Natural Physical Barriers Research Articles

How do hydroelectric dams affect non-migratory fish?: genomic evidence for Cichla temensis (Perciformes: Cichlidae) in the Uatumã River, Amazonas, Brazil

Abstract The Balbina hydroelectric dam was built in the 1980s on the Uatumã River to supply electricity to Manaus, capital of the state of Amazonas, Brazil. Its construction caused a drastic change to the alluvial landscape, forming a large, lentic, artificial reservoir rather than a previously dynamic river system. The objective of our research was to evaluate the impact of the hydroelectric dam on the microevolutionary processes of fish, taking as a model Cichla temensis, an iconic non-migratory fish from the Amazon, abundant in this ecosystem. We collected double digest restriction site-associated DNA sequencing data and extracted single nucleotide polymorphisms, which we identified at neutral and adaptive loci, for subsequent analyses. The results showed that the connectivity of the population was affected historically by natural physical barriers, before the construction of the hydroelectric dam, recognizing two independent population units. We detected that the hydroelectric dam increased the differentiation between populations and affected the genetic diversity and effective population sizes, in addition to promoting a recent population expansion upstream of the dam, as a consequence of adaptation to the new environment. This study provides the first evidence that hydroelectric dams can promote local adaptation in some fish, such as non-migratory ones.

The Role of Natural Physical, Mechanical, and Biochemical Barriers as Innate Immunity: A Narrative Literature Review

The specialized epithelial outer layer, including the skin and mucosal surfaces, is relatively resistant to most environmental hazards and resistant to infection by disease-causing microorganisms. This literature review aimed to describe the role of natural physical, mechanical, and biochemical barriers in innate immunity. The physical barrier that protects against damage and infection consists of closely related epithelial cells, including the skin and the sheet membranes that line the digestive tract, genitourinary, and breathing. The epithelial surface also provides a biochemical barrier by synthesizing and secreting substances intended to trap or destroy microorganisms (chemicals derived from the epithelium). Mucus, sweat, saliva, tears, and earwax are examples of biochemical secretions that can trap and kill potential disease-causing microorganisms. Microorganisms in the microbiome do not usually cause disease, although some are opportunistic in that they can cause disease if the integrity of the body surface is compromised or the individual's immune or inflammatory systems are damaged. In conclusion, natural barriers include physical, mechanical, and biochemical on the surface of the body and are present from birth to prevent damage by substances in the environment and prevent infection by pathogenic microorganisms.

La Mosca Blanca

Abstract This factsheet for farmers in Nicaragua provides information on whiteflies (Aleyrodidae), which transmit viruses to various crop plants, including tomatoes ( Solanum lycopersicum ), beans and peppers. It includes details about preventive control using natural enemies, physical barriers and resistant plant species, a photo of healthy plants under barrier, as there are no remedial techniques against the virus. Global Plant Clinic

Plastic pollution: why is it a public health problem?

Plastic pollution: why is it a public health problem?

Evolutionary history of the roan antelope across its African range

AbstractAimPhylogeographic studies on savanna ungulates have extensively evaluated genetic patterns mostly related to Pleistocene climatic oscillations. We address this subject through a comprehensive assessment across the pan‐African range of the roan antelope, assessing whether climatic oscillations or natural physical barriers play a predominant role in the evolutionary history of the species. We also address the spatial concordance of the genetic structure with the currently recognized subspecies.LocationSub‐Saharan Africa.TaxonRoan antelope (Hippotragus equinus).MethodsWe genotyped 43 microsatellite loci and sequenced whole‐mitochondrial genomes for 131 individuals across the species' entire African range. We performed spatial analyses of genetic diversity for contemporary and historical samples and calculated overall patterns of genetic differentiation and structure for both marker types. We also estimated the timing of divergence events and demographic trends, correlating these with the species’ biotic attributes as well as abiotic features shaping African savanna habitats.ResultsOur analyses uncovered highly structured clusters and contact zones across the distribution of the roan antelope, including five nuclear groups and four mitochondrial lineages. The north‐west group had the highest level of intra‐group diversity as well as inter‐group divergence and represents the oldest vicariant event. The central and southern groups had the lowest intra‐group diversity with low divergence values separating them, suggesting a more recent ancestry for these groups. All population groups showed signals of demographic stability over time showed signals of demographic stability over a demographic decline during the Holocene.Main conclusionsThe roan antelope exhibits significant population structure across its African range. This structure is largely associated with natural physical barriers, whereas contact zones could more easily be explained by climatic events. Based on estimates of genetic diversity, we propose a West African ancestry for this species with subsequent eastward and southern range expansions, as well as the persistence of stable population numbers within refugia. A general trend of population size decreases likely reflects Holocene extreme climatic events and increased human pressure.

Prediction of the Long-Term Potential Distribution of Cryptorhynchus lapathi (L.) under Climate Change

The poplar and willow borer, Cryptorhynchus lapathi (L.), is a severe worldwide quarantine pest that causes great economic, social, and ecological damage in Europe, North America, and Asia. CLIMEX4.0.0 was used to study the likely impact of climate change on the potential global distribution of C. lapathi based on existing (1987–2016) and predicted (2021–2040, 2041–2080, and 2081–2100) climate data. Future climate data were simulated based on global climate models from Coupled Model Inter-comparison Project Phase 5 (CMIP5) under the RCP4.5 projection. The potential distribution of C. lapathi under historical climate conditions mainly includes North America, Africa, Europe, and Asia. Future global warming may cause a northward shift in the northern boundary of potential distribution. The total suitable area would increase by 2080–2100. Additionally, climatic suitability would change in large regions of the northern hemisphere and decrease in a small region of the southern hemisphere. The projected potential distribution will help determine the impacts of climate change and identify areas at risk of pest invasion in the future. In turn, this will help design and implement effective prevention measures for expanding pest populations, using natural enemies, microorganisms, and physical barriers in very favorable regions to impede the movement and oviposition of C. lapathi.

Chorological and Geochemical Factors of Morphogenesis, Using Deviant Forms of Rana arvalis Nilsson, 1842 as an Example

The frequencies of five abnormal variants of juveniles in populations of the moor frog Rana arvalis in urbanization gradient are analyzed based on 39-year-long monitoring. The data on the limits of occurrences of this deviations in natural conditions are obtained. An increase in the frequency of features under study with the growth of concentration of certain ions, general mineralization, and pH is recorded. Notwithstanding fragmentation of environment and insulation of continuous geographical range, parallelism of the trends in morphological changes in particular isolates is shown. At the same time, the distribution of relatively rare anomalies can be limited by the presence of natural physical barriers.

Narrow hybrid zones in spite of very low population differentiation in neutral markers in an island bird species complex.

Patterns of phenotypic and genic frequencies across hybrid zones provide insight into the origin and evolution of reproductive isolation. The Reunion grey white-eye, Zosterops borbonicus, exhibits parapatrically distributed plumage colour forms across the lowlands of the small volcanic island of Reunion (Mascarene archipelago). These forms meet and hybridize in regions that are natural barriers to dispersal (rivers, lava fields). Here, we investigated the relationship among patterns of differentiation at neutral genetic (microsatellite) markers, phenotypic traits (morphology and plumage colour) and niche characteristics across three independent hybrid zones. Patterns of phenotypic divergence revealed that these hybrid zones are among the narrowest ever documented in birds. However, the levels of phenotypic divergence stand in stark contrast to the lack of clear population neutral genetic structure between forms. The position of the hybrid zones coincides with different natural physical barriers, yet is not associated with steep changes in vegetation and related climatic variables, and major habitat transitions are shifted from these locations by at least 18km. This suggests that the hybrid zones are stabilized over natural dispersal barriers, independently of environmental boundaries, and are not associated with niche divergence. A striking feature of these hybrid zones is the very low levels of genetic differentiation in neutral markers between forms, suggesting that phenotypic divergence has a narrow genetic basis and may reflect recent divergence at a few linked genes under strong selection, with a possible role for assortative mating in keeping these forms apart.

Assessing the Effectiveness of Coastal Foredune Barriers in Reducing Hurricane Washover Sedimentation

ABSTRACT Williams, H., 2018. Assessing the effectiveness of coastal foredune barriers in reducing hurricane washover sedimentation. This study tests the effectiveness of physical barriers in blocking or reducing washover sedimentation in coastal marshes. It is widely assumed that natural and artificial physical barriers, such as foredunes and roads, block or reduce storm overwash. However, there appears to be little documented assessment of this effect. This topic has gained significance recently because of concerns over sea-level rise induced by global warming creating a larger potential threat from storm overwash. Nearshore physical barriers act to protect populations and infrastructure farther inland from storm surge, but they may also reduce sediment delivery to coastal marshlands, slowing their vertical accretion and contributing to their submergence by rising sea level. Consequently, there is a critical need for more information on the effect of physical barriers on marsh sedimentation. Washover sed...

The Natural Limits of Segregation and Re--Integraton: The Case of PosttApartheid South Africa

Racial segregation results from economic, political, and social forces. We propose a new channel: natural geography may have an enabling effect on segregation. Natural physical barriers may enable states, or citizens of powerful in-groups, to partition urban and suburban spaces by race. We study the South African context, in which the fall of Apartheid in 1994 allowed for a rapid influx of black South Africans into previously exclusively white urban areas. We show that the presence of natural physical barriers enabled sustained segregation, differentially retarding the re-integration of diversity into former racial enclaves. We then explore the political consequences of sustained segregation by considering the effect of changes in the white share of the population on political behavior. We find that sustaining segregation leads whites-only areas to become less likely to vote for a non-white party, evidence in favor of recent theories that see racial contact as a positive force.

Tsunami in the Seychelles: Assessing mitigation mechanisms

A spatial statistical model determining the possible tsunami impact mitigation by coastal vegetation developed after the December 2004 earthquake event for Aceh, Indonesia, was adapted and tested under the conditions of the Seychelles in the western Indian Ocean to find out whether comparable protective effects of vegetation existed. The waves generated at the three main populated islands, Mahé, Praslin and La Digue averaged less than 2 m at the shoreline allowing assessment of effects of vegetation in mitigating impact of a low intensity tsunami event. Semi structured interviews with local witnesses of the event, field measurements of local features, as well as secondary data sources provided information on wave height at the shoreline, landscape characteristics as well as tsunami impacts inland, i.e. structural damage and maximum flood distance. Observation points at maximum flood distance and where damage occurred were geo-located and entered into a GIS. Vegetation density and resistance coefficients were determined on site and their spatial distribution through visual interpretation of Google Earth® pre tsunami imagery. Data was analyzed using a generalized linear mixed model, acknowledging the spatial distribution of data. As for Aceh, the results indicated that distance from the settlement to the shoreline was the most important factor to avoid adverse tsunami effects. In contrast to Aceh, a direct effect of coastal vegetation was not observed (p > 0.05). A significant protective effect, however, was apparent through sand dunes, stabilized by vegetation, reducing damage to buildings by up to 30% where initial water height at shoreline was 3 m. Maximum flood distance was not affected by sand dunes but was reduced (p = 0.013) by existing seawalls. A coastal planning that encompasses the promotion and protection of multi-use coastal vegetation, i.e. generating income through tourism, providing food products and protecting natural physical barriers is encouraged in order to enhance local resilience against natural wave events such as those of the 2004 tsunami.

Employing sea-level rise scenarios to strategically select sea turtle nesting habitat important for long-term management at a temperate breeding area

Management strategies to protect endangered species primarily focus on safeguarding habitats currently perceived as important (due to high-density use, rarity or contribution to the biological cycle), rather than sites of future ecological importance. This discrepancy is particularly relevant for species inhabiting beaches and coastal areas that may be lost due to sea-level rise over the next 100years through climate change. Here, we modelled four sea-level rise (SLR) scenarios (0.2, 0.6, 0.9 and 1.3m) to determine the future vulnerability and viability of nesting habitat (six distinct nesting beaches totalling about 6km in length) at a key loggerhead sea turtle (Caretta caretta) rookery (Zakynthos, Greece) in the Mediterranean. For each of the six nesting beaches, we identified (1) the area of beach currently used by turtles, (2) the area of the beach anticipated to become inundated under each SLR, (3) the area of beach anticipated to become unsuitable for nesting under each SLR, (4) the potential for habitat loss under the examined SLR, and (5) the extent to which the beaches may shift in relation to natural (i.e. cliffs) and artificial (i.e. beach front development) physical barriers. Even under the most conservative 0.2m SLR scenario, about 38% (range: 31–48%) total nesting beach area would be lost, while an average 13% (range: 7–17%) current nesting beach area would be lost. About 4km length of nesting habitat (representing 85% of nesting activity) would be lost under the 0.9m scenario, because cliffs prevent landward beach migration. In comparison, while the other 2km of beach (representing 15% nests) is also at high risk, it has the capacity for landward migration, because of an adjoining sand-dune system. Therefore, managers should strengthen actions on this latter area, as a climatically critical safeguard for future sea turtle nesting activity, in parallel to regularly assessing and revising measures on the current high-use nesting habitats of this important Mediterranean loggerhead population.

Rift Valley fever: Real or perceived threat for Zambia?

Rift Valley fever (RVF) in Zambia was first reported in 1974 during an epizootic of cattle and sheep that occurred in parts of Central, Southern and Copperbelt Provinces. In 1990, the disease was documented in nine districts of the provinces of Zambia. In the last two decades, there have been no reports of RVF. This long period without reported clinical disease raises questions as to whether RVF is a current or just a perceived threat. To address this question, World Organisation for Animal Health (OIE) disease occurrence data on RVF for the period 2005−2010 in the Southern Africa Development Community (SADC) was analysed. From the analysis, it was evident that most countries that share a common border with Zambia had reported at least one occurrence of the disease during the period under review. Due to the absence of natural physical barriers between Zambia and most of her neighbours, informal livestock trade and movements is a ubiquitous reality. Analysis of the rainfall patterns also showed that Zambia received rains sufficient to support a mosquito population large enough for high risk of RVF transmission. The evidence of disease occurrence in nearby countries coupled with animal movement, and environmental risk suggests that RVF is a serious threat to Zambia. In conclusion, the current occurrence of RVF in Zambia is unclear, but there are sufficient indications that the magnitude of the circulating infection is such that capacity building in disease surveillance and courses on recognition of the disease for field staff is recommended. Given the zoonotic potential of RVF, these measures are also a prerequisite for accurate assessment of the disease burden in humans.

The Volatility Curse: Revisiting the Paradox of Plenty

The volatility of unanticipated output growth in income per capita is detrimental to long-run development, controlling for initial income per capita, population growth, human capital, investment, openness and natural resource dependence. This effect is significant and robust over a wide range of specifications. We unravel the effects of volatility by opening the black box and conditioning the variance of growth shocks on several country characteristics. Natural resource dependence, physical and institutional barriers to trade and associated policy shocks increase volatility sharply and harm growth through this indirect channel. The robust indirect effect of natural resources through volatility trumps any direct effects on economic development, even if natural resource dependence is measured net of extraction costs. Financial development appears to mitigate the harmful causes of volatility. Our panel data estimation confirms our cross-country results, but we also offer evidence that well developed financial systems amplify the effect of short-term terms-of-trade volatility on macroeconomic volatility.

Editorial and Retrospective 2008

Editorial and Retrospective 2008

Species invasions and the changing biogeography of Australian freshwater fishes

ABSTRACTAim By dissolving natural physical barriers to movement, human‐mediated species introductions have dramatically reshuffled the present‐day biogeography of freshwater fishes. The present study investigates whether the antiquity of Australia's freshwater ichthyofauna has been altered by the widespread invasion of non‐indigenous fish species.Location Australia.Methods Using fish presence–absence data for historical and present‐day species pools, we quantified changes in faunal similarity among major Australian drainage divisions and among river basins of north‐eastern Australia according to the Sørensen index, and related these changes to major factors of catchment disturbance that significantly alter river processes.Results Human‐mediated fish introductions have increased faunal similarity among primary drainages by an average of 3.0% (from 17.1% to 20.1% similarity). Over three‐quarters of the pairwise changes in drainage similarity were positive, indicating a strong tendency for taxonomic homogenization caused primarily by the widespread introduction of Carassius auratus, Gambusia holbrooki, Oncorhynchus mykiss and Poecilia reticulata. Faunal homogenization was highest in drainages subjected to the greatest degree of disturbance associated with human settlement, infrastructure and change in land use. Scenarios of future species invasions and extinctions indicate the continued homogenization of Australian drainages. In contrast, highly idiosyncratic introductions of species in river basins of north‐eastern Australia have decreased fish faunal similarity by an average of 1.4%.Main conclusions We found that invasive species have significantly changed the present‐day biogeography of fish by homogenizing Australian drainages and differentiating north‐eastern river basins. Decreased faunal similarity at smaller spatial scales is a result of high historical similarity in this region and reflects the dynamic nature of the homogenization process whereby sporadic introductions of new species initially decrease faunal similarity across basins. Our study points to the importance of understanding the role of invasive species in defining patterns of present‐day biogeography and preserving the antiquity of Australia's freshwater biodiversity.

The evolution of groundwater quality in France: perspectives for enduring use for human consumption

France is rich in groundwater. It has many aquifers with renewable resources which are estimated at 100 billion m 3/year, of which 3.5 billion m 3, or 60% of the water used in France for human consumption, are withdrawn each year. This practice is justified by the often naturally pure quality of the water and by the regularity of the resource. Nevertheless, free aquifers, in spite of natural physical and geochemical barriers, are not sufficiently protected from anthropic surface contamination and when pollutants reach them, the consequences are never negligible, be it from a sanitary, economic or natural heritage point of view. The most extensive pollution is nitrate contamination. Nitrate concentrations have been increasing constantly over the last 30 years and in some regions have gone over the critical threshold of 50 mg/l which is the European standard, and concentrations of 100 mg/l have been measured in some places. The gravity of other types of pollution—mining, industrial or domestic—is determined by the mineral or organic products involved. The cumulative effect of all of this pollution is serious from various standpoints: from an economic and environmental point of view because aquifers contribute to the maintenance of aquatic life, and for our natural heritage because of the long-term degradation of vast aquifers in some very urban and industrial regions. We might, therefore, question the possible long-term use of aquifers as a source of drinking water.

Alternatives to Synthetic Chemical Insecticides for Use in Crucifer Crops

ABSTRACT Current public concern about the possible adverse effects of agricultural chemicals on health and the environment has generated interest in reducing chemical inputs in vegetable growing. Crucifers are important vegetable crops in Australia and are subjected to attack by lepidopterous pests especially diamondback moth (Plutella xylostella (L.)) and cabbage white butterfly (Pieris rapae (L.)). Control options for cabbage pests reviewed here include use of natural insecticides (mainly plant-based), physical barriers, biological controi, insect sterilization, intercropping, companion planting and host plant resistance. Successful reduced chemical insect control should concentrate on combining several of these options in complete pest management systems.