Risk of feather damage explains fault bar occurrence in a migrant hawk,the Swainson's hawk Buteo swainsoni

Fault bars are common stress‐induced feather abnormalities that could produce feather damage thus reducing flight performance. For that reason, it has been hypothesized that birds may have evolved adaptive strategies that reduce the costs of fault bars (the ‘fault bar allocation hypothesis’). An untested prediction of this hypothesis is that fault bars in important feathers for flight (wing and tail) should be less abundant where they produce more feather damage. We tested such a prediction using moulted wing and tail feathers of the long‐distance migrant Swainson's hawk Buteo swainsoni in its Argentinean wintering quarters. We recorded the occurrence of fault bars of different strengths (light, medium and strong) and the damage (lost of a portion of the vane) produced by them. The occurrence of fault bars was very variable, with strong ones being rare throughout and light and medium fault bars being more frequent in the tail than in the wing. Risk of feather damage was similarly high and low across feather groups for strong and light fault bars, respectively, and higher in the wing than in the tail for medium strength. The occurrence of fault bars of different strengths on different feather groups was negatively correlated with their propensity to produce feather damage. At low damage risk (<5%), the occurrence of fault bars was highly variable depending on the feather group, but above 5% of feather damage the occurrence of fault bars was highly reduced throughout. Our results supports the ‘fault bar allocation hypothesis’ of natural selection reducing fault bar occurrence where fault bars are more risky, but further suggest that selection pressure could be relaxed in other instances, leaving the way free for other mechanisms to shape fault bar occurrence.     

Latitudinal variation in population structure of wintering Pacific Black Brant

ABSTRACT.   Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.     

Production of substituted catechols from substituted benzenes by a Pseudomonas sp.

In the presence of a halobenzene or benzonitrile, Pseudomonas T-12 can produce substituted catechols from the corresponding substituted benzenes. A variety of monosubstituted benzenes with substituents containing up to four carbons, and some meta- and para- disubstituted benzenes, can serve as catechol precursors.     

Soluble minerals in chemical evolution

The adsorption of 5-AMP and 5-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na₂SO₄, MgCl₂·6H₂O, MgSO₄·7H₂O, CaCl₂·2H₂O, CaSO₄·2H₂O, SrCl₂·6H₂O, SrSO₄, and ZnSO₄·7H₂O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5-AMP or N-3 nitrogen of 5-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles.     

The metabolism of deoxyguanosine in mitochondria. Characterization of the uptake process

Summary The uptake of deoxyguanosine by rat liver mitochondria was characterized. The process required an intact mitochondrial membrane and exhibited a dependence on added phosphate. Deoxyguanosine uptake was minimally influenced by Mg²⁺ or Mn²⁺, but Ca²⁺ at concentrations above 0.5 mM were detrimental. Of the deoxynucleosides tested, only deoxyinosine inhibited the uptake of deoxyguanosine. The ribonucleoside guanosine was not observed to compete with its deoxynucleoside analog. Known inhibitors of nucleoside transport, cytochalasin B and NBMPR, did not block deoxyguanosine uptake, but the sulfhydryl reagents NEM and pCMB were both inhibitory. The uptake of deoxyguanosine was shown to be a saturable process and an apparent Km of 0.64 M was calculated from a Hanes plot.     

Convergence to equilibrium in a genetic model with differential viability between the sexes

A single locus, diallelic selection model with female and male viability differences is studied. If the variables are ratios of allele frequencies in each sex, a 2-dimensional difference equation describes the model. Because of the strong monotonicity of the resulting map, every initial genotypic structure converges to an equilibrium structure assuming that no equilibrium has eigenvalues on the unit circle.Partially supported by funds provided by a Science and Education Grant to the USDA-Forest Service, Southeastern Forest Experiment Station, Population Genetics of Forest Trees Research Unit, Raleigh, USASupported by a grant from the Max Kade Foundation, New York, USA     

Aqueous two-phase partition coefficients for Escherichia coli β-galactosidase fusions

The partition of native Escherichia coli -galactosidase and of two different fusion proteins comprised mainly of -galactosidase from E. coli was studied in aqueous two-phase systems composed of polyethylene glycol (PEG) and dextran. These fusions contain an amino-terminal segment from the E. coli outer membrane protein F (OmpF) and a linker peptide. Differences in the partition pattern could be observed for the three enzymes despite their similarity. Decreased polymer concentrations in the phase system increased the partition coefficient for all three -galactosidases.     

The effect of predation on the structure and invasibility of assembled communities

Summary Fifty four microcosmic communities were assembled over 4 months from a 28-species source pool of phytoplankton using nine different invasion patterns each replicated six times. Three communities from each set of replicates then were invaded with a cladoceran that feeds on phytoplankton. All communities were then treated identically for an additional 4 months. In all nine invasion categories species richness was greater in predated communities. Predation opened communities to invasion by increasing the representation of infrequently sampled species at the expense of more common species. Invasion rate was four times more influential than predation and over eleven times more important than either invasion order or the timing pattern of interspecific arrivals in determining species richness in this system of communitites.     

Alternative mating tactics in the Great Plains toad

Male Great Plains toads, Bufo cognatus, exhibit two mating tactics. At any time, most males give advertisement calls to attract females, while other males, ‘satellites’, remain silent and station themselves near callers in an attempt to intercept females. Females are usually capable of moving through choruses undetected by males. Those females detected by males can avoid being clasped by quickly darting away; but if clasped, can detach the male by inflating. Females initiated amplexus with callers; subsequently calling males mated with 92% of the females and satellites mated with the remaining 8%. Toads employing the satellite tactic associated with males that had longer calls and that were larger, although call duration was the stronger predictor. The percentage of males exhibiting satellite behaviour during a sampling period varied from 0 to 57%. Several hypotheses explaining satellite frequency were explored, including variation in male density, male quality, and operational sex ratio. Of the variables considered, only two aspects of male density (namely, the number of unmated males per m of shoreline and number of calling males per m shoreline) affected satellite frequency. High male density may cause at least some calling males to lose vocal conspicuousness, thereby favouring satellite behaviour. However, male density accounted for only 17% of the observed variation in satellite frequency. This, plus the fact that up to 74% of marked males switched between tactics, suggests that factors such as higher energetic demands of calling may affect satellite frequency.