摘要:

Abstract.1An extensive investigation was carried out into the structure of a large, effectively continuous population ofYponomeuta padellusLatreille, feeding on hawthorn,Crataegus monogyna, and blackthorn,Prunus spinosa.2Mark—recapture studies were used to obtain direct estimates of the male dispersal rate, σ, in two successive years.3Dispersal was found to be extremely localized with respect to the total area of the study population. Estimates of u ranged from a minimum of 2.47 m to a maximum of 12.5 m.4Limited dispersal could be an important factor governing the genetic differentiation ofY.padelluspopulations, and its implications for the supposed existence of host races in this species are discuss

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00398.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Seed beetles (Coleoptera: Bruchidae) are commonly used to study the influence of reproduction on life‐span and senescence. To study the physiological trade‐off between reproduction and mortality, many experiments rely on manipulating access to oviposition substrates to manipulate the reproductive rate of females.2The presence of host seeds, independent of reproduction, results in increased mortality of femaleCullosobruchus muculutus.This influence on mortality varies between two host seed species, suggesting a role of either allelochemicals or energetic costs associated with behaviour on hosts.3The influence of host seeds on survivorship, independent of reproduction, confounds the interpretation of cost‐of‐reproduction studies with seed beetles. This complication must thus be considered in the design and interpretation of life‐history studies of seed beetles and othe

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00399.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1We examined the effects of variation in the timing of spring leaf production and autumn leaf fall on the survival, mortality and abundance ofCameraria hamadryadellaonQuercus albaandQ.macrocarpa.2We monitored and manipulated the timing of foliation on field and pottedQ.albatrees and observed the abundance ofC.hamadryadellaon those trees. We also monitored and manipulated the timing of leaf fall onQ.albaandQ.macrocarpatrees in the field and observed its effects on survival, mortality and abundance ofC.hamadryadella.3Variation in the timing of spring leaf production has no effect onC. hamudryadellaabundance. However, a warm winter and spring in 1991 led to accelerated development and the imposition of a facultative third generation in one out of ten years of observation.4In 1989, leaves fell relatively early and leaf fall in the autumn accounted for more than 50% of the mortality ofC.hamudryadella.in 1990 and 1991 leaves fell relatively late and leaf fall induced mortality was substantially reduced and overwinter survival was markedly increased.5The abundance ofC.hamadryadellaremained constant in the spring and summer of 1990 following the previous autumn's relatively early leaf fall, but increased by 10‐fold in the spring of 1991 following the relatively late leaf fall of autumn 1990. The abundance ofC.hamadryadellaalso increased 4‐fold between the summer of 1991 and the spring of 1992 after another autumn of relatively late leaf fall. We attribute these increases in abundance in part to reduced mortality because of later leaf fall.6Variation in the timing of autumn leaf fall may be responsible for initiating outbreaks ofC.hamadryade

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00400.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Smallness in British plant‐sucking bugs is associated with feeding on the contents of individual plant cells, especially phloem.2The sizes of species of aphids living in similar habitats and the rates of water loss from those that have and lack a filter chamber do not support the contention that small size in aphids is a means of maximizing the loss of water by cuticular transpiration.3An optimum energy partitioning model, previously developed for aphids, was used to predict the interspecifie relation between adult weight and birth weight that would maximize the population growth rate,rm. Using the observedrm/IRGR ratio (0.8–0.9) and that the gonads are smaller than the soma at birth the predicted relation between the logarithm of the adult weight and the logarithm of the birth weight is linear and has a slope of 1.4The relation between the logarithm of the adult weight and the logarithm of the birth weight for eighteen species of aphids is linear and has a slope of 1.5Birth size differs between species of aphids and in each species is assumed to be the minimum size necessary for feeding. Accepting this constraint then the optimum adult size for maximizingrmis approximately 15 times the birth s

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00401.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Over 2% of British angiosperm‐feeding moths (Lepidoptera) have been recorded feeding on conifers introduced to Britain, and may be undergoing host range expansion.2We compared some of the life‐history traits and ecological characteristics of fifty such species, originally exploiting angiosperms and now recorded feeding on conifers, with those of 400 non‐shifting angiosperm‐feeding moths, to identify those factors linked with host shifting.3Shifting species attack a wider range of angiosperms than non‐shifting species, their original hosts tend to be woody tress and shrubs, and they hatch from the egg earlier in the year.4Comparisons with the random control samples suggest that larval feeding habit and overwintering stage are also important (species with less intimate relations with the host plant, and those overwintering as eggs are more likely to shift); these trends persisted when the taxonomic distribution of the shift species was controlled for, though were no longer significant.5Moth species in habitats and on host plant families which are associated with conifer afforestation in upland Britain are more likely to shift, suggesting that ecological opportunity is an important factor in host range

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00402.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Wing lengths were used as indicators of size of host‐seeking females of four species of malaria vectors captured at human or animal baits in South America.2Geographic variation in size was observed among populations ofAnopheles aquasalisandA.nuneztovari, but notA.albitarsisorA.triannulatus.3The frequency distributions of wing lengths in large collections of host‐seekingA.aquasalisandA.albitarsisexhibited significant negative skewness, suggesting that the preponderance of biting females approached maximum size.4Relationships between season or physiological state (parity, blood, eggs) and the sizes of host‐seeking females were not generally significant.5WhenA.aquasalis, A.albitarsisandA.nuneztovariwere reared separately at two larval densities, initial density, but not species, significantly affected wing lengths. Significant species × density interactions may be attributable to species‐specific responses to density.6Compared to other mosquitoes, the sizes of host‐seekingAnopheles(Nyssorhynchus) varied little within natural populations. Laboratory studies on the fitness of unnaturally small malaria vectors may bear little relevance to the fitness of host‐seekingAnophe

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00403.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1The herbivorous insects on twelve species of evergreen broadleafed trees were repeatedly sampled over a period of 11 months in a small relict forest on the east coast of South Africa. This extraordinarily speciose forest patch has an unusually high proportion of endemic tree species, some of which are extremely rare.2The insect herbivore fauna (number of species) seems to be markedly depauperate compared to that reported on native, broadleafed trees from other parts of the world. Some possible reasons for this are discussed.3The total number of herbivorous insect species on each tree species was strongly correlated with the local relative abundance of the host plant species.4There was no relationship between the total number of insect herbivore species on each tree species and the relative taxonomic isolation of the trees. The proportion of seemingly unique (= specialist) herbivorous insect species (i.e. those that occurred on one tree species only) was greatest on taxonomically isolated trees.5A fundamental deficiency in the interpretation of the data in this study, and of many other similar studies that report on the number of insect species on plants, is discussed, namely the lack of clarity on the closeness of the association between individual insect herbivore species and their respective host plants.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00404.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Aquatic larvae of the pyralid mothParapoynx rugosalisMöschler repeatedly construct protective cases by cutting portions (discs) from leaves of the waterlilyNymphaea amplaand sandwich themselves between the disc and the underside of the host leaf. Construction of a new case requires leaving the old case, thus increasing exposure to predators and parasites.2In an experiment, larvae with protective cases experienced no mortality due to predation by fish, whereas larvae without cases experienced substantial predation.3In a series of choice tests, larvae preferentially selected young, tender leaves over old, tough leaves for construction of cases, and larvae spent significantly less time completing their shelters when cutting discs from young, tender leaves.4A partial explanation of why larvae select young, tender leaves for construction of their protective shelters may be that exposure time to predatorsduringconstruction is minimized.5The same mechanism linking preferences for tender leaves to reduced exposure to predators during construction may also apply to other insect herbivores exhibiting leaf‐rolling or case‐building behav

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00405.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1The effect of weather fluctuations in a tropical rain forest upon a leaf‐miner (the coffee leaf‐minerLeucoptera coffeellaGuerin‐Meneville (Lepidoptera: Lyonetiidae)) was studied in Veracruz, Mexico. The combined effect of temperature and precipitation upon the leaf‐miner populations was investigated in coffee plantations located along an elevation transect and throughout the annual seasons. The effect of plant diversity, displayed by the presence or absence of shade trees in coffee plantations, upon the population loads of the leaf‐miner was also investigated.2The leaf‐miner population increased significantly during the period of intermediate temperature and low precipitation (spring season). Elevation also affected the population load of the insect: leaf‐miner populations were larger at low elevations (where temperatures are high and precipitation low) than at high elevations.3Plant structural diversity did not affect the population loads of the leaf‐miner.4The results indicate that the direct and indirect effects of temperature and precipitation are significant factors in the population dynamics of the coffee leafminer. It is suggested that even moderate fluctuations in climatic conditions in tropical and subtropical regions may also play an important role in the dynamics of tropical insect populations, similar to that found in temperate zones where climatic fluctuati

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00406.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.1Wing form frequencies in 255 populations of 101 species of leafhoppers (Auchenorrhyncha) in temporary and permanent habitats were documented.2The proportion of brachypterous specimens in the leafhopper assemblages on ruderal host plants in temporary habitats (median 2%, range 0–8%) was significantly lower than that on permanent host plants in undisturbed habitats (median 22%, range 0–94%).3Leafhopper species typical of temporary habitats were either monomorphic, macropterous, or wing‐dimorphic with macropterous forms prevailing in both sexes.4Among the eighty‐nine species recorded in permanent habitats, forty‐five species were wing dimorphic. In forty‐one dimorphic species, a brachypterous form prevailed. This prevalence was found for both sexes in thirty‐one species, for only females in nine species and for only males in one species.5The prevalence of brachypters in males, but not in females, found inAnoscopus flavostriatus, is probably the first such documented case in Auchenorrhyncha.6The hypothesis is proposed that in temporary habitats, density‐dependent production of macropters in wing dimorphic species is an adaptation to frequent habitat deterioration caused by factors independent of the density of the species.7The predominance of brachypters in permanent habitats indicates that a density‐dependent decrease in fitness usually does not offset the potential decrease in fitness connected with macroptery and dispersal. Because of this inability of leafhopper populations to decrease significantly the quality of their resources, a high population density cannot be used as a predictor of future quality of these resources, which is information essential for efficient di

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1994.tb00407.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY