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961.
Wildfires are rare in the disturbance history of Hawaiian forests but may increase in prevalence due to invasive species and global climate change. We documented survival rates and adaptations facilitating persistence of native woody species following 2002–2003 wildfires in Hawaii Volcanoes National Park, Hawaii. Fires occurred during an El Niño drought and were ignited by lava flows. They burned across an environmental gradient occupied by two drier shrub-dominated communities and three mesic/wet Metrosideros forest communities. All the 19 native tree, shrub, and tree fern species demonstrated some capacity of postfire persistence. While greater than 95% of the dominant Metrosideros trees were top-killed, more than half survived fires via basal sprouting. Metrosideros trees with diameters >20 cm sprouted in lower percentages than smaller trees. At least 17 of 29 native woody species colonized the postfire environment via seedling establishment. Although the native biota possess adaptations facilitating persistence following wildfire, the presence of highly competitive invasive plants and ungulates will likely alter postfire succession. 相似文献
962.
A major challenge facing studies of major histocompatibility complex (MHC) evolution in birds is the difficulty in genotyping
alleles at individual loci, and the consequent inability to investigate sequence variation and selection pressures for each
gene. In this study, four MHC class I loci were isolated from the red-billed gull (Larus scopulinus), representing both the first characterized MHCI genes within Charadriiformes (shorebirds, gulls, and allies) and the first
full-length MHCI sequences described outside Galloanserae (gamebirds + waterfowl). Complete multilocus genotypes were obtained
for 470 individuals using a combination of reference-strand conformation analysis and direct sequencing of gene-specific amplification
products, and variation of peptide-binding region (PBR) exons was surveyed for all loci. Each gene is transcribed and has
conserved sequence features characteristic of antigen-presenting MHCI molecules. However, higher allelic variation, a more
even allele frequency distribution, and evidence of positive selection acting on a larger number of PBR residues suggest that
only one locus (Lasc-UAA) functions as a major classical MHCI gene. Lasc-UBA, with more limited variation and PBR motifs that
encompass a subset of Lasc-UAA diversity, was assigned a putative minor classical function, whereas the divergent and largely
invariant binding-groove motifs of Lasc-UCA and -UDA are suggestive of nonclassical loci with specialized ligand-binding roles. 相似文献
963.
Hare KM Yeong C Cree A 《Journal of experimental zoology. Part A, Ecological genetics and physiology》2011,315(4):215-221
Prenatal sex ratio (through exposure to hormones from siblings in utero) can influence sexually dimorphic traits of many mammals; but research on viviparous reptiles has contrasting outcomes, which have yet to be resolved. The thermal environment experienced during gestation has a strong effect on the phenotype of reptiles, but whether this thermal effect overrides that of prenatal sex ratio has yet to be explored. We experimentally investigated whether the gestation temperature, or litter sex ratio, influences sexually dimorphic traits (head width and axilla-groin length) in a viviparous skink (Oligosoma maccanni). We found that gestation temperature had a significant influence on sexually dimorphic traits of neonates, and at 3 months of age still influenced head width. We found no evidence that traits in either sex were masculinized or feminized in response to litter sex ratio. The development of external sexual dimorphisms increased gradually (all thermal regimes pooled), with neonates showing no sexual dimorphism, 3-month-old juveniles showing some sexual dimorphism in head width, and adults having stronger, but incompletely separated, sexual dimorphism for both traits. We suggest that the overlap in sexually dimorphic traits of adult O. maccanni (and perhaps other reptiles) may be better explained by natural variation in temperatures experienced during embryonic development, rather than hormonal effects arising from litter sex ratio. The interaction of hormones and temperature during gestation and the effect of these factors on sexual dimorphism within reptiles deserve further exploration. 相似文献
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Desulfitobacterium chlororespirans has been shown to grow by coupling the oxidation of lactate to the metabolic reductive dehalogenation of ortho chlorines on polysubstituted phenols. Here, we examine the ability of D. chlororespirans to debrominate and deiodinate the polysubstituted herbicides bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), ioxynil (3,5-diiodo-4-hydroxybenzonitrile), and the bromoxynil metabolite 3,5-dibromo-4-hydroxybenzoate (DBHB). Stoichiometric debromination of bromoxynil to 4-cyanophenol and DBHB to 4-hydroxybenzoate occurred. Further, bromoxynil (35 to 75 microM) and DBHB (250 to 260 microM) were used as electron acceptors for growth. Doubling times for growth (means +/- standard deviations for triplicate cultures) on bromoxynil (18.4 +/- 5.2 h) and DBHB (11.9 +/- 1.4 h), determined by rate of [14C]lactate uptake into biomass, were similar to those previously reported for this microorganism during growth on pyruvate (15.4 h). In contrast, ioxynil was not deiodinated when added alone or when added with bromoxynil; however, ioxynil dehalogenation, with stoichiometric conversion to 4-cyanophenol, was observed when the culture was amended with 3-chloro-4-hydroxybenzoate (a previously reported electron acceptor). To our knowledge, this is the first direct report of deiodination by a bacterium in the Desulfitobacterium genus and the first report of an anaerobic pure culture with the ability to transform bromoxynil or ioxynil. This research provides valuable insights into the substrate range of D. chlororespirans. 相似文献
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969.
Valentina Isetta Josep M. Montserrat Raquel Santano Alison J. Wimms Dinesh Ramanan Holger Woehrle Daniel Navajas Ramon Farré 《PloS one》2016,11(3)
Bench testing is a useful method to characterize the response of different automatic positive airway pressure (APAP) devices under well-controlled conditions. However, previous models did not consider the diversity of obstructive sleep apnea (OSA) patients’ characteristics and phenotypes. The objective of this proof-of-concept study was to design a new bench test for realistically simulating an OSA patient’s night, and to implement a one-night example of a typical female phenotype for comparing responses to several currently-available APAP devices. We developed a novel approach aimed at replicating a typical night of sleep which includes different disturbed breathing events, disease severities, sleep/wake phases, body postures and respiratory artefacts. The simulated female OSA patient example that we implemented included periods of wake, light sleep and deep sleep with positional changes and was connected to ten different APAP devices. Flow and pressure readings were recorded; each device was tested twice. The new approach for simulating female OSA patients effectively combined a wide variety of disturbed breathing patterns to mimic the response of a predefined patient type. There were marked differences in response between devices; only three were able to overcome flow limitation to normalize breathing, and only five devices were associated with a residual apnea-hypopnea index of <5/h. In conclusion, bench tests can be designed to simulate specific patient characteristics, and typical stages of sleep, body position, and wake. Each APAP device behaved differently when exposed to this controlled model of a female OSA patient, and should lead to further understanding of OSA treatment. 相似文献
970.
Araminta E. W. Ledger Erica D. Scurr Julie Hughes Alison Macdonald Toni Wallace Karen Thomas Robin Wilson Martin O. Leach Maria A. Schmidt 《PloS one》2016,11(3)