bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of sterile insect releases on a population under predation or parasitism
Authors: Barclay H. , Mackauer M. 
Published: October 2006

SummaryA continuous‐time differential equation model was constructed which describes the population dynamics of a predator prey system in which sterile prey are released in a program designed to eradicate or reduce the prey population. It was found that the dynamics of the system behave quite differently when predators are present.Two conditions were found which have differing implications for the control program. If the predators still exist when the wild prey population declines to extinction, then the SIRM is assisted by the predators, sometimes to a considereble extent. If the predators decline to extinction before the wild prey population goes extinct, then the predators may or may not assist the SIRM depending on the parameters of the system. If the predators do assist the SIRM, then a potentially dangerous situation exists in which an explosion of the prey population could occur after the predators go extinct. Predator polyphagy would probably minimize this danger of an explosion since it would stabilize the predator population.
Prey preference of the wolf spider, Pardosa pseudoannulata (Boesenberg et Strand)
Authors: Heong K. L. , Bleih Saad , Rubia Elsa G. 
Published: October 2006

SummaryFunctional responses of the wolf spider, Pardosa pseudoannulata (Boesenberg et Strand) attacking the rice brown planthopper, Nilaparvata lugens (Stål.), and the mirid predator Cyrtorhinus lividipennis Reuter were both those of Holling Type II. The attack rate was higher and handling time lower for C. lividipennis. However, when caged with the two prey, the wolf spider showed a significant preference for N. lugens at a lower prey proportion. Proportions of prey attacked were significantly different from the expected ratios of prey available as well as from the predicted preferences derived from the functional response parameters. As proportions of N. lugens attacked changed from greater to less than expected as the proportions of N. lugens available increased, a “reverse switch” behaviour seems to be evident.
Contest and scramble competitions in two bruchid species, Callosobruchus analis and C. Phaseoli (Coleoptera: Bruchidae)
Authors: Toquenaga Yukihiko , Fujii Koichi 
Published: October 2006

SummaryWe performed multiple‐generation competition experiments between Callosobruchus analis and C. phaseoli with different bean sizes. In each system, we supplied 5 g of mung beans (Vigna radiata) every 10 days. We examined three types of bean conditions: 5 g of large beans, 5 g of small beans, and a mixture of 2.5 g of large and small beans. In small bean condition, C. analis dominated C. phaseoli in all three replicates and C. phaseoli was extinct by the 260th day. On the contrary, C. phaseoli overcame C. analis within 250 days in large beans in all three replicates. In mixed beans condition the two bruchid species coexisted more than 500 days in two out of the three replicates. Even in the exceptional case, both species coexisted for 460 days. These results were examined in the light of the predictions from short‐term larval competition experiments and a game theoretical model by Smith and Lessells (1985). The density and frequency dependent results during larval competition inside a bean was concluded to be a main factor to produce the above long‐term competition results.
Spatial pattern of pine wilt disease caused by Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) within a Pinus thunbergii stand
Authors: Togashi Katsumi 
Published: October 2006

SummaryTo understand the mechanism of spread of pine wilt disease caused by the pinewood nematode, Bursaphelenchus xylophilus, which is vectored by a cerambycid, Monochamus alternatus, the spatial distribution of trees weakened by the nematode was examined within a Pinus thunbergii stand from June to October for 4 years. The weakened trees were distributed in a clumped pattern in 1980 and 1981, at an early stage of infestation. In many cases, they showed a double‐clumped pattern. The degree of aggregation was higher in June or July than after August. They were uniformly distributed in June or July 1982 and in June 1983 whereas they showed a double‐clumped pattern after August. The trees were frequently weakened in June or July when they were near the trees weakened during the previous year. At quadrat sizes of more than 25 m2, spatial overlapping was pronounced between trees weakened during June–July of the current year and those weakened in the previous year. The seasonal changes in spatial distribution of weakened trees were explained by the interaction among M. alternatus, B. xylophilus and Pinus trees.
Inter‐ and intra‐population variations in diapause attribute of the two‐spotted spider mite, Tetranychus urticae Koch, in Japan
Authors: Takafuji Akio , So Ping‐Man , Tsuno Nobuko 
Published: October 2006

SummaryPopulations of the two‐spotted spider mite, Tetranychus urticae Koch collected from various localities and from various host plants in Japan showed wide variations in diapause attribute. Diapause percentages at 18°C/9L15D varied from nearly 100% in the north to 0% in the south‐west. At intermediate latitudes the mites showed wide inter‐population variations. Populations on herbaceous hosts in vinyl‐ or glass‐houses gave significantly lower incidence of diapause than those on roses and deciduous fruit trees. Presence of winter hosts and better host quality under protected environments seemed to favour non‐diapausing mites.The temperature threshold for diapause expression also varied widely among local populations. Northern populations consistently had higher and less variable thresholds than populations at intermediate latitudes with thresholds between 15 and 18°C. Inbred lines derived from a population in Kyoto exhibited a wide variation in diapause percentage at 18°C. These results show that diapause in T. urticae is a quantitative threshold trait and that populations in central Japan consist of a variety of genotypes with different diapause traits. This might provide a genetic source for adaptation to local and temporal variations in environmental conditions.
Yearly variation in recruitment and its effect on population dynamics in Yoldia notabilis (Mollusca: Bivalvia), analyzed using projection matrix model
Authors: Nakaoka Masahiro 
Published: October 2006

SummaryLong‐term variation in recruitment was estimated by constructing projection matrices for a marine bivalve, Yoldia notabilis, at two stations in Otsuchi Bay, northeastern Japan, and the effects of its variation on population dynamics were examined using a simple matrix model. The matrix model was developed from the Leslie matrix, in which the population growth rate λ was expressed as a function of recruitment rate r0. The equilibrium recruitment rate rs, or the recruitment rate required to maintain population at constant size (λ=1), was expressed by the reciprocal of the reproductive value of a newly recruited individual. The estimates of rs for the field population were lower at the shallower station than at the deeper station, reflecting higher survivorship and fecundity. Past recruitment rate estimated both by the field samplings for 3 years and by the back‐calculation from the current age structure for over 10 years showed large yearly variation, ranging between 0 and 58.6×10−4. The estimates were larger than rs, and hence, large enough to increase population size (λ>1) only in approximately one‐third of the estimated years. This suggests that the population has been maintained by occasional successful recruitment occurring once every few years.
Population‐level analysis on reduction in equilibrium population size of the azuki bean beetle
Authors: Tuda Midori , Shimada Masakazu 
Published: October 2006

SummaryResponses of laboratory population of the azuki bean beetle Callosobruchus chinensis to temperature conditions of 30°C and 32°C are compared. Equilibrium population size was found to be lower at 32°C. A one‐generation process examined by reproduction‐curve experiments is divided into two consecutive life stages specified by different habitats, i.e., outside and inside beans. Modified logistic difference equations are used to describe these population‐level responses at each life stages. Sensitivity analysis is used to determine parameters of importance, thus determining the main cause of the reduced equilibrium population size at 32°C. The reduction resulted from the decrease in maximum population size of emerged adults which have experienced inside‐bean process. The application and limitation of this population‐level analysis to different levels are discussed.
Index of intensity of sexual selection: A comment on Nishida's article
Authors: Kasuya Eiiti 
Published: October 2006

SummaryAn index of intensity of sexual selection proposed by Nishida (1992: Res. Popul. Ecol. 34: 373–382) was examined. Two examples were presented to show that Nishida's index was not free from confounding effect of mortality schedule. Importance of removing the phylogenetic effects in comparative analyses was also discussed.
Density dependence depends on scale; at larval resource patch and at whole population
Authors: Tuda Midori 
Published: October 2006

SummaryA previous study (Tuda and Shimada, 1993) has shown that the equilibrium population size of the azuki bean beetle was lower at 32°C than at 30°C and that this difference was due to a reduced maximum population size of emerged progeny through inside‐bean process. In this paper, these results were analyzed further on the scale of the individual bean where interaction among larvae took place. Per‐bean numbers of deposited eggs, hatched eggs, and emerged adults have been recorded at seven different parental densities under the two temperature conditions.Three individual‐bean‐scale process hypotheses that may explain the reduced maximum emergence density on the whole population scale are suggested: (1) a lower maximum emergence per bean at 32°C than at 30°C, if the bean scale and the wholepopulation scale share the same density‐dependent pattern in adult emergence, (2) a limited range of hatched egg number per bean at 32°C, resulting from the adult oviposition process outside beans, and (3) different patterns of density‐dependent emergence between the two different scales.This study showed that the inside‐bean pattern of responses on the bean scale was a simple saturated curve at 30°C, but one with a discontinuous decline at higher hatched egg densities at 32°C. On the contrary, during outside‐bean process, the peak number of hatched eggs decreased on this scale as observed on the wholepopulation scale. I discuss why the extracted factor of inside‐bean process on the whole‐population in the previous study could not be applied to the bean‐scale pattern.
A population dynamic model of Batesian mimicry
Authors: Yamauchi Atsushi 
Published: October 2006

SummaryA population dynamic model of Batesian mimicry, in which populations of both model and mimetic species were considered, was analyzed. The probability of a predator catching prey on each encouter was assumed to depend on the frequency of the mimic. The change in population size of each species was considered to have two components, growth at the intrinsic growth rate and carrying capacity, and reduction by predation. For simplicity in the analyses, three assumptions were made concerning the carrying capacities of each population: (1) with no density effects on the mimic population growth rate; (2) with no density effects on the model species; and (3) with density effects on both species. The first and second cases were solved analytically, whereas the last was, for the most part, investigated numerically. Under assumption (1), two stable equilibria are possible, in which both species either coexist or go to extinction. Under assumption (2), there are also two stable equilibria possible, in which either only the mimic persists or both go to extinction. These results explain the field records of butterflies (Pachliopta aristolochiae and its mimic Papilio polytes) in the Ryukyu Islands, Japan.
Intervening in pest outbreaks: Simulation studies with the western tent caterpillar
Authors: Thompson W. A. , Vertinsky I. B. , Wellington W. G. 
Published: October 2006

SummaryA stochastic model mimicking the behavior of the western tent‐caterpillar populations on Vancouver Island was used to study methods of suppressing an outbreak. Since many forest defoliators often receive only one treatment during their outbreak period, we applied a hypothetical single treatment at different times during a simulated outbreak, to assess the influence of timing.Intervening early in the cycle was the best method of suppressing numbers below a tolerable threshold during a particular outbreak. Treatment during the most rapid period of increase was less effective, and treatments at or beyond the peak provided little relief during that particular outbreak. For longer‐term protection, however, treating the refugia of a declining population was far superior to less selective intervention. Concentrating the treatment within these refuges decimated the breeding stock surviving there at a time when the population could least afford such injury. Timing and focussing the intervention to obtain that maximal impact thus prolonged the period of suppression during the next outbreak.
Some risks and causes of mortality in mountain pine beetle populations: A long‐term analysis
Authors: Cole Walter E. 
Published: October 2006

SummaryThe interpretation of the probabilities presented in this paper is that none of the competing biological risks, acting in the presence of other risks, offers much, if any, regulatory influence upon a mountain pine beetle population. Consequently, if no single risk, or combination of these risks, offers much help, then the contention that mountain pine beetle populations are food‐regulated is once again strengthened (Cole andAmman, 1969). The evidence remains (or continues) that the mountain pine beetle is food‐regulated at optimum temperature conditions and temperature‐regulated at optimum food conditions. Reducing and/or minimizing tree loss to the mountain pine beetle is thus dependent upon manipulating the food supply or management of the tree (stand) growth.
Some beneficial effects of aggregation in young larvae of Pryeria sinica moore (Lepidoptera: Zygaenidae)
Authors: Tsubaki Yoshitaka 
Published: October 2006

SummaryThe effects of group size on the survival and development of young larvae of Pryeria sinicaMoore were investigated by laboratory and field experiments.Under laboratory conditions, about 20% of isolated larvae died of unsuccessful feeding in the first instar, however, larvae survived successfully in aggregations of four or more individuals.In the field, larvae emerge in early spring and wait for new leaves to open before feeding. In this period, the larger the group size of hatchlings the survival rate became higher. The nest‐web spun by hatchlings was considered to play an important role in protecting them from desiccation. In the period that larvae began to feed on leaves, more than 36 larvae are necessary to aggregate for the successful establishment of feeding groups. The nest‐web played an important role also in the establishment of feeding group. However, the natural group size of the first instar larvae was larger than the minimum group size to spin a sound nest‐web in the field experiment.On the other hand, in later stage, larvae in a large group did not have an excess advantage in survival or developmental rate over larvae in a small group. It was found that the experiments on survival and developmental rates could not explain the reason that this species maintain large compact groups in the most part of larval period.
The effect of larval age range on survival of two Tribolium castaneum strains in mixed cultures, through pupal cannibalism
Authors: Wool David 
Published: October 2006

SummaryThe effect of larval age range on survival of two Tribolium castaneum strains in mixed cultures was studied in an experimental situation in which other selective forces were reduced to a minimum. Increasing the difference in larval age setween the strains by one day resulted in a reduction of survival of the faster‐developing mutant strain, because more of its earlier pupae were cannibalized by the larvae. General aspects of the effects of pupal cannibalism by larvae on the outcome of intra‐specific competition (sensu lato) in Tribolium are discussed.
Studies on the interspecies competition between the azuki bean weevil and the southern cowpea weevil IV. Competition between strains
Authors: Fujii Koichi 
Published: October 2006

SummaryThis study analyzes results of interspecies competition between the azuki bean weevil, Callosobruchus chinensis and the southern cowpea weevil, C. maculatus using the four geographical strains of each species.
Fifteen combinations of one strain from each species were set up to compete. The strains of C. chinensis, rather than of C. maculatus, characteristically determine the eventual outcomes of competition. Some strains of C. chinensis (jC and kC) invariably won every encounter with C. maculatus. Another strain (nC) always lost its encounters, while one other strain (iC) won some encounters (:cQ and :cQ) and lost others (:tQ and :bQ). For any combination the competition results were deterministic and no reversal in outcome was observed among the replicates.
The weakness of strain nC in competition is explained by its characteristics in single species populations, different greatly from other strains of C. chinensis, although it had the similar primary (individual) characteristics as other strains of C. chinensis. Strain iC had the shortest adult longevity in the four strains of C. chinensis although it behaved similar to strain jC at the single species population level. Especially under the food supply schedule of the present experiment the shortness of adult longevity might be the important factor determining the outcome.
The relationship of the eight strains based on the individual and single species population characteristics, and that based on the competition results were very similar. Even when the competition results could not be explained by any one or two of these characteristics alone, the outcome would be largely decided by the overall biotic profile made by several characteristics.
Host‐feeding and oviposition strategies of parasitoids in relation to host stage
Authors: Kidd N. A. C. , Jervis M. A. 
Published: October 2006

SummaryUntil now, mathematical models of parasitoid‐host interactions have not incorporated the tendency for destructively host‐feeding parasitoids to partition their feeding and oviposition behaviour in relation to different host stages. A literature survey reveals a trend for female parasitoids to feed preferentially or exclusively on earlier host stages and to oviposit preferentially or exclusively in/or later ones.We explore the relative advantages to host‐feeding parasitoids of a number of possible host stage selection strategies. We develop hypotheses, formalizing and testing them using modifications to our earlier simulation model of host‐feeding strategies (Jervis and Kidd, 1986).We conclude from our modelling that the advantage to be gained from feeding on early host stages and ovipositing in late ones is likely to be associated with: 1) reduced handling times when feeding on early stage hosts; 2) reduced wastage of progeny from mortality factors other than host‐feeding by the parent parasitoid, achieved by confining oviposition to late host stages; and 3) reduced probability of progeny mortality resulting from the parent's host‐feeding activities.
Verifying zero‐infestation in pest control: A simple sequential test based on the succession of zero‐samples
Authors: Kuno Eizi 
Published: October 2006

SummaryA simple sequential test based on the succession of ‘zero's or uninfested sampling units is proposed for use in verifying zero‐infestation in pest control surveys. The method is applicable efficiently to both finite and infinite populations. Problems concerning its efficiency on application are discussed.
Alternative models for species replacement of pelagic fishes
Authors: Matsuda Hiroyuki , Wada Tokio , Takeuchi Yasuhiro , Matsumiya Yoshiharu 
Published: October 2006

SummaryIt is well known that the stock abundance of a pelagic fish usually fluctuates and a species of pelagic fish which was dominant in abundance is often taken over by another species. Several alternative models for species replacement among pelagic fishes are presented and analyzed: (A) environmental fluctuation, (B) strong density‐dependent reproduction rate, (C) a two‐species system with phase variation (density‐dependent change of life history traits), (D) a two‐species competition system with environmental fluctuation, (E) cyclic advantage relationship among three competitive species, and (F) a two‐prey, one‐predator system. Different model requires different number of species for the occurrence of species replacement. Three criteria to test each hypothesis from qualitative properties of species replacement are proposed. Possible management policies to decrease the amplitude of stock fluctuations are discussed. As a result, if the catching effort to mackerels which is rare now is large, or if the catching effort to the sardine is still large when it begins to decline in stock abundance, fisheries may be strong destabilizing effect on the stock abundance.
Host‐feeding and oviposition by parasitoids in relation to host stage: Consequences for parasitoid‐host population dynamics
Authors: Kidd N. A. C. , Jervis M. A. 
Published: October 2006

SummaryAmong parasitoids which host‐feed destructively, there is a tendency for females to partition their feeding and oviposition behaviour in relation to different host stages, feeding preferentially or exclusively on earlier host stages and ovipositing preferentially or exclusively in (or on) later ones. We explored the dynamic implications of this behaviour for parasitoid‐host population dynamics, using modifications of the age‐structured simulation models of Kidd and Jervis (1989, 1991).Using the new versions of the models, we compared the situation where parasitoids practice host stage discrimination with respect to feeding and oviposition, with the situation where they do not. Additionally, we examined the effects of host stage discrimination on populations by (a) having generations either discrete or overlapping, (b) varying initial age structure, (c) having varying degrees of density dependence acting on host adult mortality, and (d) varying parasitoid develoment times in relation to the length of host development.With either discrete or overlapping generations of the host population, a reduction in the parasitoid development time had a destabilizing influence on the parasitoid‐host population interaction. With discrete generations stage discrimination had no effect on the risk of extinction, irrespective of either the degree of density dependence acting on the host population, or the initial age structure of the host population. When parasitoid search was uncoupled from the insect's adult energy requirements, the interaction was always unstable. With continuous generations, stage discrimination affected stability at certain parasitoid development times, but not at others. The relative lengths of parasitoid and host development times also influenced the tendency of the host population to show discrete or overlapping generations.
Dynamics of an enclosed population of pine mice, Microtus pinetorum
Authors: Gentry John B. 
Published: October 2006

SummaryEnclosed populations of pine mice were studied over a 28‐month period and compared with populations in surrounding natural areas. The enclosed populations reached densities far greater than any observed in surrounding natural areas. It is suggested that the restriction placed on dispersal by the enclosure walls and the addition of food in the form of trap bait could have allowed the enclosed populations to reach higher densities than normally observed at SRP.