64 research outputs found
Birds and people in Europe
At a regional scale, species richness and human population size are frequently positively correlated across space. Such patterns may arise because both species richness and human density increase with energy availability. If the species-energy relationship is generated through the 'more individuals' hypothesis, then the prediction is that areas with high human densities will also support greater numbers of individuals from other taxa. We use the unique data available for the breeding birds in Europe to test this prediction.
Overall regional densities of bird species are higher in areas with more people; species of conservation concern exhibit the same pattern. Avian density also increases faster with human density than does avian biomass, indicating that areas with a higher human density have a higher proportion of small-bodied individuals. The analyses also underline the low numbers of breeding birds in Europe relative to humans, with a median of just three individual birds per person, and 4 g of bird for every kilogram of human
Past connections with the mainland structure patterns of insular species richness in a continental-shelf archipelago (Aegean Sea, Greece)
Clutch size variability in an ostensibly fix-clutched lizard : effects of insularity on a Mediterranean gecko
The island syndrome describes the evolution of slow life history traits in insular environments. Animals are thought to evolve smaller clutches of larger offspring on islands in response to release from predation pressure and interspecific competition, and the resulting increases in population density and intraspecific competition. These forces become more pronounced with diminishing island size, and life histories are thus expected to become slowest on small, isolated islands. We measured clutch sizes in 12 insular populations of Mediodactylus kotschyi, a small gecko from the Cyclades Archipelago, a set of land-bridge islands in the Aegean Sea (Greece). We analyse variation in clutch size in relation to island area, island age, maternal body size, the presence of putative competitors and nesting seabirds (which increase resource abundance in the form of marine subsidies), and richness of predators. Clutch size of M. kotschyi decreases with increasing island area, in departure from classic island syndrome predictions, suggesting the evolution of faster life histories on smaller islands. There are no relationships between clutch size and island age, maternal size, the presence of competitors or predator richness. Instead, larger clutches on small islands could simply reflect the beneficial effect of marine subsidies derived from resident seabird colonies. Indeed, populations of M. kotschyi on islands with nesting seabirds have clutch sizes 30.9 % larger (1.82 vs. 1.39 eggs) than populations on islands without nesting seabirds. Thus, our data suggest that bottom-up effects of marine subsidies may supersede the expression of a simple island syndrome in the Aegean M. kotschyi
Inconsistent patterns of body size evolution in co-occurring island reptiles
Aim
Animal body sizes are often remarkably variable across islands, but despite much research we still have a poor understanding of both the patterns and the drivers of body size evolution. Theory predicts that interspecific competition and predation pressures are relaxed on small, remote islands, and that these conditions promote body size evolution. We studied body size variation across multiple insular populations of 16 reptile species co‐occurring in the same archipelago and tested which island characteristics primarily drive body size evolution, the nature of the common patterns, and whether co‐occurring species respond in a similar manner to insular conditions.
Location
Aegean Sea islands.
Time period
1984–2016.
Major taxa studied
Reptiles.
Methods
We combined fieldwork, museum measurements and a comprehensive literature survey to collect data on nearly 10,000 individuals, representing eight lizard and eight snake species across 273 islands. We also quantified a large array of predictors to assess directly the effects of island area, isolation (both spatial and temporal), predation and interspecific competition on body size evolution. We used linear models and meta‐analyses to determine which predictors are informative for all reptiles, for lizards and snakes separately, and for each species.
Results
Body size varies with different predictors across the species we studied, and patterns differ within families and between lizards and snakes. Each predictor influenced body size in at least one species, but no general trend was recovered. As a group, lizards are hardly affected by any of the predictors we tested, whereas snake size generally increases with area and with competitor and predator richness, and decreases with isolation.
Main conclusions
No factor emerges as a predominant driver of Aegean reptile sizes. This contradicts theories of general body size evolutionary trajectories on islands. We conclude that overarching generalizations oversimplify patterns and processes of reptile body size evolution on islands. Instead, species’ autecology and island particularities interact to drive the course of size evolution
Unhealthy Landscapes: Policy Recommendations on Land Use Change and Infectious Disease Emergence
Anthropogenic land use changes drive a range of infectious disease outbreaks and emergence events and modify the transmission of endemic infections. These drivers include agricultural encroachment, deforestation, road construction, dam building, irrigation, wetland modification, mining, the concentration or expansion of urban environments, coastal zone degradation, and other activities. These changes in turn cause a cascade of factors that exacerbate infectious disease emergence, such as forest fragmentation, disease introduction, pollution, poverty, and human migration. The Working Group on Land Use Change and Disease Emergence grew out of a special colloquium that convened international experts in infectious diseases, ecology, and environmental health to assess the current state of knowledge and to develop recommendations for addressing these environmental health challenges. The group established a systems model approach and priority lists of infectious diseases affected by ecologic degradation. Policy-relevant levels of the model include specific health risk factors, landscape or habitat change, and institutional (economic and behavioral) levels. The group recommended creating Centers of Excellence in Ecology and Health Research and Training, based at regional universities and/or research institutes with close links to the surrounding communities. The centers’ objectives would be 3-fold: a) to provide information to local communities about the links between environmental change and public health; b) to facilitate fully interdisciplinary research from a variety of natural, social, and health sciences and train professionals who can conduct interdisciplinary research; and c) to engage in science-based communication and assessment for policy making toward sustainable health and ecosystems
Thorough assessment of DNA preservation from fossil bone and sediments excavated from a late Pleistocenee-Holocene cave deposit on Kangaroo Island, South Australia
Fossils and sediments preserved in caves are an excellent source of information for investigating impacts of past environmental changes on biodiversity. Until recently studies have relied on morphology-based palaeontological approaches, but recent advances in molecular analytical methods offer excellent potential for extracting a greater array of biological information from these sites. This study presents a thorough assessment of DNA preservation from late Pleistocene-Holocene vertebrate fossils and sediments from Kelly Hill Cave Kangaroo Island, South Australia. Using a combination of extraction techniques and sequencing technologies, ancient DNA was characterised from over 70 bones and 20 sediment samples from 15 stratigraphic layers ranging in age from >20 ka to ~6.8 ka. A combination of primers targeting marsupial and placental mammals, reptiles and two universal plant primers were used to reveal genetic biodiversity for comparison with the mainland and with the morphological fossil record for Kelly Hill Cave. We demonstrate that Kelly Hill Cave has excellent long-term DNA preservation, back to at least 20 ka. This contrasts with the majority of Australian cave sites thus far explored for ancient DNA preservation, and highlights the great promise Kangaroo Island caves hold for yielding the hitherto-elusive DNA of extinct Australian Pleistocene species
Turnover of passerine birds on islands in the Aegean Sea (Greece)
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73442/1/j.1365-2699.2007.01695.x.pd
Environmental Temperature Affects Prevalence of Blood Parasites of Birds on an Elevation Gradient: Implications for Disease in a Warming Climate
Background: The rising global temperature is predicted to expand the distribution of vector-borne diseases both in latitude and altitude. Many host communities could be affected by increased prevalence of disease, heightening the risk of extinction for many already threatened species. To understand how host communities could be affected by changing parasite distributions, we need information on the distribution of parasites in relation to variables like temperature and rainfall that are predicted to be affected by climate change.\ud
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Methodology/Principal Findings: We determined relations between prevalence of blood parasites, temperature, and seasonal rainfall in a bird community of the Australian Wet Tropics along an elevation gradient. We used PCR screening to investigate the prevalence and lineage diversity of four genera of blood parasites (Plasmodium, Haemoproteus, Leucocytozoon and Trypanosoma) in 403 birds. The overall prevalence of the four genera of blood parasites was 32.3%, with Haemoproteus the predominant genus. A total of 48 unique lineages were detected. Independent of elevation, parasite prevalence was positively and strongly associated with annual temperature. Parasite prevalence was elevated during the dry season.\ud
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Conclusions/Significance: Low temperatures of the higher elevations can help to reduce both the development of avian haematozoa and the abundance of parasite vectors, and hence parasite prevalence. In contrast, high temperatures of the lowland areas provide an excellent environment for the development and transmission of haematozoa. We showed that rising temperatures are likely to lead to increased prevalence of parasites in birds, and may force shifts of bird distribution to higher elevations. We found that upland tropical areas are currently a low-disease habitat and their conservation should be given high priority in management plans under climate change
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