Absolute Population Research Articles

Kinetics in excited He/CO gas mixtures

Gas mixtures of He and CO were excited by electron beams. The transient species CO+(X,A,B), CO(A,C,a,b), C2(X,d), C*(3s) and O*(3p5P) were identified by fluorescence and absorption measurements. The time dependence and absolute population yield for most of these species were determined. Based on these results a reaction scheme is proposed which reproduces the experimental data quantitatively. Optical gain, previously observed by Waller et al. [Appl. Phys. Lett. 27, 323 (1975)] on the CO+(B)→CO+(X) transition was not reproduced.

Gypsy Moth (Lepidoptera: Lymantriidae) Egg Mass Distribution and Sampling in a Residential Setting

The spatial distribution of gypsy moth, Lymantria dispar (L.), egg masses was determined in 60 developed lots in a residential community in Greenbelt, Md. The community was divided into low and high gypsy moth density sections, with average densities of 393.3 and 2,656.3 egg masses per ha, respectively. In the high-density lots, the proportion of egg masses found on trees, man made objects, and houses was 73.9, 21.6, and 4.5%, respectively. The distribution in the low density lots was similar. Oaks, Quercus spp., received the highest proportion of egg masses out of all tree species subcategories at both low and high population densities. The cost effectiveness of a number of potential sampling units, including entire lots, back yards, fixed area plots, and individual trees, was evaluated. The entire lot sampling units required the fewest samples to achieve a predetermined level of precision. However, cost (= sampling time) for these sampling units was also the highest, resulting in relatively low cost effectiveness. Fixed-area plot samples (0.01 ha) were in general the most cost effective sampling units. A binomial (presence-absence) sampling approach, in which the percentage of trees in each lot with >5 egg masses is determined, was nearly as cost effective as fixed-area plots, but its usefulness is limited because it does not provide direct estimates of absolute gypsy moth population density.

DAILY TRAP CATCHES OF TWO EARWIG (DERMAPTERA) AND THREE CRICKET (ORTHOPTERA) SPECIES IN CENTRAL QUEENSLAND

AbstractDaily light trap catches of Nala lividipes (Dufour), Labidura truncata Kirby (both Dermaptera: Labiduridae), Teleogryllus oceanicus (Le Guillou), Lepidogryllus comparatus (Walker), and L. parvulus (Walker) (all Orthoptera: Gryllidae) from 1 September 1986 to 31 August 1989 at Emerald were recorded. In 1986/87 and 1988/89 more N. lividipes, L. truncata and Lepidogryllus spp. were trapped than in 1987/88. More T. oceanicus were trapped in 1988/89 than the previous 2 years. More females than males were trapped for each species, and for the Dermaptera, more major than minor males. Significant (P < 0.01) regressions of numbers caught were obtained for all species using a multiplicative logistic curve utilising average air temperature and wind‐run as the independent variables, except for T. oceanicus where average temperature alone was suitable. Daily catch numbers for these species are interpreted and discussed from the prediction equations. Further sampling of the Lepidogryllus spp. and N. lividipes over a wider range of ecosystems is suggested. Field sampling should be done concurrently to correlate relative and absolute population estimates.

Rotational Temperature, Inversion Density and Absolute Population Density for the CO2 (0002) Sequence Band Laser

Accurate values of the physical parameters such as rotational temperature, inversion density, absolute population density in the regular and (0002) sequence bands of the CO2 laser have been determined. Those parameters characterize the lasing processes and interference between both bands. The dependences of the parameters on the partial pressures of foreign gas and the effects of foreign gas are also examined. It is confirmed that the rotational temperature is always well defined in any vibrational state. However, they are not necessarily equal to each other and to the translational temperature.

Adaptive Management of Spatially Replicated Groundfish Populations

Assessment techniques that recognize information shared among substocks can help reduce uncertainty about stock size and productivity, compared with methods that treat each subpopulation independently. We develop this methodology using time series of catch and relative abundance data for six subpopulations of yellowtail flounder, Limanda ferruginea, from the Northwest Atlantic. The Deriso/Schnute delay-difference production model was fit to the data, but the model parameters associated with population productivity and absolute population size were very uncertain. Estimates of parameter uncertainty were used to identify a set of models that are consistent with the observed data and imply different management policies. The value of these different policies was estimated with a stochastic simulation program that uses a Kalman filter to predict stock size for each model and Bayesian updating to assign a probability of each model being correct. With parameters shared among stocks and a shared response to external influences, in the order of 10–20 yr was needed to distinguish the correct model. Adaptive management simulations indicated that long-term yield was greater in simulations with adaptive learning and that a lower initial exploitation rate should be applied than would be the case if adaptive learning were ignored.

ESTIMATING ADULT COCCINELLID POPULATIONS IN WHEAT FIELDS BY REMOVAL, SWEEPNET, AND VISUAL COUNT SAMPLING

AbstractRemoval sampling, sweepnet sampling, and visual count sampling conducted while walking at constant velocity through a field were used to sample populations of adults of five coccinellid species in plots established in spring wheat fields, Triticum aestivum L. Estimates of absolute population density obtained from two 20-min removal samples taken from each of six 5- by 5-m sub-plots per plot proved reliable and were used to convert estimates obtained from sweepnet sampling (180 sweeps per plot) and visual counts (36 min per plot walking at 10 m/min) into absolute estimates of population density. Population density estimates obtained by removal sampling were quite precise except for species with low capture efficiencies and low population densities.Crop plant growth stage influenced the numbers of beetles caught in sweepnet samples and was incorporated in regression models for converting sweepnet catch to absolute density. Values of R2 of regressions ranged from 0.51 to 0.90, depending on species. Visual counts were influenced by temperature and aphid density, and these variables were incorporated in regression models. Values of R2 for regressions relating visual counts to population densities ranged from 0.63 to 0.94, depending on species.

Simulation Studies of Binomial Sampling: A New Variance Estimator and Density Predictor, with Special Reference to the Russian Wheat Aphid (Homoptera: Aphididae)

Standard methods of obtaining absolute population estimates for the Russian wheat aphid, Diuraphis noxia (Mordvilko), are not feasible because of the insect’s small size, aggregated distribution, and difficulty in handling the samples. Because presence-absence information can be obtained easily, prediction of population density based on the proportion of sample units uninfested by the organism (Po) was investigated. Data on sample density ( m ) and Po for the Russian wheat aphid were obtained weekly in two winter wheat fields. The relationships between In( m ) and In(−In Po ) and between In(s2) and In( m ) were determined by regression. Several different published formulae for density predictions and their variances using the above regressions were examined analytically. New density predictor and variance estimators were developed and shown through simulation to be superior to existing estimators.

Spatial organization and population density of the fish community of the litter banks within a central Amazonian blackwater stream

Results of a study of the fish community of the leaf litter banks in the lower reaches of the Taruma‐Mirim, a small central Amazonian stream is presented. The Taruma‐Mirim is an acidic, blackwater, forest stream which flows through igapo forest and enters the Rio Negro close to Manaus. The commonly held view that these blackwaters hold an impoverished ichthyofauna is challenged. The studied litter banks hold about 20 species of fish, all of which were found to live within distinct subregions of the habitat. Average fish density was about 100 individuals m−2. Absolute population sizes were found to be remarkably small; within a 200 m2 area the most abundant species had a population size of about 104 and the least abundant <102 individuals. It is argued that high species richness linked to specialized habitat requirements and small population size indicates considerable population stability. The factors leading to the evolution of such species richness are discussed.

Growth hormone secretion by individual somatotropes of the testicular feminized rat.

To investigate the cellular mechanisms underlying the unique GH secretory apparatus of the androgen-resistant testicular feminized (Tfm) rat we employed a reverse hemolytic plaque assay to assess GH secretion by individual cells from normal male, normal female, and Tfm rats. Acutely dispersed pituitary cells were incubated for 90 min with GH anti-serum in the presence of medium alone, 0.01, 0.1, 1, 10, or 100 nM GHRH, or 3 microM forskolin after which hemolytic plaques were developed over an additional 30 min. Body weights of the Tfm rats [318 +/- 7 g (mean +/- SEM)] were intermediate between intact males (372 +/- 18 g) and females (218 +/- 7 g). The total number of cells recovered from dispersion of Tfm rat pituitaries [3.20 +/- 0.42 X 10(6) (mean +/- SEM)] was greater than that from males (1.43 +/- 0.12 X 10(6); P = 0.001), but not distinguishable from that from females (2.31 +/- 0.30 X 10(6); P = 0.06). However, the absolute population of recovered somatotropes from the Tfm animals (1.24 +/- 0.22 X 10(6) exceeded both male (0.56 +/- 0.10 X 10(6); P = 0.002) and female (0.80 +/- 0.14 X 10(6); P = 0.046) values. Mean basal and maximal GH plaque areas were greater for cells from male rats than for those from either female or Tfm rats (P less than 0.05) regardless of whether GHRH or forskolin was used as the secretagogue. Plaque areas from female and Tfm cells were indistinguishable under all study conditions. These data suggest that a deficiency of androgen receptors prevents establishment of the greater GH secretory capacity of individual somatotropes characteristic of the adult male rat. This androgen receptor-dependent modulation of GH secretory capacity appears to occur at a step distal to the GHRH receptor. The data also suggest that an increase in the absolute population of somatotropes is an additional consequence of androgen receptor deficiency. This combination of individual somatotropes, each possessing a GH secretory capacity similar to that of cells from normal females, but present in greater absolute numbers, may explain the intermediate values found during previous studies of the Tfm rat GH axis which were based on assessment of large mixed populations of pituitary cells.

Analysis of the Distribution and Abundance of Anopheles quadrimaculatus (Diptera: Culicidae) Larvae in a Marsh

Anopheles quadrimaculatus Say larvae were sampled using an area sampling method along point-quadrat transects in a marsh in 1986 and 1987 to estimate absolute population density and describe larval distribution. Larvae were significantly more abundant in 1986 than in 1987, with 152.8 ± 77.1 ($\bar x$ ± 95% CL) larvae/m2 in 1986 and 44.5 ± 21.3 ($\bar x$ ± 95% CL) larvae/m2 in 1987. Nearest neighbor estimates of larval population density (166.5 larvae/m2 for 1986; 37.1 larvae/m2 for 1987) closely approximated the absolute estimates. Taylor's power law and Iwao's density-contagiousness coefficient indicated that larvae were aggregated in distribution. Regression of larval numbers on quantified habitat variables in quadrats of 1986 showed a positive relationship between length of downed, floating plant stems and larval density, where 66% of the variation in larval density was explained by variation in this variable. Direct observations of larvae showed that typical larval posture was with body perpendicular to a downed plant stem-water interface and tail-end to the interface. However, an experiment showed that larvae did not preferentially select interfaces in the laboratory.

Chemical generation of electronically excited nitrogen in the atomic hydrogen (deuterium) + nitrogen difluoride flame

The chemistry of the H(D) + NF/sub 2/ flame has been investigated through measurements of key population profiles, production efficiencies, and rate coefficients. The absolute population profiles of N/sub 2/(B), NF(a), and NF(b) and upper limits on N/sub 2/(A) concentrations generated in the H(D) + NF/sub 2/ system are reported. From these profiles the efficiencies of NF(a) and N/sub 2/(A) and N/sub 2/(B) production were determined. For NF(a) the peak concentrations, which should also represent the production efficiency, were found to be 15-30% of the input NF/sub 2/. From the results of measurements by other investigators on the branching ratio for the H + NF/sub 2/ reaction, the authors would have expected the peak (NF(a)) to be approx. 90% of the input NF/sub 2/. Relative to N/sub 2/F/sub 4/, the N/sub 2/(B) production efficiencies were 2-4%. However, relative to peak (NF(a)) they were 20-30%. The upper limits on (N/sub 2/(A)) are consistent with N/sub 2/(A) production by radiative cascading from N/sub 2/(B). The room-temperature rate constant for the reaction N(/sup 2/D) + NF(a) ..-->.. F + N/sub 2/(B,W) was estimated to be 1 /times/ 10/sup /minus/10/ cm/sup 3/ s/sup /minus/1/. The quenching of N/sub 2/(A) by H atoms was foundmore » to have a rate constant > 5 /times/ 10/sup /minus/12/ cm/sup 3/ s/sup /minus/1/ and, as such, represents a major loss channel for N/sub 2/(A).« less

Effects of gonadal steroids on somatotroph function in the rat: analysis by the reverse hemolytic plaque assay.

The mechanism by which gonadal steroids modulate GH secretion is not known. We have used the reverse hemolytic plaque assay to examine whether gonadal steroid-induced modulation of GH secretion is effected by changes in the population of somatotrophs and/or alterations in their secretory properties. Two groups of Sprague-Dawley rats were studied: group 1 (n = 6) comprised male (M), castrate (Cx), and testosterone-replaced castrate male (Cx + T) rats and group 2 (n = 5) consisted of male (M), female (F), and 17 beta-estradiol-replaced castrate male (Cx + E) rats. The number of plaque-forming cells (expressed as both absolute number and a percentage of all cells) was determined, and secretory status was assessed by measuring plaque areas in response to 0, 0.01, 0.1, 1, 10, and 100 nM GHRH. While mean basal GH plaque areas were similar among the treatment groups of group 1, the maximal GH plaque area was significantly decreased in Cx [16.8 +/- 2.4 vs. 26.4 +/- 3.9 X 10(6) microns2 (mean +/- SEM); P less than 0.05], but not in Cx + T (27.5 +/- 4.1 microns2) rats. The GHRH EC50 was unaffected by castration or T replacement. The percentage and absolute population of somatotrophs were reduced in Cx, but not in Cx + T, rats, while the numbers of lactotrophs remained unchanged in these treatment groups. For group 2, the mean peak GH plaque area was reduced in Cx + E (16.5 +/- 2.9 microns2; P less than 0.001) compared to that in M rats (36.2 +/- 2.3 microns2), but was not significantly different from that in F (13.0 +/- 1.5 microns2) rats. The EC50 was significantly (P less than 0.025) greater in Cx + E (10.9 +/- 2.3 nM) and F (7.9 +/- 1.6 nM) compared to M rats (2.8 +/- 0.7 nM). The absolute somatotroph and lactotroph populations were increased in Cx + E compared to M and F rats, as were the populations of other pituitary cell types. Testosterone enhances GH secretion by increasing the secretory capacity, but not the sensitivity, of somatotrophs to GHRH and by recruiting the function of a subpopulation of somatotrophs. Estradiol reduces the secretory capacity and sensitivity of somatotrophs to GHRH, but increases the population of somatotrophs, lactotrophs, and non-GH- and non-PRL-secreting cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Reaction kinetics of the He(2P) and the He2*(a,v) states in high-density helium

Helium at pressures ranging from 0.5 to 8 bar is excited by an intense e-beam. The absolute population densities of the He(2 1P), He(2 3P) and He2*(a,v), v=0, 1, 2 states are determined by measuring the transient absorption of probe light delivered by a dye laser. The experimental data are readily described by a kinetic model taking into account the excitation and the de-excitation processes. The recombination of He2+ by a termolecular reaction with e+He to He(2 3P) as proposed by Bates (1984) is confirmed quantitatively. The rate constants for the termolecular reactions of He(2 1P) and He(2 3P) were deduced to be (1.8+or-0.4)*10-31 cm6 s-1 and (1.6+or-0.4)*10-32 cm6 s-1 respectively. The rotational and vibrational relaxation of He2(a) by helium is investigated.

A spectroscopic study of a He-Cd discharge created in a concentric cylinder hollow cathode structure

In this paper, a large spectroscopic study of a hollow cathode discharge produced in a concentric cylinder perforated tube is presented. First, the NCd cadmium ground state and the He(23S) metastable concentrations are determined from laser absorption measurements. Then, the thermal electron energy Te is estimated to be 0.5 eV from LIF observations, which is confirmed by probe measurements. The net thermal electron density (5*1012 to 2*1013 cm-3 for 1012<NCd<1014 cm-3 at 150 mA) is determined from H beta Stark broadening and from the He(33P) total quenching rate measured by LIF on the He 388.9 nm line. Moreover, for several experimental conditions, many Cd, Cd+, He and He+ excited state population densities are deduced from calibrated emission spectroscopy. The population inversions between the 6G and 4F levels and between the 6F and 6D levels are observed. The voltage-current characteristics versus cadmium density and helium pressure are also recorded and related to the atomic excitation in the discharge. From the behaviour of the helium and cadmium excited state population, for different experimental conditions, the part played in excitation professes by the three electron groups (thermal, secondary, primary electrons) can be discriminated. Consequently an estimate of the electron energy distribution function is deduced by combining the absolute population measurement and rate equation for several He or Cd+ excited states chosen to probe a particular range of electron energy. Finally, the populating channels of several Cd+ excited states are investigated. It is determined that the mixed 9S, 9P, 8D, 6F , 6G and 6H levels are mainly populated by a charge transfer reaction with a total rate coefficient of 4.23*10-10 cm3 s-1. The 5F, 5G and 7D levels are essentially populated by radiative cascades and the 4F, 6D and 7P levels are populated by radiative cascades and by electron excitation from the Cd+ ground state.

Evaluation of sampling methods for Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae) on cowpea

AbstractFive sampling methods were evaluated for efficiency in estimating field populations of Megalurothrips sjostedti (Trybom) on cowpeas in Nigeria. The methods (sticky traps, water traps, sweep netting, shaking plants and the collection of whole plant samples) were judged on the basis of low sample variance, low cost and fidelity to absolute population trends. Shaking plants and water traps were the best sampling techniques on the basis of sample variance and cost. Shaking plants also showed the closest correlation with absolute population trends and is therefore recommended for rapid estimation of field populations of thrips. The performance of the usual alcohol method of sampling M. sjostedti on cowpeas (collecting racemes and flowers in alcohol) was not comparable with those of shaking plants and water traps, but was considered important because it sampled the infested structures, eliminating more transient visitors which might also be sampled by shaking plants.

The Rat Populations of NIMH: Density, Reproduction, and the Neocortex

Investigations of the effects of crowding on social behavior has long been a major focus of the research on rodent populations conducted in the laboratory of John B. Calhoun, at the National Institute of Mental Health. In these studies, rats living under crowded conditions exhibited many behavioral abnormalities, including poor parental behavior, and excessive aggression. These behavior patterns are similar to those displayed by rats with neocortex damage except that the latter were tested under controlled, uncrowded conditions. An experiment was designed to examine the concomitant effects of forebrain lesions and population density upon a rat's capacity to cope with social complexity. The behaviors of rats with less than 50 percent of the normal neocortex, resulting from prenatal chemical treatment, were compared at two population densities to similar groups of normal rats. The micrencephalic rats were initially and generally less capable parents and were more aggressive than normals. In both types of rats, females in populations of eight bisexual pairs reared proportionally fewer of their offspring to weaning age than females in populations of four pairs. The overall reproductive success of normal rats at the higher population density was as poor as that of the micrencephalic rats at the lower population density. These results have been interpreted as showing that rats are sensitive to differences in population density even at relatively low absolute population sizes, and that increased population density interferes with the capacity of the neocortex to cope with environment complexity.

Estimation of nektonic insect populations

SUMMARY 1. A water column sampler is described for obtaining absolute population estimates of nektonic insects in shallow waters.2. Relative population estimates were obtained for Corixidae (Hemip‐tera) and Buenoa(Hemiptera: Notonectidae) using a standardized sweep net procedure and compared to absolute estimates from column samples. These two types of estimates were highly correlated among lakes.3. Simultaneous prediction and tolerance intervals for predictions from linear regressions indicated that reliable absolute population estimates generally cannot be expected from relative estimates

Population Projections from Simple Models

SUMMARY (1) Examples of geometric growth patterns in large-mammal populations are examined, and used to assess a 'ratio' method for estimating growth rate. (2) Simple difference equation models for populations subjected to extensive removals are used to estimate potential rates of growth in the presence of removals, using the ratio method and a minimum chi-square (x2) fitting procedure. Ten examples demonstrate use of the models and methods of estimating growth rates. (3) Density-dependence is evident in some examples, and complicates fitting and projecting into the future. (4) The approach requires absolute population estimates when removals occur, and is unsatisfactory if there is a substantial unmeasured loss associated with the known removals.

The Present and Future of Large Cities

The problems associated with large cities in the USSR are growing increasingly urgent due to the increase in their number and in the size of their populations. To date, the country has reached quite a high level of urbanization. During the years of Soviet power, 1,266 cities have been created, and the share of urban dwellers in the nation's total population has risen from 18% in 1917 to 65% in 1984. Furthermore, megalopolises [krupneishie goroda] and large cities are growing at a more rapid rate. On January 1, 1985, there were 51 cities with a population in excess of half a million persons; 22 of them had a population over a million. More than one-fourth of the nation's urban population lives in megalopolises (cities with a population over 500,000 persons). Cities with a population under 100,000 persons are the only group of urban settlements whose absolute population is more or less stable, but their share in the country's urban population is declining.

Persistence and Stability of Fish and Invertebrate Assemblages in a Repeatedly Disturbed Sonoran Desert Stream

Persistence, a measure of presence or absence of species, and stability, an estimate of assemblage equilibrium measured as constancy in species ranks or densities, should both be considered when assessing temporal change in natural assemblages. We measured persistence and stability in two distinct animal assemblages frequently disturbed by natural and severe flooding events, the fishes and benthic invertebrates in a Sonoran Desert stream. A persistence index (derived from colonization/extinction analyses) indicates high persistence of fishes for several decades, while benthic invertebrates were persistent except in periods of severe flooding. Stability of taxon rankings (measured by Kendall's W) was high for both assemblages, even though absolute population sizes fluctuated. Fish populations resisted even the most severe flood disturbances, whereas benthic invertebrates were decimated by particularly frequent and intensive flooding. The latter were resilient, however, and quickly recovered due to life history characters favoring rapid postflood recolonization. Although absolute numbers of organisms varied through orders of magnitude, more general aspects of assemblage structure (species' presence or absence, and relative rankings) remained relatively constant despite repeated and potentially devastating natural perturbations. INTRODUCTION In their synthesis of ecological stability and persistence, Connell and Sousa (1983) emphasized the utility of a multifaceted approach in temporal analyses of community structure. Drawing upon the works of Holling (1973), Boesch (1974), Orians (1974) and Whittaker (1974), among others, they presented qualitative and quantitative criteria to be considered when assessing changes in community structure over time. Qualitatively, persistence of species focuses upon their continued presence, particularly with respect to potentially devastating forces. Quantitatively, stability is the relative constancy of species abundances over time despite disturbances. Stability may result from resistance, when relative species abundances are unchanged despite potentially disruptive forces, or resilience, rapid return to the former state following disturbance. Both persistence and stability should be considered when attempting to understand community pattern and process (Holling, 1973). The possibility of destructive disturbance is a necessary feature of communities that are used to investigate temporal change. . . for any situation to be included under the concept of stability . . .there must exist disturbing forces; without them, simple lack of change in numbers is of little interest (Connell and Sousa, 1983). Consequently, responses of natural communities to disturbance are central to current ecological research (Dayton, 1971; Sousa, 1979, 1984; Matthews, 1986), and disturbance provides a framework upon which mechanistic understandings of community structure and function may be developed. We examined persistence and stability of fish and benthic invertebrate assemblages in a Sonoran Desert stream that repeatedly experiences large, quantifiable natural dis-