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Severe Decline (severe + decline)
Selected AbstractsLarge-scale spatio-temporal shifts in the diet of a predator mediated by an emerging infectious disease of its main preyJOURNAL OF BIOGEOGRAPHY, Issue 8 2009Marcos Moleón Abstract Aim, To explore the influence of an emerging infectious disease (EID) affecting a prey species on the spatial patterns and temporal shifts in the diet of a predator over a large geographical scale. We reviewed studies on the diet of Bonelli's eagles (Hieraaetus fasciatus) in order to determine the repercussions of the reduction in the density of its main prey, the rabbit (Oryctolagus cuniculus), caused by outbreaks of rabbit haemorrhagic disease (RHD) since 1988. Location, Western continental Europe. Methods, We compiled published and unpublished information on the diet of breeding Bonelli's eagles from Portugal, Spain and France for a 39-year study period (1968,2006). Nonparametric tests were used in order to analyse temporal shifts in diet composition and trophic diversity (H,) between the periods of ,high' (before outbreak of RHD) and ,low' rabbit density (after outbreak of RHD). A combination of hierarchical agglomerative clustering and non-metric multidimensional scaling (NMDS) analyses were used to test for the existence of geographical patterns in the diet of Bonelli's eagles in each period. Results, The diet of the Bonelli's eagle consisted of rabbit (28.5%), pigeons (24.0%), partridges (15.3%), ,other birds' (11.6%), ,other mammals' (7.1%), corvids (7.0%), and herptiles (6.4%). However, RHD had large consequences for its feeding ecology: the consumption of rabbits decreased by one-third after the outbreak of RHD. Conversely, trophic diversity (H,) increased after outbreak of RHD. At the same time, the analyses showed clear geographical patterns in the diet of the Bonelli's eagle before, but not after, RHD outbreak. Main conclusions, Geographical patterns in the diet of the Bonelli's eagle in western Europe seem to be driven mainly by spatio-temporal variation in the abundance of rabbits and, to a lesser extent, by the local (territorial) environmental features conditioning the presence and density of alternative prey species. We show that an EID can disrupt predator,prey relationships at large spatial and temporal scales through a severe decline in the population of the main prey species. Hence we argue that strict guidelines should be drawn up to prevent human-aided dissemination of ,pathogen pollution', which can threaten wildlife not only at the population and species level but also at the community and ecosystem scale. [source] Food Security in China and Contingency Planning: the Significance of Grain ReservesJOURNAL OF CONTINGENCIES AND CRISIS MANAGEMENT, Issue 3 2006Hendrik J. Bruins China is inhabited by ca 20 percent of the world population, but has only 7 percent of global arable land and only 6.6 percent of global freshwater resources. These unfavourable relationships between population size and the basic resources for food production , soil and water , require careful food security and contingency planning by the Chinese authorities. The country has been remarkably successful in raising its food production since 1949 at a faster rate (400 percent) than the increase in its population (240 percent). This has basically been achieved by increasing the yields per unit area with enhanced fertilizer use, as the total size of arable land has been decreasing in recent years. Though China attempts to be largely self-sufficient in food grain production, two possible contingency scenarios are suggested that might cause grave problems: (1) severe multi-annual drought; (2) reduced chemical fertilizer manufacturing. If Chinese food production would drop as a result by, say, 33 percent, famine, the dreaded scourge throughout Chinese history, might recur. A shortage of ca 150 million tons of food grains cannot easily be buffered by the volume of food grains annually traded on the world market, ca 240 million tons. Much of this amount tends to be committed already to traditional buyers, as most countries in the world have to import food grains. Cash reserves, therefore, may not guarantee food purchases, because global grain reserves are limited and declining. The formation and maintenance of large internal food grain reserves in China, common in its tradition and ancient history, seem the only realistic contingency planning strategy to avert famine in case of a severe decline in its food production in future crisis years. [source] Microsatellite markers for the endangered European mink (Mustela lutreola) and closely related mustelidsMOLECULAR ECOLOGY RESOURCES, Issue 6 2007M. T. CABRIA Abstract The European mink (Mustela lutreola L., 1761) is an endangered carnivore species whose populations suffered a severe decline during the last century. The genotyping of eight polymorphic microsatellite loci revealed a relatively low number of alleles per locus (two to eight), as well as low levels of polymorphism (observed and expected heterozygosity values per locus were 0.49 and 0.54, respectively). Cross-specific polymerase chain reaction amplifications were successful in seven closely related mustelid species suggesting that these loci may be useful not only for assessing genetic variability in European mink populations but also for determining potential hybridization events between M. lutreola and other mustelid species. [source] Spatial genetic analysis of the grass snake, Natrix natrix (Squamata: Colubridae), in an intensively used agricultural landscapeBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010BARBARA MEISTER Both the conversion of natural habitats to farmland and efforts at increasing the yield of existing crops contribute to a decline in biodiversity. As a consequence of land conversion, specialised species are restricted to remnants of original habitat patches, which are frequently isolated. This may lead to a genetic differentiation of the subpopulations. We used seven microsatellite markers to examine the genetic population structure of the grass snake, Natrix natrix (Linnaeus, 1758), sampled in remnants of pristine habitat embedded in an intensively used agricultural landscape in north-western Switzerland. The study area, a former wetland, has been drained and gradually converted into an agricultural plain in the last century, reducing the pristine habitat to approximately 1% of the entire area. The grass snake feeds almost entirely on amphibians, and is therefore associated with wetlands. In Central Europe, the species shows severe decline, most probably as a result of wetland drainage and decrease of amphibian populations. We found no genetically distinct grass snake populations in the study area covering 90 km2. This implies that there is an exchange of individuals between small remnants of original habitat. Thus, gene flow may prevent any genetic differentiation of subpopulations distributed over a relatively large area. Our results show that a specialized snake species can persist in an intensively used agricultural landscape, provided that suitable habitat patches are interconnected. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 51,58. [source] Predicting the number of ecologically harmful exotic species in an aquatic systemDIVERSITY AND DISTRIBUTIONS, Issue 2 2008Anthony Ricciardi ABSTRACT Most introduced species apparently have little impact on native biodiversity, but the proliferation of human vectors that transport species worldwide increases the probability of a region being affected by high-impact invaders , i.e. those that cause severe declines in native species populations. Our study determined whether the number of high-impact invaders can be predicted from the total number of invaders in an area, after controlling for species,area effects. These two variables are positively correlated in a set of 16 invaded freshwater and marine systems from around the world. The relationship is a simple linear function; there is no evidence of synergistic or antagonistic effects of invaders across systems. A similar relationship is found for introduced freshwater fishes across 149 regions. In both data sets, high-impact invaders comprise approximately 10% of the total number of invaders. Although the mechanism driving this correlation is likely a sampling effect, it is not simply the proportional sampling of a constant number of repeat-offenders; in most cases, an invader is not reported to have strong impacts on native species in the majority of regions it invades. These findings link vector activity and the negative impacts of introduced species on biodiversity, and thus justify management efforts to reduce invasion rates even where numerous invasions have already occurred. [source] Market Reactions to Warnings of Negative Earnings Surprises: Further EvidenceJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 7-8 2008Weihong Xu Abstract:, This study examines two plausible explanations for Kasznik and Lev's (1995) counterintuitive finding that warning firms are subject to more negative market returns than no-warning firms. Namely, are the more negative market reactions to warning firms due to their poorer future earnings performance or due to investor overreaction? I find that, compared with no-warning firms, warning firms experience more severe one-year-ahead earnings declines and these earnings declines can explain the stronger market returns to warning firms. However, my results do not support an investor overreaction explanation. The tests of subsequent abnormal returns of warning firms over various windows do not detect stock return reversals due to correction for overreaction. In addition, the greater revisions in analysts' forecasts for warning firms are found to enhance analyst accuracy rather than increase analyst pessimism. Collectively, my results suggest that the more negative market reactions to warning firms reflect investors' rational anticipation of more severe declines in future earnings for warning firms rather than investor overreaction. [source] Status, habitat use, and vulnerability of the European ggrayling in Austrian watersJOURNAL OF FISH BIOLOGY, Issue 2001F. Uiblein The European grayling Thymallus thymallus is widely distributed in Austria, occurring in all eight rural provinces. However, in recent years, an increasing number of studies report severe declines in population sizes. Since 1997, the grayling has had the status of an endangered species in Austria. In 1997 the multidisciplinary research programme ,Local Adaptation, Threat, and Conservation of European Grayling' has carried out three projects in Upper Austria, Salzburg, and Carinthia. Research has included repeated electro-fishing in selected stretches of eight rivers and the collection of data on habitat characteristics, fish species composition, population abundance and size distribution, growth and body condition, as well reproductive timing, and migratory activities of grayling. Furthermore, genetic and morphological variation among grayling populations has been studied as well as the number, habitat use and feeding activity of cormorants. Evidence is provided for the existence of distinct negative effects caused by single factors or combinations of factors on grayling stocks in each of the river stretches studied. [source] | |||||||||||||