Testing ecological and behavioral correlates of nest predation

Variation in nest predation rates among bird species are assumed to reflect differences in risk that are specific to particular nest sites. Theoretical and empirical studies suggest that parental care behaviors can evolve in response to nest predation risk and thereby differ among ecological conditions that vary in inherent risk. However, parental care also can influence predation risk. Separating the effects of nest predation risk inherent to a nest site from the risk imposed by parental strategies is needed to understand the evolution of parental care. Here we identify correlations between risks inherent to nest sites, and risk associated with parental care behaviors, and use an artificial nest experiment to assess site-specific differences in nest predation risk across nesting guilds and between habitats that differed in nest predator abundance. We found a strong correlation between parental care behaviors and inherent differences in nest predation risk, but despite the absence of parental care at artificial nests, patterns of nest predation risk were similar for real and artificial nests both across nesting guilds and between predator treatments. Thus, we show for the first time that inherent risk of nest predation varies with nesting guild and predator abundance independent of parental care.     

The effects of habitat complexity on aggression and fecundity in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Female zebrafish housed in aquaria with spatial complexity (plastic plants) over a 13–16-week period showed reduced levels of aggressive behavior compared to females in bare tanks. In tanks with plants, there was no relationship between levels of aggression and fecundity but, in bare tanks, females experiencing the highest levels of aggression showed reduced fecundity. Our results suggest that it may be beneficial, when maintaining zebrafish at moderate to high densities or working with especially aggressive strains, to house them in spatially complex conditions.     

Effect of indoleamine dioxygenase-1 deficiency and kynurenine pathway inhibition on murine cerebral malaria

Cerebral malaria (CM) can be a fatal manifestation of Plasmodium falciparum infection. In this study, two different approaches were used to examine the role of indoleamine 2,3-dioxygenase-1 (IDO-1) and its metabolites in the development of murine CM. Mice genetically deficient in IDO-1 were not protected against CM, but partial protection was observed in C57BL/6 mice treated with Ro 61-8048, an inhibitor of kynurenine-3-hydroxylase. This protection was associated with suppressed levels of picolinic acid (PA) within the brain, but not with changes in the levels of kynurenic acid (KA) or quinolinic acid (QA). These data suggest that although IDO-1 is not directly involved in the pathogenesis of CM in C57BL/6 mice, the production of the kynurenine pathway metabolite PA may contribute to the development of murine CM.     

Temporal and spatial dispersal of cladobotryum conidia in the controlled environment of a mushroom growing room

Cladobotryum spp. are responsible for cobweb disease of mushrooms. In two commercial and one experimental mushroom-growing room, Cladobotryum conidia were released into the air in direct response to physical disturbance of disease colonies during either crop watering or treatment by covering with salt to 10 mm. Conidia were detected using a Burkard spore trap or agar-based trap plates. A maximum concentration of approximately 25,000 conidia m(-3) was recorded in a small (75-m(3)) experimental growing room in the hour following the salting of 16 cobweb patches (0.55 m(2)). Concentrations of 100 and 40 conidia m(-3) were recorded in the two larger commercial growing rooms in the hour following the salting of 18 and 11 patches of cobweb (diameter, approximately 50 to 200 mm), respectively. In controlled experiments, disturbed conidia were dispersed rapidly throughout a small growing room, with 91 to 97% of conidia settling out within 15 min. Eighty-five percent of conidia settled out within a 0.5-m radius when air-conditioning fans were switched off, consistent with airborne spore dispersal. Alternative methods for treating diseased areas to minimize conidial release and distribution were investigated and included covering disease colonies with damp paper tissue prior to salt application (tissue salting) and holding a dust extractor above disease colonies during salt application. Both methods resulted in no detectable airborne conidia, but the tissue paper salting technique was more convenient. Prevention of airborne conidial release and distribution is essential to avoid mushroom spotting symptoms, secondary colonies, and early crop termination.     

Analysis of allelic variants in the catalase gene in patients with the skin depigmenting disorder vitiligo

Vitiligo is an acquired hypomelanotic skin disorder characterised by circumscribed depigmented macules resulting from the loss of functional melanocytes from the cutaneous epidermis. Conditions that might result in epidermal oxidative stress and consequently damage to pigment cells have been reported in the skin of vitiligo patients, including low catalase activity and increases in hydrogen peroxide levels. However, the cause of the decrease in catalase activity has not been equivocally determined. Several allelic variants in the catalase gene, a number of which have deleterious effects upon the expression or function of the enzyme, have been described and the aim of the present work was to assess the relevance of catalase gene variants in patients with vitiligo. Associations between ten separate allelic variants in the catalase gene and a predisposition to vitiligo were investigated in case-control studies with 166 English patients and 169 ethnically-matched controls using DNA sequencing and restriction fragment length polymorphism-polymerase chain reaction methods. Of the ten allelic variants analysed, only a C/T single nucleotide polymorphism in exon 9 of the catalase gene was associated with vitiligo. The C/T genotype was significantly over-represented in the vitiligo patient group compared with the control cohort. Of 166 vitiligo genotypes, 66 (39.8%) had the C/T variant compared to 45/169 (26.6%) control genotypes (P = 0.030). No evidence for an association between other allelic variants in the catalase gene and vitiligo susceptibility was found. The low catalase activity in vitiligo patient epidermis is more likely to result from environmental conditions such as inhibitory levels of hydrogen peroxide rather than allelic variations in the catalase gene which affect either expression or function of the enzyme.     

Three-dimensional mid-domain predictions: geometric constraints in North American amphibian, bird, mammal and tree species richness patterns

The "mid-domain effect" (MDE) has received much attention as a candidate explanation for patterns in species richness over large geographic areas. Mid-domain models generate a central peak in richness when species ranges are placed randomly within a bounded geographic area (i.e. the domain). Until now, domain limits have been described mostly in one-dimension, usually latitude or elevation, and only occasionally in two-dimensions. Here we test 1-D, 2-D and, for the first time, 3-D mid-domain models and assess the effects of geometric constraints on species richness in North American amphibian, bird, mammal and tree species. Using spatially lagged simultaneous autoregressive models, empirical richness was predicted quite well by the mid-domain predictions and the spatial autoregressive term (45–92% R²). However, our results show that empirical species richness peaks do deviate from those of the MDE predictions in 3 dimensions. Variation explained (R²) by MDE predictions generally increased with increasing mean range size of the different biotic groups (from amphibian, to tree, mammal and finally bird data), and decreased with increasing dimensions being accounted for in the models. The results suggest geometric constraints alone can explain much of the variation in species richness with elevation, specifically with respect to the larger-range taxa, birds and mammals. Our analysis addresses many of the recent methodological criticisms directed at studies testing the MDE, and our results support the hypothesis that species diversity patterns are influenced by geometric constraints.     

Mutations in pimE restore lipoarabinomannan synthesis and growth in a Mycobacterium smegmatis lpqW mutant

Lipoarabinomannans (LAMs) and phosphatidylinositol mannosides (PIMs) are abundant glycolipids in the cell walls of all corynebacteria and mycobacteria, including the devastating human pathogen Mycobacterium tuberculosis. We have recently shown that M. smegmatis mutants of the lipoprotein-encoding lpqW gene have a profound defect in LAM biosynthesis. When these mutants are cultured in complex medium, spontaneous bypass mutants consistently evolve in which LAM biosynthesis is restored at the expense of polar PIM synthesis. Here we show that restoration of LAM biosynthesis in the lpqW mutant results from secondary mutations in the pimE gene. PimE is a mannosyltransferase involved in converting AcPIM4, a proposed branch point intermediate in the PIM and LAM biosynthetic pathways, to more polar PIMs. Mutations in pimE arose due to insertion of the mobile genetic element ISMsm1 and independent point mutations that were clustered in predicted extracytoplasmic loops of this polytopic membrane protein. Our findings provide the first strong evidence that LpqW is required to channel intermediates such as AcPIM4 into LAM synthesis and that loss of PimE function results in the accumulation of AcPIM4, bypassing the need for LpqW. These data highlight new mechanisms regulating the biosynthetic pathways of these essential cell wall components.     

Fruit Development, Ripening and Quality Related Genes in the Papaya Genome

Papaya (Carica papaya L.) is the first fleshy fruit with a climacteric ripening pattern to be sequenced. As a member of the Rosids superorder in the order Brassicales, papaya apparently lacks the genome duplication that occurred twice in Arabidopsis. The predicted papaya genes that are homologous to those potentially involved in fruit growth, development, and ripening were investigated. Genes homologous to those involved in tomato fruit size and shape were found. Fewer predicted papaya expansin genes were found and no Expansin Like-B genes were predicted. Compared to Arabidopsis and tomato, fewer genes that may impact sugar accumulation in papaya, ethylene synthesis and response, respiration, chlorophyll degradation and carotenoid synthesis were predicted. Similar or fewer genes were found in papaya for the enzymes leading to volatile production than so far determined for tomato. The presence of fewer papaya genes in most fruit development and ripening categories suggests less subfunctionalization of gene action. The lack of whole genome duplication and reductions in most gene families and biosynthetic pathways make papaya a valuable and unique tool to study the evolution of fruit ripening and the complex regulatory networks active in fruit ripening.