Oferta de servicios de salud y accesibilidad geográfica.

Olivet M, Aloy J, Prat E, Pons X (2008) Oferta de servicios de salud y accesibilidad geográfica. Medicina Clínica 13: 16-22.

Holocene palaeoenvironment in a former coastal lagoon of the arid south eastern Iberian Peninsula: Salinization effects on δ15N

Estiarte M., Peñuelas J., López-Martínez C., Pérez-Obiol R. (2008) Holocene palaeoenvironment in a former coastal lagoon of the arid south eastern Iberian Peninsula: Salinization effects on δ15N. Vegetation History and Archaeobotany. 17: 667-674.
Enllaç
Doi: 10.1007/s00334-008-0153-y

Resum:

The palaeoenvironment of a former coastal lagoon in the south eastern Iberian Peninsula (San Rafael, Almeria, Spain) were inferred from one core analyzed for particulate organic matter content (POM) together with its C/N, δ13C, δ15N to depict the biogeochemical record from the Late Glacial to the Holocene. The results, complemented by previously reported pollen assemblages, indicate the appearance of a freshwater lagoon at 7300 b.p. (uncalibrated 14C age), its salinization at 6200 b.p. and its disappearance at 4400 b.p. The period of existence of the lagoon coincided with a period of wetter conditions as inferred from terrestrial vegetation. The lagoon's salinization was not related to a decrease in precipitation but to a stronger maritime influence since there were no parallel changes in terrestrial vegetation. Salinization caused an increase in δ13C, associated with a higher relative presence of C4 plants, and an increase in δ15N, due to a decrease in plant N demand. The late period of the lagoon, from about 5100 to 4400 b.p., shows a progressive drying and salinization not detected in isotopes but reflected in a decrease in POM, and in the pollen records. Increases in δ15N were related to increases in salinity within the lagoon, and are indicative of a more open N cycle, because the absence of changes in terrestrial vegetation rules out changes in the catchment area as the cause for changes in δ15N. © 2008 Springer-Verlag.

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Do non-native species invasion lead to biotic homogenization at small scales? Similarity and functional diversity of habitats compared for the alien and native components of Mediterranean floras.

Lambdon PW, Lloret F, Hulme PE (2008) Do non-native species invasion lead to biotic homogenization at small scales? Similarity and functional diversity of habitats compared for the alien and native components of Mediterranean floras. Diversity and Distributions 14: 774-785.

Do alien plants on Mediterranean islands tend to invade different niches from native species?.

Lambdon PW, Lloret F, Hulme PE (2008) Do alien plants on Mediterranean islands tend to invade different niches from native species?. Biological Invasions 10: 703-716.

How do introduction characteristics influence the invasion success of Mediterranean alien plants? .

Lambdon PW, Lloret F, Hulme PE (2008) How do introduction characteristics influence the invasion success of Mediterranean alien plants? . Perspectives in Plant, Ecology, Evolution and Systematics 10: 143-159.

Fire frequency effects on the structure and composition of a Mediterranean shrubland community.

Vilà-Cabrera A, Saura-Mas S, Lloret F (2008) Fire frequency effects on the structure and composition of a Mediterranean shrubland community. Ecoscience 15: 519-528.

Life span correlates with population dynamics in perennial herbaceous plants

García M.B., Picó F.X., Ehrlén J. (2008) Life span correlates with population dynamics in perennial herbaceous plants. American Journal of Botany. 95: 258-262.
Enllaç
Doi: 10.3732/ajb.95.2.258

Resum:

Survival and fecundity are basic components of demography and therefore have a strong influence on population dynamics. These two key parameters and their relationship are crucial to understand the evolution of life histories. It remains, however, to be empirically established how life span, fecundity, and population dynamics are linked in different organism groups. We conducted a comparative study based on demographic data sets of 55 populations of 23 perennial herbs for which structured demographic models and among-year natural variation in demographic attributes were available. Life span (from 4 to 128 yr old), estimated by using an algorithm, was inversely correlated with the deviance of the population growth rate from equilibrium as well as with among-year population fluctuations. Temporal variability was greater for short-lived species than for the long-lived ones because fecundity was more variable than survival and relatively more important for population dynamics for the short-lived species. The relationship between life span and population stability suggests that selection for longevity may have played an important role in the life history evolution of plants because of its ability to buffer temporal fluctuations in population size.

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Quercus and Pinus cover are determined by landscape structure and dynamics in peri-urban Mediterranean forest patches

Guirado M., Pino J., Rodà F., Basnou C. (2008) Quercus and Pinus cover are determined by landscape structure and dynamics in peri-urban Mediterranean forest patches. Plant Ecology. 194: 109-119.
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Doi: 10.1007/s11258-007-9278-9

Resum:

Successional dynamics in Mediterranean forests have been modulated by anthropogenic disturbances during thousands of years, especially in areas densely populated since ancient times. Our objective is to determine whether pine tree cover (early-successional species) and oak tree cover (late-successional species), used as a surrogate of successional stage of peri-urban fragmented forests in the Vallès lowlands (Catalonia, NE, Spain), are primarily determined by (1) climate and topography; (2) anthropogenic disturbances; (3) patch structure; or (4) patch dynamics from 1956 to 1993. Quercus spp. and Pinus spp. tree cover were separately recorded on 252 randomly selected plots of 100 m2, within forest patches ranging in size from 0.25 to 218 ha. Multiple linear regressions indicated that forest patch history is the most important variable determining oak and pine tree cover: new forest patches showed higher pine and lower oak tree cover than recently split patches (i.e. those that became fragmented from large forest areas after 1956). Patches already existing as such in 1956 (pre-existent patches) showed higher pine cover than recently split patches. Oak cover increased and pine cover decreased with increasing forest connectivity of the patch. Finally, highly frequented forests were related to high cover of pines. Climatic and topographic variables were not significant. We conclude that pine and oak cover in these peri-urban forests are mainly determined by recent patch dynamics, but also by the spatial pattern of patches. However, human-induced disturbance can modulate this as there is some evidence for pine being associated with a high human frequentation. © 2007 Springer Science+Business Media, Inc.

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Association between floral traits and rewards in Erysimum mediohispanicum (Brassicaceae)

Gómez J.M., Bosch J., Perfectti F., Fernández J.D., Abdelaziz M., Camacho J.P.M. (2008) Association between floral traits and rewards in Erysimum mediohispanicum (Brassicaceae). Annals of Botany. 101: 1413-1420.
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Doi: 10.1093/aob/mcn053

Resum:

• Background and Aims: Floral rewards may be associated with certain morphological floral traits and thus act as underlying factors promoting selection on these traits. This study investigates whether some traits that are under pollinator-mediated selection (flower number, stalk height, corolla diameter, corolla tube length and corolla tube width) in the Mediterranean herb E. mediohispanicum (Brassicaceae) are associated with rewards (pollen and nectar). • Methods: During 2005 the phenotypic traits and the visitation rate of the main pollinator functional groups were quantified in 720 plants belonging to eight populations in south-east Spain, and during 2006 the same phenotypic traits and the reward production were quantified in 400 additional plants from the same populations. • Key Results: A significant correlation was found between nectar production rate and corolla tube length, and between pollen production and corolla diameter. Visitation rates of large bees and butterflies were significantly higher in plants exhibiting larger flowers with longer corolla tubes. • Conclusions: The association between reward production and floral traits may be a factor underlying the pattern of visitation rate displayed by some pollinators. © The Author 2008. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

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Spatial variation in selection on corolla shape in a generalist plant is promoted by the preference patterns of its local pollinators

Gómez J.M., Bosch J., Perfectti F., Fernández J.D., Abdelaziz M., Camacho J.P.M. (2008) Spatial variation in selection on corolla shape in a generalist plant is promoted by the preference patterns of its local pollinators. Proceedings of the Royal Society B: Biological Sciences. 275: 2241-2249.
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Doi: 10.1098/rspb.2008.0512

Resum:

An adaptive role of corolla shape has been often asserted without an empirical demonstration of how natural selection acts on this trait. In generalist plants, in which flowers are visited by diverse pollinator fauna that commonly vary spatially, detecting pollinator-mediated selection on corolla shape is even more difficult. In this study, we explore the mechanisms promoting selection on corolla shape in the generalist crucifer Erysimum mediohispanicum Polatschek (Brassicaceae). We found that the main pollinators of E. mediohispanicum (large bees, small bees and bee flies) discriminate between different corolla shapes when offered artificial flowers without reward. Importantly, different pollinators prefer different shapes: bees prefer flowers with narrow petals, whereas bee flies prefer flowers with rounded overlapping petals. We also found that flowers with narrow petals (those preferred by bees) produce both more pollen and nectar than those with rounded petals. Finally, different plant populations were visited by different faunas. As a result, we found spatial variation in the selection acting on corolla shape. Selection favoured flowers with narrow petals in the populations where large or small bees are the most abundant pollinator groups. Our study suggests that pollinators, by preferring flowers with high reward, exert strong selection on the E. mediohispanicum corolla shape. The geographical variation in the pollinator-mediated selection on E. mediohispanicum corolla shape suggests that phenotypic evolution and diversification can occur in this complex floral trait even without specialization. © 2008 The Royal Society.

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