hybrid speciation, are poorly investigated in animals. In particular, when and why hybrid polyploids versus diploids are produced, and constraints on sources of paternal and maternal ancestors, remain underexplored. Using the Palearctic green toad radiation (including bisexually reproducing species of three ploidy levels) as model, we generate a range-wide multi-locus phylogeny of 15 taxa and present four new insights (...)

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8 février 2018

Cognitive performance is linked to group size and affects fitness in Australian magpies [Nature]

Keywords : behavioural ecology, evolutionary ecology

The social intelligence hypothesis states that the demands of social life drive cognitive evolution. This idea receives support from comparative studies that link variation in group size or mating systems with cognitive and neuroanatomical differences across species, but findings are contradictory and contentious. To understand the cognitive consequences of sociality, it is also important to investigate social variation within species. Here we show that in wild, cooperatively breeding Australian magpies, individuals that live in large groups show increased cognitive performance, which is linked to increased reproductive success.(...)

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7 février 2018

Genomics of the origin and evolution of Citrus [Nature]

Keywords : natural variation in plants, Plant domestication, plant evolution

The genus Citrus, comprising some of the most widely cultivated fruit crops worldwide, includes an uncertain number of species. Here we describe ten natural citrus species, using genomic, phylogenetic and biogeographic analyses of 60 accessions representing diverse citrus germ plasms, and propose that citrus diversified during the late Miocene epoch through a rapid southeast Asian radiation that correlates with a marked weakening of the monsoons. A second radiation enabled by migration across the Wallace line gave rise to the Australian limes in the early Pliocene epoch. Further identification and analyses of hybrids and admixed genomes provides insights into the genealogy of major commercial cultivars of citrus.(...)

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7 février 2018

Persistence of an extracellular systemic infection across metamorphosis in a holometabolous insect [Biology Letters]

David Duneau

Organisms with complex life cycles can differ markedly in their biology across developmental life stages. Consequently, distinct life stages can represent drastically different environments for parasites. This difference is especially striking with holometabolous insects, which have dramatically different larval and adult life stages, bridged by a complete metamorphosis. There is no a priori guarantee that a parasite infecting the larval stage would be able to persist into the adult stage. In fact, to our knowledge, transstadial transmission of extracellular pathogens has never been documented in a host that undergoes complete metamorphosis. We tested the hypothesis that a bacterial parasite originally sampled from an adult host could infect a larva, then survive through metamorphosis and persist into the adult stage. As a model, we infected the host Drosophila melanogaster with a horizontally transmitted, extracellular bacterial pathogen, Providencia rettgeri. We found that this natural pathogen survived systemic infection of larvae (L3) and successfully persisted into the adult host. We then discuss how it may be adaptive for bacteria to transverse life stages and even minimize virulence at the larval stage in order to benefit from adult dispersal.

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7 février 2018

Seasonal plasticity for anti-predatory strategies : matching colour and colour preference for effective crypsis [BioRxiv]

Patricia Beldade

Effective anti-predatory strategies typically require matching morphology and behaviour in prey and there are many compelling examples of behavioural strategies that enhance the effect of morphological defences. When protective adult morphologies are induced by a developmental environment predictive of future predation risk, adult behaviour should be adjusted accordingly to maximize predator avoidance. Behaviour is typically strongly affected by the adult environment but an effective match with a developmentally plastic morphology might be ensured when behaviour is affected the same pre-adult environmental cues. We study early and late life environmental effects on a suite of traits that are expected to work together for effective crypsis. We focused on body colour and colour preference in Bicyclus anynana , a model of developmental plasticity that relies on crypsis as a seasonal strategy for predator avoidance.(...)

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