Time filter

Source Type

Ren M.-X.,CAS Wuhan Botanical Garden | Ren M.-X.,Botanical Institute of Barcelona CSIC ICUB | Tang J.-Y.,CAS Wuhan Botanical Garden
Annals of Botany | Year: 2012

Background and AimsStamen movements directly determine pollen fates and mating patterns by altering positions of female and male organs. However, the implications of such movements in terms of pollination are not well understood. Recently, complex patterns of stamen movements have been identified in Loasaceae, Parnassiaceae, Rutaceae and Tropaeolaceae. In this study the stamen movements in Ruta graveolens (Rutaceae) and their impact on pollination are determined. MethodsPollination effects of stamen movements were studied in Ruta graveolens, in which one-by-one uplifting and falling back is followed by simultaneous movement of all stamens in some flowers. Using 30 flowers, one stamen was manipulated either to be immobilized or to be allowed to move freely towards the centre of the flower but be prevented from falling back. Pollen loads on stigmas and ovule fertilization in flowers with or without simultaneous stamen movement were determined. ResultsPollen removal decreased dramatically (P < 0·001) when the stamen was stopped from uplifting because its anther was seldom contacted by pollinators. When a stamen stayed at the flower's centre, pollen removal of the next freely moved anther decreased significantly (P < 0·005) because of fewer touches by pollinators and quick leaving of pollinators that were discouraged by the empty anther. Simultaneous stamen movement occurred only in flowers with low pollen load on the stigma and the remaining pollen in anthers dropped onto stigma surfaces after stamens moved to the flower's centre. ConclusionsIn R. graveolens pollen removal is promoted through one-by-one movement of the stamen, which presents pollen in doses to pollinators by successive uplifting of the stamen and avoids interference of two consecutively dehisced anthers by falling back of the former stamen before the next one moves into the flower's centre. Simultaneous stamen movement at the end of anthesis probably reflects an adaptation for late-acting self-pollination. © 2012 The Author. Source

Dzialuk A.,Kazimierz Wielki University in Bydgoszcz | Mazur M.,Kazimierz Wielki University in Bydgoszcz | Boratynska K.,Polish Academy of Sciences | Montserrat J.M.,Institute Of Cultura Of Barcelona | And 2 more authors.
Annals of Forest Science | Year: 2011

Introduction, Material and Methods The genetic structure and diversity of ten natural populations of Juniperus phoenicea L. from the western part of the species range have been studied using random amplified polymorphic DNA (RAPD) markers. Results and discussion Among 10 analyzed primers only 3 reproduced consistently across successful PCR reactions and gave 45 loci. The percentage of polymorphic loci (P) and Nei's heterozygosity (H e) have average values of 64.9% and 0.177. The average expected heterozygosity of particular populations positively correlate with latitude and negatively with altitude (τ=0.556, P=0.025; τ=?0.494, P=0.047, respectively). The proportion of genetic variation contributed by the differences between populations was low (GST=0.056). The gene flow (N m) has an average value of 4.2, and was higher in subsp. turbinata (7.3) than in subsp. phoenicea (4.1). Significant proportion of the variation (φST=0.106) was attributable to differences among populations, as revealed in analysis of molecular variance analysis of pair-wise RAPD distances. No evidence for isolation by distance was detected in Mantel test on genetic (φST) and geographic distances. European populations differed at a higher level from the African, subsp. phoenicea from turbinata (3.97% and 3.14% of total variance, respectively). The significant level of differences between European and African populations can result from (1) the earlier divergence and considerably low level of gene flow between them, or (2) a different mutation rate within population of different continent. Conclusion: The results suggest rather local forest economy with J. phoenicea, without seed exchange on large distance. © 2011 INRA and Springer Science+Business Media B.V. Source

Vilatersana R.,Botanical Institute of Barcelona CSIC ICUB | Garcia-Jacas N.,Botanical Institute of Barcelona CSIC ICUB | Garnatje T.,Botanical Institute of Barcelona CSIC ICUB | Molero J.,University of Barcelona | And 2 more authors.
Systematic Botany | Year: 2010

Ptilostemon is a fine example of the representatives of the eastern groups of the Cardueae that have diversified in the western Mediterranean. Relationships to Cynara, which exhibits a similar distribution, and Lamyropsis, which is morphologically closer according to previous studies, are investigated using Bayesian analysis of DNA sequences of the plastid intergenic spacer ycf3-trnS and two nuclear regions, the ETS and ITS spacers. The sectional classification and biogeography of Ptilostemon are also revised in the light of the molecular phylogeny Our results suggest that Cynara is the most plausible sister genus to Ptilostemon. Some paralogous copies of the ETS region found among species of the three genera by cloning are interpreted as incomplete lineage sorting of ancestral polymorphisms. The current sectional classification of Ptilostemon shows excessive fragmentation, which does not agree with our phylogeny, and therefore a more synthetic classification is proposed. The present distribution of Ptilostemon indicates that there were two colonization events in the western Mediterranean region, paralleling a similar pattern of successive waves already suggested for Cynara. © Copyright 2010 by the American Society of Plant Taxonomists. Source

Vegas-Vilarrubia T.,University of Barcelona | Rull V.,Botanical Institute of Barcelona CSIC ICUB | Montoya E.,Botanical Institute of Barcelona CSIC ICUB | Montoya E.,Autonomous University of Barcelona | Safont E.,Botanical Institute of Barcelona CSIC ICUB
Quaternary Science Reviews | Year: 2011

Palaeoecology, as an ecological discipline, is able to provide relevant inputs for conservation science and ecosystem management, especially for issues involving long-term processes, such as ecological succession, migration, adaptation, microevolution, and extinction. This use of palaeoecology has been noted for several decades, and it has become widely accepted, especially in the frame of ongoing and near-future global warming and its potential biotic consequences. Selected palaeoecological insights of interest for conservation include the following: 1) species respond in an individualistic manner to environmental changes that lead to changes in community composition, suggesting that future ecosystems would have no modern analogues; 2) in the short-term, acclimation is more likely a response of species that are expected to persist in the face of global warming, but the possibility of evolutionary change linked to the existence of pre-adapted genomes cannot be dismissed; 3) species unable to acclimate or adapt to new conditions should migrate or become extinct, which has been observed in past records; 4) current extinction estimates for the near-future should be revised in light of palaeoecological information, which shows that spatial reorganisations and persistence in suitable microrefugia have been more common than extinction during the Quaternary; 5) biotic responses to environmental changes do not necessarily follow the rules of equilibrium dynamics but depend on complex and non-linear processes that lead to unexpected "surprises", which are favoured by the occurrence of thresholds and amplifying positive feedbacks; 6) threshold responses can cause the movement of ecosystems among several potentially stable states depending on their resilience, or the persistence of transient states; 7) species and their communities have responded to environmental changes in a heterogeneous fashion according to the local and regional features, which is crucial for present and future management policies; 8) the global warming that occurred at the end of the Younger Drays cold reversal (ca 13.0 to 11.5 cal kyr BP) took place at similar rates and magnitudes compared to the global warming projected for the 21st century, thus becoming a powerful past analogue for prediction modelling; 9) environmental changes have acted upon ecosystems in an indirect way by modifying human behaviour and activities that, in turn, have had the potential of changing the environment and enhancing the disturbance effects by synergistic processes involving positive feedbacks; 10) the collapse of past civilisations under climate stress has been chiefly the result of inadequate management procedures and weaknesses in social organisation, which would be a warning for the present uncontrolled growth of human population, the consequent overexploitation of natural resources, and the continuous increase of greenhouse gas emissions; 11) the impact of fire as a decisive ecological agent has increased since the rise of humans, especially during the last millennia, but anthropic fires were not dominant over natural fires until the 19th century; 12) fire has been an essential element in the development and ecological dynamics of many ecosystems, and it has significantly affected the worldwide biome distribution; 13) climate-fire-human synergies that amplify the effects of climate, or fire alone, have been important in the shaping of modern landscapes. These general paleoecological observations and others that have emerged from case studies of particular problems can improve the preservation of biodiversity and ecosystem functions. Nature conservation requires the full consideration of palaeoecological knowledge in an ecological context, along with the synergistic cooperation of palaeoecologists with neoecologists, anthropologists, and conservation scientists. © 2011 Elsevier Ltd. Source

Rull V.,Botanical Institute of Barcelona CSIC ICUB | Stansell N.D.,Ohio State University | Montoya E.,Botanical Institute of Barcelona CSIC ICUB | Bezada M.,UPEL Pedagogic Institute of Caracas | Abbott M.B.,University of Pittsburgh
Quaternary Science Reviews | Year: 2010

The occurrence, or not, of the Younger Dryas cold reversal in the tropical Andes remains a controversial topic. This study reports a clear signal for this event in the Venezuelan Andes, employing high-resolution palynological analysis of a well-dated sediment core from Laguna de Los Anteojos, situated around 3900. m elevation, within grass páramo vegetation. The lake is surrounded by some Polylepis forests which are close to their upper distribution limit. The section of the core discussed here is 150-cm long and dated between about 14.68 and 9.35. cal. kyr. BP, using a polynomial age-depth model based on six AMS radiocarbon dates. Between 12.86 and 11.65. cal. kyr. BP, an abrupt shift occurred in the pollen assemblage, manifested by a decline of Podocarpus, Polylepis and Huperzia, combined with an increase in Poaceae and Asteraceae. The aquatic pteridophyte Isoëtes also decreased and disappeard, and the algae remains show their minimum values. Pollen assemblages from the Younger Dryas interval show maximum dissimilarity values compared with today's pollen assemblage, and are more similar to modern analogs from superpáramo vegetation, growing at elevations 400-500. m higher. A lowering of vegetation zones of this magnitude corresponds to a temperature decline of between 2.5 and 3.8 °C. During this colder interval lake levels may have been lower, suggesting a decrease in available moisture. The vegetation shift documented in Anteojos record between 12.86 and 11.65. cal. kyr. BP is comparable to the El Abra Stadial in the Colombian Andes but it differs in magnitude. The Anteojos shift is better dated and coincides with the Younger Dryas chron as recorded in the Cariaco Basin sea surface temperature reconstructions and records of continental runoff, as well as in the oxygen isotope measurements from the Greenland ice cores. When compared to other proxies of quasi-immediate response to climate, the time lag for the response of vegetation to climate is found to be negligible at a centennial scale. The Polylepis pollen curve is especially noteworthy, as it reproduces the overall pollen trends and matches well with paleoclimatic reconstructions based on other proxies. Hence, Polylepis might be used as a reliable paleoclimatic indicator in lake sediments close to its uppermost distribution boundary. © 2010 Elsevier Ltd. Source

Discover hidden collaborations