Copulation duration,but not paternity share,potentially mediates inbreeding avoidance in Drosophila montana

Studying the incidence of inbreeding avoidance is important for understanding the evolution of mating systems, especially in the context of mate choice for genetic compatibility. We investigated whether inbreeding avoidance mechanisms have evolved in the malt fly, Drosophila montana, by measuring mating latency (a measure of male attractiveness), copulation duration, days to remating, offspring production, and the proportion of offspring sired by the first (P₁) and second (P₂) male to mate in full-sibling and unrelated pairs. SNP markers were used for paternity analysis and for calculating pairwise relatedness values (genotype sharing) between mating pairs. We found 18 % inbreeding depression in egg-to-adult viability, suggesting that mating with close relatives is costly. Copulation duration was shorter between previously mated females and their brothers than with unrelated males. Based on an earlier study, shorter copulation is likely to decrease the number of inbred progeny by decreasing female remating time. However, shorter copulations did not lead to lower paternity (P₂) of full-sibling males. Progeny production of double-mated females was lower when the second male was a full-sibling as compared to an unrelated male, but we could not distinguish between inbreeding depression and lower female reproductive effort after mating with a relative. Relatedness estimates based on 34 SNPs did not detect any quantitative effect of relatedness variation on copulation duration and progeny production. We suggest that inbreeding depression has been strong enough to select for inbreeding avoidance mechanisms in our Finnish D. montana population.     

Organic compounds in water extracts of coal: links to Balkan endemic nephropathy

The Pliocene lignite hypothesis is an environmental hypothesis that has been proposed to explain the etiology of Balkan endemic nephropathy (BEN). Aqueous leaching experiments were conducted on a variety of coal samples in order to simulate groundwater leaching of organic compounds, and to further test the role of the Pliocene lignite hypothesis in the etiology of BEN. Experiments were performed on lignite coal samples from endemic BEN areas in Romania and Serbia, and lignite and bituminous coals from nonendemic regions in Romania and the USA. Room temperature, hot water bath, and Soxhlet aqueous extraction experiments were conducted between 25 and 80 °C, and from 5 to 128 days in duration. A greater number of organic compounds and in higher concentrations were present in all three types of leaching experiments involving endemic area Pliocene lignite samples compared to all other coals examined. A BEN causing molecule or molecules may be among phenols, PAHs, benzenes, and/or lignin degradation compounds. The proposed transport pathway of the Pliocene lignite hypothesis for organic compound exposure from endemic area Pliocene lignite coals to well and spring drinking water, is likely. Aromatic compounds leached by groundwater from Pliocene lignite deposits in the vicinity of endemic BEN areas may play a role in the etiology of the disease. A better understanding of organic compounds leached by groundwater from Pliocene lignite deposits may potentially lead to the identification and implementation of effective strategies for the prevention of exposure to the causative agent(s) for BEN, and in turn, prevention of the disease.     

Numerical modelling of horizontal sediment-laden jets

Sediment-laden turbulent flows are commonly encountered in natural and engineered environments. It is well known that turbulence generates fluctuations to the particle motion, resulting in modulation of the particle settling velocity. A novel stochastic particle tracking model is developed to predict the particle settling out and deposition from a sediment-laden jet. Particle velocity fluctuations in the jet flow are modelled from a Lagrangian velocity autocorrelation function that incorporates the physical mechanism leading to a reduction of settling velocity. The model is first applied to study the settling velocity modulation in a homogeneous turbulence field. Consistent with basic experiments using grid-generated turbulence and computational fluid dynamics (CFD) calculations, the model predicts that the apparent settling velocity can be reduced by as much as 30 % of the stillwater settling velocity. Using analytical solution for the jet mean flow and semi-empirical RMS turbulent velocity fluctuation and dissipation rate profiles derived from CFD predictions, model predictions of the sediment deposition and cross-sectional concentration profiles of horizontal sediment-laden jets are in excellent agreement with data. Unlike CFD calculations of sediment fall out and deposition from a jet flow, the present method does not require any a priori adjustment of particle settling velocity.     

Deconstructing an assemblage of “turtle” barnacles: species assignments and fickle fidelity in Chelonibia

Barnacles in the genus Chelonibia are commensal with a variety of motile marine animals including sea turtles, crustaceans, and sirenians. We conducted a worldwide molecular phylogenetic survey of Chelonibia collected from nearly all known hosts to assess species relationships, host-fidelity, and phylogeographic structure. Using DNA sequences from a protein-coding mitochondrial gene (COI), a mitochondrial rRNA gene (12S), and one nuclear rRNA gene (28S), we found that of four species, three (C. testudinaria, C. patula, and C. manati) are genetically indistinguishable. In addition, we show each utilizes a rare androdioecious mode of reproduction involving complemental males. In contrast, the fourth species (C. caretta), which is hermaphroditic and specializes on turtles, is genetically distinct—leading to the conclusion that the three former taxa are morphotypes of the same species and should be synonymized under C. testudinaria. Phylogenetic analysis resulted in three geographic clades (Atlantic, Indian Ocean/western Pacific, and eastern Pacific) with haplotype parsimony networks revealing no shared haplotypes among geographic regions. Analysis of molecular variance detected significant differences among sequences by region (p < 0.005); conversely, there were no significant differences among sequences when grouped by host or taxonomic designation. Average pairwise genetic distances were lower between the eastern Pacific and Atlantic clades (0.053 ± 0.006) than between the eastern Pacific and Indian Ocean/western Pacific clades (0.073 ± 0.008), suggesting Atlantic and eastern Pacific populations were connected more recently, perhaps until the rise of the Isthmus of Panama. Host use by Chelonibia morphotypes is discussed along with speculation on possible ancestral hosts and support for a “turtle-first” hypothesis.     

Spatial and social connectivity of fish-eating “Resident” killer whales (Orcinus orca) in the northern North Pacific

The productive North Pacific waters of the Gulf of Alaska, Aleutian Islands and Bering Sea support a high density of fish-eating “Resident” type killer whales (Orcinus orca), which overlap in distribution with commercial fisheries, producing both direct and indirect interactions. To provide a spatial context for these interactions, we analyzed a 10-year dataset of 3,058 whale photo-identifications from 331 encounters within a large (linear ~4,000 km) coastal study area to investigate the ranging and social patterns of 532 individually identifiable whales photographed in more than one encounter. Although capable of large-scale movements (maximum 1,443 km), we documented ranges generally <200 km, with high site fidelity across summer sampling intervals and also re-sightings during a winter survey. Bayesian analysis of pair-wise associations identified four defined clusters, likely representing groupings of stable matrilines, with distinct ranging patterns, that combined to form a large network of associated whales that ranged across most of the study area. This provides evidence of structure within the Alaska stock of Resident killer whales, important for evaluating ecosystem and fisheries impacts. This network included whales known to depredate groundfish from longline fisheries, and we suggest that such large-scale connectivity has facilitated the spread of depredation.     

Individual trophic specialisation and niche segregation explain the contrasting population trends of two sympatric otariids

Individual specialisation is increasingly recognised to be an ecological and evolutionary process having important consequences for population dynamics of vertebrates. The South American fur seal (SAFS) and the South American sea lion (SASL) are two otariid species with similar ecology that coexist in sympatry in the Uruguayan coast. These two species have contrasting trends and widely different population sizes. The underlying reasons for these population trends, unique in their geographical ranges, remain unknown. We studied the foraging ecology of these otariid species over 2 years at the individual- and population levels using the isotopic ratios (δ¹³C–δ¹⁵N) in whiskers of both sexes. We compared the isotope ratios between species and sexes and used several metrics to characterise the degree of overlap and distinctiveness in the use of isotopic niche space at the individual- and population levels. Interspecific trophic niche overlap was minimal, thus ruling out interspecific competition as the cause for the contrasting population trends of both species. At the intraspecific level, both species had sexual segregation in their foraging areas, but each species had a large overlap in the isotopic niches between sexes. While SAFS had a wider niche and generalist individuals, SASL had the narrower niche with a higher degree of individual specialisation. Behavioural constraints during the breeding season, intraspecific competition and a major dependence on resources of the Uruguayan coastal shelf may explain why SASL had a higher trophic individual specialisation and a larger vulnerability in a heavily exploited habitat by fisheries and, by consequence, a locally declining population trend.     

Waves and turbulence in katabatic winds

The measurements taken during the Vertical Transport and Mixing Experiment (VTMX, October, 2000) on a northeastern slope of Salt Lake Valley, Utah, were used to calculate the statistics of velocity fluctuations in a katabatic gravity current in the absence of synoptic forcing. The data from ultrasonic anemometer-thermometers placed at elevations 4.5 and 13.9 m were used. The contributions of small-scale turbulence and waves were isolated by applying a high-pass digital (Elliptical) filter, whereupon the filtered quantities were identified as small-scale turbulence and the rest as internal gravity waves. Internal waves were found to play a role not only at canonical large gradient Richardson numbers $(\overline{\hbox {Ri}_\mathrm{g} } >1)$ , but sometimes at smaller values $(0.1 < \overline{\hbox {Ri}_\mathrm{g}}<1)$ , in contrast to typical observations in flat-terrain stable boundary layers. This may be attributed, at least partly, to (critical) internal waves on the slope, identified by Princevac et al. [1], which degenerate into turbulence and help maintain an active internal wave field. The applicability of both Monin-Obukhov (MO) similarity theory and local scaling to filtered and unfiltered data was tested by analyzing rms velocity fluctuations as a function of the stability parameter z/L, where L is the Obukhov length and z the height above the ground. For weaker stabilities, $\hbox {z/L}<1$ , the MO similarity and local scaling were valid for both filtered and unfiltered data. Conversely, when $\hbox {z/L}>1$ , the use of both scaling types is questionable, although filtered data showed a tendency to follow local scaling. A relationship between z/L and $\overline{\hbox {Ri}_\mathrm{g} }$ was identified. Eddy diffusivities of momentum $\hbox {K}_\mathrm{M}$ and heat $\hbox {K}_\mathrm{H}$ were dependent on wave activities, notably when $\overline{\hbox {Ri}_\mathrm{g} } > 1$ . The ratio $\hbox {K}_{\mathrm{H}}/\hbox {K}_{\mathrm{M}}$ dropped well below unity at high $\overline{\hbox {Ri}_\mathrm{g} }$ , in consonance with previous laboratory stratified shear layer measurements as well as other field observations.     

Food allocation rules vary with age and experience in a cooperatively breeding parrot

Although it is known that parents can differ in their optimal resource allocation to offspring in size-structured broods, the mechanisms determining differences in allocation rules of carers are not yet clarified. In cooperatively breeding species, breeders and non-reproductive helpers often differ in their fitness payoffs of providing care and in their breeding experience. Cooperative breeders thus provide an appropriate system to examine two hypotheses originally proposed to explain differences in food allocation among parents: (i) food allocation between carers differs because of the distinct cost-benefit ratio of selective feeding (i.e. breeders and helpers are expected to differ in food allocation) and (ii) carers differ in their ability to feed selectively (i.e. differences in food allocation are expected between experienced adults and inexperienced yearlings). We compared feeding rates with which breeders, old helpers and yearling helpers provisioned nestlings of different hatching rank. The influence of experience upon food allocation was further assessed by comparing food allocation of yearlings early and late during nesting. We show that allocation rules differ between age classes because breeders and old helpers fed the youngest chicks most, whereas yearlings showed the opposite pattern. The role of experience was supported by the fact that yearlings adjusted food allocation to that observed in experienced adults during the breeding season. We thus suggest that food allocation in El Oro parakeets depends either on differential skills of adults to transfer food to the youngest chick or on their ability to recognize nestling needs.     

Linking marine predator diving behavior to local prey fields in contrasting habitats in a subarctic glacial fjord

Foraging theory predicts that animals will adjust their foraging behavior in order to maximize net energy intake and that trade-offs may exist that can influence their behavior. Although substantial advances have been made with respect to the foraging ecology of large marine predators, there is still a limited understanding of how predators respond to temporal and spatial variability in prey resources, primarily due to a lack of empirical studies that quantify foraging and diving behavior concurrently with characteristics of prey fields. Such information is important because changes in prey availability can influence the foraging success and ultimately fitness of marine predators. We assessed the diving behavior of juvenile female harbor seals (Phoca vitulina richardii) and prey fields near glacial ice and terrestrial haulout sites in Glacier Bay (58°40′N, ?136°05′W), Alaska. Harbor seals captured at glacial ice sites dived deeper, had longer dive durations, lower percent bottom time, and generally traveled further to forage. The increased diving effort for seals from the glacial ice site corresponded to lower prey densities and prey at deeper depths at the glacial ice site. In contrast, seals captured at terrestrial sites dived shallower, had shorter dive durations, higher percent bottom time, and traveled shorter distances to access foraging areas with much higher prey densities at shallower depths. The increased diving effort for seals from glacial ice sites suggests that the lower relative availability of prey may be offset by other factors, such as the stability of the glacial ice as a resting platform and as a refuge from predation. We provide evidence of differences in prey accessibility for seals associated with glacial ice and terrestrial habitats and suggest that seals may balance trade-offs between the costs and benefits of using these habitats.     

Mineralogical variables that control the antibacterial effectiveness of a natural clay deposit

As antibiotic-resistant bacterial strains emerge and pose increased global health risks, new antibacterial agents are needed as alternatives to conventional antimicrobials. Naturally occurring antibacterial clays have been identified which are effective in killing antibiotic-resistant bacteria. This study examines a hydrothermally formed antibacterial clay deposit near Crater Lake, OR (USA). Our hypothesis is that antibacterial clays buffer pH and Eh conditions to dissolve unstable mineral phases containing transition metals (primarily Fe²⁺), while smectite interlayers serve as reservoirs for time release of bactericidal components. Model pathogens (Escherichia coli ATCC 25922 and Staphylococcus epidermidis ATCC 14990) were incubated with clays from different alteration zones of the hydrothermal deposit. In vitro antibacterial susceptibility testing showed that reduced mineral zones were bactericidal, while more oxidized zones had variable antibacterial effect. TEM images showed no indication of cell lysis. Cytoplasmic condensation and cell wall accumulations of <100 nm particles were seen within both bacterial populations. Electron energy loss analysis indicates precipitation of intracellular Fe³⁺-oxide nanoparticles (<10 nm) in E. coli after 24 h. Clay minerals and pyrite buffer aqueous solutions to pH 2.5–3.1, Eh > 630 mV and contain elevated level (mM) of soluble Fe (Fe²⁺ and Fe³⁺) and Al³⁺. Our interpretation is that rapid uptake of Fe²⁺ impairs bacterial metabolism by flooding the cell with excess Fe²⁺ and overwhelming iron storage proteins. As the intracellular Fe²⁺ oxidizes, it produces reactive oxygen species that damage biomolecules and precipitates Fe-oxides. The ability of antibacterial clays to buffer pH and Eh in chronic non-healing wounds to conditions of healthy skin appears key to their healing potential and viability as an alternative to conventional antibiotics.