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Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB | Montoya E.,Open University Milton Keynes
Quaternary Science Reviews | Year: 2014

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. © 2014 Elsevier Ltd.


Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB
Journal of Vegetation Science | Year: 2015

When vegetation trends over time are analysed from an appropriate long-term perspective using palaeoecological records, the concept of potential natural vegetation (PNV) is unsupported because of continual vegetation changes driven by natural or anthropic forcings. However, some palaeoecological records show long-lasting (i.e. millennial) vegetation stability at multidecadal to centennial time scales in the absence of natural and human drivers of change, which fits within the definition of PNV. A more detailed palaeoecological analysis of these records shows that they are an exception rather than a rule, and that they cannot be differentiated from other transient ecological states. Therefore, long records of vegetation stability cannot be considered to be valid evidence for PNV. From a palaeoecological perspective, the PNV concept is concluded to be unnecessary, even in cases of multidecadal to centennial vegetation stability in the absence of environmental disturbance. © 2015 International Association for Vegetation Science.


Mraz P.,University of Fribourg | Garcia-Jacas N.,Botanic Institute of Barcelona IBB CSIC ICUB | Gex-Fabry E.,University of Fribourg | Susanna A.,Botanic Institute of Barcelona IBB CSIC ICUB | And 2 more authors.
Molecular Phylogenetics and Evolution | Year: 2012

Spotted knapweed (Centaurea stoebe) occurs from Western Asia to Western Europe both as diploid and tetraploid cytotypes, predominantly in single-cytotype populations with higher frequency of diploid populations. Interestingly, only tetraploids have been recorded so far from its introduced range in North America where they became highly invasive.We performed phylogenetic and network analyses of more than 40 accessions of the C. stoebe and C. paniculata groups and other related taxa using cloned internal transcribed spacer (ITS) and sequences of the chloroplast trnT- trnL and atpB. rbcL regions to (i) assess the evolutionary origin of tetraploid C. stoebe s.l., and (ii) uncover the phylogeny of the C. stoebe group. Both issues have not been studied so far and thus remained controversial.Cloned ITS sequences showed the presence of two slightly divergent ribotypes occurring in tetraploid cytotype, while only one major ribotype was present in diploid C. stoebe s.str. This pattern suggests an allopolyploid origin of tetraploids with contribution of the diploid C. stoebe s.str. genome. Although we were not able to detect the second parental taxon, we hypothesize that hybridization might have triggered important changes in morphology and life history traits, which in turn may explain the colonization success of the tetraploid taxon. Bayesian relaxed clock estimations indicate a relatively recent - Pleistocene origin of the tetraploid C. stoebe s.l. Furthermore, our analyses showed a deep split between the C. paniculata and C. stoebe groups, and a young diversification of the taxa within the C. stoebe group. In contrast to nrDNA analyses, the observed pattern based on two cpDNA regions was inconclusive with respect to the origin and phylogeny of the studied taxa, most likely due to shared ancient polymorphism and frequent homoplasies. © 2011 Elsevier Inc.


Lopez-Pujol J.,Botanic Institute of Barcelona IBB CSIC ICUB | Garcia-Jacas N.,Botanic Institute of Barcelona IBB CSIC ICUB | Susanna A.,Botanic Institute of Barcelona IBB CSIC ICUB | Vilatersana R.,Botanic Institute of Barcelona IBB CSIC ICUB
Biological Conservation | Year: 2012

Natural hybridization can be a serious threat to rare and endangered species because of the risk of extensive genetic swamping or assimilation. Hybridization, however, can be beneficial for rare species as it increases their genetic diversity, which in turn may improve their fitness and confer adaptive potential. Centaurea podospermifolia is a narrowly endemic, threatened, tetraploid species occurring only in two mountain ranges of northeastern Spain. This species may produce a highly unstable homoploid hybrid (Centaurea x loscosii) with the more widespread Centaurea cephalariifolia. Allozymes and nuclear DNA sequences (ETS and Agt1) were used to test whether C. podospermifolia populations have undergone hybridization or introgression with C. cephalariifolia, which should have left an imprint in the genetic structure of the former. Nuclear DNA sequencing indicates that all the populations from one mountain range (the Ports Massif) are introgressed, whereas those from the second (the Cardó Range) should be regarded as 'pure'. Genetic variability detected in C. podospermifolia is low for a tetraploid species, and the occurrence of population bottlenecks may have played a role in this lack of diversity. Populations from the Ports are more variable than those from Cardó, the lower genetic variability observed for Cardó populations being unequivocally related to a lack of genetic material from C. cephalariifolia. We suggest that a management plan for C. podospermifolia should address the conservation of both the pure-bred and the introgressed populations. © 2012 Elsevier Ltd.


Safont E.,University of Barcelona | Safont E.,Botanic Institute of Barcelona IBB CSIC ICUB | Vegas-Vilarrubia T.,University of Barcelona | Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB
Biological Conservation | Year: 2012

Pantepui is a biogeographical province composed of a group of approximately 50 tabular mountain summits, or tepuis, in the southeast of Venezuela. This region, also known as Guayana Highlands (GH), lies between 1500 and 3014m elevation and has an approximate extension of 6000km 2. The summits of the tepuis are characterized by exceptional vascular plant diversity and high endemism. However, it is expected that ongoing global warming will produce upward displacements of summit taxa, which may cause the extinction of certain species due to habitat loss. This study assessed the potential extinction risk of the >600 Pantepui endemic vascular plant species during the 21st century due to global warming, revealing that 30-50% of endemic species would lose their habitat by the end of this century. In light of these results, prioritization of threatened species for conservation purposes became necessary. This was achieved through the calculation of an Environmental Impact Value (EIV) for each species, and a subsequent division of these species into priority categories, which should be used in a chronological sequence to guide decision-making and future research aimed at establishing the most suitable conservation strategies. A number of in situ and ex situ conservation alternatives were discussed. In situ conservation by means of designating protected areas does not appear a viable option because of the upward habitat displacement involved in this case. Conversely, seed banks, living plant collections and managed relocation were suggested in this chronological order to preserve the species studied here. © 2012 Elsevier Ltd.


Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB
Systematics and Biodiversity | Year: 2012

In a recent paper, Ricklefs (2012) argued that the current emphasis on theoretical models undermines the relevance of natural history in ecology and advocated a return to observation of the natural world. This comment notes that part of the natural history observations needed to address keystone ecological patterns and processes are in often ignored past records. As demonstrated by Ricklefs, the origin and maintenance of extant biodiversity are used to illustrate the potential usefulness of past natural history in theoretical ecology and modelling. It is concluded that rather than testing current theories, past natural history calls for their reformulation. © 2012 The Natural History Museum.


Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB | Rull V.,CSIC - Institute of Earth Sciences Jaume Almera | Vegas-Vilarrubia T.,University of Barcelona
Vegetation History and Archaeobotany | Year: 2015

We use palynological and historical records to reconstruct the evolution of agricultural practices and their consequences on landscape development in a mid-elevation Pyrenean small lake catchment during the last millennium. A total of ten cultivated plants and eight weed taxa were recognised and their changes in time recorded in detail. Two main phases of agricultural development were identified, A1 (9th–14th centuries ad) and A2 (16th–19th centuries ad). A1 coincided with the medieval climate anomaly and began after a widespread loss of woodland by fire, as manifested in a decline of arboreal pollen from ~60 to ~30 %, which affected mainly the pine woods (~40 to ~10 %). This phase was characterised by cultivation of the cereals Secale and Triticum/Avena, with Plantago as the main weed, alternating with pastures dominated by Artemisia, in a ca. 60 year land-use rotation scheme. A1 also coincided with a feudal socio-economic system that replaced the shifting cultivation practices of the earlier inhabitants with intensive agriculture. This type of land use was interrupted by the onset of the Little Ice Age, coinciding with a great social crisis with wars and plagues, leading to the depopulation of the zone and the recovery of woodlands. The onset of A2 coincided with the Spanish monarchy of the modern age and was characterised by Cannabis cultivation, which attained a maximum in the post-modern age, at the transition between feudalism and capitalism. Hemp was mainly used to supply fibre to the Spanish navy and the cultivation of this plant was mandatory until the disestablishment of this navy in ad 1834. After this date, a second socio-economic crisis took place as a consequence of massive emigration to large cities, promoted by the growing industrialisation. The combination of fossil and historical evidence significantly improves palaeoecological reconstructions in areas under heavy human impact, which is useful to enhance historical soundness, to understand how modern landscapes have been shaped and also to disentangle natural causes of ecological change from human ones. © 2015, Springer-Verlag Berlin Heidelberg.


Montoya E.,Autonomous University of Barcelona | Montoya E.,Botanic Institute of Barcelona IBB CSIC ICUB | Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB
Quaternary Science Reviews | Year: 2011

Fires are among the most important risks for tropical ecosystems in a future climatic change scenario. Recently, paleoecological research has been addressed to discern the role played by fire in neotropical landscapes. However, given the magnitude of the Neotropics, many studies are relegated to infer just local trends. Here we present the compilation of the paleo-fire records developed until now in the southern Gran Sabana (SE Venezuela) with the aim to describe the fire history as well as to infer the possible forcing factors implied. In this sense, southern Gran Sabana has been under fire perturbation since the Lateglacial, with the concomitant effects upon vegetation, and persisted during the Holocene. Around 2000 cal yr BP onwards, the fire activity highly increased promoting the expansion of pre-existing savannas, the decrease of forests and the appearance and establishment of Mauritia palm swamps. The continuous fire incidence registered for several thousands of years has likely promoted the supremacy of treeless savannas upon other vegetation types and the degradation to secondary landscapes. Based on the available evidence, the anthropogenic nature of this high fire activity has been postulated. If so, it could be hypothesized that the timing arrival of Pemón, the present-day indigenous culture in the Gran Sabana, would be ca 2000 cal yr BP onwards, rather than the last centuries, as it has been formerly assumed. The implications of these ancient practices in the area are also discussed for present Gran Sabana landscapes sustainability and future conservation strategies. © 2011 Elsevier Ltd.


Montoya E.,Botanic Institute of Barcelona IBB CSIC ICUB | Montoya E.,Autonomous University of Barcelona | Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB | Nogue S.,UK Institute of Zoology
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

This paper shows a Holocene paleoecological reconstruction based on a peat bog sequence (El Paují, 4°28'N'61°35'W, 865. m elevation) located in the transition zone between the Gran Sabana (SE Venezuela) savannas and the Amazon rainforests. Paleoecological trends are based on the analysis of pollen and pteridophyte spores, algal and animal remains, fungal spores, and charcoal particles. The whole record embraces the last ca. 8000. cal. yr BP, and was subdivided into five pollen zones, representing the following vegetation succession: savanna/rainforest mosaic (8250-7715. yr BP), dense rainforests (7715-5040. yr BP), savanna/rainforest mosaic (5040-2690. yr BP), secondary dry forests (2690-1440. yr BP), and peat bog in an open savanna landscape (1440. yr BP-present). These vegetation changes have been attributed to the action of climate and/or land use changes, as well as the corresponding synergies between them. Fire has been determinant in the landscape evolution. Based on the reconstructed fire and vegetation shifts, a changing land use pattern could have been recognized. Between the early and the mid Holocene (ca. 8.3-5.0. kyr BP), land use practices seem to have been more linked to shifting agriculture in a rainforest landscape - as is usual in Amazon cultures - with medium fire incidence affecting only local forest spots or surrounding savannas. More extensive forest burning was recorded between ca. 5.0 and 2.7. kyr BP, followed by land abandonment and the dominance of drier climates between 2.7 and 1.4. yr BP. The modern indigenous culture, which prefers open environments and makes extensive use of fire thus preventing forest re-expansion, seem to have established during the last 1500. yr. Therefore, a significant cultural replacement has been proposed for the region, leading to the present-day situation. Changing human activities have been instrumental for ecological evolution in this savanna-rainforest transitional region, as well as for the shaping of modern landscapes. © 2011 Elsevier B.V.


Rull V.,Botanic Institute of Barcelona IBB CSIC ICUB
Journal of Biogeography | Year: 2015

A number of researchers working on the origin of extant Neotropical biodiversity implicitly and without appropriate proofs assume that Pleistocene speciation should necessarily follow the rules of the refuge hypothesis. A recent example is provided by a study of Neotropical butterflies. Although the analysis showed that these groups experienced their main diversification burst during the last 2.6 million years, coinciding with the Pleistocene glacial cycles (Garzón-Orduña et al., 2014, Journal of Biogeography, 41, 1631-1638), a causal link between the speciation chronology and the evolutionary mechanisms proposed by the refuge hypothesis is not provided. Without more detailed studies on the environmental drivers, geographical patterns and speciation modes, establishing a causal link between speciation chronology and a particular speciation model - of which the refuge hypothesis is only one among many possibilities - is too speculative. Here I provide a six-step conceptual framework for linking the speciation chronology with the environmental drivers and the ecological and evolutionary mechanisms potentially involved. © 2014 John Wiley & Sons Ltd.

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