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Orlando L.,Laboratorio Of Fisiologia Of La Reproduccion Y Ecologia Of Peces | Pereyra I.,Area de Biodiversidad y Conservacion | Silveira S.,DINARA MGAP | Paesch L.,DINARA MGAP | And 2 more authors.
Neotropical Ichthyology | Year: 2015

This work analyzed length-mass relationship, growth in length, mass variations and dynamic of yolk sac depletion of Mustelus schmitti embryos, extracted from females catched by the artisanal fishery acting off La Paloma (34°39’S, 54°10´W, Uruguay) during 2006 and 2007. Differences in total length and total mass between sexes were not significant. Embryos showed a negative allometric growth for both years with a slope change near the day 170 of the year, likely to be associated with the depletion of the external yolk sac. Gompertz and Von Bertalanffy curves were adjusted for each year. Parturition date was determined around the day 300 of the year. Yolk depletion followed a logistic dynamic Yt=1/ (1+e(-13.749 + 0.072*t)) for 2006 and Yt=1/(1+e(-10.472 + 0.054*t)) for 2007. Embryos showed a mean increase in total dry mass of 5.4g in 187 days which, together with yolk depletion dynamics, indicates additional energetic supply, suggesting that M. schmitti presents limited histotrophy. © 2015 Sociedade Brasileira de Ictiologia.

Barea-Azcon J.M.,Paseo de los Basilios 11 | Virgos E.,Area de Biodiversidad y Conservacion
Acta Theriologica | Year: 2010

The dietary preference of badgers Meles meles (Linnaeus, 1758) for earthworms and other food resources has been widely discussed. In the Mediterranean area, rabbits Oryctolagus cuniculus, fruits (mainly olives Olea europaea) and arthropods are the most important foods. We describe badger dietary habits in a xeric Mediterranean area, comparing use and availability of olives and rabbits. Our results indicated that olives and rabbits are the predominant resources consumed, however we did not detect any evidence of specialisation when we compared consumption versus field availability. In the case of olives we found that their consumption is reduced when juvenile rabbits or figs Ficus carica are widely available, which is evidence against any specialisation in this resource. Figs appear to be a key food item for badgers; they were consumed in large amounts when available. Badgers in this xeric area can be viewed as generalist or facultative specialists, using the most profitable resource when available but shifting its preferences to other less profitable food resources when availability of other primary food resource are reduced. Our results also indicated the high suitability of some human agricultural uses (eg fruit orchards) for this species, especially in the otherwise harsh Mediterranean environments.

Laskurain N.A.,University of the Basque Country | Aldezabal A.,University of the Basque Country | Olano J.M.,University of Valladolid | Loidi J.,University of the Basque Country | Escudero A.,Area de Biodiversidad y Conservacion
Journal of Vegetation Science | Year: 2013

Questions: What is the relative importance of direct herbivory compared to microsite modification in ungulate impacts on secondary forest succession? Do domestic ungulate impacts differ between small-seeded pioneers and large-seeded late successional species? Location: Birch-beech secondary forest (Betula celtiberica and Fagus sylvatica), Bizkaia, Northern Spain. Methods: We conducted a detailed spatial analysis of 216 permanent 1-m2 subplots that were distributed among six plots, of which three were fenced (each plot was 3600-m2) and three were unfenced (each plot was 1296-m2). Within each subplot, the emergence and survival rates of all tree, shrub and vine species were monitored. In total, 21 censuses of the subplots were conducted across 4 yr (1998-2001). Ungulate abundance was measured by using the pellet counting method. Structural equation models were applied to model the entire recruitment process. Results: Emergence and survival rates differed between small- and large-seeded species, and the effect of domestic ungulates (primarily sheep) on these rates depended on seed traits. Sheep did not affect the emergence of large-seeded species (e.g. beech and ivy), but did result in a decline in their survival. In contrast, the emergence of small-seeded species (e.g. birch) was promoted through an increase in bare soil cover because of trampling by the ungulates, but no significant effect on survival was observed. Interestingly, the sheep prompted differences in the role of the understorey vegetation: the understorey composition was able to promote the survival of large-seeded species growing in unfenced conditions by reducing the risk of herbivore predation, but had a negative effect on the survival of small-seeded species because of low light availability under the shaded shrub canopies. Conclusions: Our results clearly highlight that sheep can change the seedling bank structure in a secondary temperate forest, thereby affecting the dynamics and structure of forest remnants. This impact should be included as a critical driver in current predictive models of forest dynamics in temperate regions, since herbivore pressure is increasing in forests across Europe due to an increase in wild ungulate populations and livestock. © 2012 International Association for Vegetation Science.

Soutullo A.,University of Alicante | Soutullo A.,Institute Investigaciones Biologicas Clemente Estable | Lopez-Lopez P.,University of Alicante | Cortes G.D.,Area de Biodiversidad y Conservacion | And 3 more authors.
Ethology Ecology and Evolution | Year: 2013

The spatial distribution of populations is the result of individuals' movements. In territorial species, the spatial dynamics of populations is to a large degree shaped by individuals' ranging behaviour during their juvenile dispersal. Here we use information on juvenile golden eagles (Aquila chrysaetos) tracked by satellite telemetry, to explore the effects of daily behavioural decisions on their dispersal strategy during their first year of life. When analysed on a biweekly basis, the large-scale movements of golden eagles did not differ from a correlated random walk (CRW) model of dispersal. Although in the long term such a strategy maximises the acquisition of information on good hunting areas, finding a mate and a vacant territory in a landscape, it is expensive in terms of energy requirements. At the finer scale of daily foraging movements, movement patterns were non-random, probably reflecting animals' oriented movements towards sites with high chances of successful hunting. We suggest that the key issue to take into account when exploring the factors determining individuals' dispersal strategies is how strongly the daily movements are influenced by an active search for food. This is to a large degree determined by food availability and individuals' ability to accumulate reserves. In our case, the individuals with the lowest proportion of foraging habitats within their dispersal areas showed large-scale movements more restricted than expected from a CRW. Also, distances covered by individuals in their biweekly movements were both larger and more variable in winter, when food availability diminishes. © 2013 Dipartimento di Biologia, Università degli Studi di Firenze, Italia.

Maltez-Mouro S.,Center for Functional Ecology | Maestre F.T.,Area de Biodiversidad y Conservacion | Freitas H.,Center for Functional Ecology
Acta Oecologica | Year: 2010

The analysis of co-occurrence patterns between plant species is being increasingly employed to study biotic interactions at the community level. We investigated changes in such patterns along two different abiotic stress gradients in eight sand-dune plant communities of the western coast of Portugal. We sampled a total of 72 transects consisting on 25 1 m2 quadrats each, and we calculated the standardized effect size for each transect (SES), i.e. the differences between the observed co-occurrence patterns and simulated patterns for a random co-occurrence. The relationships between the average SES values for each site and the abiotic stress gradients, defined by the north-south geographic gradient (a surrogate of the climatic stress) and total plant cover (a surrogate of productivity), were analyzed. The factors driving co-occurrence patterns at smaller spatial scale were also investigated by a stepwise multiple regression analysis. Average SES values were significantly higher than zero in five of the studied sites, indicating lower species co-occurrence than expected by chance. These results suggest that the studied sand-dune communities studied are structured mainly by competitive interactions. At the site scale, SES values were not related to plant cover or the location along the north-south gradient. However, at the transect scale, SES values were inversely explained by different abiotic factors (the geographic position along the north-south gradient and the plant cover). Our results indicate that the magnitude and the shifts in co-occurrence patterns along environmental gradients varied with the spatial scale and the surrogate of abiotic stress considered. © 2009 Elsevier Masson SAS. All rights reserved.

Segura A.M.,Area de Biodiversidad y Conservacion | Segura A.M.,University of the Republic of Uruguay | Franco-Trecu V.,University of the Republic of Uruguay | Franco-Fraguas P.,University of the Republic of Uruguay | Arim M.,University of the Republic of Uruguay
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2015

We found a segmented pattern, increasing for small sizes and decreasing for larger sizes, in the relationship between trophic position and body size. This pattern provides support for a recently developed theoretical model whose derivation was based on consumers’ metabolic requirements and on basic assumptions about feeding relationships. We combined original and published information about stable nitrogen isotopes, a proxy of trophic position, for a broad range of animal body sizes (10-3–105 kg) inhabiting the southwestern Atlantic Ocean. Linear, polynomic, and piecewise segmented models were fit to species trophic position and body mass. The segmented model had the best fit, presenting a positive slope (β1 = 0.33± 0.08) for small organisms (<200 kg) and a negative slope (β2 = -1.93±0.16) for larger ones. This suggests that there are morphological restrictions to prey consumption in smaller organisms and energetic constraints to trophic position in larger ones. Furthermore, the predator–prey body mass ratio (BMR = 1.31; 95% CI = 0.9–2.40) estimated here is similar to previous reports of direct observations (BMR = 1.64 and 1.82). However, the trophic position of larger organisms decreases at a faster rate (β2 = -1.93) than expected by metabolic demand (β2expected = -0.16 to -0.82), suggesting that additional processes should be considered. Our results suggest that large species could be more vulnerable to global change than previously thought. © 2015, National Research Council of Canada. All rights reserved.

Delgado-Baquerizo M.,Pablo De Olavide University | Castillo-Monroy A.P.,Area de Biodiversidad y Conservacion | Maestre F.T.,Area de Biodiversidad y Conservacion | Gallardo A.,Pablo De Olavide University
Soil Biology and Biochemistry | Year: 2010

It has been suggested that the dominance of N forms should shift from dissolved organic nitrogen (DON) to nitrate along a gradient of increasing N availability. We aimed to apply this model at a local scale within a semi-arid ecosystem showing a high spatial heterogeneity in the distribution of vegetation and soil resources. By doing this, we seek a better understanding of the N cycling in spatially heterogeneous ecosystems. We took soil samples from the three major sources of spatial heterogeneity: the grass Stipa tenacíssima, the N-fixing shrub Retama sphaerocarpa, and open areas. We also sampled the biological soil crust (BSC) located in the latter areas as another source of spatial heterogeneity. BSC microsites were classified by four levels of soil coverage, ranging from high coverage (66%) to bare soil. The proportion of nitrate, ammonium and DON was determined in all microsites. DON was the dominant N form for open areas, while nitrate was dominant under the canopy of Retama; these microsites contained the lowest and highest N availability, respectively. Under BSC, DON was the dominant N form. We found high temporal variability in the dominance of N forms for all microsites. Our results suggest that the biome-derived model of Schimel and Bennett (2004) explaining N form dominance across N availability gradients may be extended to local gradients. © 2009 Elsevier Ltd. All rights reserved.

Eugenio M.,EU de Ingenierias Agrarias | Olano J.M.,EU de Ingenierias Agrarias | Ferrandis P.,Campus Universitario s n | Martinez-Duro E.,Campus Universitario s n | Escudero A.,Area de Biodiversidad y Conservacion
Journal of Arid Environments | Year: 2012

Land abandonment is an exceptionally important global change driver in the northern rim of the Mediterranean Basin, since dramatic changes in structure and composition of plant communities have been observed along subsequent secondary succession. Gypsum outcrops of the Iberian Peninsula constitute particular and threatened habitats where secondary succession processes differ from the amelioration mechanism generally described for Mediterranean-type ecosystems, and thus, it seems critical to assess whether succession-related changes may affect the viability of genuine specialists' populations. In this work we used dendrochronological techniques on the dominant gypsophyte shrubs Helianthemum squamatum and Lepidium subulatum to assess their longevity, population structure, and radial growth along a chronosequence after agriculture abandonment at three similar and nearby-located sites in La Mancha region, central Spain. Cohort-structured populations, resulting from effective recruitment along the first year, were observed in both species. Whereas H. squamatum, a short-lived (up to 10. yr) sub-shrub, showed different age structures as a response to varying habitat conditions related to stand age, L. subulatum, a medium-lived (up to 26. yr) sub-shrub, showed no differences in demographic parameters among study sites. Radial growth patterns were not affected by time since abandonment in either species. © 2011 Elsevier Ltd.

Olano J.M.,University of Valladolid | Eugenio M.,University of Valladolid | Escudero A.,Area de Biodiversidad y Conservacion
American Journal of Botany | Year: 2011

Premise of the study: Regional climatic patterns result in the synchrony of biological processes along large spatial areas. These patterns may be critical for effective plant recruitment in (semi)arid environments. Nevertheless, recruitment patterns of plant species within their range of distribution are still poorly known. Moreover, this response may be species-dependent, particularly between coexisting congenerics, which are thought to vary in demographic responses to climatic conditions as a coexistence-promoting mechanism. In this context, we investigated whether two congeneric plant species show synchronic age structures at varying spatial scales and whether they display demographic differences. Methods: We sampled 600 Helianthemum squamatum and H. syriacum individuals at six localities in Spain. We used dendrochronological techniques to estimate age and radial growth. We compared the age structure among populations and between species and assessed the effect of site and species on different demographic parameters. Correlations between age structure and climatic factors were also determined. Key results: We detected a very low intraspecific synchrony across sites but a high interspecific coupling in age structure within localities. Secondary growth, mean age, and flowering showed large intersite differences and small interspecific differences. Summer rainfall was a good predictor of age structure. Conclusions: Fine-scale climatic variability plays a major role in determining age structure of the studied species. Climatic variability is more relevant than interspecific differences. Our results illustrate the relevance of including spatial variation in summer rainfall patterns when modeling the impact of climate change on Mediterranean plant demography. © 2011 Botanical Society of America.

Ruibal M.,Servicio Oceanografico | Laufer G.,Area de Biodiversidad y Conservacion
Amphibia Reptilia | Year: 2012

The North American bullfrog, Lilhobates catesbeianus is a dangerous invasive species that has been introduced worldwide for commercial and ornamental purposes. Although studies of the bullfrog's effects on invaded communities have been carried out, they have focused mostly on post-metamorphic stages. However, considering the experimental evidence and its ecological attributes, the L catesbeianus tadpole could also have significant impact on invaded communities. The aim of this study was to perform a detailed qualitative and quantitative exploration of the L catesbeianus larval diet. Gut content was studied and compared for three invaded locations in Uruguay (Departments of Canelones, Soriano and Cerro Largo). Although microscopic algae (Spirogyra spp., Euglena spp., Closterium spp., Volvox spp. and Scenedesmus spp.) were the most frequent prey, the diet was also made up of small invertebrates (especially rotifers) and eggs. Statistically significant differences in diet richness and prey identity were found among the three study sites, probably due to local conditions. One common feature among the three locations was the ingestion of prey with high protein levels, filamentous algae and animal prey. The high frequency of high-protein prey could explain the substantial growth rate of these larvae. Native tadpoles appear to have a much poorer diet than bullfrogs. We can thus assume that the L catesbeianus larvae will be a major competitor and a potential predator for native communities. We propose that L catesbeianus tadpoles may have significant effects on invaded communities, and should be considered in future research and managements plans. © Koninklijke Brill NV, Leiden, 2012.

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