bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extreme adaptive life‐cycle in a high arctic aphid,Acyrthosiphon svalbardicum
Authors: STRATHDEE A. T. , BALE J. S. , BLOCK W. C. , WEBB N. R. , HODKINSON I. D. , COULSON S. J. 
Published: March 2008

Abstract.The year‐round biology of a high arctic aphid is described for the first time.The life‐cycle is shown to be genetically determined, and thus markedly different to temperate species where the observed polymorphism is governed primarily by external environmental cues.The fundatrix, which emerges from the overwintering egg, gives birth directly to sexual morphs, a phenomenon previously undescribed in the Aphidinae. This process is essentially prevented in temperate aphids by an endogenous mechanism, the interval timer.In addition to the sexual morphs, the fundatrix produces a small number of parthenogenetic individuals (viviparae) that give rise to a third generation. This last generation consists exclusively of oviparae and males that would increase the number of overwintering eggs provided there is sufficient thermal budget for them to mature and oviposit before conditions become adverse.The position of particular morphs in the birth sequences of the second and third generations maximize the chances of survival in harsh conditions, whilst enhancing the likelihood that individuals from the third generation will add to the number of overwintering eggs.Guaranteed egg production combined with an in‐built flexibility to produce an extra generation in particularly favourable seasons, confer adaptations to the high arctic environment, and ideally suit this aphid to exploit elevated temperatures in an era of climate change.
Seasonality and life cycles of woody plant‐feeding noctuid moths (Lepidoptera: Noctuidae) in Mediterranean habitats
Authors: YELA JOSÉ L. , HERRERA CARLOS M. 
Published: March 2008

Abstract.

The annual cycle of noctuid moths feeding as larvae on the foliage of eighteen woody plant species (belonging to ten different families) was studied at two southeastern Spanish Mediterranean forest habitats. Two questions were addressed in this study. (1) Does the rigorous (hot and dry) summer season characteristic of the Mediterranean‐type climate impose a constraint on noctuid life histories? (2) Are there detectable differences in abundance or phenological patterns between the noctuid assemblages feeding on evergreen and winter‐deciduous trees and shrubs?
Regardless of their leaf persistence habit, the majority of woody species studied had short shoot growth and leaf production periods in spring. Abundance of noctuid larvae peaked in May‐June, shortly after host plants started to produce new leaves. Virtually no noctuid larvae were found on the foliage of the woody species studied at other times of year. Abundance and seasonal pattern of occurrence of larvae were similar on evergreen and deciduous food plants.
In contrast with the unimodal seasonal pattern exhibited by larvae, the abundance of adult moths (assessed by light trapping) showed two distinct peaks in early summer and early autumn, and a marked minimum in mid‐summer.
Most woody plant‐feeding noctuids recorded in this study (86% of species, about 95% of individuals) were univoltine. Univoltine species fell into one of two distinct life history categories, corresponding to pre‐ and post‐summer flight periods. These two contrasting phenologies were associated with a bimodality in the duration of the pupal stage (‘short’ versus ‘long’), and were closely related to taxonomical affiliation at the subfamily level.
Within the ‘short’ pupal duration group, some species mate and oviposit shortly after emergence and pass the dry season in the egg stage, while others remain as potentially active, non‐reproductive adults over most of the summer and mate by the end of that season. Species in the ‘long’ pupal duration group pass the summer in pupal or prepupal stage.
In the Mediterranean habitats studied, the adversity of the summer dry season seems to have led to a woody plant‐feeding noctuid species assemblage almost entirely made up of univoltine species that concentrate their larval phases when suitable food (young leaves) is most abundant, and ‘avoid’ mid‐summer as a flight time by emerging either shortly before or shortly after the adverse summer drought period. Year‐round foliage availability afforded by dominant evergreen plants does not seem to have influenced the seasonal organization of noctuid cycles in any substantial way.
Effect of host availability on reproduction and survival of the parasitoid wasp Trichogramma minutum
Authors: BAI B. , SMITH S. M. 
Published: March 2008

Abstract.

We tested the hypothesis that females of the egg parasitoid, Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae), could adjust their fecundity schedule according to host availability and that there was a negative correlation between reproduction and survival in these wasps.
Newly‐emerged females were provided with an unlimited or limited number of hosts in the first trial and with either unlimited, limited or zero hosts in the second trial.
When hosts were unlimited, wasps had the highest rate of reproduction in the first day, which decreased dramatically thereafter. When hosts were limited, wasps from the two trials differed in their response. In Trial I, females with limited hosts had lower first‐day fecundity than, and the same subsequent‐day fecundity as, those with unlimited hosts. However, in Trial II, females with limited host had a lower first‐day but a higher subsequent‐day fecundity than those with unlimited hosts. This indicates variation in Trichogramma's ability to shift its fecundity schedule in response to host availability.
There was a positive (rather than a negative) correlation between reproduction and survival. Wasps that oviposited (in host‐unlimited treatment) had greater longevity than those that could not (in host‐unavailable treatment).
The sex ratio of the progeny produced by wasps in both host‐unlimited and limited treatments shifted gradually from a female to a male bias as the wasps aged.
We consider the ability of parasitoids to adjust their fecundity schedule as an adaptation to changing host resources and discuss our findings with regard to theories of life history evolution.
Mutual use of leaf‐shelters by lepidopteran larvae on paper birch
Authors: CAPPUCCINO NAOMI 
Published: March 2008

Abstract.

Many species of birch‐feeding Lepidoptera make leaf‐shelters by tying leaves together with silk. Several species, or several instars of a single species, may be found together within a single leaf‐shelter.
Shelters made in June by the birch tube‐maker Acrobasis betulella (Pyralidae) are colonized throughout the season by other Lepidoptera. Artificial A.betulella shelters, made by tying leaves together with string, were colonized at a greater rate than nearby control foliage, indicating that secondary species are indeed responding to the presence of the shelter, and not to some other aspect of plant quality.
Several species in the families Oecophoridae, Gelichiidae and Stenomidae make ‘leaf‐sandwiches’ by tying two leaves together; these are later colonized by oviposition from adult A.betulella. Artificial sandwiches made by joining leaves together with paperclips were colonized by several species of sandwich‐makers, as well as by A.betulella. Colonization occurred mainly via oviposition, although some sandwiches may have been colonized by wandering larvae.
First instar A.betulella, which cannot form their own shelter, enjoyed greater survivorship when placed in artificial leaf‐sandwiches than when placed on leaves without sandwiches.
Superparasitism and mutual interference in the egg parasitoidAnagrus delicatus(Hymenoptera: Mymaridae)
Authors: CRONIN JAMES T. , STRONG DONALD R. 
Published: March 2008

Abstract.In nature, interference amongAnagrus delicatus(Hymenoptera: Mymaridae) parasitoids reduced the per‐capita number of hosts parasitized. Interference increased with parasitoid density.Anagrus delicatusdid not avoid parasitizing hosts that had recently been parasitized by conspecific wasps. Evidence indicated that this superparasitism was largely a random process, increasing with the ratio of parasitized to unparasitized hosts.Individual parasitoid efficiency, the number of hosts killed per wasp per unit time, decreased with increasing wasp density. This occurred whether wasps searched the patch together (simultaneously) or one by one (sequentially), and was the result of an increase in time spent superparasitizing hosts at higher wasp density. This is known as indirect mutual interference.Increasing numbers of parasitoids together on the same patch caused a significant decline in the rate and per‐capita number of hosts parasitized. However, there was not a correspondent decline in searching efficiency with increasing wasp density (i.e. no direct mutual interference).These forms of parasitoid density dependence should contribute to the stability of the host—parasitoid interaction.
Self and conspecific superparasitism by the solitary parasitoid Antrocephalus pandens
Authors: GATES SIMON 
Published: March 2008

Abstract.

The fitness consequences of superparasitism for a solitary parasitoid depend on whether the host was first parasitized by itself (‘self‐superparasitism’) or a different individual (‘conspecific superparasitism’). Self superparasitism is usually expected to be avoided.
A.pandens females showed no difference in their probability of superparasitism between self‐parasitized and conspecifically‐parasitized hosts. The probability of superparasitism decreased as time from the laying of the first egg in a host increased, from about 0.29–0.46 at a time interval of 1 h to 0.10–0.14 at 72 h.
The egg distribution of wasps foraging alone on a patch showed significant avoidance of superparasitism, but that of wasps foraging in the presence of conspecifics was not significantly different from a random distribution. This suggests that wasps switch from avoidance of superparasitism when alone to acceptance of all hosts when in a group.
When wasps foraged in a group, the hosts had many more ovipositor puncture marks than when wasps foraged singly. This suggests that either hosts were attacked several times per encounter, or that the wasps' encounter rate with hosts was much higher when in a group. If the latter is true, it is possible that, although the egg distribution suggested a higher rate of superparasitism when wasps foraged in a group, the ratio of acceptances to contacts of parasitized hosts may in fact have been lower.
Mate finding, dispersal, number released, and the success of biological control introductions
Authors: HOPPER KEITH R. , ROUSH RICHARD T. 
Published: March 2008

Abstract.

An analysis of published data and a mathematical model of the population dynamics of introduced parasitoids were used to explore the possibility that biological control introductions fail because an Allee effect drives small, introduced populations extinct. Such an Allee effect would arise because low densities, resulting from dispersal into a new environment, lead to failure to mate, which leads to a male‐biased sex ratio, which, if extreme enough, could cause population extinction.
For chalcidoids, ichneumonoids and tachinids, the proportion of parasitoid populations that established when introduced for control of lepidopteran pests increased with the number of parasitoids per release, the total number released, and the number collected when each variable was analysed separately. For chalcidoids alone, establishment increased with the number of releases for this variable analysed separately. However, stepwise logistic regression of establishment on these variables included only the total number released for chalcidoids and the number per release for ichneumonoids and tachinids. This suggests that an Allee effect may limit the establishment of introduced parasitoids more than stochastic environmental variation or lack of genetic variation.
A reaction‐diffusion model of parasitoid introductions was developed, which included mate finding, dispersal, reproduction and survival. Sensitivity analysis showed that the critical number of females needed to establish a population decreased hyperbolically as mate detection distance and net reproductive rate were increased, but the critical number increased linearly as mean‐square displacement was increased. The critical number of females did not change when the gross distance traversed per generation was varied. This was because increased area searched by males compensated for increased displacement. Changing from virgin females producing all males (arrhenotoky) to virgin females producing no progeny increased the critical number of females by over 30%.
The analysis of past introductions and the sensitivity analysis of the reaction‐diffusion model both suggested a threshold of about 1000 insects per release to ensure establishment of introduced parasitoids. The implications of our results for the design of biological control introductions are discussed. Limitations in retrospective analyses and current knowledge indicate the need for an experimental approach to introductions.
Leaf miners on Ochna ciliata (Ochnaceae) growing on Aldabra Atoll: patterns of herbivory in relation to goat browsing and exposure to the sun
Authors: LINFIELD MARK C. J. , RAUBENHEIMER DAVID , HAMBLER CLIVE , SPEIGHT MARTIN R. 
Published: March 2008

Abstract.

The patterns of herbivory by leaf miners on the shrub Ochna ciliata growing on Aldabra Atoll were studied in relation to browsing by feral goats and exposure to the tropical sun versus shading.
Damage due to both tunnelling (Diptera) and ‘blotch‐making’ (Lepidoptera) leaf miners was statistically greater on trees that had been browsed and on those that received more extensive exposure to the sun.
Effects of exposure and browsing were additive, as evidenced by the lack of statistical interaction between these factors.
There was a significant negative correlation between the numbers of tunnelling and blotch‐making miners in trees that had been browsed, but not in unbrowsed trees.
Three geographical areas were sampled to test whether the effects of browsing on leaf mining were invariant or influenced by as yet unknown environmental factors. A statistically significant interaction between browsing and geographical region indicated that, while browsed trees had significantly more mines whatever the habitat, the extent of this effect differed across the habitats.
Influence of intra‐tree variation in time of budburst of white spruce on herbivory and the behaviour and survivorship of Zeiraphera canadensis
Authors: QUIRING DAN T. 
Published: March 2008

Abstract.

Field studies were carried out to determine the effects of intra‐tree variation in the time of budburst of white spruce, Picea glauca Moench (Voss.), on the behaviour and survivorship of, and herbivory by, the spruce bud moth, Zeiraphera canadensis Mutt. & Free.
There was significant variation in the time of budburst among whorls, shoots and buds. Budburst was acropetal, with buds in the interior of the lower crown bursting first and terminal buds on terminal shoots in the upper crown bursting last.
Bud moths laid the greatest proportion of their eggs in the middle of the crown and egg hatch was usually best synchronized to budburst in this region. Many eggs hatched before terminal buds on terminal shoots in the upper crown had burst and thus intra‐tree variation in budburst decreased the probability that first‐instar larvae would colonize the most important plant parts for growth.
However, many later instars dispersed upwards and outwards in the crown and colonized the late bursting buds in the upper crown. Such dispersal reduces the effectiveness of intra‐plant variation in budburst to reduce herbivory and permits Z.canadensis to eat young nutritious buds for a longer period of time.
Intra‐tree variance in the date of budburst was greater than that between trees but there were no consistent differences between the intra‐tree variance of trees in half‐sib families with high or low susceptibility to Z.canadensis. Differences between trees in herbivory, bud moth density and survivorship were not related to the amount of intra‐tree variation in budburst.
Population dynamics of the yew gall midge Taxomyia taxi and its chalcid parasitoids: a 24‐year study
Authors: REDFERN M. , CAMERON R. A. D. 
Published: March 2008

Abstract.

The dynamics of three populations of Taxomyia taxi (Inchbald) (Diptera: Cecidomyiidae) and its chalcid parasitoids have been studied over a 24‐year period. Most individuals have a 2‐year life cycle but some develop in 1 year. Details of within‐generation mortalities in T.taxi are used for life table analyses.
Mortality in the period between emergence of adult T.taxi and larval infestation of buds appears to be density‐dependent and is the largest component of overall mortality. In 2‐year life cycles, this mortality and that caused by Torymus nigritarsus (Walker) contribute equally to variance in overall mortality. In 1‐year cycles, mortality caused by Mesopolobus diffinis (Walker) is density‐dependent and accounts for most within‐gall losses.
T. nigritarsus, which attacks only 2‐year galls, is absent from all populations for a number of years in the middle of the study period. Its searching efficiency declines as its density and that of its host increase.
Densities of M.diffinis are strongly correlated with those of available hosts. Percentage parasitism of 2‐year galls is less than that of 1‐year galls, suggesting the occurrence of enemy‐free space.
Although there are some correlations in densities and mortality between trees, the dynamics of populations on each are frequently different.
An earlier analysis of 10 years' data failed to demonstrate density‐dependent effects. The extension to a 24‐year run has revealed such effects, but also demonstrates long‐term fluctuations in population densities, with corresponding changes in the balance of advantage between 1‐ and 2‐year life cycles of T.taxi.
Oviposition habitat selection by the mosquito, Culiseta longiareolata: effects of conspecifics, food and green toad tadpoles
Authors: BLAUSTEIN LEON , KOTLER BURT P. 
Published: March 2008

Abstract. 1. Ovipositing females should choose egg‐laying sites which maximize the growth and survivorship of their offspring. Accordingly, they should avoid habitats with high densities of competitors and predators and should choose sites with adequate food. We tested experimentally the oviposition response of the mosquito, Culiseta longiareolata Macquart, to extra food and two species which are both potential competitors and predators of its offspring: conspecific larvae and green toad (Bufo viridis) tadpoles.2. We conducted the experiment in outdoor artificial pools where wild C. longiareolata females were presented with choices of all combinations of the presence or absence of: (1) C.longiareolata larvae, (2) B.viridis tadpoles, and (3) extra food (a mixture of ground fish food and mouse chow).3. Oviposition rates averaged approximately 4 times greater in response to extra food.4. The presence of the tadpoles, particularly later in the experiment when they were larger, caused a significant reduction (approximately 50%) in oviposition rate.5. We did not detect a statistically significant effect of conspecific larvae on oviposition habitat selection.6. Our results indicate that Culiseta females choose habitats for oviposition based on food availability. They also tend to avoid habitats containing Bufo tadpoles, presumably to avoid predation and/or competition.
Complex dynamics of desert locust plagues
Authors: CHEKE ROBERT A. , HOLT JOHNSON 
Published: March 2008

Abstract. 1. Spectral analysis of 66 years of locust swarm abundance data failed to reveal any significant cycles although the dominant cycle detected in a de‐trended series, adjusted to take account of a significant partial autocorrelation for a lag of 1 year, had a periodicity of 16 years.2. Although some estimates of the intrinsic rate of increase (r) of desert locusts are indicative of chaos, reconstructions of locust dynamics using response surface methodology (RSM) suggested exponential stability. This was also true for data for the West African Region alone and inclusion of rainfall data from the Sahel improved the significance of an RSM model for West Africa.3. The observed positive relationship between locust abundance and rainfall in West Africa confirmed the importance of rain; but the variance of the locust abundance also increased with rainfall, making rainfall alone a poor predictor. However, this heteroscedastic pattern was reproducible by a simple logistic model with a chaotic r and a variable K. This was not the case when a stable value for r was used.4. The available data and current methodologies are insufficient to provide unequivocal conclusions on locust dynamics, which are complicated by phase changes and associated switches in r values.
The natural dynamics of the eulophid parasitoid Melittobia australica
Authors: FREEMAN B. E. , ITTYEIPE K. 
Published: March 2008

Abstract. 1. The ecology of the eulophid parasitoid Melittobia australica Girault was studied in the laboratory and field in Jamaica. Further field observations were conducted in Trinidad.2. The sphecid, mud‐daubing wasp Sceliphion assimile (Dahlbom) was the main host in Jamaica, but nineteen out of twenty‐two investigated species of sphecid, eumenid and pompilid wasps, and apid and megachilid bees were attacked in Jamaica and Trinidad. The nineteen susceptible hosts suffered an average of 23.6% mortality due to Melittobia. Resin is a totally effective deterrent, spaces within the nest less so.3. Laboratory studies on Sceliphron hosts estimated that developmental survival was greatest at 26°C and 83% r.h., duration of development shortest at 32°C and 72% r.h., longevity of adult fliers greatest (>13 days) at <25°C and 80% r.h., and fecundity greatest (454 eggs/female) at 28°C and 90% r.h. A separate experiment gave a maximum fecundity of 461.4. At 27°C and 71% r.h. the duration of development (egg‐adult) in the laboratory was 13.1 days for males, 13.9 days for crawlers and 17.4 days for fliers.5. Field studies showed that developmental mortality was low, while laboratory studies revealed it to be density dependent, ranging from 13% at the lowest densities to 39% at the highest. Estimated mortality at field densities was ∼25% on Sceliphron.6. Field estimates of fecundity gave a mean of 429.5 eggs/female on Sceliphron but are positively biased by superparasitism. Fecundity is probably reduced to about 346 eggs in the field and further to about 289 as a result of superparasitism. Other hosts generally reduced the parasitoid's fecundity, and this always occurs when Melittobia becomes a hyperparasite.7. Superparasitism in the field on Sceliphron was 2.3 females/host for crawler morph females, 1.2 females/host for jumper females and 1.2 females/host for flier females.8. A cyclic budget using log10K; values (Freeman, 1976) revealed that the effect of superparasitism (K0= 0.124), the physical environment (K0= 0.078), developmental mortality (K1= 0.125), and the loss to males (K2= 0.020) to be small, but losses of dispersing females (k3= 2.326) to be massive.9. The individual chance for the three female morphs of finding a new host are very different. For crawlers (which search the natal host nest) it is 0.034 (1 in 29), for jumpers (which search the host nesting site) it is 0.0098 (1 in 102) and for fliers (which seek distant host nesting sites) 0.0021 (1 in 485). Risk is thus directly proportional to distance travelled (cm, m and km). Morph production is related to this risk.