Sexual and natural selection in a continuous time model

We call sexual selection the selection attributable only to the mating system, to distinguish it from other forms of selection (i.e. viability or fertility) which we call natural selection. We introduce a new continuous time model of sexual selection and we explore its relationship with natural selection. This model is an extension of the model proposed by Hoppensteadt [Hoppensteadt, F., 1977. Mathematical Theories of Populations: Demographics, Genetics and Epidemics. SIAM] and considers the three genotypes determined by two alleles in a locus, each with its own mortality and fertility rates, and the respective mating preferences.     

Statistical accuracy for estimations of large wood blockage in a reservoir environment

Environmental Fluid Mechanics - The blockage of weirs or bridges by in-stream wood can reduce the flood discharge capacity, leading to hazardous situations. To assess the related risk, blocking...     

Factors driving the seasonal dynamics of Pseudo-nitzschia species and domoic acid at mussel farming in the SW Mediterranean Sea

ABSTRACT

The seasonal variations in Pseudo-nitzschia species and domoic acid (DA) concentration were investigated, at three shellfish farms in SW coastal Mediterranean. In parallel, the toxicity of mussels was tested. Two distinct groups of species were enumerated according to morphology and size (Pseudo-nizschia delicatissima and P. seriata groups). DA was detected over a nine-week period from July to October 2012 in the Lagoon, with a maximum concentration recorded in July (12.71?ng?DA?L^?1). DA was positively correlated with the presence of P. seriata-group and P. delicatissima-group and was mostly occurred during P limitation period in seawater. No DA was found in mussels that were collected during the period of DA absence in seawater. Our results suggest that temperature, salinity, inorganic and organic nutrients were significant for the seasonal dynamics of P. seriata and P. delicatissima groups, but that the P limitation was the most driving factor for DA production in these areas. The relative influence of environmental factors should be further studied to better understand the recent surfacing of massive blooms of toxigenic Pseudo-nitzschia in SW Mediterranean coast.     

SIMULATING FLOW IN REGIONAL WETLANDS WITH THE MODFLOW WETLANDS PACKAGE1

ABSTRACT: As part of the Comprehensive Everglades Restoration Plan (CERP), various water supply projects have been proposed in a region located between the Miami metropolitan area and the extensive regional wetland systems that are part of the Everglades or remnant Everglades. A ground water flow model of the surficial aquifer within northern Miami‐Dade County was constructed using MODFLOW to evaluate the effects of these projects on water levels in the wetlands and the underlying surficial aquifer. The new Wetlands package was used to conjunctively simulate overland flow through these wetlands and the shallow ground water system. Comparisons of simulated to measured ground water levels and wetland stages were very satisfactory, where computed and measured water levels agreed within 0.5 ft over most of the period of record at nearly all of the monitoring sites. Temporal trends in water levels were also replicated. It was concluded that the assumptions and methodologies inherent to the Wetlands package were suitable for simulating regional wetland hydrology within the Everglades area.     

Heavy metal contamination in sediments of an artificial reservoir impacted by long-term mining activity in the Almadén mercury district (Spain)

Sediments from the Castilseras reservoir, located downstream on the Valdeazogues River in the Almadén mercury district, were collected to assess the potential contamination status related to metals(oids) associated with river sediment inputs from several decommissioned mines. Metals(oids) concentrations in the reservoir sediments were investigated using different physical and chemical techniques. The results were analyzed by principal component analysis (PCA) to explain the correlations between the sets of variables. The degree of contamination was evaluated using the enrichment factor (EF) and the geoaccumulation index (Igeo). PCA revealed that the silty fraction is the main metals(oids) carrier in the sediments. Among the potentially harmful elements, there is a group (Al, Cr, Cu, Fe, Mn, Ni, and Zn) that cannot be strictly correlated to the mining activity since their concentrations depend on the lithological and edaphological characteristics of the materials. In contrast, As, Co, Hg, Pb, and S showed significant enrichment and contamination, thus suggesting relevant contributions from the decommissioned mines through fluvial sediment inputs. As far as Hg and S are concerned, the high enrichment levels pose a question concerning the potential environmental risk of transfer of the organic forms of Hg (mainly methylmercury) from the bottom sediments to the aquatic food chain.     

Potential of microalgae as biopesticides to contribute to sustainable agriculture and environmental development

The loss of yields from agricultural production due to the presence of pests has been treated over the years with synthetic pesticides, but the use of these substances negatively affects the environment and presents health risks for consumers and animals. The development of agroecological systems using biopesticides represents a safe alternative that contributes to the reduction of agrochemical use and sustainable agriculture. Microalgae are able to biosynthesize a number of metabolites with potential biopesticidal action and can be considered potential biological agents for the control of harmful organisms to soils and plants. The present work aims to provide a critical perspective on the consequences of using synthetic pesticides, offering as an alternative the biopesticides obtained from microalgal biomass, which can be used together with the implementation of environmentally friendly agricultural systems.     

Arsenic chemistry in the rhizosphere of Pteris vittata L. and Nephrolepis exaltata L

This greenhouse experiment evaluated the influence of arsenic uptake by arsenic hyperaccumulator Pteris vittata L. and non-arsenic hyperaccumulator Nephrolepis exaltata L. on arsenic chemistry in bulk and rhizosphere soil. The plants were grown for 8 weeks in a rhizopot with a soil containing 105 mg kg(-1) arsenic. The soil arsenic was fractionated into five fractions with decreasing availability: non-specifically bound (N), specifically bound (S), amorphous hydrous-oxide bound (A), crystalline hydrous-oxide bound (C), and residual (R). P. vittata produced larger plant biomass (7.38 vs. 2.32 mg plant(-1)) and removed more arsenic (2.61 vs. 0.09 mg pot(-1) arsenic) than N. exaltata. Plant growth reduced water-soluble arsenic, and increased soil pH (P. vittata only) in the rhizosphere soil. P. vittata was more efficient than N. exaltata to access arsenic from all fractions (39-64% vs. 5-39% reduction). However, most of the arsenic taken up by both plants was from the A fraction (67-77%) in the rhizosphere soil, the most abundant (61.5%) instead of the most available (N fraction).     

Molecular receptive ranges of olfactory receptor neurones responding selectively to terpenoids, aliphatic green leaf volatiles and aromatic compounds, in the strawberry blossom weevil Anthonomus rubi

Summary. An important question in insect-plant interactions is which of the numerous plant compounds contribute to the perception of odour qualities in herbivorous insects and are likely to be used as cues in host-searching behaviour. In order to identify which plant-produced volatiles the strawberry blossom weevil Anthonomus rubi detects, we have used electrophysiological recordings from single olfactory neurones linked to gas chromatography and mass spectrometry. We here present 15 receptor neurone types specialised for naturally produced compounds present in the host and nonhost plants and two types for two aggregation pheromone components. The active compounds were terpenoids, aromatic and aliphatic esters, alcohols and aldehydes, some of which are induced by feeding activity of the weevils. The neurones were characterised by a strong response to one or two primary odorants and weaker responses to a few others having similar chemical structure. With one exception, the molecular receptive range of each neurone type was within one chemical group. Enantiomers of linalool separated on a chiral column activated two neurone types with different enantioselectivity. Inhibition by linalool of another neurone type, excited by α-pinene, indicated an additional mechanism for coding the information about this compound. Altogether, detection of 54 compounds by olfactory receptor neurones is shown, of which 40 have been chemically identified in this study. Thus A. rubi has the ability to detect a large number of odorants that may be used in host selection behaviour.     

Design of water quality monitoring networks with two information scenarios in tropical Andean basins

Design and redesign of water quality monitoring networks were evaluated for two similarly sized watersheds in the tropical Andes via optimization techniques using geographic information system technology (GIS) and a matter-element analysis of 5-day biological oxygen demand (BOD₅) and total suspended solids (TSS). This resulted in a flexible, objectively based design for a 1128-km² watershed without prior water quality data (La Miel River), and a network redesign of a 1052-km² watershed with historical water quality monitoring (Chinchiná River). Monitoring design for the undocumented basin incorporated mathematical expressions for physical, anthropological, and historical factors—and was based on clear objectives for diagnosis and intervention of water pollution. Network redesign identified network redundancy, which resulted in a 64% reduction in the number of water quality monitoring stations along the channel, and a 78% reduction of stations throughout the basin. Most tropical drainage basins throughout the world have little to no prior water quality data. But even in well-studied drainage basins like the Chinchiná River, which is among the most thoroughly studied basins in Colombia, redesign of historical and existing monitoring networks will become a standard tool to advance the restoration of polluted surface waters, not only in Colombia, but also throughout the world.     

Polyhydroxyalkanoates: Biosynthesis from Alternative Carbon Sources and Analytic Methods: A Short Review

Journal of Polymers and the Environment - In recent decades, the global accumulation of plastics and the resulting pollution, as well as the increase in the price of oil, have driven studies aimed...