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16 juillet 2018

Diversification rates and phylogenies : what are we estimating, and how good are the estimates ? [BioRxiv]

Species-specific diversification rates, or "tip rates", can be computed quickly from phylogenies and are widely used to study diversification rate variation in relation to geography, ecology, and phenotypes. These tip rates provide a number of theoretical and practical advantages, such as the relaxation of assumptions of rate homogeneity in trait-dependent modeling approaches. However, there is significant confusion in the literature regarding whether these metrics estimate speciation or net diversification rates. Additionally, no study has yet compared the relative performance and accuracy of tip rate metrics. We compared the statistical performance of three model-free rate metrics (inverse terminal branch lengths ; node density metric ; DR statistic) and a model-based approach (BAMM). We applied each method to a large set of simulated phylogenies that had been generated under different diversification processes ; scenarios included multi-regime time-constant and diversity-dependent trees, as well as trees where the rate of speciation evolves under a diffusion process.(...)

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16 juillet 2018

Migration strategies of brown trout (Salmo trutta) in a subarctic river system as revealed by stable isotope analysis [Ecology of Freshwater Fish]

Keywords : anadromy, life‐history strategies, partial migration, residency, salmonid

We estimated the proportions of anadromous and freshwater‐resident brown trout (Salmo trutta) in different parts of the subarctic River Näätämöjoki/Neidenelva system (Finland and Norway) using carbon, nitrogen and hydrogen stable isotope analyses of archived scales as identifiers of migration strategy. Our results showed that carbon stable isotope values were the best predictor of migration strategy. Most individuals fell into two clearly distinct groups representing anadromous (47%) or freshwater‐resident (42%) individuals, but some fish had intermediate carbon values suggesting repeated movement between freshwater and the sea.(...)

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16 juillet 2018

An Algal Greening of Land [Cell - Preview]

Photosynthetic eukaryotes arose ∼1.5 billion years ago by endosymbiosis with a cyanobacterium. Algae then evolved for a billion years before one lineage finally colonized land. Why the wait ? The Chara braunii genome details a decisive step linking plant origins with Earth’s history.

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16 juillet 2018

Evolution of a central neural circuit underlies Drosophila mate preferences

Courtship rituals serve to reinforce reproductive barriers between closely related species. Drosophila melanogaster and Drosophila simulans exhibit reproductive isolation, owing in part to the fact that D. melanogaster females produce 7,11-heptacosadiene, a pheromone that promotes courtship in D. melanogaster males but suppresses courtship in D. simulans males. Here we compare pheromone-processing pathways in D. melanogaster and D. simulans males to define how these sister species endow 7,11-heptacosadiene with the opposite behavioural valence to underlie species discrimination.(...)

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13 juillet 2018

Concordant divergence of mitogenomes and a mitonuclear gene cluster in bird lineages inhabiting different climates [Nature Ecology & Evolution]

Metabolic processes in eukaryotic cells depend on interactions between mitochondrial and nuclear gene products (mitonuclear interactions). These interactions could have a direct role in population divergence. Here, we study mitonuclear co-evolution in a widespread bird that experienced population divergence followed by bidirectional mitochondrial introgression into different nuclear backgrounds. Using >60,000 single nucleotide polymorphisms, we quantify patterns of nuclear genetic differentiation between populations that occupy areas with different climates and harbour deeply divergent mitochondrial lineages despite ongoing nuclear gene flow.(...)

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