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Background and Aims Cunoniaceae are woody plants with a distribution that suggests a complex history of Gondwanan vicariance, long-distance dispersal, diversification and extinction. Only four out of ~27 genera in Cunoniaceae are native to South America today, but the discovery of extinct species from Argentine Patagonia is providing new information about the history of this family in South America. Methods We describe fossil flowers collected from early Danian (early Palaeocene, ~64 Mya) deposits of the Salamanca Formation. We compare them with similar flowers from extant and extinct species using published literature and herbarium specimens. We used simultaneous analysis of morphology and available chloroplast DNA sequences (trnL – F , rbcL , matK , trnH – psbA) to determine the probable relationship of these fossils to living Cunoniaceae and the co-occurring fossil species Lacinipetalum spectabilum. Key Results Cunoniantha bicarpellata gen. et sp. nov. is the second species of Cunoniaceae to be recognized among the flowers preserved in the Salamanca Formation. Cunoniantha flowers are pentamerous and complete, the anthers contain in situ pollen, and the gynoecium is bicarpellate and syncarpous with two free styles. Phylogenetic analysis indicates that Cunoniantha belongs to crown-group Cunoniaceae among the core Cunoniaceae clade, although it does not have obvious affinity with any tribe. Lacinipetalum spectabilum , also from the Salamanca Formation, belongs to the Cunoniaceae crown group as well, but close to tribe Schizomerieae. Conclusions Our findings highlight the importance of West Gondwana in the evolution of Cunoniaceae during the early Palaeogene. The co-occurrence of C. bicarpellata and L. spectabilum , belonging to different clades within Cunoniaceae, indicates that the diversification of crown-group Cunoniaceae was under way by 64 Mya. [ABSTRACT FROM AUTHOR]

Azorella is a genus with 26 species of Azorelloideae (Apiaceae) that grow from Costa Rica to the subantartic islands, being distintive and dominant in different environments of the Andean Cordilleras from Venezuela to Patagonia. The species of Azorella that grow in Argentina have been revised taxonomically in a previous study. However, knowledge of the remaining species is fragmentary and uneven. The aim of this paper is to update and standardize the information of the 11 species of Azorella absent in Argentina and present in Bolivia, Chile, Colombia, Ecuador, Peru and/or Venezuela. We provide descriptions for those species and update distributional maps, and we solve nomenclatural and typification problems for 41 names, designating 2 type species, 16 lectotypes and 1 neotype. In addition, we provide 10 new illustrations, and an identification key for all the species of the genus. [ABSTRACT FROM AUTHOR]

Guadua tagoara subsp. tagoara is reported for the first time in Argentina, it is described and illustrated. A map showing its geographical distribution in South America and a key to the species and subspecies in Argentina are also provided. A lectotype for Bambusa distorta is here designated. [ABSTRACT FROM AUTHOR]

Abstract: The Río de la Plata grasslands (RPG) in South America are one of the largest temperate grasslands regions of the world. This region plays a key role in international crop production and land use change rates in some areas are among the highest detected nowadays. Our objective was to characterize the spatial heterogeneity of land use change dynamics in the RPG and to relate it with biophysical and political boundaries. Based on Landsat imagery we characterized land use changes at two time periods (1986–1990, 2002–2005) and we performed a comparison of markovian models and their properties (stable proportion vector and sensitivity analysis) for each phytogeographic district and country of the region. Temporal transitions between natural and implanted forests (Fo), crops (Cr), and grasslands (Gr) were calculated in order to build matrix probabilistic models. We found that 1.2×106 ha of grassland surface has been transformed into implanted forests and croplands (6% reduction of grasslands, 60% increase of afforestations, 3% increase of croplands). Transition probability Cr→Cr displayed the largest spatial variation, followed by the other three transitions linking croplands and grasslands (Cr→Gr, Gr→Gr, Gr→Cr). The less variable transition rate among districts was Cr→Fo. Projections for Argentina and parts of Uruguay suggest that grassland loss would continue in most of analyzed territory, whereas in Brazil and parts of Uruguay the projected trend was the opposite, grassland cover would increase. Forested area increment would continue in Uruguay and partially in Argentina, while in Brazil it would decrease. Considering the whole region, crop area would maintain the increasing trends. Transition probabilities for the same phytogeographical district (Northern Campos) differed significantly among the three countries that occupy it, showing the relative importance of human context driving land use change. [Copyright &y& Elsevier]