Differing climate and landscape effects on regional dryland vegetation responses during wet periods allude to future patterns

Dryland vegetation is influenced by biotic and abiotic land surface template (LST) conditions and precipitation (PPT), such that enhanced vegetation responses to periods of high PPT may be shaped by multiple factors. High PPT stochasticity in the Chihuahuan Desert suggests that enhanced responses across broad geographic areas are improbable. Yet, multiyear wet periods may homogenize PPT patterns, interact with favorable LST conditions, and in this way produce enhanced responses. In contrast, periods containing multiple extreme high PPT pulse events could overwhelm LST influences, suggesting a divergence in how climate change could influence vegetation by altering PPT periods. Using a suite of stacked remote sensing and LST datasets from the 1980s to the present, we evaluated PPT‐LST‐Vegetation relationships across this region and tested the hypothesis that enhanced vegetation responses would be initiated by high PPT, but that LST favorability would underlie response magnitude, producing geographic differences between wet periods. We focused on two multiyear wet periods; one of above average, regionally distributed PPT (1990–1993) and a second with locally distributed PPT that contained two extreme wet pulses (2006–2008). 1990–1993 had regional vegetation responses that were correlated with soil properties. 2006–2008 had higher vegetation responses over a smaller area that were correlated primarily with PPT and secondarily to soil properties. Within the overlapping PPT area of both periods, enhanced vegetation responses occurred in similar locations. Thus, LST favorability underlied the geographic pattern of vegetation responses, whereas PPT initiated the response and controlled response area and maximum response magnitude. Multiyear periods provide foresight on the differing impacts that directional changes in mean climate and changes in extreme PPT pulses could have in drylands. Our study shows that future vegetation responses during wet periods will be tied to LST favorability, yet will be shaped by the pattern and magnitude of multiyear PPT events.     

Kinetics of Mx expression in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar L.) parr in response to VHS-DNA vaccination

The duration of the Mx mRNA response to an intramuscular injection of the viral haemorrhagic septicaemia virus (VHSV) glycoprotein (G) gene DNA vaccine as well as to the control plasmid was determined in rainbow trout at 14 degrees C over a period of 11 weeks. The Mx response was detectable on day 7, peaked on day 14 and returned to pretreatment levels on day 21 and thereafter. No increase in Mx expression was detectable to the control plasmid. In further experiments, the kinetics of the Mx response were compared in rainbow trout and Atlantic salmon parr kept at 10 degrees C and injected with the DNA vaccine or the synthetic double-stranded RNA, poly I:C. In both species there was a rapid response to poly I:C detectable from day 1, reaching maximum from days 3 to 9 and decreasing to background level by day 12. The peak level and return to background was reached slightly later in salmon. In both species the response to the VHS/DNA vaccine was slower to begin, not being detectable on days 1 and 3, but elevated levels were found on day 6. However, in the salmon parr, the peak level was on day 6 and the signal disappeared by day 12, while in the rainbow trout, the response peaked at day 12 and lasted until day 21. The kinetics of the Mx response to the VHS/DNA vaccine in rainbow trout correlate with the early non-specific protection against VHS in this species following vaccination. It is speculated that the more transient Mx response in Atlantic salmon parr to the DNA vaccine may be related to the innate resistance of salmon to VHS.     

Quantitative aspects of metal ion binding to certain transfer RNA anticodon loop modified nucleosides

Magnesium and manganese ions bind strongly to the unusual transfer RNA anticodon loop nucleotides, N-[(9-beta-D-ribofuranosyl-9H-purin-6-yl)carbamoyl]-L-threonine 5'-monophosphate (pt6A) and uridine-5-oxyacetic acid 5'-monophosphate (pV). Potentiometric measurements have shown that the delta G for metal ion-pt6A complex formation is 2-3-times more exothermic than for AMP. Electron-nuclear longitudinal dipolar relaxation data yielded manganese-ligand atom distances which permit a three-dimensional construct of the complex in which metal is coordinated to the phosphate, carboxylate of the threonine side-chain (with the nucleotide in the anti glycosidic conformation) and N7 of the adenine ring. Similarly, manganese binds strongly to pV, involving phosphate and carboxylate functions. It is possible that a facet of the functional role of these unusual residues is to chelate magnesium ions and in so doing permit optimum anticodon loop conformational stability and stability of tRNA-mRNA-ribosome complexes.     

Variation in the train morphology of peacocks (Pavo cristatus)

A sample of full-trained adult male peacocks was collected and measured to determine whether or not there were any morphological correlates of train elaboration. Peacocks with longer or heavier trains are those with relatively large fat reserves for their overall body mass. The proportion of feathers in the train which have eyespots is also greater in peacocks with a relatively large muscle. These relationships indicate that train elaboration may be condition-dependent. Females that prefer males with larger trains may therefore gain good condition males, which may reflect overall genetic quality. There is also a significant tendency for larger-trained peacocks to have high louse loads, after controlling for body mass. It may be that larger-trained males are older, and have accrued more lice than younger ones. Alternatively, long-trained males may have acquired more lice through direct contact with more females than shorter-trained birds.