Teresa Vegas-Vilarrúbia

Surface palynology of a small coastal basin from Venezuela and potential paleoecological applications

The palynomorph content of surface samples from a sea-land transect in a small coastal basin was analysed, in order to characterise palynologically the sedimentary subenvironments and vegetation types. These results should provide the basis for the interpretation of further palaeoecological analyses on stratigraphical samples from the same site. The main vegetation types are mangroves, swamps, Cocos plantations and abandoned crops, arranged in a zonal pattern. All the palynomorph types found were recorded and counted, including pollen, fern and allied spores, fungi spores and unknown remains (probably algal material and animal parts). Both general and individual trends of these palynomorphs followed the main vegetation patterns, and both zonal sea-land arrangement of plant communities and their disturbance patterns were reproduced by them. Furthermore, particular types were found to be direct or indirect indicators of given plant zones and local disturbance. Detrended correspondence analysis allowed definition of the sedimentary attraction domains for the involved communities and ordination of both samples and palynomorphs with respect to them. The results are encouraging for palaeoecological studies, since the main key environmental and vegetational patterns are reflected by the palynomorphs of surface sediments. Limitations are also discussed.

What is long-term in ecology?

A recent issue of TREE (volume 25, issue 10, 2010), is dedicated to “long-term ecological research”. Here, we question whether most of the papers in this issue really deal with long-term studies and briefly discuss the meaning of this expression in ecology. Although there is no any formal definition of what long-term means in ecology, the time frame generally considered in all the papers of this issue is decadal to multidecadal, except for one dealing with paleoecological data in which the time frame is centennial to millennial [1].

Conservation of the Unique Neotropical Vascular Flora of the Guayana Highlands in the Face of Global Warming

VALENTI RULL,∗†† TERESA VEGAS-VILARRUBIA,† SANDRA NOGUE,∗‡ AND OTTO HUBER§∗∗ ∗CSIC-Botanic Institute of Barcelona, Palynology & Paleoecology, Pg. del Migdia s/n, 08038 Barcelona, Spain †University of Barcelona, Department of Ecology, Av. Diagonal 645, 08028 Barcelona, Spain ‡Autonomous University of Barcelona, Department of Animal Biology, Plant Biology and Ecology, Campus Bellaterra, 08193 Barcelona, Spain §Trauttmansdorff Botanical Gardens, Via San Valentino 51a, 39012 Merano, Italy ∗∗Botanical Institute of Venezuela Dr. Tobias Lasser, Av. Salvador Allende, Caracas 1050, Venezuela

Biopiracy rules hinder conservation efforts.

SIR — The summits of the neotropical Guayana Highlands in Venezuela have a unique biodiversity that is under serious threat because of habitat loss resulting from climate warming. Although conservation studies are urgently needed, these are blocked by official bodies that will not grant permits for fieldwork in the region. The bureaucratic process starts with the Venezuelan government’s agency for science and technology, FONACIT, and involves a network of different organizations controlled by the ministry of the environment. These include the national tepui (table-mountain) commission, the biodiversity office, the office of indigenous affairs and the national institute of parks. We have been involved since July 2005 in an international conservation project, funded by the Spanish BBVA Foundation, on the Guayana Highlands flora, in collaboration with several Venezuelan universities, research institutes and other organizations. It took us two years to obtain permits from FONACIT and for sample collection to be authorized. For unspecified reasons, the permits do not allow genetic studies, so molecular phylogenetic analysis is impossible. We are still trying to obtain approval from the office of indigenous affairs, but the people are reluctant to comply: they consider themselves owners of the summits, which are sacred lands to them. The lengthy bureaucratic procedures have prevented scientific fieldwork in the Guayana Highlands for almost twenty years, when permissions to visit the summits for any purpose were suspended to avoid human disturbance and biopiracy (see below, ‘Biopiracy: conservationists have to rebuild lost trust’ Nature 453, 26; 2008). It is to be hoped that the situation may be reversed before it is too late to undertake suitable conservation strategies. Valentí Rull*, Teresa Vegas-Vilarrúbia† *Department of Animal Biology, Plant Biology and Ecology, Autonomous University of Barcelona, Faculty of Biosciences C1-339, Bellaterra, 08193 Barcelona, Spain †Department of Ecology, University of Barcelona, Faculty of Biology, Av. Diagonal 645, 08028 Barcelona, Spain

Chrysophycean stomatocysts in a Caribbean mangrove

A chrysophyte cyst assemblage from surface sediments of a tropical, brackish-water environment in the southern Caribbean coast is described and depicted. All the cysts are unornamented and relatively large. The taxonomic diversity is low, due probably to human disturbance or salinity stress. It is assumed that the chrysophyte taxa involved are salinity-tolerant, freshwater algae. This is the first record of chrysophyte cysts in mangrove environments, and extends the range of habitats in which they are commonly found.

Establishing a baseline of plant diversity and endemism on a neotropical mountain summit for future comparative studies assessing upward migration: an approach from biogeography and nature conservation

Climate change is forcing many plant species to shift their range in search of adequate environmental conditions, being localized endemic species particularly at risk on mountain summits. The Pantepui biogeographic province, a set of flat-topped mountain summits (called tepuis) of northern South America, contains both high plant diversity and a high degree of endemism. Previous studies based on warming projections for the area suggested that half of the Pantepui endemic flora would disappear due to habitat loss by 2100. In this study, we selected one of the best-explored tepuis, Roraima-tepui, to establish the baseline of diversity and endemism for comparisons with historical data and future monitoring surveys, aimed at testing the hypothesis of upward migration of plants in response to global warming. We also analysed floristic and physiognomic features of the Eastern Tepui Chain (ETC, the mountain range where Roraima is located), and the phytogeographic patterns of both the ETC and Pantepui. The Roraima summit contains 227 species, including 44 new records, 13 exotic species (some of them with high invasive potential), and at least one species new to science. At the ETC level, Roraima is the tepui with highest species richness and degree of endemism, and shows a relatively high floristic similarity with Kukenán and Ilú. Herbaceous species dominate over shrubs on these tepuis, Tramen and Maringma, whereas on Yuruaní, Karaurín and Uei, they reach similar abundances. At the Pantepui level, endemic species have highly localized distribution patterns (17% local endemics). Conservation opportunities are evaluated in light of these results.

Preliminary report on a mid-19th century Cannabis pollen peak in NE Spain: Historical context and potential chronological significance

Cannabis sativa L. (hemp) was introduced in Europe from Asia Minor during classical Greek and Roman times. Since then, hemp pollen abundances between 10% and 80% in Late Holocene sediments have been considered indicative of the local or regional cultivation and/or retting of this plant. In this paper, a unique pollen peak of >60% recorded in Lake Montcortès (pre-Pyrenean foothills, NE Spain) is evaluated as a potential chronostratigraphic marker. Previously, this pollen peak was dated to ad 1757 using a depth–age model based on AMS 14C dates from sedimentary macrofossils, but a recent calibration of the model using varve counting has refined the date of the hemp pollen maximum to ad 1839. This date coincides with an outstanding socio-political shift from feudalism to liberalism in Spain and the corresponding dismantling of the royal navy, the main consumer of hemp fibre. These events produced a well-documented decline in Cannabis cultivation across the Iberian Peninsula. The sharpness of the Cannabis pollen peak, its accurate dating using annual varves and its almost exact coincidence with outstanding and widespread historical events suggest that this palynological landmark could be used as a chronostratigraphic marker for recent centuries. This possibility, as well as the geographical extent of this potential datum, should be confirmed with further studies.

Connection between El Niño-Southern Oscillation events and river nitrate concentrations in a Mediterranean river

The causes of interannual nitrate variability in rivers remain uncertain, but extreme climatic events have been suggested as drivers of large nitrate inputs to rivers. Based on a 24-year data set (1983-2006), we suggest that El Niño-Southern Oscillation (ENSO) can affect nitrate behavior in a seasonal extra-tropical stream, the Llobregat (NE Iberian Peninsula), located thousands of kilometers away from the ENSO oscillating system via atmospheric teleconnections. Two commonly used indices, the Southern Oscillation Index (SOI) and the self-calibrating-Palmer Drought Severity Index (scPDSI) showed highly significant correlations with nitrate concentrations, which recurrently increased during La Niña phases, coinciding with severe droughts.

An 8700-year record of the interplay of environmental and human drivers in the development of the southern Gran Sabana landscape, SE Venezuela

The vegetation of the southern Gran Sabana (SE Venezuela) consists primarily of a treeless savanna with morichales (Mauritia flexuosa palm stands), despite the prevailing climate being more favorable for the development of extensive rainforests. Here, we discuss the results of our 8700-year paleoecological reconstruction from Lake Encantada based on the analysis of pollen, algal remains, charcoal, and geochemical proxies. We use the findings to assess a number of hypotheses that seek to explain the dominance of savanna vegetation and consider the relative importance of factors such as climate, fire, and erosion on the landscape. The reconstruction of vegetation changes suggests the following trends: open savanna with scattered forest patches (8700–6700 yr BP), forest-savanna mosaic (6700–5400 yr BP), open savanna with forest patches (5400–1700 yr BP), and treeless savanna with morichales (1700 yr BP–the present). We conclude that the interplay between climate and fire and the positive feedback between the presence of grasses and increased fire frequency played a major role in the vegetation dynamics from the early to middle Holocene (8700–6700 yr BP). The synergistic action between reduced fires and wetter conditions appears to be a determinant in the development of rainforest around 6700 yr BP. Despite higher available moisture at ~5400 yr BP, the savanna expanded with the increased frequency of fire, potentially driven by human land-use practices. We also propose that the interplay between fire and erosion created forest instability during the middle and late Holocene. The current southern Gran Sabana landscape is the result of the complex interplay between climate, fire, erosion, and vegetation.

Vegetation shifts, human impact and peat bog development in Bassa Nera pond (Central Pyrenees) during the last millennium

High-mountain lakes are suitable ecosystems for studying local environmental shifts driven by large-scale climate changes, with potential applications to predict future scenarios. The precise features in the response of species assemblages are not fully understood, and human pressure may often hide climatic signals. To investigate the origin and impact of past environmental changes in high-mountain ecosystems and apply this palaeoecological knowledge to anticipate future changes, we performed a multi-proxy study of a sediment core from Bassa Nera, a pond located close to montane–subalpine ecotone in the southern central Pyrenees. Combining pollen and diatom analysis at multidecadal resolution, we inferred vegetation shifts and peat bog development during the past millennium. We introduced a montane pollen ratio as a new palaeoecological indicator of altitudinal shifts in vegetation. Our results emphasize the sensitivity of the montane ratio to detect upward migrations of deciduous forest and the presence of the montane belt close to Bassa Nera pond during the Medieval Climate Anomaly. Changes in aquatic taxa allowed to date the onset of the surrounding peat bog which appeared and infilled the coring site around AD 1565. Overall, our results suggest a low-intensity human pressure and changes in management of natural resources during the last millennium, where farming was the main activity from the Medieval Climate Anomaly until AD 1500. Afterwards, people turned to highland livestock raising coinciding with the ‘Little Ice Age’.