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1.
The hypothesis that vegetational diversity may lessen the impact of forest insect pests by favoring natural enemies is appealing
to those who seek ecologically sound solutions to pest problems. We investigated the effect of forest diversity on the impact
of the spruce budworm Choristoneurafumiferana following the last outbreak, as well as the budworm's current abundance and parasitism rate, in the boreal forest of northwestern
Québec. Mortality of balsam fir caused by the budworm was greater in extensive conifer stands than either in “habitat islands”
of fir surrounded by deciduous forest or on true islands in the middle of a lake. Adult spruce budworm abundance, assessed
by pheromone traps, did not differ significantly between the three types of sites. Larval and pupal parasitism rates were
examined by transferring cohorts of laboratory-reared larvae and pupae to trees in the three site types and later collecting
and rearing them. The tachinid Actiainterrupta, a parasitoid of fifth and sixth instar larvae, as well as the ichneumonid pupal parasitoids Itoplectesconquisitor, Ephialtesontario and Phaeogenesmaculicornis, caused higher mortality in the habitat islands than on true islands or in extensive stands. Exochusnigripalpistectulum, an ichneumonid that attacks the larvae and emerges from the pupae, caused greater mortality in the extensive stands of conifers.
Received: 17 March 1997 / Accepted: 18 November 1997 相似文献
2.
Social insect societies are considered to be composed of many extremely cooperative individuals. While workers are traditionally
believed to behave altruistically, recent studies have revealed behaviors that are more selfish. One such example is intraspecific
social parasitism, where workers invade conspecific colonies and produce male offspring that are reared by unrelated host
workers. Such intraspecific parasitism has been reported in honeybees (Apis cerana, and A. florea) and “semi-wild” bumblebee colonies of Bombus terrestris. Here we report on intraspecific social parasitism by workers in “wild” colonies of the bumblebee B. deuteronymus. Three of the 11 B. deuteronymus colonies studied were invaded by non-natal workers, of which 75% became reproductive and produced 19% of the adult males.
The invading non-natal workers produced significantly more males than resident natal workers and the non-natal brood was not
discriminated against by the natal workers. 相似文献
3.
Larval tobacco hornworms,Manduca sexta (L.), of 2 different colonies were exposed to parasitism by the gregarious endoparasitoid,Cotesia congregata (Say). A comparison was made of parasitoid larval, pre-pupal, and pupal mortality, female and male dry weight and larval
development time. In general, “Maryland” hornworms were more suitable hosts than “North Carolina” hornworms. Although the
presence of dietary nicotine increased parasitoid mortality in individuals reared from hornworms of both colonies, the effect
was more severe among individuals parasitizing the North Carolina hornworms.
Scientific contribution No. 8125, article No. A-5066 of the Maryland Agricultural Experiment Station, Department of Entomology. 相似文献
4.
Parasites often confront conflicting demands when evaluating and distributing themselves among host individuals, in order to attain maximum reproductive success. We tested two alternative hypotheses about host preference by fleas in relation to the age of their rodent host. The first hypothesis suggests that fleas select adult over juvenile rodents because the latter represent a better nutritional resource (the “well-fed host” hypothesis), whereas the second hypothesis suggests that fleas prefer the weaker and less resistant juveniles because they are easier to colonise and exploit (“poorly fed host” hypothesis). We sampled fleas (Synosternus cleopatrae) on the gerbil (Gerbillus andersoni) in 23 different plots in the Negev desert and found an unequal distribution of fleas between adult and juvenile hosts. Furthermore, flea distribution changed as a function of flea density—from juvenile-biased flea parasitism (the “poorly fed host” hypothesis) at low densities to adult-biased flea parasitism (the “well-fed host” hypothesis) at high densities. Other factors that influenced flea preference were soil temperature and the presence of ticks. These results suggest that host selection is not an explicit alternative choice between adults and juveniles (“well-fed host” versus “poorly fed host” hypotheses), but rather a continuum where the distribution between adults and juveniles depends on host, parasite, and environmentally related factors. 相似文献
5.
Koichi Tanaka 《Oecologia》1992,90(4):597-602
Summary Stage-specific mortality rates and mortality factors for the web-building spiderAgelena limbata, which is suggested to be food-limited, were studied, and the relationship between body size of spiders and survivorship for instar 3 to adults was examined. The mortality rate of the egg sac stage including eggs, deutova (prenymphal stage), and overwintering instar 1 nymphs was low. The low mortality of this stage was partly due to maternal care that reduced the mortality caused by predation and/or abiotic factors. From emergence of instar 1 nymphs from egg sacs to reproduction, the stagespecific mortality rates were almost constant, 32–47%, and the time-specific mortality rates were also constant. These results suggest a Deevey (1947) type II survivorship curve inA. limbata, in contrast to other reports on the wandering or burrowing spiders which suggested type III curves. Important mortality factors for nymphs and adults were parasitism by an ichneumonid wasp and predation by spiders. There were great variations in body size (carapace width) ofA. limbata in the field. Smaller individuals survived at a lower rate to the next stage than larger individuals. This tendency was clearer for the population living under poorer prey availability.A. limbata was unlikely to starve to death in the field because every stage ofA. limbata could survive starvation for a long time in the laboratory, 22–65 days on average. I suggest that the size-dependent survivorship of this spider is associated with vulnerability of smaller individuals to parasitism and predation. 相似文献
6.
Summer mortality of Crassostrea gigas is the result of a complex interaction between oysters, their environment, and pathogens. A high heritability was estimated
for resistance to summer mortality, which provided an opportunity to develop lines of oysters that were resistant (R) or susceptible
(S) to summer mortality. Previous genome-wide expression profiling study of R and S oyster gonads highlighted reproduction
and antioxidant defense as constitutive pathways that operate differentially between these two lines. Here, we show that signaling
in innate immunity also operates differentially between these lines, and we hypothesize that this is at the main determinant
of their difference in survival in the field. A reanalysis of our published microarray data using separate ANOVAs at each
sampling date revealed a specific “immune” profile at the date preceding the mortality. In addition, we conducted additional
microarray profiling of two other tissues, gills, and muscle, and both showed an overrepresentation of immune genes (46%)
among those that are differentially expressed between the two lines. Eleven genes were pinpointed to be simultaneously differentially
expressed between R and S lines in the three tissues. Among them, ten are related to “Immune Response.” For these genes, the
kinetics of R mRNA levels between sampling dates appeared different just before the morality peak and suggests that under
field conditions, R oysters had the capacity to modulate signaling in innate immunity whereas S oysters did not. This study
enhances our understanding of the complex summer mortality syndrome and provides candidates of interest for further functional
and genetics studies. 相似文献
7.
Sex pheromone of the larch caterpillar moth, Dendrolimus superans, from northeastern China 总被引:2,自引:0,他引:2
A study was set up to determine the sources and rates of mortality of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on field‐grown cassava in Uganda. Using a cohort‐based approach, daily direct observations were used to construct partial life tables for 12 generations of egg and nymph populations which were studied over a 1‐year period. Mortality was categorized as dislodgement, predation, parasitism (for nymphs only), unknown death, and inviability (for eggs only). The highest mean rate of marginal mortality across all stages was attributed to parasitism, with dislodgement and predation following, respectively. Across all factors, the highest mean rate of marginal mortality was observed in the fourth instar followed by the eggs, first‐, second‐, and third‐instars, respectively. Key factor analysis revealed that dislodgement was the major mortality factor contributing to generational mortality in eggs while for nymphs, parasitism in the fourth instar was the main driving force behind the observed generational mortality. Highest irreplaceable mortality in both the egg and nymph stages was attributed to dislodgement followed by parasitism and predation, and least was due to unknown death. Across stages, highest irreplaceable mortality rates were observed in the eggs and the fourth‐instar nymphs. The other stages had relatively low rates of irreplaceable mortality. Rain‐protection experiments revealed no significant differences in marginal mortality rates when compared to the open field situation. 相似文献
8.
Guillermo A. Logarzo Eduardo G. Virla Erica Luft Albarracin Serguei V. Triapitsyn Walker A. Jones Jesse H. de León Juan A. Briano 《BioControl》2012,57(1):37-48
The South American egg parasitoid Gonatocerus sp. near tuberculifemur “Clade 1” (G. sp. “Clade 1”) (Hymenoptera: Mymaridae) is a new association of the glassy-winged sharpshooter (GWSS), Homalodisca
vitripennis (Germar) (Cicadellidae) and a candidate for its biological control in California, USA. In Argentina, G. sp. “Clade 1” was screened in the laboratory (no-choice tests) and in the field (multiple choice tests) against eggs of 32
Auchenorrhyncha host species and other four potential hosts unrelated to sharpshooters. In no-choice assays, it parasitized
only eggs within the leafhopper tribe Proconiini. In contrast, in the long term field tests, it emerged not only from eggs
of the Proconiini but also from two species of Cicadellini at low numbers (five wasps out of 698 exposed eggs). Two interpretations
arise from the results: (1) Host associations of G. sp. “Clade 1” are restricted to the Proconiini whereas field parasitization of the Cicadellini species were false positive,
or (2) G. sp. “Clade 1” parasitizes also some Cicadellini species and its rejection in the laboratory was a false negative. Both interpretations
are discussed. Insect motivation could be the explanation for the negative results in the no-choice tests. On the other hand,
in the more natural field situations, the host selection process and oviposition behavior should not have been affected and
host range would be more realistic. The parasitism of the Cicadellini species would be indicative of a potential non-target
effect on the sharpshooters in the USA. 相似文献
9.
Giuseppe C. Zuccarello Alan T. Critchley Jennifer Smith Volker Sieber Genevieve Bleicher Lhonneur John A. West 《Journal of applied phycology》2006,18(3-5):643-651
The systematics and taxonomy of Kappaphycus and Eucheuma (Solieriaceae) is confused and difficult due to morphological plasticity, lack of adequate characters to identify species and commercial names of convenience. These taxa are geographically widely dispersed through cultivation. Commercial, wild and herbarium sources were analysed; molecular markers provided insights into taxonomy and genetic variation, and where sources of genetic variation may be located. The mitochondrial cox2-3 and plastidal RuBisCo spacers were sequenced. There is a clear genetic distinction between K. alvarezii (“cottonii”) and K. striatum (“sacol”) samples. Kappaphycus alvarezii from Hawaii and some samples from Africa are also genetically distinct. Our data also show that all currently cultivated K. alvarezii from all over the world have a similar mitochondrial haplotype. Within Eucheuma denticulatum (“spinosum”) most African samples are again genetically distinct. Our data also suggest that currently cultivated E. denticulatum may have been “domesticated” several times, whereas this is not evident for the cultivated K. alvarezii. The present markers used do not distinguish all the morpho-types known in cultivation (e.g. var. tambalang, “giant” type) but do suggest that these markers may be useful to assess introductions and species identification in samples. 相似文献
10.
George D. Koufos Louis de Bonis Dimitris S. Kostopoulos Laurent Viriot Theodora D. Vlachou 《Pal?ontologische Zeitschrift》2004,78(1):213-228
Two skulls, two mandibles and some postcranials ofMesopithecus from the locality “Vathylakkos 2” of Axios Valley (Macedonia, Greece) enlarge our knowledge about the genus and its differentiation.
The new material together with an old skull from the same locality is compared with the Pikermi, “Ravin des Zouaves 5” (Axios
Valley), and Maramena (Serres basin) samples. It is concluded that the VathylakkosMesopithecus resemblesM. pentelicus from Pikermi, as wellM. delsoni from “Ravin des Zouaves 5” and it is referred asMesopithecus sp. aff.M. pentelicus. The biochronological age of “Vathylakkos 2” has been considered as MN 12, while recent magnetostratigraphic data indicate
an age of about 7.5 Ma. This age confirms the position of the VathylakkosMesopithecus between Pikermi and “Ravin des Zouaves 5”. Some dental indices compared with those of the RecentCercopithecus suggest that the Vathylakkos sample is monospecific.
相似文献
11.
A reevaluation of floral and vegetative morphology together with data from analysis of floral fragrance and flavonoid co-pigment
chemistry suggest that specific status is warranted for the two kinds ofPhalaenopsis violacea Witte known informally as the “Bornean type” and the “Malayan type.”Phalaenopsis violacea var.bellina Rchb.f. is elevated to specific rank, providing a name for the “Bornean type” plants. 相似文献
12.
Showe-Mei Lin 《Journal of applied phycology》2006,18(3-5):671-678
Four flattened Gracilaria species have been reported from Taiwan: G. spinulosa, G. vieillardii, G. textorii and G. punctata, identified based on branching pattern, the presence or absence of spines, and characters that often vary seasonally. Gracilaria spinulosa was originally described from the type locality, Tainan. Species with toothed margins are usually referred to G. “vieillardii”; those with smooth margins to G. “textorii”, and those with smooth margins and dark spots scattered over the blade to G. “punctata”. Molecular analyses show that specimens with marginal teeth cluster in three different groups: a G. “vieillardii” clade, a G. spinulosa clade, and a clade sister to G. spinulosa. An undescribed species comprises the third clade, which is distinguished by its relatively large gonimoblast cells and weakly developed tubular nutritive cells. The three clades can be separated by the character of the tubular nutritive cells, the size of gonimoblast cells and certain vegetative features. Plants with entire margins form a single clade characterized by cystocarps with basal tubular nutritive cells and their absence in the cystocarp cavity. They are nested in the Hydropuntia complex and are referred to as Gracilaria “punctata” here. The records of G. textorii and G. punctata from Taiwan require reinvestigation in comparison with the Japanese species. 相似文献
13.
New species of Pogonophryne (Pisces, Artedidraconidae) from the Bellingshausen Sea, Antarctica 总被引:1,自引:1,他引:0
A new species of notothenioid fish, Pogonophryne bellingshausenensis n. sp., is described from the Bellingshausen Sea, Antarctica. The new species belongs to the dorsally-spotted “mentella”
group of the genus and is characterized by having a short (about 13% SL) mental barbel with a short (about 16% of barbel length),
narrow (barely wider than the stalk), and relatively inconspicuous terminal expansion composed of short, irregular, fingerlike
processes. Compared to most other dorsally-spotted species of Pogonophryne (“barsukovi”, “marmorata”, and “mentella” groups), P. bellingshausenensis has a relatively wide (about 7% SL) interorbital region. An unspotted patch on the median dorsal surface of the head, posterior
to the posttemporal ridges and anterior to the first dorsal fin, has not been observed previously in any dorsally-spotted
species. The holotype was collected at 1,947 m, one of the deepest records for any species of Pogonophryne. A revised key to the ten species of the “mentella” group of Pogonophryne is also provided. 相似文献
14.
J. Wilson White 《Theoretical Ecology》2011,4(3):357-370
All else being equal, inversely density-dependent (IDD) mortality destabilizes population dynamics. However, stability has
not been investigated for cases in which multiple types of density dependence act simultaneously. To determine whether IDD
mortality can destabilize populations that are otherwise regulated by directly density-dependent (DDD) mortality, I used scale
transition approximations to model populations with IDD mortality at smaller “aggregation” scales and DDD mortality at larger
“landscape” scales, a pattern observed in some reef fish and insect populations. I evaluated dynamic stability for a range
of demographic parameter values, including the degree of compensation in DDD mortality and the degree of spatial aggregation,
which together determine the relative importance of DDD and IDD processes. When aggregation-scale survival was a monotonically
increasing function of density (a “dilution” effect), dynamics were stable except for extremely high levels of aggregation
combined with either undercompensatory landscape-scale density dependence or certain values of adult fecundity. When aggregation-scale
survival was a unimodal function of density (representing both “dilution” and predator “detection” effects), instability occurred
with lower levels of aggregation and also depended on the values of fecundity, survivorship, detection effect, and DDD compensation
parameters. These results suggest that only in extreme circumstances will IDD mortality destabilize dynamics when DDD mortality
is also present, so IDD processes may not affect the stability of many populations in which they are observed. Model results
were evaluated in the context of reef fish, but a similar framework may be appropriate for a diverse range of species that
experience opposing patterns of density dependence across spatial scales. 相似文献
15.
Chang-Gi Kim Bumkyu Lee Dae In Kim Ji Eun Park Hyo-Jeong Kim Kee Woong Park Hoonbok Yi Soon-Chun Jeong Won Kee Yoon Chee Hark Harn Hwan Mook Kim 《Journal of Plant Biology》2008,51(1):74-77
Gene flow from genetically modified (GM) crops to conventional non-GM crops is a serious concern for protection of conventional
and organic farming. Gene flow from GM watermelon developed for rootstock use, containing cucumber green mottle mosaic virus
(CGMMV)-coat protein (CP) gene, to a non-GM isogenic control variety “Clhalteok” and grafted watermelon “Keumcheon” was investigated
in a small scale field trial as a pilot study. Hybrids between GM and non-GM watermelons were screened from 1304 “Chalteok”
seeds and 856 “Keumcheon” seeds using the duplex PCR method targeting theCGMMV- CP gene as a marker. Hybrids were found in all pollen recipient plots. The gene flow frequencies were greater for “Chaiteok”
than for “KeumcheonD; with 75% outcrossing in the “Chaiteok” plot at the closest distance (0.8 m) to the GM plot. A much larger
scale field trial is necessary to identify the isolation distance between GM and non-GM watermelon, as the behaviors of insect
pollinators needs to be clarified in Korea. 相似文献
16.
Summary The shallow marine subtropical Northern Bay of Safaga is composed of a complex pattern of sedimentary facies that are generally
rich in molluscs. Thirteen divertaken bulk-samples from various sites (reef slopes, sand between coral patches, muddy sand,
mud, sandy seagrass, muddy seagrass, mangrove channel) at water depths ranging from shallow subtidal to 40m were investigated
with regard to their mollusc fauna >1mm, which was separated into fragments and whole individuals.
Fragments make up more than 88% of the total mollusc remains of the samples, and their proportions correspond to characteristics
of the sedimentary facies. The whole individuals were differentiated into 622 taxa. The most common taxon,Rissoina cerithiiformis, represented more than 5% of the total mollusc content in the samples. The main part of the fauna consists of micromolluscs,
including both small adults and juveniles. Based on the results of cluster-, correspondence-, and factor analyses the fauna
was grouped into several associations, each characterizing a sedimentary facies: (1) “Rhinoclavis sordidula—Corbula erythraeensis-Pseudominolia nedyma association” characterizes mud. (2) “Microcirce sp.—Leptomyaria sp. association” characterizes muddy sand. (3)”Smaragdia spp.-Perrinia stellata—Anachis exilis—assemblage” characterizes sandy seagrass. (4) “Crenella striatissima—Rastafaria calypso—Cardiates-assemblage” characterizes muddy seagrass. (5) “Glycymeris spp.-Parvicardium sueziensis-Diala spp.-assemblage” characterizes sand between coral patches. (6) “Rissoina spp.-Triphoridae —Ostreoidea-assemblage” characterizes reef slopes. (7) “Potamides conicus—Siphonaria sp. 2—assemblage” characterizes the mangrove.
The seagrass fauna is related to those of sand between coral patches and reef slopes with respect to gastropod assemblages,
numbers of taxa and diversity indices, and to the muddy sand fauna on the basis of bivalve assemblages and feeding strategies
of bivalves. The mangrove assemblage is related to those of sand between coral patches and the reef slope with respect to
taxonomic composition and feeding strategies of bivalves, but has a strong relationship to those of the fine-grained sediments
when considering diversity indices. Reef slope assemblages are closely related to that of sand between coral patches in all
respects, except life habits of bivalves, which distincly separates the reef slope facies from all others. 相似文献
17.
Labreuche Y Pallandre L Ansquer D Herlin J Wapotro B Le Roux F 《Microbial ecology》2012,63(1):127-138
Two recurring syndromes threaten the viability of the shrimp industry in New Caledonia, which represents the second largest
export business. The “Syndrome 93” is a cold season disease due to Vibrio penaeicida affecting all shrimp farms, while the “Summer Syndrome” is a geographically restricted vibriosis caused by a virulent lineage
of Vibrio nigripulchritudo. Microbiological procedures for diagnosis of these diseases are time-consuming and do not have the ability to discriminate
the range of virulence potentials of V. nigripulchritudo. In this study, we developed a multiplex PCR method to simultaneously detect these two bacterial species and allow for pathotype
discrimination. The detection limits of this assay, that includes an internal amplification control to eliminate any false-negative
results, were determined at 10 pg purified DNA and 200 cfu/ml. After confirming the effectiveness of our method using experimentally
infected animals, its accuracy was compared to standard biochemical methods during a field survey using 94 samples collected
over 3 years from shrimp farms encountering mortality events. The multiplex PCR showed very high specificity for the detection
of V. penaeicida and V. nigripulchritudo (inclusivity and exclusivity 100%) and allowed us to detect the spreading of highly pathogenic isolates of V. nigripulchritudo to a farm adjoining the “Summer Syndrome area.” This assay represents a simple, rapid, and cost-effective diagnostic tool
for implementing timely risk management decisions but also understanding the seasonal and geographical distribution of these
pathogens. 相似文献
18.
The concept of “enemy-free space” (EFS) refers to ways of living that reduce or eliminate the vulnerability of a species to
natural enemies. It has been invoked to explain host shifts of phytophagous insects. A demonstrated cause of EFS is escape
from enemies in time, through phenological mismatching of herbivore development and enemy occurrence, leading to low percentages
of predation/parasitism of herbivores occurring at a certain time. The mere measurement of percentage parasitism, however,
is not sufficient to demonstrate EFS in certain cases. Here we present such a case, where parasitism was studied of a phytophagous
insect (Phyllotreta nemorum), using two different host plant species in the field: an atypical, relatively rarely used, plant (Barbarea vulgaris), and a more widely used one (Sinapis arvensis). At one location we found a paradoxical result: on each separate sampling day throughout the season the percentage of parasitism
of P. nemorum using a patch of B. vulgaris was not significantly different from, or even significantly higher than on a nearby patch of S. arvensis. The overall season-wide proportion parasitism of the flea beetle cohort using the B. vulgaris patch, however, was lower. We conclude that, in the year and at the location we studied, the patch of B. vulgaris provided enemy-free space to the herbivore in the form of a temporal refuge, and that the importance of enemy-free space
in the use of an atypical host plant should be evaluated on the basis of season-wide sampling, including estimation of host
population size. 相似文献
19.
The Macrotermitinae are a large and successful subfamily of fungus-growing termites, characterised by their symbiotic association
with white-rot fungi of the genus Termitomyces. The taxonomy of the subfamily, and in particular of the largest genus Odontotermes, is problematic. We used sequences of the mitochondrial 16S gene from termites occurring in East Africa and Malawi to explore
the phyletic relationships within the genus Odontotermes and to place the genus in the broader context of other fungus-growing termites. We also interpret this phylogeny in relation
to classical morphological taxonomy in the form of absolute and relative dry weights of the sterile castes, and in relation
to innate behaviour as shown by nest architecture and fungus comb structure. This work lays the foundations of a complete
taxonomic revision of the Macrotermitinae.
The phylogeny supports one clear subdivision, here called the “tanganicus” group, within the genus Odontotermes. It also supports the significance of field observations on the structure of fungus combs, as the whole “tanganicus” group
builds fungus combs of the sponge type (or modified forms thereof) which are hardly known elsewhere. Other phyletic relationships
are less clear, the residual sequences being referred to as the “latericius” group. We recognise three probable miniature
species within the “tanganicus” group and another possible one in the residual “latericius group”.
Received 16 January 2007; revised 30 October 2007 and 11 March 2008; accepted 4 April 2008. 相似文献
20.
C. M. M. Meireles M. I. C. Sampaio H. Schneider M. P. C. Schneider 《Primates; journal of primatology》1992,33(2):227-238
The electrophoretic patterns of 15 protein systems codified for 20 genetic loci were investigated using horizontal electrophoresis.
A total of 150 blood samples, from five species of the genusCallithrix were analyzed. Polymorphic variation was observed in 10 out 20 loci analyzed. The genotypic distributions are in Hardy-Weinberg
equilibrium. The average heterozygosity (H) varied from 1% to 5%, similar to those observed for other Neotropical primates.
The genetic distance coefficients revealed a phylogenetic separation of these species into two groups: (1) “argentata” (C. humeralifer andC. emiliae); (2) “jacchus” (C. jacchus, C. penicillata, andC. geoffroyi). This arrangement is according to the taxonomic arrangement proposed byHershkovitz (1977),de Vivo (1988), andMittermeier et al. (1988). The results in each group are compatible with the subspecies values recorded for the Platyrrhini. These values
showed that:C. humeralifer andC. emiliae are subspecies ofC. argentata;C. jacchus, C. penicillata, andC. geoffroyi are subspecies ofC. jacchus. These results also suggest thatC. j. geoffroyi is the “jacchus” group taxon, most similar genetically to the “argentata” group. 相似文献