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Vieu, Julien

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Vieu, Julien
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https://libra.unine.ch/handle/123456789/374

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  • Publication
    Accès libre
    Evolutionary diversification in the hyper-diverse montane forests of the tropical Andes: radiation of Macrocarpaea (Gentianaceae) and the possible role of range expansion
    (2021-11-19)
    Kissling, Jonathan 
    ;
    Vieu, Julien 
    ;
    Hughes, Colin
    ;
    Grant, Jason 
    The humid mid-elevation montane forests (MMF) of the tropical Andes harbour high levels of plant species diversity, contributing to the exceptional overall diversity of the tropical Andean biodiversity hotspot. However, little is known about the diversification dynamics of MMF plant lineages compared to lineages in other Andean biomes. Here, we use Macrocarpaea (Gentianaceae) to investigate patterns of plant diversification in the MMF, using molecular dating with fossils and secondary calibration (from a family-wide phylogenetic analysis of Gentianaceae). We sequenced 76 of 118 recognized Macrocarpaea spp. for six markers to reconstruct a time-calibrated phylogenetic tree and infer the historical biogeography of Macrocarpaea using maximum-likelihood methods implemented in BioGeoBEARS, estimating diversification rates through time and among lineages with BAMM. We document a rapid radiation of Macrocarpaea in Andean MMF coinciding with rapid colonization and range expansion across the entire distribution of the genus in the Andes starting 7.2 Mya. Our results support allopatric founder-event speciation as the dominant process contributing to geographical phylogenetic structure across the genus. We propose that establishment of the MMF in the late Miocene, when the Andes attained critical elevation to modify regional climates, provided large new areas of suitable habitat for Macrocarpaea to quickly colonize and expand through repeated founder-events. We suggest that this wave of colonization and range expansion triggered rapid diversification, and, as the MMF became progressively occupied, the diversification rate slowed. Our study also supports the idea that MMF plant radiations are older and more slowly evolving than the quickly evolving lineages in the recent Andean high-elevation grasslands.
  • Publication
    Accès libre
    Molecular phylogenetics supports widespread cryptic species in moonworts (Botrychium s.s., Ophioglossaceae)
    Dauphin, Benjamin
    ;
    Vieu, Julien 
    ;
    Grant, Jason 
    Premise of the study: Previous phylogenetic studies of moonworts (Botrychium sensu stricto (s.s.)) included few taxa from outside of North America. This low geographical representation limited interpretations of relationships of this group rich in cryptic species. With 18 out of 30 species in the genus being polyploid, understanding their evolutionary history remains a major challenge.
    Methods: A new molecular phylogeny was reconstructed using Maximum Likelihood (ML) and Bayesian Inference (BI) analyses based on multiple accessions of the most wide- ranging Arctic taxa of Botrychium in North America and Europe using three noncoding plastid DNA regions (psbA-trnHGUG, trnLUAA- trnFGAA intergenic spacer, and rpL16 intron).
    Key results: The new phylogeny confirms the identity of several recently described species and proposed new taxa. Nine subclades are newly identified within the two major clades in Botrychium s.s.: Lanceolatum and Lunaria. Chloroplast DNA was variable enough to separate morphologically cryptic species in the Lunaria clade. On the contrary, much less variation is seen within the morphologically variable Lanceolatum clade despite sampling over the same broad geographic range. The chloroplast region psbA-trnHGUG is identified as an efficient DNA barcode for the identification of cryptic taxa in Botrychium s.s.
    Conclusions: The combined increase in species representation, samples from throughout the geographic range of each species, and sequencing of multiple plastid DNA regions supports morphologically cryptic species in Botrychium s.s.
  • Publication
    Accès libre
    DE MACROCARPAEAE GRISEBACH (EX GENTIANACEIS) SPECIEBUS NOVIS XII: THREE NEW SPECIES FROM THE ANDES OF PERU
    Grant, Jason 
    ;
    Vieu, Julien 
    Three new species from Peru, Macrocarpaea abiseo, M. felicitata, and M. huamantanga, are described and illustrated.