Fossil pollen records reveal a late rise of open-habitat ecosystems in Patagonia

The timing of major turnovers in terrestrial ecosystems of the Cenozoic Era has been largely interpreted from the analysis of the assumed feeding preference of extinct mammals. For example, the expansion of open-habitat ecosystems (grasslands or savannas) is inferred to have occurred earlier in Patagonia than elsewhere because of the early advent of high-crowned teeth (hypsodont) mammals ∼26 Ma ago. However, the plant fossil record from Patagonia implies another evolutionary scenario. Here we show that the dominance of key open-habitat species - amaranths, Ephedra, asters and grasses - occurred during the last 10 Ma, about 15 Ma later than previously inferred using feeding/habitat ecology of extinct mammals. This late rise of open-landscapes in southern South America brings into question whether the expansion of open-habitat vegetation could have been the prime factor of high-crowned mammal diversification.Fil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin

Pollen morphology of Nothofagus (Nothofagaceae, Fagales) and its phylogenetic significance

Nothofagaceae (southern beeches) are a relatively small flowering plant family of trees confined to the Southern Hemisphere. The fossil record of the family is abundant and it has been widely used as a test case for the classic hypothesis that Antarctica, Patagonia, Australia and New Zealand were once joined together. Although the phylogenetic relationships in Nothofagus appear to be well supported, the evolution of some pollen morphological traits remains elusive, largely because of the lack of ultrastructural analyses. Here we describe the pollen morphology of all extant South American species of Nothofagus, using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy (LM), and reconstruct ancestral character states using a well-supported phylogenetic tree of the family. Our results indicate that the main differences between pollen of subgenera Fuscospora (pollen type fusca a) and Nothofagus (pollen type fusca b) are related to the size of microspines (distinguishable or not in optical section), and the thickening of colpi margins (thickened inwards, or thickened both inwards and outwards). In particular, Nothofagus alessandrii, the only extant South American species of subgenus Fuscospora, presents distinctive pollen features that have not been observed in any other species of the genus (i.e. a large granular infratectum and spongy apertural endexine). Species of subgenus Lophozonia are characterized by having the largest pollen grains, with polygonal outline in polar view, microspines distinguishable in optical section, long and non-thickened colpi, and a thin endexine. The reconstruction of character states for the node corresponding to the common ancestor to genus Nothofagus leads us to conclude that the ancestral form of Nothofagaceae should have had: equatorial diameter < 40 μm, circular outline in polar view, microspines distinguishable in optical section, short colpi thickened inwards, and a thin endexine. These features are fully consistent with those present in Nothofagidites senectus Dettmann & Playford, the oldest fossil species of Nothofagaceae recorded in Campanian-Maastrichtian sediments of Gondwana.Fil: Fernández, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Santamarina, Patricio Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Tellería, María Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Pollen morphology of the least known families of the order Asterales

The recent discovery of pollen grains assigned to the earliest branch of Asteraceae from Cretaceous sediments in Antarctica prompted us to examine the pollen from five lesser known members of Asterales (Alseuosmiaceae, Argophyllaceae, Pentaphragmataceae, Phellinaceae and Roussaceae) that might also be represented in fossil sediments. Detailed pollen morphology in the basal members of the order Asterales has, until now, been incomplete. Our study reveals a highly variable pollen morphology of these small, and poorly explored families. The tricolporate character of Phelline macrophylla and the zono-hexaporate aperture of Roussea simplex are described for the first time. Pollen of Alseuosmiaceae share granulate structure and tectum little sculpturate, with the exception of Periomphale which is verrucate; Crispiloba has an isolated position due to very large size and porate aperture. Pollen of Argophyllaceae is relatively homogeneous sharing tricolporate aperture, tectum little sculpturate and columellate structure. Pentaphragmataceae is distinguished by its smallest pollen, with oblate-peroblate shape, di or tricolporate aperture and psilate exine. Roussaceae is the most diverse family at level of dispersion unit, aperture type, sculpture and structure of exine. The morphological characters here analysed can be potentially used to unmask fossil dispersed pollen grains with unknown botanical affinity.Fil: Tellería, María Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

First Miocene fossils of Vivianiaceae shed new light on phylogeny, divergence times, and historical biogeography of Geraniales

The origin of Geraniales (approximately 900 species in three families: Geraniaceae, Melianthaceae, and Vivianiaceae) is traced back to the Cretaceous of Gondwana, yet their geotemporal history is largely unknown because of a limited fossil record and incomplete phylogenies. In the present study, we provide the first fossil record of Vivianiaceae and a highly resolved molecular phylogeny for all extant Geraniales genera. Our results support the hypothesis that five (instead of three) families should be recognized in the order Geraniales: Francoaceae A. Juss. (Francoa, Greyia, Tetilla), Geraniaceae Juss. (Erodium, Geranium, Monsonia, Pelargonium), Hypseocharitaceae Wedd. (monogeneric), Melianthaceae Horan. (Bersama, Melianthus), and Vivianiaceae Klotzsch (Balbisia, Rhynchotheca, Viviania). The four major lineages (i.e. Geraniaceae, Francoaceae+Melianthaceae, Hypseocharitaceae, Vivianiaceae) all originated within a narrow time frame during the Eocene (36.9-49.9Mya) based on the five fossil calibration points. The divergence of most of the extant genera occurred much later, from the Miocene onwards. The South American-South African disjunction in Francoaceae apparently goes back to long distance dispersal with an estimated divergence time of the lineages in the Middle Miocene [11.2 (5.9-17.7)Mya]. Diversification in Melianthus appears to be much more recent than previously assumed [starting approximately 3.4 (1.9-5.2)Mya rather than approximately 8-20Mya]. However, divergence of the Andean Hypseocharis lineage [36.9 (31.9-42.8)Mya] significantly predates the main Andean uplift: Current distributions likely go back to northward migrations and subsequent extinctions in Patagonia. Similarly, Rhynchotheca, Balbisia, and Viviania have a current southern distribution limit >10°N of the fossil finds, indicating a massive northward displacement. The present evidence suggests that niche conservatism likely played a major role in the historical biogeography of Geraniales. © 2012 The Linnean Society of London.Fil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Freie Universität Berlin; AlemaniaFil: Gottschling, Marc. Ludwig Maximilians Universitat; AlemaniaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Weigend, M. Freie Universität Berlin; Alemani

Early history of Asteraceae in Patagonia: Evidence from fossil pollen grains

The Asteraceae are classified into three subfamilies: Barnadesioideae, Cichorioideae, and Asteroideae. It has been suggested that the southern South American subfamily Barnadesioideae is the basal branch of the phylogenetic tree of the family, and Patagonia is the ancestral area of Asteraceae. Here we explore the chronological records of some members of the family, with findings of Mutisiinae (tribe Mutisieae, subfamily Cichorioideae) from the Late oligocene (28–23 Ma) and of Barnadesioideae and Nassauviinae (Mutisieae) from the early Miocene (23–20 Ma), all recovered from marine deposits of Patagonia. even though the succession of fossil appearances (first Mutisieae) differs from that provided by molecular data (first Barnadesioideae), this new scheme offers additional evidence towards the understanding of the early history of ancestral Asteraceae.Facultad de Ciencias Naturales y Muse

Early history of Asteraceae in Patagonia: Evidence from fossil pollen grains

The Asteraceae are classified into three subfamilies: Barnadesioideae, Cichorioideae, and Asteroideae. It has been suggested that the southern South American subfamily Barnadesioideae is the basal branch of the phylogenetic tree of the family, and Patagonia is the ancestral area of Asteraceae. Here we explore the chronological records of some members of the family, with findings of Mutisiinae (tribe Mutisieae, subfamily Cichorioideae) from the Late oligocene (28–23 Ma) and of Barnadesioideae and Nassauviinae (Mutisieae) from the early Miocene (23–20 Ma), all recovered from marine deposits of Patagonia. even though the succession of fossil appearances (first Mutisieae) differs from that provided by molecular data (first Barnadesioideae), this new scheme offers additional evidence towards the understanding of the early history of ancestral Asteraceae.Facultad de Ciencias Naturales y Muse

Pollen morphology of <i>Nothofagus</i> (Nothofagaceae, Fagales) and its phylogenetic significance

Nothofagaceae (southern beeches) are a relatively small flowering plant family of trees confined to the Southern Hemisphere. The fossil record of the family is abundant and it has been widely used as a test case for the classic hypothesis that Antarctica, Patagonia, Australia and New Zealand were once joined together. Although the phylogenetic relationships in Nothofagus appear to be well supported, the evolution of some pollen morphological traits remains elusive, largely because of the lack of ultrastructural analyses. Here we describe the pollen morphology of all extant South American species of Nothofagus, using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy (LM), and reconstruct ancestral character states using a well-supported phylogenetic tree of the family. Our results indicate that the main differences between pollen of subgenera Fuscospora (pollen type fusca a) and Nothofagus (pollen type fusca b) are related to the size of microspines (distinguishable or not in optical section), and the thickening of colpi margins (thickened inwards, or thickened both inwards and outwards). In particular, Nothofagus alessandrii, the only extant South American species of subgenus Fuscospora, presents distinctive pollen features that have not been observed in any other species of the genus (i.e. a large granular infratectum and spongy apertural endexine). Species of subgenus Lophozonia are characterized by having the largest pollen grains, with polygonal outline in polar view, microspines distinguishable in optical section, long and non-thickened colpi, and a thin endexine. The reconstruction of character states for the node corresponding to the common ancestor to genus Nothofagus leads us to conclude that the ancestral form of Nothofagaceae should have had: equatorial diameter < 40 μm, circular outline in polar view, microspines distinguishable in optical section, short colpi thickened inwards, and a thin endexine. These features are fully consistent with those present in Nothofagidites senectus Dettmann & Playford, the oldest fossil species of Nothofagaceae recorded in Campanian-Maastrichtian sediments of Gondwana.Facultad de Ciencias Naturales y Muse

Pollen morphology of <i>Nothofagus</i> (Nothofagaceae, Fagales) and its phylogenetic significance

Nothofagaceae (southern beeches) are a relatively small flowering plant family of trees confined to the Southern Hemisphere. The fossil record of the family is abundant and it has been widely used as a test case for the classic hypothesis that Antarctica, Patagonia, Australia and New Zealand were once joined together. Although the phylogenetic relationships in Nothofagus appear to be well supported, the evolution of some pollen morphological traits remains elusive, largely because of the lack of ultrastructural analyses. Here we describe the pollen morphology of all extant South American species of Nothofagus, using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and light microscopy (LM), and reconstruct ancestral character states using a well-supported phylogenetic tree of the family. Our results indicate that the main differences between pollen of subgenera Fuscospora (pollen type fusca a) and Nothofagus (pollen type fusca b) are related to the size of microspines (distinguishable or not in optical section), and the thickening of colpi margins (thickened inwards, or thickened both inwards and outwards). In particular, Nothofagus alessandrii, the only extant South American species of subgenus Fuscospora, presents distinctive pollen features that have not been observed in any other species of the genus (i.e. a large granular infratectum and spongy apertural endexine). Species of subgenus Lophozonia are characterized by having the largest pollen grains, with polygonal outline in polar view, microspines distinguishable in optical section, long and non-thickened colpi, and a thin endexine. The reconstruction of character states for the node corresponding to the common ancestor to genus Nothofagus leads us to conclude that the ancestral form of Nothofagaceae should have had: equatorial diameter < 40 μm, circular outline in polar view, microspines distinguishable in optical section, short colpi thickened inwards, and a thin endexine. These features are fully consistent with those present in Nothofagidites senectus Dettmann & Playford, the oldest fossil species of Nothofagaceae recorded in Campanian-Maastrichtian sediments of Gondwana.Facultad de Ciencias Naturales y Muse

Impact of mid Eocene greenhouse warming on America’s southernmost floras

A major climate shift took place about 40 Myr ago—the Middle Eocene Climatic Optimum or MECO—triggered by a significant rise of atmospheric CO2 concentrations. The biotic response to this MECO is well documented in the marine realm, but poorly explored in adjacent landmasses. Here, we quantify the response of the floras from America’s southernmost latitudes based on the analysis of terrestrially derived spores and pollen grains from the mid-late Eocene (~46–34 Myr) of southern Patagonia. Robust nonparametric estimators indicate that floras in southern Patagonia were in average ~40% more diverse during the MECO than pre-MECO and post-MECO intervals. The high atmospheric CO2 and increasing temperatures may have favored the combination of neotropical migrants with Gondwanan species, explaining in part the high diversity that we observed during the MECO. Our reconstructed biota reflects a greenhouse world and offers a climatic and ecological deep time scenario of an ice-free sub-Antarctic realm.Fil: Fernández, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: González Estebenet, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Tellería, María Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Biostratigraphy based neogene dinoflagellate cysts in northeast of Patagonia, Argentina

This paper presents the biostratigraphic results based on dinoflagellate cysts from two Neogene lithostratigraphic units cropping out in northeastern Patagonia. The Barranca Final Formation, located in the southwestern Colorado Basin, is exposed along the northern coast of San Matías Gulf, Río Negro Province, and the Puerto Madryn Formation in the Península Valdés, Chubut Province. The low-to-moderate diverse dinoflagellate cyst assemblages present are dominated by neritic taxa with subordinate oceanic indicators. Towards the top of both sections, the relative frequencies of the dinoflagellate cyts decrease, whereas acritarchs and continental palynomorphs proportions increase, indicating a shallowing upwards trend. The stratigraphic range of Labrynthodinium truncatum truncatum in the lower part of the Barranca Final Formation indicate age between the late Burdigalian (ca. 16.5 Ma) and the late Tortonian (ca. 7.5 Ma). Labrynthodinium truncatum truncatum and Habibacysta tectata constrain the age of the Puerto Madryn Formation to the Serravalian to Tortonian interval (late middle miocene to early late Miocene). Theses ages are consistent with the 87Sr/86Sr isotopic analysis of the oyster valves at 9.61 and 8.3 and with the 87Sr/86Sr ratios on calcitic shells at about 10 Ma, respectively.O presente artigo inclui resultados bioestratigráficos baseados em cistos de dinoflagelados de duas unidades litoestratigráficas do Neógeno que afloram no nordeste da Patagônia. A Formação Barranca Final, localizada no sudoeste da Bacia do Rio Colorado, que está exposta ao longo da costa norte do Golfo San Matías Golfo, Província de Rio Negro, e a Formação Puerto Madryn na Península Valdés, Província de Chubut. Os conjuntos de dinocistos das seções estudadas exibem uma diversidade moderada a baixa, composta principalmente dos táxons neríticos, com indicadores oceânicos, como Nematosphaeropsis rigida e Impaginidium ssp., sendo apenas subordinados. As frequências relativas de cistos decrescem na porção superior de ambas as secções, enquanto os acritarcas e palinomorfos continentais aumentam suas proporções, indicando uma tendência à redução da profundidade. O intervalo estratigráfico de Labrynthodinium truncatum truncatum na parte inferior da Formação Barranca Final indica idade entre o final do Burdigaliano (ca. 16,5 Ma) e o Tortoniano final (cerca de 7,5 Ma). Labrynthodinium truncatum truncatum, Habibacysta tectata restringe a idade da Formação Puerto Madryn ao intervalo entre o Serravaliano ou Tortoniano (final do Mesomioceno ao Neomioceno). Essas idades são consistentes com as análises isotópicas 87Sr/86Sr das conchas de ostras que resultam em valores de 9,61 e 8,3 e com as proporções de 87Sr/ 86Sr em conchas calcíticas de uns 10 Ma, respectivamente.Fil: Fuentes, Sabrina Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Guler, Maria Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Palazzesi, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Scasso, Roberto Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin