Optimum Biased Spring Balance Weighing Designs Under Equal Correlations of Errors

The paper deals with the problem of estimating the individual weights of objects under a biased spring balance weighing design with equal correlations of errors in the model. A lower bound for the variance of each of the estimated weights resulting from this biased spring balance weighing design is obtained and a necessary and sufficient condition for this lower bound to be attained is given. The incidence matrix of a BIB design has been used to construct optimum biased spring balance weighing designs.     

The Limits of Artificial Stimuli in Behavioral Research: The Umwelt Gamble

The use of artificial stimuli in behavioral experimentation is pervasive and well precedented. A perspective by Hauber et al. (2014) Ethology describes advantages of this approach and highlights the use of model bird eggs and artificial egg coloration in research on egg rejection in the context of brood parasitism. Here, as a companion piece focused on quality control, I outline limitations and pitfalls associated with the use of artificial stimuli. In general, the practice makes assumptions about the perception and cognition of the study organism, therefore involving what could be called an umwelt gamble. The magnitude of this gamble and the prospects for interpretable results depend on the experimental design, the particular stimulus, and its intended role. Common roles are (1) as a representative stimulus to be generalized to a broader class; (2) as a substitute for a natural stimulus; (3) as a modification or exaggeration of natural stimuli; or (4) as an entirely novel stimulus. Whether the gamble is successful—whether the methodology navigates peculiarities of the study organism in the way the researchers intend—can be tested with controls that function as artifact detection tests. Given the propensity of animals to be biased, sometimes in unforeseen ways, in the way they perceive and interpret their environments, researchers should be careful when considering the use of artificial stimuli, weighing the advantages against the risks in any particular case.     

Confirmation of QTL controlling seed yield in spring canola (Brassica napus L.) hybrids

Allelic effects observed in QTL discovery experiments must be confirmed to be useful in subsequent breeding efforts. Two QTL affecting seed yield of spring hybrid canola (Brassica napus L.) were previously identified in two populations of inbred backcross lines (IBLs) containing germplasm introgressed from a winter cultivar. The effects of favorable alleles at these QTL were retested by crossing two selected IBLs (M5 and M31) to three spring canola lines having different genetic backgrounds. Doubled haploid (DH) lines derived from each F₁ were genotyped with RFLP markers flanking the QTL and grouped into the four possible QTL genotypes. For the first field experiment, DH lines derived by crossing the M5 line to one spring line were crossed to two female testers and evaluated as individual testcross progenies in one environment. QTL genotypes had large variances and were not significantly different. A second field experiment was conducted using the DH lines from the first experiment and two other sets of DH lines derived from the M31 line crossed to two different spring canola lines. Individual lines within each QTL genotype of each set were bulked and crossed to the same testers used in Experiment 1. Bulked hybrid seeds of each QTL genotype were planted in a split-split plot randomized block design and 12 replicates. QTL genotypes had smaller variances in this experiment, and the effects of one QTL were confirmed in some genetic backgrounds. These results suggest that bulking of QTL genotypes and use of an appropriate experimental design with many replicates are needed to detect small differences between QTL genotypes.     

A rapid method for measuring production of yellow rust spores on single seedlings to assess differential interactions of wheat cultivars with Puccinia striiformis

Uredospore production of Puccinia striiformis in single wheat seedlings was assessed by weighing spores on an electrical microbalance, by counting on a haemocytometer or by measuring turbidity of spore suspensions with a spectrophotometer and compared with production from groups of seedlings determined by weighing spores on an analytical balance. The data were used to assess differential interaction of wheat cultivars Hybrid 46 and Joss Cambier with two isolates of race 104 E137 of P. striiformis and cvs Maris Templar and Joss Cambier with two isolates of race 41 E136. A significant differential interaction was shown in both experiments by each method but most rapidly and with the minimum of materials by the single-plant microbalance technique. Measurements of spore production demonstrated differences between isolates within races more clearly than the conventional visual assessment of yellow rust symptoms.     

Aspects of risk-aversion in foraging white-crowned sparrows

Two series of aviary experiments with white-crowned sparrows (Zonotrichia leucophrys) are reported. The first series attempts to mimic foraging choices between microhabitats. The second series examines foraging choices made within a single artificial patch, a design intended to resemble dietary selection. In all experiments subjects chose between a constant food reward and a variable reward, the mean of which equalled the constant reward. Each experiment allowed the bird to feed at an overall rate greater than that minimally required for daily energy balance. In both series of experiments, the birds usually preferred the constant reward. Results of the first series do not differ significantly from previously reported preferences of dark-eyed juncos (Junco hyemalis), birds weighing 10 g less than the white-crowned sparrows.     

A model-independent approach to the theory of experimental designs and a special discussion of bib. i general definition and designs with one or two block factors

Experimental designs are definded by introducing an assignment matrix Z. It is shown by block designs and double block designs that using Z or an operator on Z otherwise defined, well known designs can be got as special cases. Till now we didn' find an experimental design which could not be defined by our matrix Z. The definitions of properties of experimental designs can be given independently of the model of the statistical analysis. This is shown for the property of balance of block designs.     

Conditional Markov Chain Design for Accrual Clinical Trials

Randomization in a comparative experiment has, as one aim, the control of bias in the initial selection of experimental units. When the experiment is a clinical trial employing the accrual of patients, two additional aims are the control of admission bias and control of chronologic bias. This can be accomplished by using a method of randomization, such as the “biased coin design” of Efron, which sequentially forces balance. As an extension of Efron's design, this paper develops a class of conditional Markov chain designs. The detailed randomization employed utilizes the sequential imbalances in the treatment allocation as states in a Markov process. Through the use of appropriate transition probabilities, a range of possible designs can be attained. An additional objective of physical randomization is to provide a model for data analysis. Such a randomization theoretic analysis is presented for the current designs. In addition, Monte Carlo sampling results are given to support the proposed normal theory approximation to the exact randomization distribution.     

Sex ratios and Ophryocystis elektroscirrha infection levels of Danaus plexippus during spring migration through Oklahoma,USA

Monarch butterflies, Danaus plexippus L. (Lepidoptera: Nymphalidae), have a multiple brood migration in the spring as they move between their overwintering grounds and summer breeding grounds. In Oklahoma, USA, monarchs produce at least one generation in the spring, which develops and continues the northward migration, leaving Oklahoma without a breeding population during the hot summer months. Female monarchs leave the overwintering grounds prior to males, but it is not clear whether females re‐colonize areas along the migration route prior to, or at the same time as males. Male‐to‐female ratios are 1:1 at emergence, but studies have identified a male‐biased sex ratio in the field. Both males and females are susceptible to infection by the obligate protozoan parasite, Ophryocystis elektroscirrha McLaughlin & Myers (OE), which reduces flight abilities and life spans of infected individuals. We examine sex ratios during the spring migration through Oklahoma and whether sex ratios or OE infection estimates vary with capture technique (active or passive). Our data suggest populations are male‐biased during the 1st week of spring migration in Oklahoma, but shift to female‐biased by the 3rd week in both cool and warm springs. Therefore, males may leave southern areas prior to females or migrate longer distances per day. Active sampling (i.e., netting) did not bias sex compared to passive sampling (i.e., sticky traps). Significantly fewer OE‐carrying monarchs (with two or more spores) were captured via netting than by sticky traps which may be caused by sticky trap glue affecting tape sampling effectiveness, but there was no difference in the number of heavily infected individuals (more than 100 spores). Therefore, data from netted monarchs may underestimate OE infection rates within populations.     

Propensity Score Matching in Randomized Clinical Trials

Summary Cluster randomization trials with relatively few clusters have been widely used in recent years for evaluation of health‐care strategies. On average, randomized treatment assignment achieves balance in both known and unknown confounding factors between treatment groups, however, in practice investigators can only introduce a small amount of stratification and cannot balance on all the important variables simultaneously. The limitation arises especially when there are many confounding variables in small studies. Such is the case in the INSTINCT trial designed to investigate the effectiveness of an education program in enhancing the tPA use in stroke patients. In this article, we introduce a new randomization design, the balance match weighted (BMW) design, which applies the optimal matching with constraints technique to a prospective randomized design and aims to minimize the mean squared error (MSE) of the treatment effect estimator. A simulation study shows that, under various confounding scenarios, the BMW design can yield substantial reductions in the MSE for the treatment effect estimator compared to a completely randomized or matched‐pair design. The BMW design is also compared with a model‐based approach adjusting for the estimated propensity score and Robins‐Mark‐Newey E‐estimation procedure in terms of efficiency and robustness of the treatment effect estimator. These investigations suggest that the BMW design is more robust and usually, although not always, more efficient than either of the approaches. The design is also seen to be robust against heterogeneous error. We illustrate these methods in proposing a design for the INSTINCT trial.     

Wind pollination and insect pollination of two temperate willow species,Salix miyabeana and Salix sachalinensis

Pollination systems of Salix miyabeana and Salix sachalinensis were studied at a riverside in northern Japan in order to measure the balance of wind pollination and insect pollination. In 1996, 19 clones of each species were selected, and seed-set success by a net-bagging (to exclude insect visitation) and an artificial pollination (to remove pollen limitation) were compared to by natural pollination. For S. miyabeana, the same experiment was repeated in two populations in 1997. Proportion of seed set through wind pollination dominated in both species in this study. Pollen limitation was common under natural conditions, and S. sachalinensis relied more on insect pollination for seed production than S. miyabeana. Meteorological factors such as precipitation and hours of sunshine during the flowering season influenced the potential reproductive activity of the willow between years. In the wet and cloudy spring of 1996, clones which obtained high seed set depended more on insect pollination for both species, whereas in the dry and sunny spring of 1997, such clones depended more on wind pollination for S. miyabeana. Because the efficiency of wind pollination seemed to be more sensitive to fluctuating weather conditions than insect pollination, insect pollination was considered to play an assurance role for seed production in these willows.     

Effects of Ulva spp. and seasonal disturbances on the recovery of a temperate rocky intertidal community

The inhibitory effects of ulvoid algae and their seasonality on the recovery and succession of an intertidal algal community were investigated under field conditions using a two‐factorial design. The experiment was conducted in the mid‐low intertidal zone on the Southern coast of Korea. In spring and fall, each of the ten 50 × 50 cm plots was disturbed artificially, and Ulva spp. were continuously excluded from five plots of the seasonal plots. The succession of spring plots was nearly twice as fast as that of the fall plots (spring, 4–6 months; fall, 10–15 months), indicating that the seasonal effects contributed significantly to the speed of the succession. The inhibition by Ulva species delayed the succession; however, the strength of this delay was limited largely by the duration and persistence of Ulva mass, which was also highly seasonal. The presence of Ulva spp. did not alter the final assemblage at the climax stage; instead, it caused a delay in community resilience. This study provides a few analytical factors for community‐wise comparison during the evaluation of the status of successional stages.     

Competition and the distribution of spring peeper larvae

Studies of tadpole distributions have shown that despite overlapping affinities for semipermanent and permanent ponds, distributions of the spring peeper (Pseudacris crucifer) and the green frog (Rana clamitans) tend to be nonoverlapping. Because spring peepers are believed to be poor competitors, I hypothesized that competition from green frog larvae limits the distribution of spring peeper larvae. I stocked field enclosures with a constant density of spring peeper larvae, and one of four densities of green frog larvae (a target-neighbor design). Increased green frog density had a small effect on metamorphic size and no effects on survivorship, larval period or growth rates of spring peepers. In contrast to these small interspecific effects, green frogs had a large effect on their own performance. Intraspecific competition resulted in a 50% decline in growth rate and an 11% decline in metamorphic size. These results suggest that the species are segregated in resource use, or that compared with green frogs, spring peepers are better able to cope with depressed resource densities. In either case, this field experiment provides no evidence that interspecific competition from green frogs limits distributions of spring peepers. Other factors such as predation and breeding site choice by adults may contribute to the absence of spring peeper larvae from many semipermanent and permanent ponds.     

Reduced Selection for Codon Usage Bias in <Emphasis Type="Italic">Drosophila miranda</Emphasis>

Biased codon usage in many species results from a balance among mutation, weak selection, and genetic drift. Here I show that selection to maintain biased codon usage is reduced in Drosophila miranda relative to its ancestor. Analyses of mutation patterns in noncoding DNA suggest that the extent of this reduction cannot be explained by changes in mutation bias or by biased gene conversion. Low levels of variability in D. miranda relative to its sibling species, D. pseudoobscura, suggest that it has a much smaller effective population size. Reduced codon usage bias in D. miranda may thus result from the reduced efficacy of selection against newly arising mutations to unpreferred codons. [Reviewing Editor: Dr. Richard Kliman]     

Strongly female‐biased sex allocation in a trivoltine population of Trypoxylon (Trypargilum) opacum Brèthes (Hymenoptera,Crabronidae)

Buschini, M.L.T. and Bergamaschi, A.C.B. 2009. Strongly female‐biased sex allocation in a trivoltine population of Trypoxylon (Trypargilum) opacum Brèthes (Hymenoptera, Crabronidae). —Acta Zoologica (Stockholm) 91 : 433–439. This study was carried in southern Brazil from December 2001 to December 2004. The aim of this paper is to provide additional information on the life‐history and sex allocation of this little known species. This wasp’s species has two alternative life histories: either they pupated immediately and emerged as adults later in the same season (direct development) or they entered diapause, overwintering and pupating the following spring (delayed development). The numerical sex ratio of overwintering and of direct developing wasps were strongly female biased in 2002, 2003 and 2004.     

Seasonal reversal of competitive advantage between two spider species

Summary To test for inter- and intraspecific competition between two common orb-weaving spiders, Metepeira grinnelli and Cyclosa turbinata, I conducted separate field experiments in the spring and summer. During the spring experiment, the prey-consumption rate of Metepeira was reduced at higher inter- and intraspecific densities, but Cyclosa was only affected by intraspecific density. During the summer experiment, Metepeira prey-consumption was not affected by inter- or intraspecific densities, while Cyclosa was affected by both inter- and intraspecific densities. In addition to competition for food, during the spring experiment Cyclosa was observed displacing Metepeira but not vice versa, whereas during the summer experiment Metepeira displaced Cyclosa but not vice versa. The seasonal reversal in the competitive advantage between the species was linked to their asynchronous phenologies; in the spring most Cyclosa were larger than Metepeira, whereas in the summer most Metepeira were larger than Cyclosa. I suggest that in this system, temporal variability in the competitive abilities may promote species coexistence.     

Breeding patterns in the pre-desert oniscid isopod Porcellio buddelundi of Matmata (Gabès,Tunisia)

Porcellio buddelundi inhabits arid areas in Tunisia. The reproductive pattern of a population at Oued El Jir, Matmata (Tunisia) was studied from July 2005 to June 2006. Monthly samples were taken during the study period. The overall sex ratio was biased toward females. Males, females, and newborns all had greater body-mass in autumn than in spring and their lowest mean body-mass was in June and July. Ovigerous females greater than 41.1 mg in body-mass, were collected from March through May and from September through October, suggesting seasonal reproduction with two breeding seasons: the longer one in spring (3 months) and another in the fall (2 months). Fecundity, which was positively correlated with the body-mass of females, varied between breeding seasons with a large number in spring and a small number in autumn. Seasonal variation of fecundity could be explained by the growth rate of ovigerous females affecting the fecundity more in spring than in autumn. The onset of breeding, in P. buddelundi, takes place when the day-length exceeds 12 h and the soil moisture decreases.     

Estimating population parameters of broadnose sevengill sharks (Notorynchus cepedianus) using photo identification capture-recapture

The broadnose sevengill shark (Notorynchus cepedianus) is a common high trophic-level predator around coastal New Zealand. Data on the ecology of the species in New Zealand are severely lacking, and anthropogenic impacts are unquantified. To partially address this, the authors undertook a study of the demographics of a population at Stewart Island. Sampling trips were carried out seasonally from winter 2016 to spring 2017. A baited underwater video system (BUV) was deployed on 133 occasions (mean = 22.2 deployments per season) in a shallow coastal embayment to capture underwater video of N. cepedianus for photo identification of individuals. N. cepedianus was detected on all but one deployment. Images extracted from video recorded the presence of 149 different individuals. Capture-recapture analysis of these data using robust design methods indicated a seasonal trend in abundance of the population using the study area, ranging from 34 (95% C.I. = 21–55) during winter 2016, to 94 (95% C.I. = 44–199) during spring 2017. This study presents the first data on demographic parameters of N. cepedianus in New Zealand.     

The reproductive ecology of the invasive Asian paddle crab,Charybdis japonica (Brachyura: Portunidae), in northeastern New Zealand

The Asian paddle crab, Charybdis japonica, native to the northwest Pacific, is an invasive species that has established populations within northeastern New Zealand. Here, we provide a detailed examination of C. japonica's reproductive seasonality and gametogenesis, sizes at physiological maturity, and sex ratios outside its native range. Trapping in the Weiti River Estuary, Whangaparoa (36°38.4′S, 174°43.6′E) from February 2010 to May 2012 indicated a male‐biased population. Reproductive seasonality largely depended on female condition, since males contained ripe spermatozoa year‐round. Female gametogenesis began during late autumn, with oocyte development occurring throughout winter to early spring. Based on the presence of mature gametes during late winter and the appearance of gravid females in early November, mating began during early spring, with spawning in mid‐spring. Spawning coincided with a large drop in the gonad index, and occurred between sea surface temperatures of 17–22°C and 11.75–13.5 h day length. Females remained reproductive for up to 5 months of the year. Histological observation suggested that CW50 (the carapace width at which 50% of the population is mature) for females was 46.39 mm, while CW50 for males could not be determined due to a paucity of immature males. Histological analysis also suggested that females of C. japonica could produce store sperm and multiple broods annually.     

A new method to measure substrate coherent strength of <Emphasis Type="Italic">Stenopsyche marmorata</Emphasis>

We developed a method for estimating the substrate coherent strength of a net-spinning caddis larva, Stenopsyche marmorata, in the field. Plastic experimental cages (prefabricated containers with 5-mm mesh; 0.1 m high, 0.12 m wide, 0.2 m long) that enclosed gravel substrate and an objective stone (5–6 cm in diameter) were prepared. We expected the caddisflies to build a retreat(s) between the objective stone and cage substrate when submerged in a riffle channel reach for 6 days. Ten final-instar larvae (4–5 cm long) were placed in the cage and allowed to form retreats. Two treatments (cages with and without larvae) with 15 replicates each were used in two experimental trials. The vertical lift-force of objective stones associated with a retreat (coherent strength) was measured using a spring weighing scale. In 87% of 30 cages of with-larvae treatment, retreats were formed between the objective stone and cage substrate. Coherent strength ranged from 0.0 to 1.6 kg. Our approach can be used under varying flow velocities, substrate conditions, and larval biomass, all of which are normally difficult to test in flume experiments. Findings based on our field method provide unique physical properties of the caddisfly retreats in stream ecosystems.     

Apparent directional selection by biased pleiotropic mutation

Pleiotropic effects of deleterious mutations are considered to be among the factors responsible for genetic constraints on evolution by long-term directional selection acting on a quantitative trait. If pleiotropic phenotypic effects are biased in a particular direction, mutations generate apparent directional selection, which refers to the covariance between fitness and the trait owing to a linear association between the number of mutations possessed by individuals and the genotypic values of the trait. The present analysis has shown how the equilibrium mean value of the trait is determined by a balance between directional selection and biased pleiotropic mutations. Assuming that genes act additively both on the trait and on fitness, the total variance-standardized directional selection gradient was decomposed into apparent and true components. Experimental data on mutation bias from the bristle traits of Drosophila and life history traits of Daphnia suggest that apparent selection explains a small but significant fraction of directional selection pressure that is observed in nature; the data suggest that changes induced in a trait by biased pleiotropic mutation (i.e., by apparent directional selection) are easily compensated for by (true) directional selection.