Forcing of Atlantic Equatorial and Subpolar Millennial Cycles by Precession

Abundance cycles of the marine alga Florisphaera profunda centered on a period of 7600 carbon-14 years (8400 calendar years) are present in high-resolution records from the equatorial Atlantic spanning 0 to 45,000 years ago. These cycles correlate with Heinrich events 1 through 5, which document rapid changes in continental ice melting around the subpolar North Atlantic. These variations in F. profunda are a direct response to modulation in zonal wind-driven divergence produced by a precessional component of orbital variation during a time of reduced eccentricity modulation.     

Skills required of dairy veterinarians in western Canada: A survey of practicing veterinarians

This study determined skills required of entry-level veterinarians for dairy practice in western Canada and compared mixed and dairy practitioners in the skills that they perform. We surveyed western Canadian veterinarians involved in dairy practice, focusing primarily on clinical activity of respondents. Response rate was 39.4% (281/714). Respondents were classified as either mixed practitioners (< 10% time in dairy practice) or dairy practitioners (> 75% time in dairy practice). For both groups, individual animal medicine and surgery skills were performed more commonly than herd health skills. The most important skills identified were those required for basic theriogenology, physical examination, treatment of common disorders, and general surgery. These results underscore the continued importance of individual animal skills in food animal practice in western Canada.     

Phylogeography,genetic stocks,and conservation implications for an Australian endemic marine turtle

1. Identification of the geographic extent of population boundaries, the distribution of genetic lineages, and the amount of genetic exchange among breeding groups is needed for effective conservation of vulnerable marine migratory species. This is particularly true of the flatback turtle (Natator depressus), which only breeds in Australia but has extensive migrations that can include international waters.
2. This study investigated the phylogeography and genetic structure among 17 flatback turtle rookeries across their range by sequencing an 810 bp portion of the mitochondrial DNA in 889 samples and genotyping 10 microsatellite loci in 598 samples.
3. There was low phylogenetic divergence among haplotypes and evidence of recent population expansion, likely in the late Pleistocene. A predominant haplotype was found across all rookeries, but other haplotype groups were regionally specific.
4. In general, there was agreement in patterns of genetic differentiation in the mitochondrial DNA and microsatellite data, and in some pairwise comparisons a higher mutation rate of microsatellites provided stronger evidence of differentiation.
5. These results suggest natal philopatry operates in the choice of breeding locations for males as well as females.
6. Evidence of genetic connectivity among neighbouring rookeries led to the identification of seven genetic stocks. Geographic boundaries of rookeries used by genetic stocks varied widely (160–1,300 km), highlighting a need for field studies to better understand movement patterns.
7. Hierarchical analysis of molecular variance identified significant genetic differentiation based upon genetic stock, nesting phenology (summer vs. winter nesters), and a west–east discontinuity across Torres Strait. A pattern of isolation by distance was identified, which was most strongly observed in the microsatellite data.
8. In combination with tagging and telemetry studies, these results will allow better quantification of stock‐specific threats along migratory routes and in foraging habitats. Implications of climate change will be stock specific and may depend upon the extent of genetic connectivity between neighbouring stocks.

     

Molecular mapping of adult plant stripe rust resistance in wheat and identification of pyramided QTL genotypes

The Puccinia striiformis f. sp. tritici (Pst) pathotype, 134 E16A+, detected in 2002 in Australia, produced relatively lower and higher adult plant stripe rust responses, respectively, on cultivars Kukri and Janz in comparison to the pre-2002 Pst pathotype 110 E143A+. Molecular mapping of adult plant stripe rust response variation among 180 Kukri/Janz-derived doubled haploid lines over 4 years, two each with Pst pathotypes 110 E143A+ and 134 E16A+, was performed. QYr.sun-7B and QYr.sun-7D were consistently contributed by Kukri and Janz, respectively. QYr.sun-7D corresponded to the genomic location of Yr18 and QYr.sun-7B remains to be formally named. QYr.sun-1B, QYr.sun-5B, and QYr.sun-6B were detected during more than one season irrespective of the Pst pathotypes used, whereas QYr.sun-3B was identified only during the 2003 crop season. QYr.sun-1A contributed by Janz, and QYr.sun-2A from Kukri, were detected only against Pst pathotypes 110 E143A+ and 134 E16A+, respectively. The DH lines showing better resistance than the either parent carried combinations of 4 to 6 QTL. These lines are currently being used as stripe rust resistance donors in wheat breeding programs.     

An assessment of the genetic relationship between sweet and grain sorghums, within Sorghum bicolor ssp. bicolor (L.) Moench, using AFLP markers

Compared to grain sorghums, sweet sorghums typically have lower grain yield and thick, tall stalks which accumulate high levels of sugar (sucrose, fructose and glucose). Unlike commercial grain sorghum (S. bicolor ssp. bicolor) cultivars, which are usually F₁ hybrids, commercial sweet sorghums were selected as wild accessions or have undergone limited plant breeding. Although all sweet sorghums are classified within S. bicolor ssp. bicolor, their genetic relationship with grain sorghums is yet to be investigated. Ninety-five genotypes, including 31 sweet sorghums and 64 grain sorghums, representing all five races within the subspecies bicolor, were screened with 277 polymorphic amplified fragment length polymorphism (AFLP) markers. Cluster analysis separated older sweet sorghum accessions (collected in mid 1800s) from those developed and released during the early to mid 1900s. These groups were emphasised in a principle component analysis of the results such that sweet sorghum lines were largely distinguished from the others, particularly by a group of markers located on sorghum chromosomes SBI-08 and SBI-10. Other studies have shown that QTL and ESTs for sugar-related traits, as well as for height and anthesis, map to SBI-10. Although the clusters obtained did not group clearly on the basis of racial classification, the sweet sorghum lines often cluster with grain sorghums of similar racial origin thus suggesting that sweet sorghum is of polyphyletic origin within S. bicolor ssp. bicolor     

Nanocatalysis by the tip of a scanning tunneling microscope operating inside a reactor cell

The platinum-rhodium tip of a scanning tunneling microscope that operates inside of an atmospheric-pressure chemical reactor cell has been used to locally rehydrogenate carbonaceous fragments deposited on the (111) surface of platinum. The carbon fragments were produced by partial dehydrogenation of propylene. The reactant gas environment inside the cell consisted of pure H(2) or a 1:9 mixture of CH(3)CHCH(2) and H(2) at 300 kelvin. The platinum-rhodium tip acted as a catalyst after activation by short voltage pulses. In this active state, the clusters in the area scanned by the tip were reacted away with very high spatial resolution.     

Physiological responses of ponderosa pine in western Montana to thinning, prescribed fire and burning season

Low-elevation ponderosa pine (Pinus ponderosa Dougl. ex. Laws.) forests of the northern Rocky Mountains historically experienced frequent low-intensity fires that maintained open uneven-aged stands. A century of fire exclusion has contributed to denser ponderosa pine forests with greater competition for resources, higher tree stress and greater risk of insect attack and stand-destroying fire. Active management intended to restore a semblance of the more sustainable historic stand structure and composition includes selective thinning and prescribed fire. However, little is known about the relative effects of these management practices on the physiological performance of ponderosa pine. We measured soil water and nitrogen availability, physiological performance and wood radial increment of second growth ponderosa pine trees at the Lick Creek Experimental Site in the Bitterroot National Forest, Montana, 8 and 9 years after the application of four treatments: thinning only; thinning followed by prescribed fire in the spring; thinning followed by prescribed fire in the fall; and untreated controls. Volumetric soil water content and resin capsule ammonium did not differ among treatments. Resin capsule nitrate in the control treatment was similar to that in all other treatments, although burned treatments had lower nitrate relative to the thinned-only treatment. Trees of similar size and canopy condition in the three thinned treatments (with and without fire) displayed higher leaf-area-based photosynthetic rate, stomatal conductance and mid-morning leaf water potential in June and July, and higher wood radial increment relative to trees in control units. Specific leaf area, mass-based leaf nitrogen content and carbon isotope discrimination did not vary among treatments. Our results suggest that, despite minimal differences in soil resource availability, trees in managed units where basal area was reduced had improved gas exchange and growth compared with trees in unmanaged units. Prescribed fire (either in the spring or in the fall) in addition to thinning, had no measurable effect on the mid-term physiological performance and wood growth of second growth ponderosa pine.