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Montoya E.,Botanical Institute of Barcelona | Montoya E.,Autonomous University of Barcelona | Rull V.,Botanical Institute of Barcelona | Stansell N.D.,Ohio State University | And 6 more authors.
Journal of Quaternary Science | Year: 2011

The occurrence of the Younger Dryas cold reversal in northern South America midlands and lowlands remains controversial. We present a palaeoecological analysis of a Late Glacial lacustrine section from a midland lake (Lake Chonita, 4.6501°N, 61.0157°W, 884m elevation) located in the Venezuelan Gran Sabana, based on physical and biological proxies. The sediments were mostly barren from ∼15.3 to 12.7k cal a BP, probably due to poor preservation. A ligneous community with no clear modern analogues was dominant from 12.7 to 11.7k cal a BP (Younger Dryas chronozone). At present, similar shrublands are situated around 200m elevation above the lake, suggesting a cooling-driven downward shift in vegetation during that period. The interval from 11.7 to 10.6k cal a BP is marked by a dramatic replacement of the shrubland by savannas and a conspicuous increase in fire incidence. The intensification of local and regional fires at this interval could have played a role in the vegetation shift. A change to wetter, and probably warmer, conditions is deduced after 11.7k cal a BP, coinciding with the early Holocene warming. These results support the hypothesis of a mixed origin (climate and fire) of the Gran Sabana savannas, and highlight the climatic instability of the Neotropics during the Late Glacial. © 2011 John Wiley & Sons, Ltd.

Pellicer J.,Jodrell Laboratory | Hidalgo O.,Jodrell Laboratory | Garnatje T.,Botanical Institute of Barcelona | Kondo K.,Tokyo University of Agriculture | Valles J.,University of Barcelona
Turkish Journal of Botany | Year: 2014

Artemisia L. comprises ca. 20 annual species out of ca. 500, which are distributed mainly across the Old World grades, accounting for multiple independent acquisitions of annual habit throughout the evolutionary history of the genus. This makes Artemisia an interesting subject for the study of plant life cycle evolution in a phylogenetic context and its consequences at genomic level. The main aim of this phylogenetic analysis was to circumscribe 17 of the annual representatives within the major lineages of Artemisia. Genome size has been assessed and ancestral values reconstructed on the tree. Fluorescent in situ hybridisation (FISH) has also been performed to characterise the physical distribution of ribosomal DNA loci. Our results show that annual Artemisia have been especially misassigned at subgeneric level and confirm that they are phylogenetically restricted to basal grades, while absent from the derived ones. Annuals display great diversity of genomic traits; however, although most of them show genome downsizing with respect to their most recent common ancestors, no apparent correlation exists between this trait, the number of rDNA sites, and the phylogenetic placement. Nonetheless, such diversity suggests that higher rates of genome restructuring may have been key in governing genome evolution in annual species. © TÜBİTAK.

Rull V.,Botanical Institute of Barcelona
Journal of Biogeography | Year: 2010

The existence of microrefugia and/or cryptic refugia has been proposed to explain the colonization patterns of temperate continents after the Last Glacial Maximum, as well as to gain an understanding of the present genetic structure of species and their populations. The concepts 'microrefugia' and 'cryptic refugia' largely overlap but do not fully coincide, which may lead to terminological duplication and eventual semantic misconceptions. Here, after a terminological and conceptual analysis, it is proposed that most situations currently characterized as cryptic refugia can be accommodated within the definition of microrefugia, with one single exception, for which some alternative terms are suggested. Moreover, the concept and definition of cryptic refugia are considered to be more imprecise, perishable and subjective than those of microrefugia, which is the preferred term in the current context. © 2010 Blackwell Publishing Ltd.

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