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24 January 2018

High intraspecific genome diversity in the model arbuscular mycorrhizal symbiont Rhizophagus irregularis [New Phytologist]

Keywords : arbuscular mycorrhizal fungi (AMF), gene exchange, intraspecific variation, pan-genome, Rhizophagus irregularis, transposable elements

Arbuscular mycorrhizal fungi (AMF) are known to improve plant fitness through the establishment of mycorrhizal symbioses. Genetic and phenotypic variations among closely related AMF isolates can significantly affect plant growth, but the genomic changes underlying this variability are unclear. To address this issue, we improved the genome assembly and gene annotation of the model strain Rhizophagus irregularis DAOM197198, and compared its gene content with five isolates of R. irregularis sampled in the same field. All isolates harbor striking genome variations, with large numbers of isolate-specific genes, gene family expansions, and evidence of interisolate genetic exchange.(...)

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24 January 2018

Evolutionary history of mycorrhizal symbioses and global host plant diversity [New Phytologist]

Keywords : evolution, habitat specialization, host plant diversity, mycorrhizal associations, plant nutrition

The majority of vascular plants are mycorrhizal: 72% are arbuscular mycorrhizal (AM), 2.0% are ectomycorrhizal (EcM), 1.5% are ericoid mycorrhizal and 10% are orchid mycorrhizal. Just 8% are completely nonmycorrhizal (NM), whereas 7% have inconsistent NM–AM associations. Most NM and NM–AM plants are nutritional specialists (e.g. carnivores and parasites) or habitat specialists (e.g. hydrophytes and epiphytes). Mycorrhizal associations are consistent in most families, but there are exceptions with complex roots (e.g. both EcM and AM). We recognize three waves of mycorrhizal evolution, starting with AM in early land plants, continuing in the Cretaceous with multiple new NM or EcM linages, ericoid and orchid mycorrhizas. The third wave, which is recent and ongoing, has resulted in root complexity linked to rapid plant diversification in biodiversity hotspots.

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24 January 2018

Salamander morph frequencies do not evolve as predicted in response to 40 years of climate change [Ecography]

Keywords : adaptation, Plethodon cinereus, polymorphism

The global climate is changing rapidly, yet biotic responses remain uncertain. Most studies focus on changes in species ranges or plastic responses like phenology, but adaptive evolution could be equally important. Studying evolutionary responses is challenging given limited historical data and a poor understanding of genetically variable traits under selection. We take advantage of a historical dataset to test for an adaptive response to climate change in a widespread, polymorphic amphibian, the eastern red-backed salamander, Plethodon cinereus. We resurveyed color morph frequencies across New England to test for an adaptive shift in response to climate change. We modeled historical and present-day morph proportions as a function of climate and tested the accuracy of predictions both within and across different time periods.(...)

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24 January 2018

Geographical range size and latitude predict population genetic structure in a global survey [Biology Letters]

Keywords : GBIF, genetic structure, machine learning, latitude, elevation

While genetic diversity within species is influenced by both geographical distance and environmental gradients, it is unclear what other factors are likely to promote population genetic structure. Using a machine learning framework and georeferenced DNA sequences from more than 8000 species, we demonstrate that geographical attributes of the species range, including total size, latitude and elevation, are the most important predictors of which species are likely to contain structured genetic variation. While latitude is well known as an important predictor of biodiversity, our work suggests that it also plays a key role in shaping diversity within species.

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24 January 2018

Cuckoos host range is associated positively with distribution range and negatively with evolutionary uniqueness [Journal of Animal Ecology]

Keywords : Cuculidae, distribution range, evolutionary uniqueness, host species richness, worldwide distribution

1.The evolutionary distinctiveness (ED) score is a measure of phylogenetic isolation that quantifies the evolutionary uniqueness of a species.
2.Here, we compared the ED score of parasitic and non-parasitic cuckoo species worldwide, to understand whether parental care or parasitism represent the largest amount of phylogenetic uniqueness. Next, we focused only on 46 cuckoo species characterized by brood parasitism with a known number of host species, we explored the associations among ED score, number of host species and breeding range size for these species. We assessed these associations using phylogenetic generalized least squares (PGLS) models, taking into account the phylogenetic signal.(...)

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