摘要:

Abstract.1The structure of local populations of a monophagous butterfly, the bog fritillaryProclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.2An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta‐population structure.3This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.4Males and females ofP.eunomiaexhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating s

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00382.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1The potential for host plant‐mediated interactions between leaf‐chewers and the aphidSymydobius americanuson paper birch (Betula papyrifera) was investigated experimentally.2Datana ministraandMalacosoma disstriacaterpillars were caged on randomly chosen, undamaged branches until they had eaten 30–50% of the leaf area. Control branches received cages but no larvae.3Alates ofS.americanuswere than caged on the experimental and control branches to assess the effect of chewing damage on colony performance.4Chewing damage had no detectable effect on initiation of alate reproduction, development time, mortality of nymphs or colony growth

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00383.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1By examining potential sources of intraspecific variation in sperm precedence, the underlying mechanisms of sperm competition inCallosobruchus maculatus(F.) (Coleoptera: Bruchidae) were investigated.2The extent of sperm precedence was not related to either copulatory behaviour or body size (male and female).3The extent of sperm precedence increased during the egg‐laying period, suggesting that the stratification of sperm within the spermatheca is not the mechanism of sperm precedence.4Direct removal of sperm from the female's reproductive tract was not observed.5Four other mechanisms (not mutually exclusive) are proposed to account for last‐male sperm precedence in this spec

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00384.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Field studies were carried out during 4 years to determine the effects of inter‐tree variability in the time of budburst of white spruce,Picea glaucaMoench (Voss.), on the distribution, behaviour and survivorship of, and herbivory by, the spruce bud moth,Zeiraphera canadensisMutt.&Free.2Differences between trees in herbivory, bud moth density and survivorship were inversely related to the mean date of budburst. The most and least susceptible half‐sib‘families’evaluated were the first and last to flush, respectively. Differences in herbivory for trees in two families with similar phenologies were partially due to oviposition preference.3Oviposition and larval survivorship were highest on trees in the most susceptible families. Although egg hatch was more closely synchronized with budburst in warm than in cool springs, between tree differences in the time of budburst were consistent ove

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00385.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1The larvae of the chequered skipper butterflyCarterocephalus palaemonnotch the blades of purple moor‐grassMolinia caeruleabefore feeding.2The nutrient concentrations above and below these notches were measured and the nutrient concentrations of undamaged blades of the host plant.3Nutrient concentrations above the notches remained similar to undamaged blades for a short period, whilst concentrations below declined, especially nitrogen, calcium and magnesium.4The feeding behaviour ofC.palaemonlarvae is discussed in relation to declining levels of nutrients in the food plant over the larval season and to other possible reasons for this behaviour, such as avoidance of host defences initiated in response to attac

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00386.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Generalist predators are repelled by chrysomelid (Chrysomelaspp.,Phratora vitellinueL.) larval defensive secretions that are obtained from salicin in their host plants. But little is known about the effect of these secretions on specialist predators.2In this study, we describe the feeding behaviour of a fly,Parasyrphus melanderiCurran (Diptera: Syrphidae), which feeds onChrysomela aeneicollisSchaeffer (Coleoptera: Chrysomelidae).Parasyrphus melanderilays its eggs onC.aeneicollisegg clutches, and its larvae consumeC.aeneicolliseggs and larvae.3Chrysomela aeneicollishatching rates were significantly lower (20%) on clutches with fly eggs than on clutches without them (40%). Half of the clutches with one fly egg had survival rates below 5%, and when two fly eggs were present (four clutches), the entire clutch was consumed.4In nature,P.melanderieggs were 3 times more abundant on a salicylaterich willow speciesS.oresteraSchneider, than on the medium‐salicylateS.geyerianaAnderss. (1.8v0.6 eggs per clutch). On 18% of theS.oresteraclones, all the beetle clutches contained fly eggs. In laboratory‐choice tests,P.melanderilarvae fed equally rapidly onC.aeneicollislarvae that were chemically defended (feeding onS.orestera) as on larvae that produced no secretion (feeding on the salicylate‐poorS.luteaNutt.). This predator does not appear to be deterred byC.aeneicollis'sdefensive secretion. We discuss the implications of specialist predators on determining host suitability to herbivorous in

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00387.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Pissonotus quadripustulatusis a brachypterous planthopper that feeds on the clonal salt marsh plant, sea oxeye daisy,Borrichia frutescens. Asphondylia borrichiaeis a macropterous gall fly that creates galls on the apical meristems. MostBorrichiaoccurs in isolated patches consisting of more than one genotype.2Densities ofPissonotusandAsphondyliado not significantly differ within patches but they do differ between patches. I tried to find out why some patches ofBorrichiasupport consistently higher densities ofPissonotusandAsphondyliathan others.3Reciprocal transplants ofBorrichiabetween patches showed that for bothPissonotusandAsphondyliarecipient site (local environment) had a strong effect on population densities. However, the best sites forAsphondyliawere generally the worst sites forPissonotusand vice versa.4Donor site (local plant genotypes) was not significant forPissonotusbut was marginally significant forAsphondylia.However, forAsphondyliarecipient site had a greater effect. Local plant genotype effects may be greater for gall‐forming insects, which tend to be specialists, than for more generalist sapsucking insect

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1We studied among‐tree and within‐tree variation in the growth of larvae of a geometrid,Epirrita autumnata, on mountain birch (Betula pubescensssp.tortuosa) leaves at different hierarchical levels: among trees (genets), among ramets within trees, among branches within ramets, among shoots within branches and among leaves within shoots. We used only short shoot leaves, which burst simultaneously in spring.2Trees accounted for most of the variation in larval growth rate, but there was substantial variation also among ramets within trees, among branches within ramets, and among short shoots within branches. Variation among leaves within short shoots was negligible. When the probabilities from different experiments were combined, the differences were statistically significant at the tree, ramet and branch levels, and approached significance at the shoot level.3In different experiments, larval growth was from 9% to 54% lower on the worst tree than on the best tree of the experiment. On average, larval growth rate was in different experiments from 11% to 32% lower on the worst ramet than on the best ramet within tree, from 8% to 18% lower on the worst than on the best branch within ramet, and from 12% to 30% lower on the worst than on the best shoot within branch.4The amount of among‐and within‐tree variation shown by our results may have ecological and evolutionary implications: among‐tree variation should select for discrimination by ovipositing females and dispersing larvae, within‐tree variation should select also for optimal foraging behaviou

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1This study examined the importance of forager polymorphism and division of labour among foragers of different size for the economics of load delivery in a leaf‐cutting ant,Atta cephalotes(L.). I collectedA.cephalotesforagers coming down trees carrying leaf fragments to evaluate the degree of match between forager mass and the density (mass per unit area) of leaves being cut, and to quantify how this match affects whether the mass of leaf fragments cut by the ants are within the range which maximizes the rate and efficiency of load delivery.2Foragers ranged 23‐fold in mass (1.4–32.1 mg). On average, larger workers cut at denser leaf sources. Leaf fragment area increased with ant mass, but relative area (fragment area/ant mass) decreased with ant mass. The density of a leaf type had little or no effect on the area cut by ants of a given size. As a result, ants of a given mass cut heavier fragments from the denser leaves. The effect of leaf density, however, was partly counteracted at the colony level by recruitment of larger ants, which cut smaller area fragments relative to their body mass, to cut at denser leaf sources.3Despite a fairly high variance in the relationship between ant mass and fragment mass, overall 87% of the laden ants (74–100% for different trees) carried leaf fragments in the 1.5–6 times body mass range. Earlier studies indicate that loads in this range yield the highest biomass transport rate and transport efficiency. Thus, the variance falls within bounds such that it has little effect on load transport efficiency. Having a broad range in optimal load mass may be considered an adaptation to the expected variability in load masses.4If there were no correlation between ant mass and leaf density, mismatches between ant mass and load mass would be more common than observed. Thus, size‐matching of larger workers to cut denser leaves increases the rate and ergonomic efficiency of lo

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Two closely related species ofColocasiomyia alocasiae(Okada) andC.xenalocasiae(Okada) (Diptera, Drosophilidae) breed in inflorescences ofAlocasia odoraC. Koch (Araceae), a hermaphroditic understorey clonal herb.2The two drosophilid species form a synhospitalic pair in Okinawa withalocasiaebreeding in the upper half of the inflorescence andxenalocasiaebreeding in the lower half.3C.alocasiaealso has the following combination of life history traits: small body size, many eggs, and early reproductive maturity. In contrast,xenalocasiaecan be described as having larger body size, fewer eggs, and delayed reproductive maturity.4Resource partitioning between the two species on the same host may be affected by these life history traits which are associated with their larval habitats.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00391.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY