Parallels,nonparallels, and plasticity in population differentiation of threespine stickleback within a lake

The frequent occurrence of parallel phenotypic divergence in similar habitats is often evoked when emphasizing the role of ecology in adaptive radiation and speciation. However, because phenotypic plasticity can contribute to the observed pattern of divergence, confirmation of divergence at loci underlying phenotypic traits is important for confirming adaptive divergence. In the present study, we examine parallel morphological, neutral, and potentially adaptive genetic divergence of threespine stickleback inhabiting different habitats within a lake. Three genetic clusters best explained the neutral genetic structure within the lake; however, morphological differences were only weakly connected to genetic clusters and there was considerable phenotypic variation within clusters. Among the factors that could contribute to the observed pattern of morphological and genetic divergence are phenotypic plasticity, selective mortality of hybrids, and habitat choice based on morphology. Several loci are identified as outliers indicating divergent selection between the morphs and some parallels in morphological and adaptive genetic divergence are found in stickleback spawning at two lava sites. However, neutral genetic structure indicates considerable genetic connectivity among the two lava sites, and the parallels in morphology may therefore represent selective distribution of phenotypes rather than parallel divergence. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 803–813.     

Do leucocytes reflect condition in nestling burrowing parrots Cyanoliseus patagonus in the wild?

The different leucocyte types are an important part of the immune system. Thus, they have been used in ecological studies to assess immune function and physiological stress in wild birds. It is generally assumed that increased stress and decreased condition are associated with an increase in the ratio of heterophils to lymphocytes, the H/L ratio. We studied leucocyte profiles in relation to body condition in nestling Burrowing Parrots (Cyanoliseus patagonus) in North-eastern Patagonia, Argentina. As in other wild parrots, heterophils were the most numerous leucocyte type, suggesting strong investment into innate immunity. Leucocyte profiles did not change with the age, while nestlings in better body condition increased the number of heterophils. Because the number of lymphocytes was independent of body condition, as a result we observed a positive correlation between body condition and the H/L ratio. The total number of leucocytes relative to erythrocytes increased in nestlings in better body condition, indicating a larger overall investment into immune function in well-nourished nestlings. The observed heterophilic profiles of nestling Burrowing Parrots together with the positive relationship between H/L ratio and body condition may indicate a favoured investment in a robust innate immunity that reduces the risk of infection taking hold in these long-lived birds.     

Modeling brewers' yeast flocculation

Flocculation of yeast cells occurs during the fermentation of beer. Partway through the fermentation the cells become flocculent and start to form flocs. If the environmental conditions, such as medium composition and fluid velocities in the tank, are optimal, the flocs will grow in size large enough to settle. After settling of the main part of the yeast the green beer is left, containing only a small amount of yeast necessary for rest conversions during the next process step, the lagering. The physical process of flocculation is a dynamic equilibrium of floc formation and floc breakup resulting in a bimodal size distribution containing single cells and flocs. The floc size distribution and the single cell amount were measured under the different conditions that occur during full scale fermentation. Influences on flocculation such as floc strength, specific power input, and total number of yeast cells in suspension were studied. A flocculation model was developed, and the measured data used for validation. Yeast floc formation can be described with the collision theory assuming a constant collision efficiency. The breakup of flocs appears to occur mainly via two mechanisms, the splitting of flocs and the erosion of yeast cells from the floc surface. The splitting rate determines the average floc size and the erosion rate determines the number of single cells. Regarding the size of the flocs with respect to the scale of turbulence, only the viscous subrange needs to be considered. With the model, the floc size distribution and the number of single cells can be predicted at a certain point during the fermentation. For this, the bond strength between the cells, the fractal dimension of the yeast, the specific power input in the tank and the number of yeast cells that are in suspension in the tank have to be known. Copyright 1998 John Wiley & Sons, Inc.     

ISOLATED GRAPTOLITES FROM THE LITUIGRAPTUS CONVOLUTUS BIOZONE (SILURIAN, LLANDOVERY) OF DALARNA, SWEDEN

Abstract:  Isolated material of 13 graptolite species from the Aeronian (middle Llandovery) Lituigraptus convolutus Biozone is described. A considerable amount of late astogenetic peridermal thickening is revealed in Normalograptus scalaris and Rivagraptus bellulus . As a result, in the former, thecal morphology is modified from climacograptid to pseudoglyptograptid; in both species, the virgella becomes robust. In Metaclimacograptus minimus and Me. sp., it is shown that the dorsal metathecal wall forms the genicular hood, whereas in N. nikolayevi , the infragenicular wall of the succeeding theca forms the distal thecal apertural margin. Pribylograptus argutus exhibits typical pribylograptid thecae along the length of the available rhabdosome fragments. Characters differentiating Campograptus lobiferus from C. harpago include the greater dorso-ventral width and more rapid increase in dorso-ventral width of the former and the greater recurving of distal thecae and presence of thecal spines/processes on all thecae of the latter. Lituigraptus convolutus has rastritiform thecae proximally; thecal apertures throughout the rhabdosome are crescentic and laterally expanded.     

Limitations to the inference of gene flow at regional geographic scales–an example from the Pieris napi group (Lepidoptera: Pieridae) in Europe

We used hierarchical and pairwise F-statistics to describe genetic differentiation and infer gene flow (M) on local and regional scales within and among parapatric European butterfly taxa in the Pieris napi (L.) group. Within-population allozyme variability is consistently high, and local effective population sizes are inferred to be in the thousands of individuals. The pairwise analysis yields an average neighbourhood area of radius 3.5 km. Among populations within most regions, differentiation is low and M > 2 effective individuals population^-1generation^-1. Pairwise comparisons within the brilannica group show a disjunction indicating that it is out of equilibrium, perhaps as a result of secondary contact between highland and lowland groups. Comparison between meridionalis groups on mainland Italy and Corsica yields M > 12; this is surely loo high and lack of equilibrium resulting from initial colonization is suspected. The hierarchical analysis indicates that 23 ≤0020M≤ 88 among the taxa napi, bryoniae and meridionalis that meet in hybrid zones; no effective gene flow barrier exists among them. This high estimate could also result from recent primary contact, but such a genetic barrier should produce the ‘edge effects' seen in population genetic simulations, and no evidence of this was found among geographically close samples of napi and bryoniae populations from Switzerland. Studies of gene flow among geographic regions are greatly limited by the equilibrium assumption, though studies of local differentiation are much less so. Population studies of gene flow on local scales at regional boundaries provide limited means of testing the equilibrium assumption, and both regional and local analyses provide testable predictions about local population structure. When the equilibrium assumption is not upheld, local patterns at regional boundaries can provide historical information about primary vs. secondary contact.     

The innate immune receptor MDA5 limits rotavirus infection but promotes cell death and pancreatic inflammation

Melanoma differentiation‐associated protein 5 (MDA5) mediates the innate immune response to viral infection. Polymorphisms in IFIH1, the gene coding for MDA5, correlate with the risk of developing type 1 diabetes (T1D). Here, we demonstrate that MDA5 is crucial for the immune response to enteric rotavirus infection, a proposed etiological agent for T1D. MDA5 variants encoded by minor IFIH1 alleles associated with lower T1D risk exhibit reduced activity against rotavirus infection. We find that MDA5 activity limits rotavirus infection not only through the induction of antiviral interferons and pro‐inflammatory cytokines, but also by promoting cell death. Importantly, this MDA5‐dependent antiviral response is specific to the pancreas of rotavirus‐infected mice, similar to the autoimmunity associated with T1D. These findings imply that MDA5‐induced cell death and inflammation in the pancreas facilitate progression to autoimmune destruction of pancreatic β‐cells.     

Effect of NSAIDs and Diuretics on Nephrogenesis in an Ex Vivo Embryogenic Kidney Model

The kidney is one of the key organs in clearing foreign compounds. The effects of drugs on the developing kidney are relatively unknown. We studied the direct effect of furosemide, hydrochlorothiazide, ibuprofen, and indomethacin on kidney development in an ex vivo embryonic kidney model. At embryonic day 13, metanephroi were dissected from mice and cultured in control media or media supplemented with various clinically relevant concentrations of drugs. The ureteric tree was visualized by whole‐mount staining and branching was evaluated by counting. Additionally, gene expression levels of Wt1, Sox9, Bmp7, Fgf8, and Gdnf were investigated. No distinct differences were noted on either ureteric tip development or gene expression analysis for each drug after 24 hr of exposure. Even though short‐term exposure to clinically relevant concentrations seems not to disturb renal development, future research is needed to study prolonged or repeated exposures.     

Subalpine grassland carbon dioxide fluxes indicate substantial carbon losses under increased nitrogen deposition,but not at elevated ozone concentration

Ozone (O₃) and nitrogen (N) deposition affect plant carbon (C) dynamics and may change ecosystem C‐sink/‐source properties. We studied effects of increased background [O₃] (up to [ambient] × 2) and increased N deposition (up to +50 kg ha^?1 a^?1) on mature, subalpine grassland during the third treatment year. During 10 days and 13 nights, distributed evenly over the growth period of 2006, we measured ecosystem‐level CO₂ exchange using a static cuvette. Light dependency of gross primary production (GPP) and temperature dependency of ecosystem respiration rates (R_eco) were established. Soil temperature, soil water content, and solar radiation were monitored. Using R_eco and GPP values, we calculated seasonal net ecosystem production (NEP), based on hourly averages of global radiation and soil temperature. Differences in NEP were compared with differences in soil organic C after 5 years of treatment. The high [O₃] had no effect on aboveground dry matter productivity (DM), but seasonal mean rates of both R_eco and GPP decreased ca. 8%. NEP indicated an unaltered growing season CO₂–C balance. High N treatment, with a +31% increase in DM, mean R_eco increased ca. 3%, but GPP decreased ca. 4%. Consequently, seasonal NEP yielded a 53.9 g C m^?2 (±22.05) C loss compared with control. Independent of treatment, we observed a negative NEP of 146.4 g C m^?2 (±15.3). Carbon loss was likely due to a transient management effect, equivalent to a shift from pasture to hay meadow and a drought effect, specific to the 2006 summer climate. We argue that this resulted from strongly intensified soil microbial respiration, following mitigation of nutrient limitation. There was no interaction between O₃ and N treatments. Thus, during the 2006 growing season, the subalpine grassland lost >2% of total topsoil organic C as respired CO₂, with increased N deposition responsible for one‐third of that loss.