Second nesting record and northward advance of the Great-tailed Grackle ( Quiscalus mexicanus ) in Nevada

The second nesting record for the Great - tailed Grackle ( Quiscalus mexicanus ) in Nevada is reported from the central part of the state approximately 240 km north of the previous record. Since 1912 this species has undergone a dramatic northward extension of its previous range in the United States, presumably as a result of increased agricultural irrigation in areas that were previously desert or short - grass prairie.         

Ecology of Celtis reticulata in Idaho

The small deciduous tree Celtis reticulata (neatleaf hackberry) reaches its northern limit in Idaho, where, contrary to most of its western range, it often occurs as an overstory dominantly. Two hundred fifty stands of this tree were sampled throughout Idaho. Celtis is slow-growing, averaging 4 m tall at 50 yr, and long-lived (to 300-400yr). It occurs in a variety of habitats, from riparian to rocky uplands. Trees grow best where topographically sheltered, such as in draws and narrow canyons, and were soils are loamy. Although plants grow more slowly as surface rock cover increases, stands are often associated with rock, with a mean surface cover of 39% rock. Differences in growth rates were unrelated to parent material and aspect. Most stands are reproducing, in spite of habitat degradation caused by overgrazing, alien plant invasion, and increasing fire frequencies. Stands are typically represented by one dominant cohort; however, young, even-aged stands are rare and are generally found along waterways on stream terraces or at the high-water line. Although slow growing, C. reticulata shows promise for land mangers interested in site enhancement. This native species is long-lived, produces fruit used by wildlife, and provides structural diversity in a semiarid landscape (with a maximum height o 12 m) in areas that are becoming increasingly dominated by exotic plant species.     

Laboratory fattening and dietary-fat effects on Meadow voles ( Microtus pennsylvanicus )

When removed from the field and maintained under laboratory conditions, meadow voles exhibited significant change in body composition. Voles increased body mass due primarily to large gains in lipid mass combined with small losses in fat-free mass. Lipid deposition amounts increased as dietary fat was increased, and animals demonstrated a leveling of body mass instead of continuous unregulated obesity. When dietary fat content was changed, lipid deposition or utilization responded directly. Thus, meadow voles regulate overall body mass and body composition (lipid and fat-free mass) at levels that correspond to dietary quality (fat) and abundance in the laboratory, and they deposit considerably more lipid than do animals in the field. Our experiments demonstrate that food quality has a substantial effect on the body composition of wild-caught animals maintained in the laboratory.     

Genetic structure in striped skunks ( Mephitis mephitis ) on the Southern High Plains of Texas

Genetic variation within populations reflects population-level social and demographic processes and influences how a population behaves as an evolutionary unit. We examined partitioning of genetic variation in striped skunks ( Mephitis mephitis ) from the Southern High Plains of Texas during 1994-1995. Sixty-nine male and 35 female skunks were sampled on four 12.8-km 2 study plots. Plot centers ranged from 17.6 to 61.6 km apart. We used multi-locus DNA fingerprinting with 2 probes, pV47 and CTTxAGG, to test 3 hypotheses: (1) females are more genetically similar to other females than males are to other males on the same plot (indicating greater female philopatry than male philopatry), (2) genetic similarity is greater within plots than among plots (indicating partitioning of genetic variation in space), and (3) genetic similarity of males decreases as the distance separating males increases (indicating geographic distance affects rates of gene flow). In general, males on a plot had lower average genetic similarity than females. Genetic similarity within plots was not different from genetic similarity among plots for males or for females. Genetic similarity of males did not decrease with increasing distance among plots. The lack of geographical genetic structure in striped skunks suggests at the scale of this study (< 60 km) that gene flow of biparentally inherited genes is not distance-mediated. However, the higher similarity values for females than for males on the same plot supports an effect of male-biased dispersal and female philopatry on partitioning of genetic variation between sexes.     

The conserved protein DCN-1/Dcn1p is required for cullin neddylation in C. elegans and S. cerevisiae

SCF-type E3 ubiquitin ligases are multi-protein complexes required for polyubiquitination and subsequent degradation of target proteins by the 26S proteasome. Cullins, together with the RING-finger protein Rbx1, form the catalytic core of the ligase, and recruit the substrate-recognition module. Cycles of covalent modification of cullins by the ubiquitin-like molecule Nedd8 (neddylation) and removal of Nedd8 by the COP9 signalosome (deneddylation) positively regulate E3 ligase activity. Here we report the identification and analysis of a widely conserved protein that is required for cullin neddylation in the nematode Caenorhabditis elegans and the yeast Saccharomyces cerevisiae. C. elegans DCN-1 and S. cerevisiae Dcn1p (defective in cullin neddylation) are characterized by a novel UBA-like ubiquitin-binding domain and a DUF298 domain of unknown function. Consistent with their requirements for neddylation, DCN-1 and Dcn1p directly bind Nedd8 and physically associate with cullins in both species. Moreover, overexpression of Dcn1p in yeast results in the accumulation of Nedd8-modified cullin Cdc53p. Both in vivo and in vitro experiments indicate that Dcn1p does not inhibit deneddylation of Cdc53p by the COP9 signalosome, but greatly increases the kinetics of the neddylation reaction.     

Newton's solution of the one-body problem

Communicated by C. A. Wilson     

Uridine-33 in yeast tRNA not essential for amber suppression

The nucleotide at position 33 on the 5' side of the anticodon of almost all tRNAs is a uridine. Crystallographic studies of different tRNAs reveal that although the precise orientation of uridine-33 is not always the same, it connects the anticodon stacked along the 3' side of the loop with the pyrimidine-32 stacked on the 5' side of the loop. The remarkably conserved nature of uridine-33 and its unique position in the anticodon loop structure has led to suggestions that this nucleotide has an essential role in the translational mechanism. We have developed a biochemical procedure to replace nucleotides 33-35 in yeast tRNATyr with any desired sequence and used it to construct amber suppressor tRNAs having different nucleotides at position 33. As all of these synthetic amber suppressor tRNAs functioned well in eukaryotic in vitro suppression assays, we conclude that uridine-33 does not have an obligatory role in the translation mechanism.     

Forecasting new product trial in a controlled test market environment

A number of researchers have developed models that use test market data to generate forecasts of a new product's performance. However, most of these models have ignored the effects of marketing covariates. In this paper we examine what impact these covariates have on a model's forecasting performance and explore whether their presence enables us to reduce the length of the model calibration period (i.e. shorten the duration of the test market). We develop from first principles a set of models that enable us to systematically explore the impact of various model ‘components’ on forecasting performance. Furthermore, we also explore the impact of the length of the test market on forecasting performance. We find that it is critically important to capture consumer heterogeneity, and that the inclusion of covariate effects can improve forecast accuracy, especially for models calibrated on fewer than 20 weeks of data. Copyright © 2003 John Wiley & Sons, Ltd.