bluuebunny/crossref_metadata_2025_split huggingface dataset:
Is one parasitoid enough? A test comparing one with a pair of parasitoid species in the biological control of arrowhead scales
Authors: Matsumoto Takashi , Itioka Takao , Nishida Takayoshi , Kaneko Shuji 
Published: March 2004

AbstractIn classic biological control using natural enemies, the question of whether a single species or multiple species should be introduced has been a matter of debate. The introduction of two parasitoids,Aphytis yanonensisandCoccobius fulvus(Hymenoptera: Aphelinidae), to control the arrowhead scale,Unaspis yanonensis(Hemoptera: Diaspididae), which is a serious pest in Japanese citrus orchards, has been one of the most successful biological control projects in Japan. The success of this program may be explained by two alternative hypotheses: (1) the parasitoid species work complementarily, or (2) only one of them plays a major role. To test which hypothesis is applicable to this host‐parasitoid system, we conducted caging experiments and observed temporal changes in the proportion of the parasitisms and the densities of arrowhead scales enclosed with one of the following combinations of parasitoids: (1)A. yanonensisandC. fulvustogether, (2)A. yanonensisalone, (3)C. fulvusalone, or (4) neither parasitoid. Parasitisms in the cohorts withA. yanonensisandC. fulvustogether andC. fulvusalone rapidly increased to approximately 70%; parasitism withA. yanonensisalone also increased slightly, although it remained consistently lower that those withA. yanonensisandC. fulvustogether andC. fulvus.At the end of the experiment, parasitisms withA. yanonensisandC. fulvustogether andC. fulvusalone were significantly higher than that withA. yanonensisalone. Parasitism byC. fulvusconstituted most of (74%) the parasitism in the cohort withA. yanonensisandC. fulvustogether. Further, onlyC. fulvussuppressed the population growth rates of scales significantly. These results suggest thatC. fulvusalone successfully suppresses scale populations as efficiently as both species together do.
Demographic sensitivity and persistence of the threatened white‐ and orange‐bellied frogs of Western Australia
Authors: Conroy Simon D. S. , Brook Barry W. 
Published: March 2004

AbstractAnurans have been the subject of numerous experimental and monitoring studies, yet their autecology under natural conditions remains poorly understood. Previous work has focussed on the pre‐metamorphic life stages, with data suitable for estimating demographic parameters for all life stages collected in few species. This deficiency has almost certainly confounded current views of amphibian autecology and understanding of which mechanisms of decline represent the greatest threats to the persistence of amphibian species. We used a stage‐structured metapopulation model, parameterised with comprehensive field data, to explore the sensitivity of two species of myobatrachid frogs from the southwest of Australia,Geocrinia albaandG. vitellina, to changes in demographic parameters at all life stages. The simulation modelling indicated that the population dynamics of both species were consistently most sensitive to changes in juvenile survival, then to fecundity, and third to both adult survival and standard deviation of survival to about equal extent. In practical terms, this indicates that management interventions which attempt to mitigate reductions in juvenile survival are likely to be most successful in arresting anuran metapopulation declines.
Herbivore response to vegetational diversity: spatial interaction of resources and natural enemies
Authors: Harmon Jason P. , Hladilek Erin E. , Hinton Jennifer L. , Stodola Timothy J. , Andow D. A. 
Published: March 2004

AbstractVegetational diversity in agricultural systems is predicted to reduce herbivore populations, but we observed the opposite effect: higher nymph population densities of a functionally monophagous herbivore, the squash bug, Anasa tristis (Hemiptera: Coreidae) in a vegetationally diverse squash‐bean‐corn polyculture than in a squash monoculture. We examined spatial and temporal aspects of squash bug and predator populations in relation to vegetational diversity. Average colonization, oviposition, and mortality rates for the herbivore were similar in monocultures and polycultures. In the polyculture, however, we found that squash bugs eggs were highly aggregated on plants on the outer edges of plots. Predation was also lower on plants near the edges, allowing the large aggregations of eggs found in the polyculture to escape predation and ultimately produce more squash bugs. Spatial interactions between herbivores and natural enemies may underlie some of the general effects of vegetational diversity on herbivores.
Effects of grazing by leaf beetle Galerucella nipponensis on growth and seed production of the aquatic plant Trapa japonica
Authors: Ikeda Kousuke , Nakasuji Fusao 
Published: March 2004

AbstractThis paper investigated the effects of grazing by Galerucella nipponensis (Coleoptera: Chrysomelidae) on growth and seed production of its host plant Trapa japonica (Trapaceae). A water tank experiment demonstrated that the new rosette leaves grazed upon by the beetles had a shorter life span than those of ungrazed rosettes. In ponds, severely grazed T. japonica rosettes produced more new leaves than slightly grazed rosettes. The period of seed production was delayed in years when leaves were severely grazed during the flowering seasons. Grazing peaked in later growing seasons when rosettes produce seeds. The ratio of seed production in the latter half of the peak to that in the early half was higher under severe grazing conditions than slight or moderate grazing conditions. A higher density of seeds in ponds in the current year tended to produce more abundant rosettes in the following spring. These results suggest that the herbivory of G. nipponensis induces compensatory reproduction of T. japonica in a complicated manner.
Niche division and abundance: an evolutionary perspective
Authors: Tokeshi M. , Schmid P. E. 
Published: March 2004

AbstractIn recent years, biodiversity has become an issue of broad academic interest, and its assessment and maintenance are now recognized as an important area of ecological research. While the concept of biodiversity encompasses, first and foremost, the total number of species co‐occurring in a locality, it has increasingly been realized that information on the relative abundances of co‐occurring species is also required for a better understanding of the patterns and dynamics of biodiversity. In many areas of ecological research, “abundance” constitutes a key variable that characterizes populations and communities. The relative abundances of species in natural communities reflect evolutionary and contemporary processes occurring on different spatiotemporal scales. The idea of niche apportionment has been developed to provide an integrated conceptual framework for the study of species abundance patterns in communities. This article reviews a number of important issues surrounding the concept of niche apportionment, including some aspects that have received very little or no consideration in previous ecological literature. The main emphasis here is on possible evolutionary implications and backgrounds. Further, as a universal factor which affects species abundance in one way or another, body size is highlighted and its relationship with abundance (“density–body‐size relation”) is considered, referring in particular to a recent comprehensive analysis of freshwater benthic data. Consideration of this and other studies has led to the formulation of the biomass equivalence rule, that suggests the independence of the biomass measure of abundance from body size, which strengthens the logical basis of niche apportionment models. It is suggested that, compared with Hubbell's neutral theory of biodiversity, niche apportionment with the biomass equivalence rule represents a conceptually more sound and widely applicable approach to elucidating species abundance patterns.
Pleiotropic effect, clock genes, and reproductive isolation
Authors: Miyatake T. 
Published: March 2004

AbstractThe mechanism by which a clock gene pleiotropically controlling life history and behavioral traits causes reproductive isolation is explained using a model species, the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae). Melon flies mate once a day, at dusk. The population selected for life history traits exhibits correlated responses in the time of mating during the day. For example, the fly populations selected for faster (slower) development have an earlier (later) time of mating. A circadian rhythm controls the time of mating. The circadian periods in constant darkness were about 22 h in lines selected for a short developmental period and about 31 h in lines selected for a long developmental period. The data on crosses between the selected lines indicated that the developmental period is controlled by a polygene, whereas the circadian period may be controlled by a single clock gene. These results suggest a clock gene pleiotropically controls developmental and circadian periods in the melon fly. Reproductive isolation may often evolve as an indirect (pleiotropic) consequence of adaptation to different environments or habitats. For example, niches that are temporally or seasonally offset can select organisms with different developmental characteristics. These developmental differences can inadvertently cause reproductive isolation by a variety of means including shifts in mating activity patterns. The difference in time of mating between populations selected for developmental period translated into significant prezygotic isolation, as measured by mate choice tests. If the mating time between populations differed more than 1 h, the isolation index was significantly higher than zero. These findings indicate that premating isolation can be established by a pleiotropic effect of a clock gene. There are many examples in which the difference in timing of reproduction prevents gene flow between populations, such as the egg spawning time in marine organisms, the flowering time in angiosperms, and the time of mating in insects. In such organisms, if genetic correlations between circadian rhythm and reproductive traits exist, multifarious divergent selection for life history traits would often accelerate the evolution of reproductive isolation through clock genes. Natural populations may diverge in reproduction time through drift, direct natural selection for time of reproduction, or as a by‐product effect of genetic correlations. In any case, clock genes are keys in reproductive isolation.
Do sex divergences in reproductive ecophysiology translate into dimorphic demographic patterns?
Authors: Lourdais O. , Bonnet X. , DeNardo D. , Naulleau G. 
Published: March 2004

AbstractWe examined the influence of sex divergences in reproductive role and physiology on catchability and demographic patterns in a closed population of aspic viper (Vipera aspis Linné). During 8 years, there were 4800 captures of 988 adults. In both sexes, captures were more frequent in spring when climatic conditions and reproductive activities impose extended basking periods that make animals more detectable. On average, males were captured more than females, reflecting intense sexual activity (i.e., mate searching) in spring. Reproductive females were more catchable than nonreproductive females, illustrating a major increase in basking behavior associated with reproduction. Estimates of population size revealed a sexually dimorphic demographic system with marked year‐to‐year fluctuations in females contrasting with a more stable male population. This sex difference in population dynamic reflects sex divergences in the acquisition and allocation of energy for reproduction. In both sexes, reproduction is fueled by body reserves. Females, however, need to accumulate substantial body reserves to reach a high body condition threshold before reproduction, whereas the male pattern of energy allocation is more gradual (i.e., no fixed threshold). In addition, reproduction entails major survival cost in females (i.e., most females reproduce just once), whereas males are generally annual breeders. As a consequence of this sex divergence, food abundance, through its direct effect on body store dynamics, influenced major demographic parameters of females (e.g., proportion of reproducing individuals, annual changes in population size) but not males.
Relative importance of weather and density dependence on the dispersal and on‐plant activity of the predator Orius minutus
Authors: Tuda M. , Shima K. 
Published: March 2004

AbstractThe present study evaluated the relative effects of abiotic (weather: temperature, wind speed, and rain) and biotic (intra‐ and intertrophic density dependence: densities of conspecifics, prey per predator individual and leaves on plants) factors on the dispersal and on‐plant activity (foraging and oviposition) of the predatory bug, Orius minutus, under seminatural field conditions. Experiments were conducted at plots, each comprising 25 potted azuki bean plants, placed symmetrically in concentric circles, in 1998 and 1999. At the central pot within each plot, 5 marked females of O. minutus (with a male in 1998) were released, and their location and activity were recorded hourly up to 24 h. A total of 78 individuals were released. Stepwise multiple logistic regression was used to select among weather, density dependence, and time variables. Hourly dispersal probability of individuals was positively correlated with temperature and negatively with time since release and with prey density per individual O. minutus. Hourly probability of individuals being active was positively correlated with temperature and negatively with number of leaves of visited plants and conspecific density per leaf. Between‐year difference was observed in the probability of individuals being active, which was higher in 1998 than in 1999, probably generated by hunger and higher age. By contrast, diffusion rate was estimated to be lower in 1998, suggesting a trade‐off between foraging/oviposition and dispersal by flight. The results indicate that dispersal is affected by temperature and intra‐/intertrophic‐level density dependence within and between trophic levels, as are foraging/oviposition. The importance of incorporating both abiotic and biotic factors should be stressed when modeling predator–prey metapopulation dynamics on a greenhouse scale.
Adolescents’ experiences of parental employment and parenting: connections to adolescents’ well‐being
Authors: Sallinen Marjukka , Kinnunen Ulla , Rönkä Anna 
Published: March 2004

AbstractThis paper examines whether the relationship between parental work and adolescents’ well‐being would be mediated through parenting behaviour. The primary focus was on the experiences of adolescents. Questionnaire‐based data from families (both parents and one children, n=77) and adolescents (n=126) were collected in Finland in 2000 and 2001, respectively. The adolescents were on average 14 years old. Results showed that the relationships between parents’ negative work experiences and adolescents’ depression (all perceived by adolescents) were partially mediated by adolescents’ experience of lessened autonomy granting in parenting and increased conflicts between parents and adolescents. In addition, the relations between fathers’ negative work experiences and adolescents’ negative attitude regarding school (all reported by adolescents) were mediated by adolescents’ perceptions of increased conflicts between fathers and adolescents.
Patterns of species assemblages and geographical distributions associated with mandible size differences in coastal tiger beetles in Japan
Authors: Satoh Aya , Uéda Tetsuyuki , Enokido Yoshihiro , Hori Michio 
Published: March 2004

AbstractNine species of tiger beetle (Cicindelidae) occur in coastal habitats in Japan, with two to four species co‐occurring at each locality. To examine the patterns of coexistence and geographical distribution, the mandible size of co‐occurring species at 17 localities in Japan was examined, based on the assumption that competition for food is an important factor in determining these patterns. The interspecific overlap of mandible length was absent or very low in localities with two or three species, whereas it was more or less evident in localities with four species. For four large coastal species, the geographical distributions of two species with similar mandible lengths are either allopatric or parapatric, whereas those of two species with different mandible lengths largely overlap. These results strongly suggest that size‐assortment in mandible length is important in determining species assemblage and distribution in coastal tiger beetles in Japan.
Moth outbreaks in relation to oak masting and population levels of small mammals: an alternative explanation to the mammal‐predation hypothesis
Authors: Selås Vidar 
Published: March 2004

AbstractThe relationship between population outbreaks of the gypsy moth (Lymantria dispar) and oak masting in North America has been interpreted as an effect of reduced predation on moth pupae from small mammals after years of acorn failure. However, moth defoliation could be a consequence of high acorn production rather than of acorn failure, as all moth outbreaks in two time series presented by Liebhold et al. [Popul Ecol (2000) 42:257–266] were reported shortly after mast years. A similar pattern has been found for the green oak leaf roller moth (Tortrix viridana) in southern Norway. Because predation from small mammals should be less important for the latter species, I argue that the acorn‐moth relationships are most likely caused by mast‐induced changes in the chemical composition of oak leaves. Given the high number of eggs laid by each moth female, there is a huge potential for population growth in or shortly after a mast year if larval survival is no longer limited by low food quality.
Modeling temporal and spatial colony‐site dynamics in a long‐lived seabird
Authors: Martínez‐Abraín Alejandro , Oro Daniel , Forero Manuela G. , Conesa David 
Published: March 2004

AbstractWe studied the determinants of colony site dynamics in Audouin's gull,Larus audouinii, breeding in a small archipelago of the western Mediterranean. Data on island occupation were available for a series of 25 years, since first colonization of the archipelago in 1973. Group behavior was studied in relation to the components of dispersal: permanence or abandonment (extinction) on an island previously occupied and permanence or occupation (colonization) of another island. Generalized Linear Mixed Models (GLMMs) were used to identify the relative contribution of each explanatory variable to the probability of colony abandonment. Gulls showed a low probability (3%) of abandoning one of the islands (Grossa I.), especially when the colony was increasing in numbers from timeti‐1toti. However, the probability of abandoning Grossa increased up to 31% when the colony was declining. The probability of island abandonment was very high for all other islands (range 66–99%) when the colony was declining, but much lower (range 36–82%) when it was increasing. Hence, we suggest that island abandonment by Audouin's gull is at least a two‐step process. The first step (dispersal of a portion of the colony) probably takes place at random, as an evolutionary load typical of a species evolved in unstable habitats. The second step, a further loss of breeding pairs, seems to feedback on the first loss of members of the colony (public information), likely perceived as a loss of colony quality. Colonization of islands by gulls abandoning Grossa I. was marginally and negatively affected by the density of breeding yellow‐legged gulls, a predatory species. Results apply to conservation ecology since they highlight the need to protect not only occupied patches but also those empty at present.
Dimorphic migration, growth, and fecundity in a seasonally split population of Littorina brevicula (Mollusca: Gastropoda) on a boulder shore
Authors: Takada Yoshitake 
Published: March 2004

AbstractLittorina brevicula (Philippi) is an abundant herbivorous gastropod species inhabiting intertidal zones of the north‐western Pacific and has internal fertilization with planktonic eggs and a larval stage. A population of L. brevicula on a shore in Amakusa, Japan, splits into an upper and a mid shore sub‐population during the mating season in winter, while all individuals occurred in the upper zone in summer. Transplant and recapture experiments have shown that snails from each sub‐population have a distinct pattern of seasonal migration, suggesting that the snail population consists of two behavioral morphs. To explore the relationship between migration pattern and life history characteristics in the snails of the two migration morphs, monthly quantitative samplings and a mark‐release and recapture survey were carried out for the population of L. brevicula over a 1‐year period. In autumn, some of the adults migrated downward to the mid shore and formed the lower sub‐population from October to April. Migration between the upper and lower sub‐populations was minimal from December to February, when L. brevicula copulate actively. The shell growth rates of the snails in the lower zone were slightly higher than those in the upper zone, but the shell width of females was not a good predictor of the number of mature ova they contained. The number of mature ova was not significantly different between the females of the two migration morphs. In addition, the mortality of marked snails did not differ significantly between the upper and lower zones. Thus, no evidence was obtained to indicate a difference in the reproductive fitness between the two migration morphs.
Land snails as a model to understand the role of history and selection in the origins of biodiversity
Authors: Davison A. 
Published: March 2004

AbstractIt is nearly 100 years since the first studies on variation in the shell patterns of land snails. Subsequently, snails have come to play an important role in our understanding of natural selection in the wild. In particular, snails have been an ideal model to understand the roles of history and selection in the origins of diversity. More recently, many studies have investigated the molecular genetic variation within snails. It is clear that snails are unusual, because some genes may vary by 10%–30% within a species. This molecular variation affords an excellent opportunity to further understand the action of natural selection in shaping the present‐day phenotypic diversity. In the first part of this review, I illustrate the distinction between the historical and selective interpretations using one of the best‐studied species, Cepaea nemoralis, and the example of “area effects.” In the second part, studies that have compared patterns of morphological and molecular variation (especially DNA) are examined.