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- Why do raptors take domestic prey? The case of Bonelli's eagles and pigeonsPublication . Palma, Luis; Beja, Pedro; Pais, Miguel; Cancela Da Fonseca, LuísPredator conservation management requires detailed understanding of the ecological circumstances associated with predation, especially that on economically valuable prey. We examined the mechanisms behind Bonelli's eagle Hieraaetus fasciatus predation on prey of domestic origin, using dietary data from 22 pairs breeding in south-west Portugal (1992-2001) together with information on landscape composition and prey availability. 2. Numerically, 42.7% (37.7% in biomass) of eagle prey comprised domestic species, about 70% of which were rural pigeons Columba livia and the remainder were racing pigeons Columba livia and domestic fowl Gallus gallus. Rabbits Oryctolagus cuniculus, red-legged partridges Alectoris rufa and jays Garrulus glandarius were the most frequent wild prey (43.1%; 50.8% in biomass). This dietary pattern was remarkably stable over a decade, but within each year the intake of pigeons almost halved over the course of the breeding season. 3. Landscape composition significantly affected the dietary proportion of wild and domestic prey items. This was particularly evident in territories dominated by eucalyptus Eucalyptus globulus plantations, where there was reduced consumption of rural pigeons and partridges, an increased intake of minor avian prey items and greater diversity in the diet overall. 4. Bonelli's eagles showed type II functional responses while preying on the most important wild (rabbit) and domestic (rural pigeon) prey, although the former was much stronger. Eagle predation on rabbits declined with increasing abundance of pigeons, and vice versa, but there was no switching in the traditional sense, as selection between these two species was inversely frequency dependent. 5. Synthesis and applications. Predation by Bonelli's eagle on domestic pigeons results from a combination of high vulnerability of the pigeons to eagles and a shortage of key wild prey such as rabbits and partridges, especially during the early breeding season. Given the relatively low economic value of rural pigeons and their importance in the diet of Bonelli's eagles, they could probably be used as a conservation tool to enhance food resources in breeding territories and to deflect predation from more valuable prey such as partridges and racing pigeons.
- Highly polymorphic microsatellite loci for the Parsley frog (Pelodytes punctatus): characterization and testing for cross-species amplificationPublication . Van De Vliet, M. S.; Diekmann, O. E.; Serrão, Ester; Beja, PedroA microsatellite library was developed using genomic DNA of the Parsley frog, Pelodytes punctatus, an amphibian species which inhabits Mediterranean temporary pond systems. Number of alleles and heterozygosity ranged from 10 to 25 and from 0.66 to 0.90, respectively. Crossspecies amplification was successful for 13 of the 15 developed loci for the related species, Pelodytes ibericus. The high levels of polymorphism revealed by these loci will be extremely useful for characterizing the population genetic diversity and structure and to estimate levels of dispersal and gene flow in the species P. punctatus and P. ibericus.
- Isolation of highly polymorphic microsatellite loci for a species with a large genome size: Sharp-ribbed salamander (Pleurodeles waltl)Publication . Van De Vliet, M. S.; Diekmann, O. E.; Serrão, Ester; Beja, PedroFourteen highly polymorphic microsatellite markers were developed and characterized for the sharp-ribbed salamander, Pleurodeles waltl. Isolating microsatellites with more than 12 single repeat type units was only successful for a tetranucleotide repeat (ATAG). Compared to microsatellite libraries constructed simultaneously for two anuran amphibian species, a greater number of primer pairs designed for P. waltl had to be discarded, due to consistent amplification problems. Low amplification success rate for P. waltl may be due to its larger genome size. Consequently, to avoid nonspecific binding and to increase amplification success, polymerase chain reaction programmes with touchdown cycles were used. For 14 microsatellite markers, amplification was successful and consistent with number of alleles and expected heterozygosity ranging from seven to 22 and from 0.79 to 0.94, respectively. All 14 microsatellite markers will be extremely useful for metapopulation studies of this unique amphibian species.
- Development and characterization of highly polymorphic microsatellite loci for the Western Spadefoot toad, Pelobates cultripesPublication . Van De Vliet, M. S.; Diekmann, O. E.; Serrão, Ester; Beja, PedroNine highly polymorphic microsatellite markers were isolated and characterized for the Western Spadefoot, Pelobates cultripes. Remarkably, for this amphibian species high numbers of microsatellites were found as part of larger repeat containing regions, making primer design difficult. For nine loci, primers were designed successfully and genotyping of individuals was reliable and consistent. Number of alleles and heterozygosity for these loci ranged from 9 to 34 and from 0.72 to 0.94, respectively. The high levels of polymorphism revealed by our developed loci should provide insight into population genetic structure and levels of dispersal for this typical Mediterranean temporary pond-breeding amphibian.
- Relationships between nutrient composition of flowers and fruit quality in orange trees grown in calcareous soilPublication . Pestana, M.; Beja, Pedro; Correia, P. J.; Varennes, Amarilis de; Faria, E. A.A field experiment was conducted in a commercial orange orchard (Citrus sinensis (L.) Osb. cv. ‘Valencia late’ grafted on Citrange Troyer) established on a calcareous soil in the south of Portugal, to investigate if flower analysis could be used to predict fruit quality. In April 1996, during full bloom, flowers were collected from 20 trees. In March 1997 the fruits were harvested and their quality evaluated. This procedure was repeated every year during three years. Principal Component Analysis was used to evaluate the patterns of covariation in the concentrations of nutrients in flowers and in fruit quality parameters. Stepwise selection procedures wer then used to develop regression models relating fruit quality parameters to the mineral composition of flowers. The predictive power of the regression models was evaluated using an independent set of data. The mineral composition of flowers at full bloom could be used to predict quality parameters of fruit in the following year, namely fruit fresh weight and the maturation index. Magnesium, Ca and Zn registered in flowers were related to fruit fresh weight estimations and N, P, Mg and Fe were related to fruit maturation index. Reference values were determined for the mineral composition of flowers, corresponding to trees where fruits had a diameter > 76 mm.
- Relationships between nutrient composition of flowers and fruit quality in orange trees grown in calcareous soilPublication . Pestana, M; Beja, Pedro; Correia, PJ; De Varennes, A; Faria, EATo determine if flower nutrient composition can be used to predict fruit quality, a field experiment was conducted over three seasons (1996-1999) in a commercial orange orchard (Citrus sinensis (L.) Osbeck cv. 'Valencia Late', budded on Troyer citrange rootstock) established on a calcareous soil in southern Portugal. Flowers were collected from 20 trees during full bloom in April and their nutrient composition determined, and fruits were harvested the following March and their quality evaluated. Patterns of covariation in flower nutrient concentrations and in fruit quality variables were evaluated by principal component analysis. Regression models relating fruit quality variables to flower nutrient composition were developed by stepwise selection procedures. The predictive power of the regression models was evaluated with an independent data set. Nutrient composition of flowers at full bloom could be used to predict the fruit quality variables fresh fruit mass and maturation index in the following year. Magnesium, Ca and Zn concentrations measured in flowers were related to fruit fresh mass estimations and N, P, Mg and Fe concentrations were related to fruit maturation index. We also established reference values for the nutrient composition of flowers based on measurements made in trees that produced large (> 76 mm in diameter) fruit.