ESPECIES

Spatial patterns of seed dispersal and seedling recruitment in Corema album (Empetraceae): the importance of unspecialized dispersers for regeneration

Enlace mardeaves Larus michahellis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,

Calviño-Cancela, M. Spatial patterns of seed dispersal and seedling recruitment in Corema album (Empetraceae): the importance of unspecialized dispersers for regeneration. Journal of Ecology 90, 775–784 (2002). DOI: 10.1046/j.1365-2745.2002.00711.x

  • Spatial patterns of seed dispersal and seedling recruitment of Corema album were examined among and within habitats to determine the quantitative importance of different dispersers in each type of habitat, and their effectiveness in carrying seeds to suitable habitats for seedling recruitment.
  • Gulls, blackbirds and rabbits were, respectively, the main dispersers (45%, 40% and 15% of Corema album seeds). Within habitats, blackbirds disperse seeds mainly to female Corema album shrubs, while gulls and rabbits disperse seeds mainly to open ground.
  • The quantitative role of dispersers varies among habitats because of their habitat preferences, causing the spatial pattern of seed rain to differ.
  • Open ground has the highest density of seedlings and the highest seedling-to-seed ratios. Regeneration is more active in the pioneer scrub than in the mature scrub and the herbaceous vegetation.
  • Gulls, rather than specialist frugivores, are the most effective dispersers in carrying seeds to suitable sites for recruitment.

Effectiveness of a varied assemblage of seed dispersers of a fleshy-fruited plant

Enlace mardeaves Larus michahellis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,

Calviño-Cancela, M. & Martín-Herrero, J. Effectiveness of a varied assemblage of seed dispersers of a fleshy-fruited plant. Ecology 90, 3503–3515 (2009).

Disperser effectiveness is the number of new plants resulting from the activity of one disperser relative to other dispersers or to nondispersed seeds. Effectiveness remains largely uninvestigated due to the complexity of its measurement. We measured the effectiveness of seed dispersers (Larus michahellis, Turdus merula, and Oryctolagus cuniculus) of the shrub Corema album (Empetraceae) using a simulation model of the recruitment process that was parameterized with field data of seed dispersal, predation, and seedling emergence and validated with independent data on seedling density. The model allows tracking the fate of seeds dispersed by each animal and estimating, for the first time, disperser effectiveness as seedlings per square meter contributed by each disperser. It also allows quantifying the relative importance of different recruitment processes in determining the quantity and spatial distribution of recruitment. Larus michahellis was the most effective disperser in two of the three habitats studied,contributing 3–125 times more than the other two species, whose lower effectiveness depended
mostly on deposition patterns (T. merula) or deleterious effects on seedling emergence (O.cuniculus). The dependence of the plant on each disperser differed between habitats and was the greatest in sparse scrub, where recruitment depended almost exclusively on gulls (90%). Quantity and quality of dispersal were not correlated; quality was a better predictor of disperser effectiveness. Seedling emergence was the most crucial process in determining both the spatial pattern of recruitment among microhabitats (99.8% of variance explained) and the quantity of recruitment within microhabitats (43–83%). A sensitivity analysis showed that increasing seed dispersal improved the recruitment for all dispersers when there was no competition for fruits. However, with limited fruits, increased dispersal of lower quality dispersers reduced overall recruitment. Our results show important differences in effectiveness among dispersers and illustrate the different influences of the components of effectiveness, which varied depending not only on the disperser but also on the circumstances (e.g., type of habitat).

Long-term reproductive impairment in a seabird after the Prestige oil spill

Enlace mardeaves Phalacrocorax aristotelis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,,,,

Barros, Á., Álvarez, D. & Velando, A. Long-term reproductive impairment in a seabird after the Prestige oil spill. Biology letters 10, 20131041 (2014). DOI: 10.1098/rsbl.2013.1041

Large oil spills are dramatic perturbations on marine ecosystems, and seabirds are one of the worst affected organisms in such events. It has been argued that oil spills may have important long-term consequences on marine organisms, but supporting evidence remains scarce. The European shag (Phalacrocorax aristotelis) was strongly impacted at population level by the Prestige oil spill, the biggest spillage in the eastern North Atlantic. In this paper, we report on the long-term consequences on reproduction of this coastal seabird, using temporal and spatial replicated data (before–after–control–impact design). Our study revealed long-term reproductive impairment during at least the first 10 years since the Prestige oil spill. Annual reproductive success did not differ before the impact, but after the impact it was reduced by 45% in oiled colonies compared with unoiled ones. This is a rare documentation of long-term effects after a major oil spill, highlighting the need for long-term monitoring in order to assess the real impact of this type of disturbance on marine organisms.

Análisis de la mortalidad de las poblaciones de cormorán moñudo (Phalacrocorax aristotelis) en artes de pesca en la Demarcación Marina Noratlántica

Enlace mardeaves INFORME,Phalacrocorax aristotelis,REPOSITORIO ,,

Alvarez, D. Análisis de la mortalidad de las poblaciones de cormorán moñudo (Phalacrocorax aristotelis) en artes de pesca en la Demarcación Marina Noratlántica. (2015). Aplicación 23.06.456D.640. Ministerio de Agricultura, Alimentación y Medio Ambiente (MAGRAMA).

 

Artrópodos asociados a nidos de cormorán moñudo (Phalacrocorax aristotelis Linnaeus, 1761)

Enlace mardeaves Phalacrocorax aristotelis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,

Alonso Pérez, A. I. Artrópodos asociados a nidos de cormorán moñudo (Phalacrocorax aristotelis Linnaeus, 1761). Boletín BIGA 7–86 (2010).

En este trabajo se describe la composición de la comunidad faunística de artrópodos en diecinueve nidos de cormorán moñudo (Phalacrocorax aristotelis Linnaeus, 1761). La fauna fue recogida en 1997 en las colonias de las Islas Cíes y Ons, localizadas en el NO de la Península Ibérica y pertenecientes al Parque Nacional de las Islas Atlánticas. Se ha estudiado la presencia y la abundancia de artrópodos en nidos en tres diferentes estados de ocupación: nidos con huevos, nidos con pollos y nidos vacíos. En los diecinueve nidos estudiados, se han identificado 25 familias de ácaros (92.1% del total de la fauna), 14 familias de dípteros, 8 familias de himenópteros, 16 familias de coleópteros y 5 familias de arañas. Además se han estudiado las relaciones ecológicas y tróficas de estas familias. Los nidos proporcionan a un pequeño grupo de artrópodos las condiciones necesarias para desarrollar y completar su ciclo biológico. Los artrópodos saprófagos fueron los más abundantes independientemente del estado de ocupación del nido.

Female body condition and brood sex ratio in yellow-legged gulls Larus cachinnans

Enlace mardeaves Larus michahellis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,

Alonso-Alvarez, C. & Velando, A. Female body condition and brood sex ratio in yellow-legged gulls Larus cachinnans. Ibis 145, 220–226 (2003).

In the Yellow-legged Gull (Larus cachinnans), males are the larger sex, and show more reproductive variance than females. We predicted that the proportion of male chicks in a brood should increase with female body condition. We investigated brood sex ratio by using DNA markers taken from samples of hatchlings or dead embryos, and female body condition using plasma cholesterol concentration as a reliable indicator. The brood sex ratio of females in good condition was male biased and the sex ratio of females in poor condition was female biased. This relationship was also significant in those nests where all the eggs laid were sexed. Thus, manipulation of embryo mortality cannot explain the biases reported in this study, suggesting that the sex ratio of the eggs was biased prior to laying. These results confirm that sex-ratio manipulation in gulls operates under natural conditions, and supports earlier experimental findings.

Changes in plasma biochemistry and body mass during incubation in the yellow-legged gull

Enlace mardeaves Larus michahellis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,,,,

Alonso-Alvarez, C., Velando, A., Ferrer, M. & Veira, J. A. Changes in plasma biochemistry and body mass during incubation in the yellow-legged gull. Waterbirds 25, 253–258 (2002).

The “Incubatory Reserves Constancy” hypothesis asserts that incubation could be a departure from breeding stress that allows for the maintenance or recovery of body reserves after laying effort (females) or territory defense (males) in those species with bi-parental incubation such as gulls. The plasma composition and body mass of incubating Yellow-legged Gulls (Larus cachinnans) were analyzed and related to the number of days after egg-laying. Female gulls showed an increase in uric acid and cholesterol levels, whereas males showed only an increase in uric acid values throughout this period. Moreover, females increased while males maintained their body masses. These results could reflect a recovery process after the laying effort supporting the Incubatory Reserves Constancy hypothesis in females. Uric acid and urea levels are positively correlated to body condition in Yellow-legged Gulls, which could be the result of a change in diet composition. This disagrees with recent findings on body composition in incubating gulls and could be related to variations in food availability among populations or years, and could reflect flexibility in the investment devoted by each sex.

Effects of Acute Exposure to Heavy Fuel Oil from the Prestige Spill on a Seabird

Enlace mardeaves Larus michahellis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,,

Alonso-Alvarez, C., Pérez, C. & Velando, A. Effects of acute exposure to heavy fuel oil from the Prestige spill on a seabird. Aquatic Toxicology 84, 103–110 (2007). doi:10.1016/j.aquatox.2007.06.004.

Large quantities of petroleum products are released into the marine environment as result of tanker wrecks. Such catastrophic events have a dramatic impact on marine ecosystems, affecting a broad range of species. Seabirds are placed at the uppermost trophic level of the marine food chain. Therefore, important toxic effects are expected in these organisms. The recent Prestige oil spill gave the opportunity to test this. A previous study reported that yellow-legged gulls (Larus michahellis) breeding in the oiled area (17 months after the spill) showed differences both in plasma biochemistry and in the total circulating levels of polycyclic aromatic hydrocarbons (TPAHs) in blood regard to gulls sampled in clean areas. In the present study, wild yellow-legged gulls were fed with heavy fuel oil from the Prestige oil spill (P-gulls) and compared with control gulls (C-gulls) fed only with the vehicle (vegetable oil). Consistent with the cited previous findings, gulls fed with fuel oil showed reduced glucose and inorganic phosphorus levels in plasma, as well as a trend to significantly reduced creatinine values. In addition, glucose concentration was negatively related to TPAH levels. Males but not females fed with fuel oil showed higher plasma activity of asparatate aminotransferase (AST) than controls. With regard to plasma activity of gamma-glutamyl transferase (GGT), the results were opposite to the previous study. The GGT activity increased in C-females, apparently to meet with increased liver metabolism due to egg laying demands, but not in P-females. Differences to the previous study possibly reflect different adaptive responses of these enzymes to an acute short-term exposure to heavy fuel oil. Since the yellow-legged gull belongs to a complex of species widely distributed throughout the Northern hemisphere, the results as a whole might provide a tool for future evaluations of short- and long-term effects of oil spills on seabirds. Decreased glucose and inorganic phosphorus levels in plasma are expected in both short- and long-lasting exposures to fuel oil, whereas responses of AST and GGT enzymes would depend on both the sex of individuals and the temporal pattern of exposure.

Sublethal Toxicity of the Prestige Oil Spill on Yellow-Legged Gulls

Enlace mardeaves Larus michahellis,PUBLICACIÓN CIENTÍFICA,REPOSITORIO ,,,

Alonso-Alvarez, C., Munilla, I., López-Alonso, M. & Velando, A. Sublethal toxicity of the Prestige oil spill on yellow-legged gulls. Environment International 33, 773–781 (2007).

The Prestige oil spill in November 2002 is considered the biggest large-scale catastrophe of its type in Europe, thousands of seabirds dying in the subsequent months. Here, the total concentration of 16 polycyclic aromatic hydrocarbons (TPAH) was measured in the blood cell fraction of adult and chick yellow-legged gulls (Larus michahellis) from unoiled and oiled coastal areas in North Western Spain. In addition, hematocrit, plasma metabolites, electrolytes and enzymes, as well as body mass were determined in the same individuals. Our results strongly suggest the presence of health damages of sublethal nature in adult gulls breeding in oiled colonies 17 months after the Prestige oil spill. This is supported by the following evidences: (1) gulls sampled in unoiled and oiled colonies differed in blood TPAH levels, (2) gulls sampled in unoiled and oiled colonies differed in several blood parameters indicative of physiological disorders, and (3) TPAH in blood was significantly related to several of these parameters. Differences in the level of asparatate aminotransferase (AST), gamma-glutamyl transferase (GGT), total protein, glucose and inorganic phosphorus suggest damages on some vital organs (i.e. liver and kidney) in adult birds from oiled areas. Meanwhile, chicks presented weaker effects than adults, showing only between-area differences in hematocrit. Since TPAH levels in blood did not differ between both age groups, the stronger effects on adults should be due to their longer exposure to these pollutants and/or to severe exposure in the months following the spill. The presence of PAHs in chicks indicates that these pollutants were incorporated into the food chain because nestlings would have been only exposed to contaminated organisms in the diet (e.g. fishes and crustaceans). Our findings support the view that PAHs may deeply alter the physiology of seabirds, and emphasize the necessity of quantifying the circulating levels of these compounds in order to evaluate the sublethal effects associated to large oil spills.