bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lattice population dynamics for plants with dispersing seeds and Vegetative propagation
Authors: Harada Yuko , Iwasa Yoh 
Published: October 2006

AbstractThe population dynamics of plants in a lattice structured habitat are studied theoretically. Plants are assumed to propagate both by producing seeds that scatter over the population and by vegetative reproduction by extending runners, rhizomes, or roots, to neighboring vacant sites. In addtion, the seed production rate may be dependent on the local density in the neighborhood, indicating beneficial or harmful crowding effects. Two sets of population dynamical equation(s) are derived: one based on mean‐field approximation and the other based on pair approximation (tracing both global and local densities simultaneously). We examine the accuracy of these approximate dynamics by comparing them with direct computer simulation of the stochastic lattice model. Pair approximation is much more accurate than mean‐field approximation. Mean‐field approximation overestimates the parameter range for persistence if crowding effects on seed production are harmful or weakly beneficial, but underestimates it if crowding effects are highly beneficial. Dynamics may show bistability (both population persistence and extinction) if the effect of crowding is strongly beneficial. If there is a linear trade‐off between seed production and vegetative reproduction, the equilibrium abundance of the population may be maximised by a mixture of seed production and vegetative reproduction, rather than by pure seed production or by pure vegetative reproduction. This result is correctly predicted by pair approximation but not by mean‐field approximation.
Effects of capacity on resource input and the aquatic metazoan community structure in phytotelmata
Authors: Sota Teiji 
Published: October 2006

AbstractAquatic metazoan communities in treeholes and bamboo stumps were studied on Tsushima Island, Japan, in March and June in relation to the habitat size and the resouce amount. The amount of leaf detritus increased with an increase in the capacity (volume) of the phytotelma. The input rate of leaves depended upon the opening area of the phytotelma. Twenty‐one metazoan inhabitant taxa consisted of 17 dipteran saprophages, a helodid beetle larva, a nematoda, a naidid, and a predator,Toxorhynchites towadensismosquito larva. Treeholes harbored 17 taxa and bamboo stumps 20; 16 taxa were common in both phytotelmata. The number of taxa and the biomass of metazoa per phytotelma was positively correlated with the capacity. The densities of dominant saprophages such as helodid, chironomid, andCulicoideslarvae were positively correlated with the capacity of phytotelmata, and the variation in their abundance contributed much to the variation in the species composition in individual phytotelmata. With an increase in capacity, treeholes harbored more helodids andCulicoides, whereas bamboo stumps harbored more chironomids andDasyhelea. Thus, the amount of resource, species richness and biomass per phytotelma largely depended upon the capacity, and the difference in community structure between treeholes and bamboo stumps was attributable to the differential colonization patterns of different taxa.
The learning abilities of the white cabbage butterfly, Pieris rapae, foraging for flowers
Authors: Kandori Ikuo , Ohsaki Naota 
Published: October 2006

AbstractThis study examines the role of learning and memory in the butterfly Pieris rapae crucivora Boisduval during foraging for flowers. In an outdoor cage with 6 flower species, P. rapae showed various visiting patterns: some visited only one species, while others visited several species in a day. The foraging process for flowers of Erigeron annuus (L.) Pers. could be divided into two successive steps: (1) landing on the nectaring caputs, and (2) finding the source of nectar in the caput. Butterflies learned to proceed through the two steps more efficiently with successive attempts: they gradually decreased landings on nectarless caputs and probings on the nectarless petals of ligulate flowers respectively. As a result, handling time per unit caputs became shorter, and apparent rewards per unit time, i.e. the efficiency of collecting nectar, increased. In addition, once learned, P. rapae could remember a rewarding flower color for 3 days, which was not interfered with by learning another flower color. This indicates that P. rapae keeps memory for a period longer than 3 days, and that they can remember at least two flower species as suitable flower resources. Furthermore, data indicated that they sometimes can apply the foraging skills obtained on other flower species to a novel one. These abilities could enable butterflies to easily switch flower species, or to enhance labile preference. It has been known that P. rapae also shows flower constancy, which may be due to memory constraints. Therefore, they may appropriately use two foraging tactics: visit consistency and labile preference, to get enough nectar according to their circumstances.
Flower nectar of an autogamous perennialRorippa indicaas an indirect defense mechanism against herbivorous insects
Authors: Yano Shuichi 
Published: October 2006

AbstractThis report shows that one of the most important roles of the flower nectar of an autogamous perennialRorippa indica(L.) Hieron is as an attractant for employing some ant species as a defense against herbivorous insects. The plant has flowers from spring to early winter. Its flower nectar is frequently stolen by some ant species (hereafter cited as ants) which also feed on small herbivorous insects on the plant. Internations among the tritrophic levels (R. indica, herbivores, ants) were experimentally examined and the followings became clear. (1) Ants were attracted toR. indicain search of its flower nectar. (2) The gradual secretion of flower nectar seemed to detain ants on the plant. (3)Pierisbutterfly lavae were the major herbivores onR. indicaand were potentially harmful to the plant. (4) The presence of ants reduced the survival rate ofP. rapaelarvae onR. indica. (5) The presence of ants reduced the feeding damage toR. indica. (6) The disadvantage of nectar use by ants seemed to be minimal for the plant since the ants did not disturb the other flower visitors. These facts suggest a mutualistic relationship betweenR. indicaand ants. That is, the flower nectar serves as an indirect defense against herbivorous insects.
Implications of changes in arthropod distribution following chemical application
Authors: Trumble John T. 
Published: October 2006

SummaryThe influence of pesticide application on the within‐field distribution of arthropods was investigated for Tetranychus urticae, the twospotted spider mite, on strawberries. Analyses of dispersions based onGreen's coefficient,Iwao's regression of mean crowding on the mean, andTaylor's power law all indicated that mite populations were highly aggregated initially. As densities increased, more of the avialable niches were filled, leading to a less clumped dispersion. However, pesticide applications causing greater than 99.9% mortality acted in a nearly density independant fashion and, although the originating populations were similar in number, did not produce dispersions equivalent to the initial migrants. As a result, ignoring these changes by developing sampling plans based on dispersion indices which generated a single slope for an entire data set, led to statistical errors that invalidated the sampling programs. In order to accurately reflect the field biology of the spidermites, sampling plans for pre and post‐treatment populations were substantially different.The impact of such changes in dispersion were graphically demonstrated using both sequential and binomial sampling techniques. Both methods showed that fewer samples were necessary to estimate densities at a given precision level for post‐treatment populations. Also, these techniques indicated that post‐treatment populations had similar, but significantly different, dispersions. The implications of changes in pre and post‐treatment dispersions, as well as problems associated with inconsistant dispersions following pesticide use, are discussed.
Population dynamics of a phytophagous lady‐beetle, Henosepilachna vigintioctopunctata (Fabricius), living in spatio‐temporally heterogeneous habitats. I. Estimation of adult population parameters based on a capture‐recapture census
Authors: Hirano Kohji 
Published: October 2006

Summary
The population processes of the lady‐beetle, Henosepilachna vigintioctopunctata (F.), were studied from the spring of 1976 to 1979 in an area (about 150,000 m2) including 17 patches of host plants.
Amplitudes of yearly fluctuations of adult densities were 2.9 for overwintered adults, and 1.4 and 1.9 for the first and the second generation adults, respectively.
The higher the adult density, the lower the rate of increase of the number of adult females to the next generation. However, the density dependent decrease in the reproductive rate was not caused by starvation.
The patchy nature of the farmland habitats seemed to have effects on the stabilization of population numbers.
Metastability of forest ecosystems infested by bark beetles
Authors: Berryman Alan A. , Stenseth Nils Chr , Wollkind David J. 
Published: October 2006

SummaryA simple two‐species differential equation model is used to investigate the intrinsic metastability of forest ecosystems subjected to bark beetle infestations. We demonstrate that only one globally stable node or limit cycle is likely under biologically plausible conditions, but that, in the former case, this equilibrium is very sensitive to external perturbation.
Mining pattern of the honeysuckle leaf‐miner Phytomyza lonicerae
Authors: Katô Makoto 
Published: October 2006

SummaryThe mining pattern of the honeysuckle leaf‐miner Phytomyza lonicerae which feeds on Lonicera gracilipes was analyzed with special reference to the avoidance of parasitoids' attacks. The leaf‐miner makes the linear mine with branches and crosses by turning and branching, off the backtracking mine. Both average numbers of turnings and branchings were about 4. The speed of mining was 1.5 times faster in backtracking than in advancing. The mine width increased as the mining larva grew and total volume of consumed plant tissue was nearly constant independent of variability of the number of turnings and other characteristics of the mine. The majority of larval mortality were due to attacks by parasitoid wasps (Chrysochairs pentheus and Diglyphus minoeus), which locate the present position of leaf‐miners, by tracing mine tracks, and wasps attack leaf‐miners at a higher rate in backtracking than in advancing. The adaptive significance of branching and crossing by leaf‐miners was discussed in terms of the reduction of parasitoids' attacks.
Life cycle of a non‐diapausing population of the two‐spotted spider mite, Tetranychus urticae Koch in a pear orchard
Authors: Takafuji Akio , Kamibayashi Mitsuji 
Published: October 2006

SummaryThe life cycle of a non‐diapausing T. urticae population was studied in a pear orchard in the southern part of Okayama Prefecture, western Honshû, Japan. The mites overwintered only on biennial weeds in the orchard without entering diapause, started to increase in number in early spring on them and then moved to other weeds as they emerged. The occurrence of the mites on pear began in early May several weeks after the unfolding of pear leaves and the population on pear was initiated by the migrants from the weeds around the base of pear trees. The population on pear showed two distinct peak occurrences, one in June and the other in mid‐autumn. After pear leaves dropped in late autumn, the mites returned to biennial weeds for overwintering.
Evaluation of the role of Microvelia douglasi atrolineata (Bergroth) (Heteroptera: Veliidae) as predator of the brown planthopper Nilaparvata lugens (Stål) (Homoptera: Delphacidae)
Authors: Nakasuji Fusao , Dyck V. A. 
Published: October 2006

SummaryThe biology of the veliid bug M. d. atrolineata, its predatory behavior, and the effects of plural hunting were studied to evaluate its role as a predator of the brown planthopper Nilaparvata lugens in the Philippines. The probability of planthoppers falling onto the water surface and provision of habitat continuity was measured by a sticky trap placed at the base of rice hills in a greenhouse and in paddy fields.The developmental period of immature stages combined was 21 days. If given prey, females laid 25 eggs on the average during an adult life span of 18 days. Starved adults could survive for only 3–5 days.The functional response to prey density was sigmoid, and the maximum number of prey killed was 7 per day. Prey feeding was completed in 12–36 min. The percentage of successful prey attacks averaged 5–8%, decreasing with higher (and larger) developmental. stages of prey, but adult prey were found the soonest. Plural hunting increased the probability of capturing prey by as much as 2.5 times that by individual hunting.Late‐instar nymphs, which may be more active, fell from rice hills in a greenhouse more than early‐instar nymphs, and the number falling increased with density. In the field the percentage of planthoppers falling to the water in 1 day varied considerably, from 1% for nymphs in one field to 67% for adults in another field.On the basis of work described above and given the high density of veliid predators in flooded paddy fields of tropical Asia, M. d. atrolineata is considered one of the most important natural enemies of the brown planthopper.
Component analysis and modelling of the movement process: Analysis of simple tracks
Authors: Kitching R. L. , Zalucki M. P. 
Published: October 2006

SummaryThe construction of a general model of animal movement using the ‘experimental components' approach ofC. S. Holling is proposed. The process of ‘movement’ is interpreted very generally as any displacement of the whole organism in space. The rationale for modelling such processes rests upon the idea that there is a basic “canonical” pattern of movement characteristic of a species moving in a homogeneous environment, which pattern is overlaid by the various directional stimuli present in more usual heterogeneous environments.The ‘canonical movement model’ is a necessary first step in construction of more realistic representations. We suggest it can be made using six components viz. the initial heading of the animal, the mean and variance of the angular displacements made by the animal as it moves, the mean and variance of the speed of the animal, and a term for the continuity of the movement. We have measured all these components in the field for the two‐dimensional movement of the inter‐tidal snail, Polinices incei and these results are presented here. Difficulties inherent in the measure ment of angular displacement in particular are discussed and means of resolving them proposed.The shortcomings involved in the measurements and techniques for their more detailed representation and the next steps in the proposed modelling sequence are discussed.
Pest population stability under sterile releases
Authors: Barclay Hugh J. 
Published: October 2006

SummaryThe stability of a pest population is one of the critical features to be examined when considering a control strategy for a given pest species. Four models involviing sterile male releases are examined for various stability characteristics; the models examined were: (i) a simple one stage model with no species interactions, (ii) a two life‐stage model, (iii) a model involving two competing species, (iv) a model in which the pest is under predation. Of the four, the simple model was the most stable and the predation model was the least stable under continued sterile releases.
Evolution of litter size
Authors: Itô Yosiaki , Iwasa Yoh 
Published: October 2006

SummaryTheories on the evolution of litter size among organisms were reexamined. The competition theories, including that based on the r−K‐selection hypothesis, could not explain well why low‐fecundity strategies have often evolved in stressful environments such as mountain streams, deep sea and the antarctic, where interspecies competition is considered to be lax. The theory, based on Itô's (1980) concept of the procurability of food by the young, was considered to have greater generality because it could explain not only the above‐mentioned cases but also those where small litter size is observed in habitats with high species diversity (where interspecific competition may be keen), such as tropical rain forest. Examination of the process of selection of high‐fecundity and low‐fecundity genotypes also suggested that the procurability of food by the young can best explain the evolution of low‐fecundity. The concept of density‐induced dispersal and a distinction between density‐dependent and density‐independent predation pressures should be incorporated into our discussions on the evolution of reproductive rates.
Contest and scramble competitions in Callosobruchus maculatus (Coleoptera: Bruchidae) II. Larval competition and interference mechanisms
Authors: Toquenaga Yukihiko 
Published: October 2006

SummaryCompetition between contest and scramble strategists was examined using two strains of Callosobruchus maculatus, the contest strain (iQ) and the scramble strain (tQ). The direct larval interference experiment within each strain showed that the contest strain performed strong direct interference throughout its larval stage against the conspecific opponent(s). The scramble strain also performed its interference, but only during the 3rd and the 4th larval stages. The inter‐strain larval competition experiments inside a large and small mung bean (Vigna radiata) showed that the contest strain was, in general, superior to the scramble strain in competition, but the competition results were density‐ and frequency‐dependent. In the large beans, the proportion of adult emergence of the contest strain increased with the increase of its own initial density but decreased as the initial density of the scramble strain increased. The shape of the proportion of adult emergence became nonlinear in the small beans. The cause of the complexity of inter‐strain competition results was discussed in the light of the difference in larval interference ability between the two strains.
Altered levels of PP2A regulatory B/PR55 isoforms indicate role in neuronal differentiation
Authors: Schild Andreas , Schmidt Karsten , Lim Yun‐An , Ke Yazi , Ittner Lars M. , Hemmings Brian A. , Götz Jürgen 
Published: October 2006

AbstractThe ubiquitously expressed serine/threonine‐specific protein phosphatase 2A (PP2A) is prominent in brain where it serves a wide range of functions under both physiological and pathological conditions. PP2A holoenzymes are composed of a catalytic subunit and a tightly complexed scaffolding subunit. This core enzyme associates with regulatory subunits of the B/PR55, B′/PR56/PR61, B″/PR72 and B‴/PR93/PR110 families. We previously determined distribution and expression levels of the four members of the B/PR55 family in brain, as dysregulation of this subunit family has been specifically implicated in neurodegenerative disorders including Alzheimer's disease. In the present study, we used cell lines widely used in neuroscience research to determine levels of the four PR55 isoforms by qRT‐PCR under different experimental conditions. We show that PR55α mRNA levels are highest in both HEK293 cells and SH‐SY5Y neuroblastoma cells whereas PR55β levels are lowest. Stepwise neuronal differentiation of SH‐SY5Y cells causes the selective upregulation of PR55β, and to some extent PR55γ and PR55δ, but not PR55α mRNAs. In agreement with the qRT‐PCR analysis, neuronal differentiation does not alter PR55α protein levels, whereas interestingly, PR55β and PR55γ protein levels are reduced when compared to undifferentiated cells. Our data point at specific roles for distinct regulatory B/PR55 subunits of PP2A in neuron‐like cells with PR55α being the major isoform.
Costs, valuation, and long‐term operating effects of global strategic alliances
Authors: Ojah Kalu 
Published: October 2006

AbstractUsing global product design and development as an example of global strategic alliance, I find that successful global strategic competition is still largely a variable cost reduction game as opposed to the recently touted fixed cost amortization game. Further, the firm's cost efficiency is enhanced when its global production initiative is characterized by a high degree of strategic alliances. Importantly, I find that global strategic alliances have both valuation effects and long‐term operating effects, and that both effects are positive functions of the degree of strategic alliances. After controlling for pertinent explanatory factors such as competitive strategy posture, industry concentration, geographic spread of operation, product‐type, and information technology infrastructure of firms, I find that variable cost and production efficiencies remain significant determinants of the valuation effects of global business alliances. Overall, results in this study suggest partnering firms should consider the relative efficiencies of inputs and production technology as effective ways of leveraging the benefits of global strategic alliances.
Does the El Niño–Southern Oscillation control the interhemispheric radiocarbon offset?
Authors: Turney Chris S.M. , Palmer Jonathan G. 
Published: October 2006

AbstractSince the 1970s it has been recognised that Southern Hemisphere samples have a lower radiocarbon content than contemporaneous material in the Northern Hemisphere. This interhemispheric radiocarbon offset has traditionally been considered to be the result of a greater surface area in the southern ocean and high-latitude deepwater formation. This is despite the fact that the El Niño–Southern Oscillation (ENSO) is known to play a significant role in controlling the interannual variability of atmospheric carbon dioxide by changing the flux of ‘old’ CO2 from the tropical Pacific. Here we demonstrate that over the past millennium, the Southern Hemisphere radiocarbon offset is characterised by a pervasive 80-yr cycle with a step shift in mean values coinciding with the transition from the Medieval Warm Period to the Little Ice Age. The observed changes suggest an ENSO-like role in influencing the interhemispheric radiocarbon difference, most probably modulated by the Interdecadal Pacific Oscillation, and supports a tropical role in forcing centennial-scale global climate change.