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9 mai 2018

Lethal trap created by adaptive evolutionary response to an exotic resource [Nature]

Keywords : conservation biology, evolution

Global transport of organisms by humans provides novel resources to wild species, which often respond maladaptively. Native herbivorous insects have been killed feeding on toxic exotic plants, which acted as ‘ecological traps’. We document a novel ‘eco-evolutionary trap’ stemming from the opposite effect ; that is, high fitness on an exotic resource despite lack of adaptation to it. Plantago lanceolata was introduced to western North America by cattle-ranching. Feeding on this exotic plant released a large, isolated population of the native butterfly Euphydryas editha from a longstanding trade-off between maternal fecundity and offspring mortality. Because of this release—and despite a reduced insect developmental rate when feeding on this exotic—Plantago immediately supported higher larval survival than did the insects’ traditional host, Collinsia parviflora. Previous work from the 1980s documented an evolving preference for Plantago by ovipositing adults. We predicted that if this trend continued the insects could endanger themselves, because the availability of Plantago to butterflies is controlled by humans, who change land management practices faster than butterflies evolve. Here we report the fulfilment of this prediction.(...)

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7 mai 2018

Genomic analysis of European Drosophila melanogaster populations on a dense spatial scale reveals longitudinal population structure and continent-wide selection [BioRxiv]

Genetic variation is the fuel of evolution. However, analyzing dynamics of evolutionary change in natural populations is challenging, genome sequencing of entire populations remains costly and comprehensive sample collection logistically challenging. To tackle this issue and to define relevant spatial and temporal scales of variation for a population genetic model system, the fruit fly Drosophila melanogaster, we have founded the European Drosophila Population Genomics Consortium (DrosEU). Our principal objective is to employ the strengths of this collaborative consortium to extensively sample and sequence natural populations on a continent-wide scale and across distinct timescales. Here we present the first analysis of the first DrosEU pool-sequencing dataset, consisting of 48 population samples collected across the European continent in 2014.(...)

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4 mai 2018

Climate models predict increasing temperature variability in poor countries [Science Advances]

Extreme events such as heat waves are among the most challenging aspects of climate change for societies. We show that climate models consistently project increases in temperature variability in tropical countries over the coming decades, with the Amazon as a particular hotspot of concern. During the season with maximum insolation, temperature variability increases by 15% per degree of global warming in Amazonia and Southern Africa and by up to 10%°C−1 in the Sahel, India, and Southeast Asia. Mechanisms include drying soils and shifts in atmospheric structure.(...)

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3 mai 2018

Male-killing toxin in a bacterial symbiont of Drosophila [Nature]

Keywords : entomology, symbiosis

Several lineages of symbiotic bacteria in insects selfishly manipulate host reproduction to spread in a population, often by distorting host sex ratios. Spiroplasma poulsonii is a helical and motile, Gram-positive symbiotic bacterium that resides in a wide range of Drosophila species. A notable feature of S. poulsonii is male killing, whereby the sons of infected female hosts are selectively killed during development. Although male killing caused by S. poulsonii has been studied since the 1950s, its underlying mechanism is unknown.(...)

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3 mai 2018

Pollen metabarcoding as a tool for tracking long-distance insect migrations [BioRxiv]

Insects account for the main fraction of Earth’s biodiversity and are key players for ecosystems, notably as pollinators. While insect migration is suspected to represent a natural phenomenon of major importance, remarkably little is known about it, except for a few flagship species. The reason for this situation is mainly due to technical limitations in the study of insect movement. Here we propose using metabarcoding of pollen carried by insects as a method for tracking their migrations. We developed a flexible and simple protocol allowing high multiplexing and not requiring DNA extraction, one of the most time consuming part of metabarcoding protocols, and apply this method to the study of the long-distance migration of the butterfly Vanessa cardui, an emerging model for insect migration.(...)

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