Phylogeography and palaeodistribution modelling of Nassauvia subgenus Strongyloma (Asteraceae): exploring phylogeographical scenarios in the Patagonian steppe

The Patagonian steppe is an immense, cold, arid region, yet phylogeographically understudied. Nassauvia subgen. Strongyloma is a characteristic element of the steppe, exhibiting a continuum of morphological variation. This taxon provides a relevant phylogeographical model not only to understand how past environmental changes shaped the genetic structure of its populations, but also to explore phylogeographical scenarios at the large geographical scale of the Patagonian steppe. Here, we (1) assess demographic processes and historical events that shaped current geographic patterns of haplotypic diversity; (2) analyze hypotheses of isolation in refugia, fragmentation of populations, and/or colonization of available areas during Pleistocene glaciations; and (3) model extant and palaeoclimatic distributions to support inferred phylogeographical patterns. Chloroplast intergenic spacers, rpl32–trnL and trnQ–5′rps16, were sequenced for 372 individuals from 63 populations. Nested clade analysis, analyses of molecular variance, and neutrality tests were performed to assess genetic structure and range expansion. The present potential distribution was modelled and projected onto a last glacial maximum (LGM) model. Of 41 haplotypes observed, ten were shared among populations associated with different morphological variants. Populations with highest haplotype diversity and private haplotypes were found in central-western and south-eastern Patagonia, consistent with long-term persistence in refugia during Pleistocene. Palaeomodelling suggested a shift toward the palaeoseashore during LGM; new available areas over the exposed Atlantic submarine platform were colonized during glaciations with postglacial retraction of populations. A scenario of fragmentation and posterior range expansion may explain the observed patterns in the center of the steppe, which is supported by palaeomodelling. Northern Patagonian populations were isolated from southern populations by the Chubut and the Deseado river basins during glaciations. Pleistocene glaciations indirectly impacted the distribution, demography, and diversification of subgen. Strongyloma through decreased winter temperatures and water availability in different areas of its range.Fil: Nicola, Marcela Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Nicola, Marcela Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Pozner, Raul Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Johnson, Leigh. University Brigham Young; Estados Unido

A new species of Minuartia (Caryophyllaceae) restricted to the high Andes of South America

A new apetalous species of Minuartia from the high Andes of northwestern Argentina, M. altoandina, is here described and illustrated. At first sight, M. altoandina is morphologically very similar to the European M. sedoides because of the absence of petals and ciliate leaf margin with narrow hyaline teeth; however, from a biogeographical point of view, it will probably be related to the North American M. rossii complex through the morphology of M. austromontana.Fil: Nicola, Marcela Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Pozner, Raúl Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentin

Revision of Paspalum group Gardneriana (Poaceae, Paspaleae)

El presente tratamiento incluye una revision taxonómica de las especies de Paspalum grupo Gard-neriana. Dentro de este grupo se consideran siete especies, caracterizadas por incluir plantas anuales o perennes, con espiguillas usualmente obovoides, gluma superior ausente o reducida y antecio superior endurecido y marcadamente papiloso, con papilas verrugosas en toda su superficie. Se incluye una clave de las especies, descripciones, ilustraciones y fotos de los antecios, junto con un análisis de la relación del grupo dentro del género Paspalum. Se consideran dentro del grupo las siguientes especies: Paspalum burchellii, P. delicatum, P. gardnerianum, P. nudatum, P. pictum, P. reduncum y P. subsesquiglume. Se designan lectotipos para P. burchellii, P. connectens, P. reduncum y P. subsesquiglume; P. gemmosum es sinónimo de P. subsesquiglume.Species of Paspalum group Gardneriana are revised as a whole for the first time. Seven species are treated in this work, being the group characterized by including annual or perennial species, with spikelets usually obovoid, upper glume absent or reduced, and upper anthecium indurate and strongly papillose, with verrucose papillae all over its surface. A key to the species is provided, together with a discussion of previous infrageneric classifications and relationships of Gardneriana; morphological descriptions, and illustrations of all species are also presented. The following species are included in Paspalum group Gardneriana: Paspalum burchellii, P. delicatum, P. gardnerianum, P. nudatum, P. pictum, P. reduncum, and P. subsesquiglume. Also, lectotypes are designated for P. burchellii, P. connectens, P. reduncum and P. subsesquiglume; P. gemmosum is defined as a new synonym of P. subsesquiglume.Fil: Nicola, Marcela Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Salomón, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Zuloaga, Fernando Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Morrone, Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentin

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements