Browsing by Author "Hinojosa, LF"

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    Are Chilean coastal forests pre-Pleistocene relicts?: Evidence from foliar physiognomy, palaeoclimate, and phytogeography
    (2006) Hinojosa, LF; Armesto, JJ; Villagrán, C
    Aim We ask whether contemporary forests of the Chilean Coastal Range can be considered to be direct and conservative descendants of pre-Pleistocene palaeofloras that occurred in southern South America from the Palaeogene to early Neogene periods (65-10 Ma), maintaining foliar physiognomies that do not match their present-day climate. We also identify the most likely ancestors of present-day coastal forests.
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    Did South American Mixed Paleofloras evolve under thermal equability or in the absence of an effective Andean barrier during the Cenozoic?
    (2005) Hinojosa, LF; Villagrán, C
    Two hypotheses have attempted to explain the development of Mixed Paleofloras during the Cenozoic in South America. One of them postulates changes in the climatic tolerances of its component taxa and the other calls for the establishment of atmospheric thermal stability ("equable climate') at the time these floras came into existence. We set out to test these hypotheses using leaf physiognomical analyses for eight Mixed fossil floras of the Cenozoic of Chile and Argentina. In addition to physiognomic analyses of the complete dicotyledonous flora as known from each site, we also evaluated the physiognomic significance of fossil Nothofagus leaves in relation to current Chilean species of the genus. Our results suggest that fossil Nothofagus leaves have a broader climatic envelope relative to the extant species. This divergence could be accounted by differences in their respective climatic tolerances. We postulate that the Mixed Paleoflora evolved in a subtropical climate that extended as far south as 40degreesS, with relatively warm temperatures and high annual rainfall with little seasonal variation. This climatic scenario is possible only with a much-reduced Andean massif, which would have permitted the spillover of moisture of easterly origin to the Pacific Andean slopes. (C) 2004 Elsevier B.V. All rights reserved.
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    On the persistence of Tropical Paleofloras in central Chile during the Early Eocene
    (2005) Gayó, E; Hinojosa, LF; Villagrán, C
    Mixed paleofloras first appeared during the Early Eocene of southern South America. These floras were a blend of cold and warm taxa with Austral-Antarctic and Neotropical affinities. Despite the onset of mixed floras, Neotropical floras persisted in central Chile during the Early Eocene. In this study, we analyze the reasons for this persistence and also show that a relationship exists between this persistence and regional paleoclimate. We established the taxonomical composition, associated paleoclimate and phytogeographic affinities of an Early Eocene flora at Caleta Cocholgue, coastal central Chile. Our results indicate that tropical and subtropical taxa prevailed at Caleta Cocholgue. These were chiefly Lauraceae, today associated with a humid-warm climate. Physiognomic analyses indicate Mean Annual Temperature and Mean Annual Precipitation above 19 degrees C and 260 cm, respectively. Moreover, a phytogeographic analysis demonstrates that the Caleta Cocholg-be is closely related to other tropical floras, and poorly linked to contemporary mixed floras. These results strongly suggest that tropical floras persisted in central Chile during the Early Eocene and formed a belt across current subtropical latitudes from southern South America, between 25 degrees S and 37 degrees S. This persistence might be related to the Early Eocene Climatic Optimum and to a shrinking tropical belt, compared to its former Paleocene/Eocene extension. (c) 2005 Elsevier B.V. All rights reserved.