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1.
Plant–insect interactions, which are strongly mediated by chemical defenses, have the potential to shape invasion dynamics. Despite this, few studies have quantified natural variation in key defensive compounds of invasive plant populations, or how those defenses relate to levels of herbivory. Here, we evaluated variation in the iridoid glycosides aucubin and catalpol in rosette plants of naturally occurring, introduced populations of the North American invader, Verbascum thapsus L. (common mullein; Scrophulariaceae). We examined two scales that are likely to structure interactions with insect herbivores—among populations and within plant tissues (i.e., between young and old leaves). We additionally estimated the severity of damage incurred at these scales due to insect chewing herbivores (predominantly grasshoppers and caterpillars), and evaluated the relationship between iridoid glycoside content and leaf damage. We found significant variation in iridoid glycoside concentrations among populations and between young and old leaves, with levels of herbivory strongly tracking leaf-level investment in defense. Specifically, across populations, young leaves were highly defended by iridoids (averaging 6.5× the concentration present in old leaves, and containing higher proportions of the potentially more toxic iridoid, catalpol) and suffered only minimal damage from generalist herbivores. In contrast, old leaves were significantly less defended and accordingly more substantially utilized. These findings reveal that quantitative variation in iridoid glycosides is a key feature explaining patterns of herbivory in an introduced plant. In particular, these data support the hypothesis that defenses limit the ability of generalists to feed on mullein’s well-defended young leaves, resulting in minimal losses of high-quality tissue, and increasing performance of this introduced species. 相似文献
2.
Summary Chemical analysis of each individual leaf of fivePlantago lanceolata (Plantaginaceae) plants showed that iridoid glycoside content increased from undetectable in the oldest photosynthetic leaves to over 9% dry weight in the youngest leaves. The relative proportion of the two iridoid glycosides inP. lanceolata also changed with leaf age: older leaves had significantly more aucubin, whereas the youngest leaves had primarily or solely catalpol. Oviposition tests with femaleJunonia coenia (Nymphalidae) butterflies, showed that they laid most of their eggs on new leaves. 相似文献
3.
We analyzed several species of the weevil family Mecininae (Coleoptera, Curculionidae) that all feed on iridoid glycoside
(IG) containing plants of the Plantaginaceae to investigate whether the beetles sequester these deterrent substances from
their host plants. Within the Mecininae two genera of the tribe Cionini were found to sequester aucubin and catalpol: Cionus Clairville
and Schellenberg and Cleopus Dejean. Both analyzed genera of the Mecinini, Mecinus Germar and Rhinusa Stephens, do not sequester IGs although the compounds are present in their food plants. They thus represent the first case of specialists
on IG plants that have not evolved adaptations to use the compounds. However, in contrast to the Cionini these genera have
a hidden lifestyle, so that their need for defence might be lower. Both Cionus and Cleopus, sequester catalpol with a higher efficiency than aucubin. However, in contrast to Cionus species, Cleopus species only sequester catalpol. In species feeding on Scrophularia, the aucubin concentration is higher while in beetles on Verbascum catalpol is usually dominating. This pattern can also be detected in the only species living on both plants, Cionus hortulanus. The ability to sequester IGs must have a single origin at the base of the sister genera Cionus and Cleopus. 相似文献
4.
A. Mosleh Arany T. J. de Jong H. K. Kim N. M. van Dam Y. H. Choi R. Verpoorte E. van der Meijden 《Chemoecology》2008,18(2):65-71
Because many secondary metabolites in plants act as defense against herbivores it has been postulated that these compounds
have evolved under selective pressure by insect herbivores. One explanation for the within-species variation in metabolite
patterns in a particular species is that different populations are under selection by different herbivores. We tested this
hypothesis, using Arabidopsis thaliana plants that originated from dune and inland areas. We analyzed Arabidopsis thaliana leaves using NMR spectroscopy and multivariate data analysis. Major differences in chemical composition were found in water-methanol
fractions and were due to higher concentrations of sinigrin and fumaric acid in dune plants. Inland plants showed lower levels
of glucose. Quantitative analysis of glucosinolates was performed with HPLC. Individual plants and populations demonstrated
differences in glucosinolate composition and concentration. In growth chamber experiments, the generalist herbivore, Spodoptera exigua grew significantly better on the inland plants, while the specialist herbivore Plutella xylostella performed equally well on plants of both origins. Aliphatic glucosinolate as well as total glucosinolate concentrations negatively
correlated with larval mass of Spodoptera exigua. No significant correlations, however, were found between larval mass of Plutella xylostella and glucosinolates in the leaves. A specialist and a generalist herbivore were responding differently to plant secondary
chemistry, as was also found in several other studies. This is an important indication that differences in glucosinolate concentrations
among populations may result from differential selection by different guilds of herbivores. 相似文献
5.
Resistance of the generalist moth Trichoplusia ni (Noctuidae) to a novel chemical defense in the invasive plant Conium maculatum 总被引:1,自引:0,他引:1
Summary.
Conium maculatum is an apiaceous species native to Eurasia that is highly toxic to vertebrates due to the presence of piperidine alkaloids,
including coniine and γ-coniceine. More than 200 years after invading the United States this species remains mostly free from
generalist insect herbivores. The presence of novel chemical defenses in the introduced range could provide invasive species
with a competitive advantage relative to native plants. The cabbage looper (Trichoplusia ni) is a generalist lepidopteran found throughout the US that occasionally feeds on C. maculatum. We evaluated the toxicity of piperidine alkaloids to T. ni and determined putative resistance mechanisms, both behavioral and physiological, that allows this insect to develop successfully
on C. maculatum foliage. T. ni larvae raised on diets enriched with coniine and γ-coniceine showed a decrease in consumption and longer development time,
but no effects on growth were found at any alkaloid concentration. In a diet choice experiment T. ni larvae showed no avoidance of alkaloid-enriched diets, suggesting that the deterrence produced by alkaloids was related to
a post-ingestive metabolic response. The ability of T. ni to consume diets high in alkaloid content could be due to at least three different mechanisms: 1) a decreased consumption
rate, 2) efficient excretion of at least 1/3 of ingested alkaloids unmetabolized in frass, and 3) partial detoxification of
alkaloids by cytochrome P450 s, as shown by the decreased larval growth in the presence of piperonyl butoxide, a P450 inhibitor.
Even though T. ni tolerates C. maculatum alkaloids, the use of this species as a host plant could be ecologically disadvantageous due to prolonged larval growth and
thus increased exposure to predators. Novel plant secondary compounds do not guarantee increased resistance to generalist
herbivores. 相似文献
6.
Plant chemistry and insect sequestration 总被引:2,自引:1,他引:1
Most plant families are distinguished by characteristic secondary metabolites, which can function as putative defence against
herbivores. However, many herbivorous insects of different orders can make use of these plant-synthesised compounds by ingesting
and storing them in their body tissue or integument. Such sequestration of putatively unpalatable or toxic metabolites can
enhance the insects’ own defence against enemies and may also be involved in reproductive behaviour. This review gives a comprehensive
overview of all groups of secondary plant metabolites for which sequestration by insect herbivores belonging to different
orders has been demonstrated. Sequestered compounds include various aromatic compounds, nitrogen-containing metabolites such
as alkaloids, cyanogenic glycosides, glucosinolates and other sulphur-containing metabolites, and isoprenoids such as cardiac
glycosides, cucurbitacins, iridoid glycosides and others. Sequestration of plant compounds has been investigated most in insects
feeding or gathering on Apocynaceae s.l. (Apocynoideae, Asclepiaoideae), Aristolochiaceae, Asteraceae, Boraginaceae, Fabaceae and Plantaginaceae, but it also occurs
for some gymnosperms and even lichens. In total, more than 250 insect species have been shown to sequester plant metabolites
from at least 40 plant families. Sequestration predominates in the Coleoptera and Lepidoptera, but also occurs frequently
in the orders Heteroptera, Hymenoptera, Orthoptera and Sternorrhyncha. Patterns of sequestration mechanisms for various compound
classes and common or individual features occurring in different insect orders are highlighted. More research is needed to
elucidate the specific transport mechanisms and the physiological processes of sequestration in various insect species. 相似文献
7.
Summary. Sequestration of plant toxins in herbivores is often
correlated with aposematic coloration and gregarious behaviour. Larvae
of Pieris brassicae show these conspicuous morphological and behavioural
characteristics and were thus suggested to sequester glucosinolates that
are characteristic secondary metabolites of their host plants. P. rapaeare camouflaged and solitary, and are thus not expected to sequester. To
test this hypothesis and to check the repeatabi-lity of a study that did
report the presence of the glucosinolate sinigrin in P. brassicae,
larvae were reared on three species of Brassicaceae (Sinapis alba,
Brassica nigra and Barbarea stricta), and different leaf and insect
samples were taken for glucosinolate analysis. The major host plant
glucosinolates could only be found in traces or not at all in larval
haemolymph, bled or starved larvae, faeces or pupae of both species or
P. brassicae regurgitant. Haemolymph of both Pieris spp. was not
rejected by the ant Myrmica rubra in dual-choice assays; the regurgitant
of P. brassicae was rejected. This suggests the presence of compounds
other than glucosinolates that might be sequestered in or produced by P.
brassicae only. In faeces of both Pieris spp. a compound which yielded
4-hydroxybenzylcyanide (HBC) upon incubation with sulfatase was detected
in high concentrations when larvae had been reared on S. alba. This
compound may be derived from hydrolysis of sinalbin, the main
glucosinolate of that plant. The unidentified HBC progenitor was
apparently not sequestered in the two Pieris spp., and was not detected
in faeces of larvae reared on B. nigra or B. stricta.
Received 18 July 2002; accepted 11 September 2002. 相似文献
8.
Preferences of six leaf beetle species among qualitatively different leaf age classes of three Salicaceous host species 总被引:2,自引:0,他引:2
Arsi Ikonen 《Chemoecology》2002,12(1):23-28
Summary. As Salicaceous plants produce new leaves for a prolonged period of time, they expose a wide range of differentially aged
leaves to herbivores during the growing season. In this work, I show that young leaves of three Salicaceous species, Populus tremula L., Salix phylicifolia L. and S. pentandra L., contain more nitrogen than conspecific old leaves. In P. tremula and S. pentandra young leaves also contained more low-molecular weight secondary compounds, phenolic glucosides. Leaves of S. phylicifolia did not contain phenolic glucosides in detectable amounts. Furthermore, in P. tremula and S. pentandra young leaves contained less polymeric digestability-reducing phenolics, condensed tannins, than old leaves. In S. phylicifolia, higher concentrations of condensed tannins were found in young leaves. In laboratory feeding trials with six leaf beetle
species, young leaves of the studied plants were invariably preferred in all tested herbivore × host species combinations.
In particular, it is remarkable that three leaf beetle species with known different overall relationships to phenolic glucosides
equally preferred more glucoside-containing young S. pentandra leaves over conspecific old ones. Four beetle species were found to prefer young leaves of S. phylicifolia despite the higher content of condensed tannins in young leaves. These results indicate that the general preference of leaf
beetles for young leaves of Salicaceous plants probably does not primarily result from variable distribution of secondary
compounds. Apparently, the preference for young leaves is fundamentally due to variation in leaf nutritive traits, such as
nitrogen content.
Received 9 February 2001. 相似文献
9.
Allocation of resources to growth and defense against herbivores crucially affects plant competitiveness and survival, resulting
in a specific distribution of assimilates and defense compounds within plant individuals. Additionally, plants rarely experience
stable environmental conditions, and adaptations to abiotic and biotic stresses may involve shifts in resistance to herbivores.
We studied the allocation of phytochemicals in Brassica oleracea (Brussels sprouts) due to leaf age, drought stress and herbivore damage and assessed effects on two lepidopteran herbivores
differing in diet breadth: the generalist Spodoptera littoralis and the specialist Pieris brassicae. Glucosinolates as secondary defense compounds and total nitrogen and carbon were quantified and linked to plant palatability,
i.e., herbivore feeding preference. Herbivore responses were highly species-specific and partially related to changes in phytochemicals.
Spodoptera littoralis preferred middle-aged leaves with intermediate levels of glucosinolates and nitrogen over young, glucosinolate and nitrogen
rich leaves, as well as over old leaves, poor in glucosinolates and nitrogen. In contrast, P. brassicae preferred young leaves. Both species preferred severely drought-stressed plants to the well-watered control, although analyzed
glucosinolate concentrations did not differ. Both S. littoralis and P. brassicae feeding induced an increase of indole glucosinolate levels, which may explain a reduced consumption of damaged plants detected
for S. littoralis but not for P. brassicae. By revealing distinct, sometimes contrasting responses of two insect herbivores to within-plant and stress-mediated intraspecific
variation in phytochemistry of B. oleracea, this study emphasizes the need to consider specific herbivore responses to understand and predict the interactions between
herbivores and variable plants. 相似文献
10.
Letizia Mattiacci Sara Rudelli Bettina Ambühl Rocca Sem Genini Silvia Dorn 《Chemoecology》2001,11(4):167-173
Summary. Plant responses to herbivory might directly affect the herbivore (“direct” defences) or might benefit the plant by promoting
the effectiveness of natural antagonists of the herbivores (“indirect” defences). Brussels sprouts attacked by Pieris brassicae larvae release volatiles that attract a natural antagonist of the herbivores, the parasitoid Cotesia glomerata, to the damaged plant. In a previous study, we observed that feeding by caterpillars on the lower leaves of the plant triggers
the systemic release of volatiles detectable by the parasitoids from upper leaves of the same plant.?The role of these systemically
induced volatiles as indirect defence and the dynamics of their emission were investigated in wind-tunnel dual choice tests
with C. glomerata. The systemically induced emission of volatiles varied depending on leaf age and on plant age. Systemic induction affected
parasitoid effectiveness, as induced plants could be more easily located by parasitoids than non-induced ones.?The role of
the systemic induction as a direct defence was investigated through behavioural and feeding tests with P. brassicae. In dual choice assays, 1st instar larvae preferred to feed and fed more on systemically induced than on non-induced leaves.
In single choice assays, the leaf area consumed by caterpillars was larger on systemically induced leaves than on non-induced
control leaves. However, caterpillars fed on systemically induced leaves attained the same weight as those feeding on non-induced
controls. In addition, P. brassicae pupae whose larvae were fed on systemically induced leaves had longer developmental times than those of larvae fed on non-induced
leaves. Adult oviposition behavior was not influenced by systemic induction.?We conclude that systemically induced responses
in cabbage might reduce P. brassicae fitness both directly, by affecting their development and feeding behavior and indirectly by making caterpillars and pupae
more vulnerable to attack by carnivores. The occurrence of a possible relationship between direct and indirect defence is
discussed.
Received 24 January 2001; accepted 3 May 2001. 相似文献
11.
Optimal defense theory posits that plants with limited resources deploy chemical defenses based on the fitness value of different tissues and their probability of attack. However, what constitutes optimal defense depends on the identity of the herbivores involved in the interaction. Generalists, which are not tightly coevolved with their many host plants, are typically deterred by chemical defenses, while coevolved specialists are often attracted to these same chemicals. This imposes an "evolutionary dilemma" in which generalists and specialists exert opposing selection on plant investment in defense, thereby stabilizing defenses at intermediate levels. We used the natural shift in herbivore community composition that typifies many plant invasions to test a novel, combined prediction of optimal defense theory and the evolutionary dilemma model: that the within-plant distribution of defenses reflects both the value of different tissues (i.e., young vs. old leaves) and the relative importance of specialist and generalist herbivores in the community. Using populations of Verbascum thapsus exposed to ambient herbivory in its native range (where specialist and generalist chewing herbivores are prevalent) and its introduced range (where only generalist chewing herbivores are prevalent), we illustrate significant differences in the way iridoid glycosides are distributed among young and old leaves. Importantly, high-quality young leaves are 6.5x more highly defended than old leaves in the introduced range, but only 2x more highly defended in the native range. Additionally, defense levels are tracked by patterns of chewing damage, with damage restricted mostly to low-quality old leaves in the introduced range, but not the native range. Given that whole-plant investment in defense does not differ between ranges, introduced mullein may achieve increased fitness simply by optimizing its within-plant distribution of defense in the absence of certain specialist herbivores. 相似文献
12.
Summary. Colonies of two species of Metapone (M. madagascarica, M. new species.) were collected in Madagascar and established in laboratory nests. It could be demonstrated that both species
are specialist predators of termites (Cryptotermes kirbyi). During hunting the ants sting the termites and thereby paralyze and preserve the prey alive. In this way prey can be stored
in the ant nest for extended periods. During foraging and colony emigrations the ants lay chemical trails with poison gland
secretions. Among the seven compounds identified in the venom only methyl pyrrole-2-carboxylate elicits trail following behavior
in both Metapone species.
Received 11 February 2002, accepted 23 February 2002. 相似文献
13.
Susanna Andersson 《Chemoecology》2003,13(1):13-20
Summary. To better understand the biological role of floral scents for
butterflies, electrophysiological responses to floral scents were
investigated using combined gas chromatography and electroantennographic
detection (GC-EAD). The antennal responses of three butterfly species,
Aglais urticae L. (Nymphalidae), Inachis io L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae) to floral scent compounds from both
natural and synthetic mixtures were examined. Floral scents were
collected from the butterfly nectar plants Cirsium arvense (L.)
(Asteraceae), and Buddleja davidii Franchet cv. (Loganicaeae) with
dynamic head-space methods on Tenax-GR and eluted with pentane. These
eluates, composed of natural floral scent blends, represent an array of
compounds in their natural state. In the GC-EAD analyses eleven
compounds were identified from C. arvense with the benzenoid compound
phenylacetaldehyde in highest abundance. Seventeen compounds were
identified from B. davidii with the irregular terpene oxoisophorone in
highest abundance. Thirty-nine synthetic floral scent compounds were
mixed in pentane, in equal amounts; about 35 ng were allowed to reach
the antennae. The butterflies showed antennal responses to most of the
floral scent compounds from both natural and synthetic blends except to
the highly volatile monoterpene alkenes. Certain benzenoid compounds
such as phenylacetaldehyde, monoterpenes such as linalool, and irregular
terpenes such as oxoisophorone, were emitted in relatively large amounts
from C. arvense and B. davidii, and elicited the strongest antennal
responses. These compounds also elicited strong antennal responses when
present in the synthetic scent blends. Thus, the butterflies seem to
have many and /or sensitive antennal receptors for these compounds,
which points to their biological importance. Moreover, these compounds
are exclusively of floral scent origin. For B. davidii, which depends
highly on butterflies for pollination, the exclusive floral scent
compounds emitted in high abundance could be the result of an adaptive
pressure to attract butterflies.
Received 2 Septemter 2001; accepted 9 September 2002. 相似文献
14.
Franziska Rohr Christian Ulrichs Monika Schreiner Chau Nhi Nguyen Inga Mewis 《Chemoecology》2011,21(3):171-180
Glucosinolates (GSs) are part of a two-component defence system, characteristic for the Brassicales, including the model species
Arabidopsis thaliana (L.) Heynh. The defence activity of GSs is associated with different side chain structures. The AOP genes are central in side-chain modification. AOP2 mediates formation of alkenyl GS from a methylsulfinyl precursor, whereas
AOP3 catalyzes production of hydroxy-alkyl GSs from the same precursor. Although several studies have assessed the role of
GSs in plant defence, the function of specific aliphatic GSs in plant defence is still not clarified. Structural different
GSs may influence insect herbivores differentially. We created a set of plant lines derived of a cross between two A. thaliana accessions, Gie-0 × Sap-0, which dominantly accumulate either 3-methylsulfinylpropyl GS or 3-hydroxypropyl GS. The generalist
Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) and the crucifer-specialist Pieris brassicae (L.) (Lepidoptera: Pieridae) were used as model insects, to study effects of individual aliphatic GSs on lepidopteran herbivores
with a different feeding specialization. However, the experiments revealed that weight gain of S. exigua and P. brassicae third and fourth-larval instars was similar on both chemotypes. But leaf consumption of the generalist was higher on 3-methylsulfinylpropyl-producing
lines with low GS levels (23.2 μmol g−1) than on 3-hydroxypropyl-producing lines that contained a more than twofold higher amount of GSs (60 μmol g−1). In contrast, no differential effects of non-hydroxylated and hydroxylated GSs were found on the specialist P. brassicae. Our study indicates that there is no simple relationship between GS content and insect responses. 相似文献
15.
Summary. Chemical defense against herbivores has rarely been investigated for freshwater plants, possibly due to the common misconception
that herbivory on aquatic macrophytes is low and would not select for chemical defenses. In previous work, the freshwater
angiosperm Saururus cernuus was shown to be a low preference food for omnivorous crayfish despite its high nutrient value and relatively soft texture.
We used feeding by the crayfish Procambarus clarkii to guide fractionation of the deterrent lipid-soluble extract of this plant, leading to the identification of seven deterrent
lignoid metabolites, (–)-licarin A, (+)-saucernetin, (–)-dihydroguaiaretic acid, (–)-sauriols A and B, (–)-saucerneol, and
(–)-saucerneol methyl ether. Lignans have been implicated in terrestrial plant chemical defenses as insect growth inhibitors,
insect toxins, nematocides, antibacterial, and antifungal agents. However, these activities have rarely been demonstrated
using ecologically relevant methodologies in terrestrial systems, and never before in freshwater systems. The widespread nature
of lignans amongst very distantly related plants, along with their rich diversity of molecular structure, suggests that they
could play a large role in mediating plant-herbivore interactions. In addition to the lignoid compounds we identified, there
were other compounds present in low concentration or unstable compounds that were deterrent, that did not appear to be lignans,
but that we were unable to identify. This plant thus appears to be defended by a complex mixture of natural products.
Received 6 June 2000; revised 23 August 2000; accepted 2 September 2000 相似文献
16.
Summary. Phytotoxic activity of single and combined application of water soluble and volatile compounds of Cistus ladanifer on germination and early root growth of subterranean clover was investigated. Total germination, lag and speed of germination
were both inhibited and stimulated, with the activity of volatiles on total germination depending upon the presence of water
solubles. Antagonism between water solubles and volatiles was always found, resulting in a reduction of inhibition or a shift
from inhibition to stimulation. It is suggested that the simultaneous presence of water solubles and volatiles might result
in changes of the chemical nature of metabolites released by C. ladanifer. Early root growth was always inhibited but only by water solubles, and no interaction was found. The ecological implications
of these results are discussed in terms of the exhaustion of competitors seedbanks by a two-step process in which germination
is less inhibited or even stimulated by water solubles and volatiles, followed by a stronger and volatiles-independent inhibition
of early root growth.
Received 13 June 2001; accepted 13 Dezember 2001. 相似文献
17.
Andrés González Frank C. Schroeder Athula B. Attygalle Aleš Svatoš Jerrold Meinwald Thomas Eisner 《Chemoecology》1999,9(3):105-112
Summary. Female Photuris fireflies sequester defensive steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus. Lucibufagin analyses of Photuris females and Photinus ignitus males show that the lucibufagin mixtures of predator and prey differ in their composition. Analyses of whole body extracts
showed that P. ignitus males contain a mixture of eight non-glycosylated lucibufagins, composed mostly of compounds with two oxygenated positions
in the steroidal A-ring (C-3, C-5). After feeding on P. ignitus males, Photuris females contain six major lucibufagins. Three of these compounds are not present in the prey, including the novel lucibufagin
glycoside 5β,11α-dihydroxy-12-oxo-3β-O-β-D-xylopyranosylbufalin, and two other lucibufagins with a trioxygenated A-ring (C-2,
C-3, C-5). These results indicate that Photuris females transform the sequestered lucibufagins both by glycosylation and oxidation, which could affect the systemic transportability
of these compounds due to an increase in their polarity.
Received 18 February 1999; accepted 19 April 1999. 相似文献
18.
Summary. The ability to perceive and respond to phytochemicals that reliably indicate poor suitability of a potential host plant confers
a selective advantage to ovipositing female swallowtail butterflies. Papilio glaucus females are generalists that nonetheless do not oviposit on red bay (Persea borbonia: Lauraceae). Red bay is toxic to P. glaucus neonates but is commonly found in habitats alongside their principal host plant, Magnolia virginiana, in central Florida. The hypothesis that deterrent compounds present in the leaves of red bay mediate its rejection by P. glaucus was evaluated in our study. Florida populations of P. glaucus did not oviposit on host leaves sprayed with the methanol extract of red bay foliage, although they accepted solvent-treated
and untreated tulip tree leaves in 3 choice bioassays. Additionally, tulip tree leaves sprayed with methanolic extracts of
red bay also deterred oviposition by P. glaucus females from Ohio, Kentucky and Pennsylvania, although these populations do
not naturally encounter red bay. Clearly, deterrent compounds found within this non-host are the basis of its rejection by
populations of P. glaucus and such recognition is fundamental to the species, not just a reflection of local adaptations.
Received 2 April 1999; accepted 11 June 1999. 相似文献
19.
Summary. Africanized honey bees (AHBs) of Brazil and Mexico have proven to be tolerant to Varroa destructor mites. In contrast, European honey bees (EHBs: Apis mellifera carnica) at the same tropical study site are highly intolerant to these ectoparasites. A lower attractiveness of Varroa-tolerant AHB larvae has been hypothesised to be an important trait in reducing the susceptibitlity of AHBs to these mites.
Thus, selection for EHB brood that is less attractive to mites is thought to be one possibility for limiting mite population
growth and thus increase the tolerance of EHBs to the mite.?In Ribeir?o Preto, Brazil, European A. m. carnica bees and AHBs were tested with respect to their rate of brood infestation and brood attractiveness to Varroa mites. For the comparison of brood infestation rates, we introduced combs with pieces of EHB and AHB brood into honey bee
colonies (18 repetitions). The relative infestation rate of EHB brood was significantly higher compared to AHB brood.?The
preference behaviour of single Varroa mites was tested in a laboratory bioassay where either living host stages were offered or host extracts were presented on
dummies. By these tests we could confirm the preference of Varroa females for certain developmental host stages and for their corresponding extracts. In contrast to the within-colony results,
Varroa mites in the laboratory bioassay showed a slight preference for AHB compared to EHB larvae.?The gas chromatographic analysis
revealed differences in the chemical spectrum of extracts obtained from different larvae. In accord with the results of the
bioassays, we could detect stage-specific odour differences in larval cuticular compounds, including methyl esters and hydrocarbons
that have been described as kairomones. None of these substances, however, revealed significant race-specific differences.
Therefore, the quantity and composition of certain cuticular compounds seem to be responsible only for the recognition of
a suitable host stage by Varroa females. The different infestation rates in the colonies, however, seem to be caused neither by race-specific differences
in attractiveness of bee larvae nor by an extended attractive period of EHB larvae: both AHB and EHB larvae become attractive
approximately 21 h before capping of the brood cell, and thus have the same window of time when they can be parasitised.?Therefore
differential Varroa-infestation rates are not related to larval attraction but probably are determined by other race-specific and colony-related
factors.
Received 11 June 2001; accepted 19 November 2001. 相似文献
20.
Summary. Analysis of South-East Asian troidine swallowtails revealed high variability in the content of aristolochic acids among individuals.
The presence or absence of these compounds depends on the Aristolochia species available as food plant for the larvae. Only one plant species (Aristolochia philippinensis) contained a high concentration of aristolochic acids, while other species from various localities contained none or only
marginal amounts. Whether aristolochic acids have a distinct function in chemical defense of these swallowtails is still an
open question.
Received 11 December 2000; accepted 4 August 2001. 相似文献