Updated site compilation of the Latin American Pollen Database

Flantua, Suzette G A et al.The updated inventory of the Latin American Pollen Database (LAPD) offers a wide range of new insights. This paper presents a systematic compilation of palynological research in Latin America. A comprehensive inventory of publications in peer-reviewed and grey literature shows a major expansion of studies over the last decades. The inventory includes 1379 cores and sections with paleoecological data and more than 4800 modern samples from throughout the continent. Through the years, pollen datasets extend over increasing spans of time and show improved taxonomic and temporal resolution. Currently, these datasets are from 12 modern biomes and 30 countries, covering an altitudinal range of 0 to 6300. m asl. The most densely sampled regions are the Colombian Andes, the southeast coast of Brazil, and Patagonia. Underrepresented biomes are the warm temperate mixed forest (3%), dry forests (3%), and warm temperate rainforest (1%); whereas steppe, tropical rainforest, and cool grass shrublands, such as the páramos, are generally well represented (all >. 17%). There are 126 records that span the late Pleistocene to the Last Glacial Maximum transition (21,000. cal. yr BP), and >. 20% of the records cover the Younger Dryas interval and the Pleistocene/Holocene transition. Reanalysis of numerous sites using multiproxy tools emphasize the informative value of this approach in paleoenvironmental reconstruction. We make suggestions for several pollen sites and regions to be visited again; similarly we identify some key research questions that have yet to be answered. The updated LAPD now provides the platform to support an exciting new phase of global palynological research in which multi-site data are being integrated to address current cutting-edge research questions. The LAPD compilation of sites and the literature database will be available through the Neotoma Paleoecology Database website and a new LAPD website by the end of 2015We thank the Netherlands Organization for Scientific Research (NWO, grant 2012/13248/ALW) for financial support of this project.Peer reviewe

<i>Mauritia flexuosa</i> palm swamp communities: natural or human-made? A palynological study of the Gran Sabana region (northern South America) within a neotropical context

Mauritia flexuosa L.f. is one of the more widely distributed neotropical palms and is intensively used by humans. This palm can grow in tropical rainforests or can develop a particular type of virtually monospecific communities restricted to warm and wet lowlands of the Orinoco and Amazon basins. It has been proposed that, during the Last Glacial Maximum (LGM), the Mauritia swamp communities were restricted to the core of the Amazon basin from where they expanded favoured by the Holocene warmer and wetter climates. It has also been suggested that some of these palm communities might have been the result of human dispersal during the last millennia. Here, we evaluate both hypotheses using the case study of the Venezuelan Gran Sabana (GS) region, where the M. flexuosa swamp communities (locally called morichales) are common and well developed. The morichales did not reach the GS until the last 2000 years, as manifested by sudden increases of Mauritia pollen parallelled by similar trends in charcoal particles as proxies for fire. During the last two millennia, the situation was very similar to the present, characterised by extensive burning practices affecting savannas and savanna–forest ecotones but rarely morichales (selective burning). This strongly suggests that human activities could have been responsible for the penetration of the morichales to the GS. A meta-analysis of the available records of Mauritia pollen across northern South America shows that this palm has been present in the region since at least the last four glacial cycles. During the LGM, Mauritia was likely restricted to few but widespread sites of favourable microclimatic conditions (microrefugia) from where the palm expanded during the Holocene. During the last 2000 years, Mauritia underwent a remarkable expansion in northern South America, which includes the GS. It is proposed that humans could have played a role in this regional expansion of Mauritia communities

El origen de la Gran Sabana: pistas del pasado.

[About the book] Prólogo del Editor Los fósiles son los testimonios directos del pasado. Su estudio enriquece nuestra comprensión de los procesos que han llevado a la actual biodiversidad del planeta. El estudio de los fósiles es tarea de la paleontología. A diferencia de la arqueología, que se ocupa de los restos culturales de los humanos, a la paleontología le concierne el estudio de los organismos que vivieron en edades geológicas pretéritas, incluso en aquellas en las cuales los humanos no existían ¿Cómo y cuando ocurrieron los cambios en la biodiversidad en nuestro planeta? ¿Qué explicaciones científicas podemos encontrar para entender la naturaleza que nos rodea? Estas son preguntas fundamentales y hacérselas es diferenciarse de los otros animales. El ser humano comparte un pasado biológico con otros organismos, pero a diferencia de ellos es capaz de razonar y cuestionar el pasado y el futuro. Para investigar estas preguntas universales ¿qué mejor que empezar con lo que existe en tu propia ‘casa’? Venezuela tiene mucho que ofrecer al entendimiento de la evolución de la biodiversidad, no sólo con el estudio de las formas actuales de animales y plantas, sino también de las formas extintas. Este libro presenta diversos temas que involucran a los fósiles de Venezuela. Los autores provienen de diversos lugares y poseen distintos intereses, pero a todos los une una experiencia en el norte del Neotrópico. Sus publicaciones son generalmente dirigidas a otros expertos en su campo, pero aquí ellos han intentado de manera menos especializada, con claridad pero también en detalle, algunos de los puntos más relevantes de su campo de investigación. Considero que han hecho un excelente trabajo y espero que las numerosas ilustraciones puedan ayudar a la comprensión. Algunos pasajes serán más difíciles que otros, pero lo que se consigue con esfuerzo tiene más valor ¡Como los fósiles mismos colectados en el campo y estudiados por años hasta llegar a las lindas reconstrucciones de Jorge González de este libro! Las ilustraciones de este libro intentan ejemplificar el trabajo paleontológico y de los fósiles mismos, y además pretenden dar vida a las formas extintas con las reconstrucciones artísticas. Para la documentación gráfica de los fósiles de Venezuela, se recomienda recurrir a los excelentes libros de Orangel Aguilera (2004, 2006, 2010) sobre todo para los vertebrados. En lo referente a otros grupos de organismos, la bibliografía al final de este libro provee muchas de las referencias idóneas, como es el caso de los moluscos con los trabajos de Jung (1965) y de Macsotay y Campos Villarroel (2001). Sería muy afortunado si los ejemplos de los diversos fósiles presentados en este libro llegan a servir no como un curioso catálogo de formas raras y menos raras de animales y plantas, sino más bien sirvan como fuente de reflexión sobre aspectos fundamentales de la vida y su evolución. Los fósiles de Venezuela permiten conocer el pasado de un contexto geográfico conocido, pero lo fundamental que estos fósiles representan tiene relevancia universal. Marcelo R. Sánchez-Villagra Zürich, Septiembre del 201

Montcortès: Pallars Sobirà, Baix Pallars, Lleida Holoceno tardío, último milenio (1150-30 años cal. BP, 800-1920 años AD)

El sondeo (MON-04-1A-1K) corresponde a una secuencia del Lago Montcortès (42º 19’ N, 00º 59’ E; 1027 m s.n.m.). Se trata de una cuenca pequeña, alimentada principalmente por aguas subterráneas y enclavada en una zona kárstica (Fig. 355). El lago posee una forma aproximadamente circular, con un diámetro entre 400 y 500 m y una profundidad máxima de unos 30 m (Corella et al. 2010). En cuanto a la vegetación actual, cabe señalar inicialmente que el lago se encuentra en el límite altitudinal entre los pisos supramediterráneo y montano (Fig. 356). Aunque para la cuenca se han distinguido doce tipos de vegetación, existen tres formaciones forestales principales en la zona: en primer lugar, los bosques de Quercus rotundifolia representativos del piso supramediterráneo, en segundo lugar, los robledales de Q. pubescens típicos del piso montano y, finalmente, los bosques de coníferas dominados por Pinus nigra subsp. salzmanii, supuestamente de origen secundario (Carreras et al. 2005-2006). Cerca de los bordes del lago, existe un cinturón de vegetación litoral dominado por especies de Juncus, Scirpus, Phragmites, Typha y Sparganium

Preliminary palynological analysis of a Holocene peat bog from Apakará-tepui (Chimantá massif, Venezuelan Guayana)

Preliminary palynological analysis of a Holocene peat bog from Apakará-tepui (Chimantá Massif, Venezuelan Guayana).- This paper reports the preliminary palynological results, at a millennial scale, of a Holocene peat bog sequence, since around 8.0 cal kyr BP to the present, obtained in the summit of the Apakará-tepui (2170 m elevation), in the Chimantá massif, located in the neotropical Venezuelan Guayana. The early Holocene was characterized by a vegetation different to the present, in which trees and shrubs dominated and Myrica (Myricaceae) was the main element of the gallery forests around a permanent water body, as indicated by the continuous presence of Isoëtes (Isoëtaceae) in high percentages. Around the middle Holocene (5.3 cal kyr BP), a shift towards more herbaceous and non-flooded communities occurred, and the present day vegetation established. This has been interpreted as a shift from warmer and wetter climates to cooler and drier conditions. The first phase, from 8.0 to 5.3 cal kyr BP, falls within a warming phase widely documented worldwide, known as the Holocene Thermal Maximum. The millennial trends shown here will be refined with further studies at centennial to decadal time scales. These results support the hypothesis that the best sites to detect paleoenvironmental changes in the summits of the tabular Guayana mountains are close to altitudinal ecotones

Ecological palaeoecology in the neotropical Gran Sabana region: Long-term records of vegetation dynamics as a basis for ecological hypothesis testing

Long-term palaeoecological records are needed to test ecological hypotheses involving time, as short-term observations are of insufficient duration to capture natural variability. In this paper, we review the published palaeoecological evidence for the neotropical Gran Sabana (GS) region, to record the vegetation dynamics and evaluate the potential effects of natural climatic and anthropogenic (notably fire) drivers of change. The time period considered (last 13,000 years) covers major global climate changes and the arrival of humans in the region. The specific points addressed are climate–vegetation equilibrium, reversibility of vegetation changes, the origin of extant biodiversity and endemism patterns and biodiversity conservation in the face of global warming. Vegetation dynamics is reconstructed by pollen analysis and fire incidence is deduced from microscopic charcoal records. Palaeoclimatic inferences are derived from global and regional records using independent physico-chemical evidence to avoid circular reasoning. After analyzing all the long-term records available from both GS uplands and highlands, we conclude that: (1) Upland vegetation (mostly treeless savannas and savanna–forest mosaics, with occasional Mauritia palm swamps) is not in equilibrium with the dominant climates, but largely conditioned by burning practices; (2) a hypothetical natural or “original” vegetation type for these uplands has not been possible to identify due to continuous changes in both climate and human activities during the last 13,000 years; (3) at the time scale studied (millennial), the shift from forest to savanna is abrupt and irreversible due to the existence of tipping points, no matter the cause (natural or anthropogenic); (4) on the contrary, the shift from savanna to palm swamps is reversible at centennial time scales; (5) some of the reconstructed past vegetation types have no modern analogues owing to the individual species response to environmental shifts, leading to variations in community composition; (6) extant biodiversity and endemism patterns are not the result of a long history of topographical isolation, as previously proposed but, rather, the consequence of the action of climatic and palaeogeographic variations; (7) the projected global warming will likely exacerbate the expansion of upland savannas by favouring positive fire-climate feedbacks; (8) in the highlands, extinction by habitat loss will likely affect biodiversity but to a less extent that prognosticated by models based only on present-day climatic features; (9) future highland communities will likely be different to present ones due to the prevalence of individual species responses to global warming; and (10) conservation strategies at individual species level, rather than at community level, are enriched by long-term palaeoecological studies analyzed here. None of these conclusions would have been possible to derive from short-term neoecological observations

Paleoenvironmental trends in Venezuela during the last glacial cycle

This chapter summarizes and updates the main Quaternary paleoclimatic and sea-level trends recorded in Venezuela, and provides a paleoenvironmental framework for studies addressing biogeographical, ecological, and evolutionary topics. Venezuela has a number of localities that have provided paleoenvironmental sequences in the neotropical, circum-Caribbean domain, such as the Cariaco basin, Lake Valencia, the Mérida Andes, and the Guayana region (e.g., Markgraf 2000). Venezuela encompasses a wide range of physiographic, climatic, and biogeographic conditions because of its geographic location. This spatial heterogeneity has led to complex, but interesting, paleoenvironmental reconstructions