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1.
We investigated host race formation in Galerucella tenella, a leaf beetle which feeds preferentially on meadowsweet (Rosaceae) in its natural habitats, but has become an important pest on strawberry (Rosaceae) in agricultural areas. Beetles from two isolated sites (Skeppsvik in Sweden and Solf in Finland) were compared with respect to preference and performance. At Skeppsvik the beetles were found feeding on meadowsweet, while at Solf large populations only develop in strawberry plantations, despite the presence of meadowsweet.In reciprocal field transplantations and laboratory bioassays, beetles from both sites discriminated against their foreign host, using their natal plant to a significantly higher degree for both egg laying and feeding, but with one interesting exception, namely that beetles from Solf increased their use of and even preferred meadowsweet for feeding in the laboratory. This increased use of meadowsweet by adult Solf beetles in the laboratory (without conspecific competitors) may be attributed to a density-dependent strategy, whereby mothers avoid pre-emptying the nutritional resources of the plants that will host their offspring in cases where no competitors are present.Larval fitness did not differ significantly between host plants, although larval survival of Solf beetles was halved when reared on their non-natal host plant (meadowsweet). Although beetles from both sites preferred to oviposit on their local host plant, our results provide little evidence that this presumed adaptation has to do with the nutritional quality of the plants involved. Instead, we suggest that other factors associated with the plants, such as enemy-free space and resistance to drought may be more important selective agents, shaping host preference in the field. 相似文献
2.
Both the length of the growing season and the intensity of herbivory often vary along climatic gradients, which may result in divergent selection on plant phenology, and on resistance and tolerance to herbivory. In Sweden, the length of the growing season and the number of insect herbivore species feeding on the perennial herb Lythrum salicaria decrease from south to north. Previous common‐garden experiments have shown that northern L. salicaria populations develop aboveground shoots earlier in the summer and finish growth before southern populations do. We tested the hypotheses that resistance and tolerance to damage vary with latitude in L. salicaria and are positively related to the intensity of herbivory in natural populations. We quantified resistance and tolerance of populations sampled along a latitudinal gradient by scoring damage from natural herbivores and fitness in a common‐garden experiment in the field and by documenting oviposition and feeding preference by specialist leaf beetles in a glasshouse experiment. Plant resistance decreased with latitude of origin, whereas plant tolerance increased. Oviposition and feeding preference in the glasshouse and leaf damage in the common‐garden experiment were negatively related to damage in the source populations. The latitudinal variation in resistance was thus consistent with reduced selection from herbivores towards the northern range margin of L. salicaria. Variation in tolerance may be related to differences in the timing of damage in relation to the seasonal pattern of plant growth, as northern genotypes have developed further than southern have when herbivores emerge in early summer. 相似文献
3.
We examined the effects of leaf herbivory by the dorcas gazelle, Gazella dorcas, on the compensatory growth of the geophyte Pancratium sickenbergeri (Amaryllidaceae) in the Negev desert, Israel. In three populations exposed to different levels of herbivory, we removed different
amounts of photosynthetic leaf area from plants in five clipping treatments: 0, 25, 50%-dispersed over all leaves, 50%-entire
area of half the leaves, 100%. The population with the lowest level of herbivory showed the lowest relative regrowth rate
after clipping. In the population with a constantly high level of herbivory, plants in intermediate-clipping treatments overcompensated
in leaf area after clipping. For all the populations, clipped plants produce more new leaves than unclipped plants. In the
population with the highest level of herbivory, clipping treatments did not have a significant effect on the number of fruits
per plant. In addition, we did not find a trade-off between investments in growth and reproduction in this population. Our
results indicated that, in the desert lily, herbivores may select for plant mechanisms that compensate after damage as a tolerant
strategy to maintain fitness. 相似文献
4.
Herbivory can induce changes in plant traits that may involve both tolerance mechanisms that compensate for biomass loss and
resistance traits that reduce herbivore preference. Seagrasses are marine vascular plants that possess many attributes that
may favour tolerance and compensatory growth, and they are also defended with mechanisms of resistance such as toughness and
secondary metabolites. We quantified phenotypic changes induced by herbivore damage on the temperate seagrass Posidonia oceanica in order to identify specific compensatory and resistance mechanisms in this plant, and to assess any potential trade-offs
between these two strategies of defence. We simulated three natural levels of fish herbivory by repeatedly clipping seagrass
leaves during the summer period of maximum herbivory. Compensatory responses were determined by measuring shoot-specific growth,
photosynthetic rate, and the concentration of nitrogen and carbon resources in leaves and rhizomes. Induced resistance was
determined by measuring the concentration of phenolic secondary metabolites and by assessing the long-term effects of continued
clipping on herbivore feeding preferences using bioassays. Plants showed a significant ability to compensate for low and moderate
losses of leaf biomass by increasing aboveground growth of damaged shoots, but this was not supported by an increase in photosynthetic
capacity. Low levels of herbivory induced compensatory growth without any measurable effects on stored resources. In contrast,
nitrogen reserves in the rhizomes played a crucial role in the plant’s ability to compensate and survive herbivore damage
under moderate and high levels of herbivory, respectively. We found no evidence of inducibility of long-term resistance traits
in response to herbivory. The concentration of phenolics decreased with increasing compensatory growth despite all treatments
having similar carbon leaf content, suggesting reallocation of these compounds towards primary functions such as cell-wall
construction. 相似文献
5.
We examined whether heavy browsing by sika deer, Cervus nippon Temminck, changed morphological characteristics of a Japanese nettle, Urtica thunbergiana Sieb. et Zucc., in Nara Park, where a large population of sika deer has been maintained for more than 1,200 years. Wild nettles
of Nara Park exhibited smaller leaf area, 11–223 times more stinging hairs per leaf, and 58–630-times higher stinging hair
densities than those of other areas where there was no evidence of sika deer browsing. There were no significant differences
in stinging hair length between the areas. Nettles from Nara Park that were cultivated from seeds in a greenhouse retained
a larger number and higher density of stinging hairs. In the field, nettles of Nara Park were less frequently browsed by sika
deer and showed higher survivorship than nettles that were transplanted from an unbrowsed area into Nara Park. These results
indicate that: (1) the U. thunbergiana population of Nara Park has an extremely high stinging hair density compared with those of unbrowsed areas; (2) this characteristic
has a genetic basis, and (3) stinging hairs serve as a defensive structure against sika deer, contributing to an increase
in survivorship. Thus, we conclude that a U. thunbergiana population in Nara Park, with extremely high stinging hair densities, has evolved through natural selection due to heavy
browsing by sika deer. 相似文献
6.
Habitat-corridors are assumed to counteract the negative impacts of habitat loss and fragmentation, but their efficiency in
doing so depends on the maintenance of ecological processes in corridor conditions. For plants dispersing in linear habitats,
one of these critical processes is the maintenance of adequate pollen transfer to insure seed production within the corridor.
This study focuses on a common, self-incompatible forest herb, Trillium grandiflorum, to assess plant–pollinator interactions and the influence of spatial processes on plant reproduction in hedgerow corridors
compared to forests. First, using pollen supplementation experiments over 2 years, we quantified the extent of pollen limitation
in both habitats, testing the prediction of greater limitation in small hedgerow populations than in forests. While pollen
limitation of fruit and seed set was common, its magnitude did not differ between habitats. Variations among sites, however,
suggested an influence of landscape context on pollination services. Second, we examined the effect of isolation on plant
reproduction by monitoring fruit and seed production, as well as pollinator activity and assemblage, in small flower arrays
transplanted in hedgerows at increasing distances from forest and from each other. We detected no difference in the proportion
of flowers setting fruit or in pollinator activity with isolation, but we observed some differences in pollinator assemblages.
Seed set, on the other hand, declined significantly with increasing isolation in the second year of the study, but not in
the first year, suggesting altered pollen transfer with distance. Overall, plants in hedgerow corridors and forests benefited
from similar pollination services. In this system, plant–pollinator interactions and reproduction seem to be influenced more
by variations in resource distribution over years and landscapes than by local habitat conditions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
The stoloniferous herb Trifolium repens was used to study the expression of induced systemic resistance (ISR) to the generalist caterpillar Spodoptera exigua in interconnected ramets of clonal fragments. The ISR was assessed as caterpillar preference in dual choice tests between control and systemically induced plants. The ISR was detected in young ramets, after inducing older sibling ramets on the same stolon by a controlled herbivore attack. However, older ramets did not receive a defense induction signal from younger ramets unless the predominant phloem flow was reversed by means of basal shading. This provides evidence for the notion that in T. repens the clone-internal expression of ISR is coupled to phloem transport and follows source–sink gradients. The inducibility of the genotypes was not linked to their constitutive ability to produce cyanide, implying the absence of a trade-off between these two defense traits. To our knowledge, this is the first study that explores ISR to herbivory in the context of physiological integration in potentially extensive clonal plant networks. 相似文献
8.
Correlation between plant size and reproductive output may be modified by herbivory in accordance with host plant density
and the presence of nonhost plants. To elucidate the effects of nonhost plant density and host plant density on the intensity
of herbivory and reproductive output of the host plant in relation to plant size under natural conditions, we investigated
the abundance of three lepidopteran insects, Plutella maculipennis, Anthocharis scolymus, and Pieris rapae the intensity of herbivory, and fruit set of their host plant, Turritis glabra (Cruciferae). To elucidate the effects of nonhost and host plant density, we selected four categories of plots under natural
conditions: low density of nonhost and high density of host plants; low density of both nonhost and host plants; high density
of both nonhost and host plants; and high density of nonhost and low density of host plants. The plant size indicated by stem
diameter was a good predictor of the abundance of all herbivorous species. The effects of density of nonhost and host plants
on the abundance of insects varied among species and stages of insects. As the abundance of insects affected the intensity
of herbivory, herbivory was more apparent on larger host plants in plots with low density of both nonhost and host plants.
Consequently, the correlation between plant size and the number of fruits disappeared in low plots with density of both nonhost
and host plants. In this T. glabra– herbivorous insect system, the density of nonhost plants and host plants plays an important role in modifying the relationship
between plants and herbivores under natural conditions.
Received: July 19, 1999 / Accepted: June 15, 2000 相似文献
9.
10.
The majority of studies exploring interactions between above- and below-ground biota have been focused on the effects of root-associated
organisms on foliar herbivorous insects. This study examined the effects of foliar herbivory by Pieris brassicae L. (Lepidoptera: Pieridae) on the performance of the root herbivore Delia radicum L. (Diptera: Anthomyiidae) and its parasitoid Trybliographa rapae (Westwood) (Hymenoptera: Figitidae), mediated through a shared host plant Brassica nigra L. (Brassicaceae). In the presence of foliar herbivory, the survival of D. radicum and T. rapae decreased significantly by more than 50%. In addition, newly emerged adults of both root herbivores and parasitoids were
significantly smaller on plants that had been exposed to foliar herbivory than on control plants. To determine what factor(s)
may have accounted for the observed results, we examined the effects of foliar herbivory on root quantity and quality. No
significant differences in root biomass were found between plants with and without shoot herbivore damage. Moreover, concentrations
of nitrogen in root tissues were also unaffected by shoot damage by P. brassicae larvae. However, higher levels of indole glucosinolates were measured in roots of plants exposed to foliar herbivory, suggesting
that the development of the root herbivore and its parasitoid may be, at least partly, negatively affected by increased levels
of these allelochemicals in root tissues. Our results show that foliar herbivores can affect the development not only of root-feeding
insects but also their natural enemies. We argue that such indirect interactions between above- and below-ground biota may
play an important role in the structuring and functioning of communities. 相似文献
11.
Changes in morphology and chemistry of leaf surface in response to herbivore damage may increase plant resistance to subsequent herbivore attack; however, there is lack of studies on induced responses of glandular trichomes and their exudates in woody plants and on effects of these changes on herbivores. We studied delayed induced responses in leaf surface traits of five clones of silver birch (Betula pendula Roth) subjected to various types of mechanical defoliation and simulated winter browsing. Glandular trichome density and concentrations of the majority of surface lipophilic compounds increased in trees defoliated during the previous summer. This induced response was systemic, since control branches in branch defoliated trees responded to the treatments similarly to defoliated branches, but differently from control trees. In contrast to defoliation treatments, simulated winter browsing reduced glandular trichome density on the following summer and had fewer effects on individual surface lipophilic compounds. Moreover, constitutive density of glandular trichomes was negatively correlated with induced total amount of lipophilic compounds per trichome, indicating a trade-off between constitutive and induced resistance in silver birch. Induced changes in leaf surface traits had no significant effect on leaf damage by chewers, miners and gall mites, but increased susceptibility of birch trees to aphids. However, leaf damage by chewers, miners and gall mites in defoliated (but not in control) trees was correlated with concentrations of some fatty acids and triterpenoids, although the direction of relationships varied among herbivore species. This indicates that induction of surface lipophilic compounds may influence birch resistance to herbivores. Our study thus demonstrated both specificity of elicitation of induced responses of birch leaf surface traits by different types of damage and specificity of the effects of these responses on different types of herbivores.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
12.
Takaaki Nishida Naoyuki Izumi Noboru Katayama Takayuki Ohgushi 《Population Ecology》2009,51(2):329-334
We examined effects of aboveground herbivory by spider mites (Tetranychus urticae) on colonization and activity of arbuscular mycorrhizal fungi (AMF; Gigaspora margarita) using potted plants (Lotus japonicus). We evaluated changes in arbuscular mycorrhizal (AM) association two ways: (1) conventional trypan blue staining of mycorrhizal
hyphae to examine AMF biomass in roots (mycorrhizal colonization) and (2) vital staining for a mycorrhizal enzyme (succinate
dehydrogenase, SDH) to examine mycorrhizal activity (SDH activity). Mycorrhizal colonization and SDH activity started to increase
4 days after aboveground herbivory, and returned to the initial levels in the absence of mite herbivory in 7 and 12 days,
respectively. These results suggest that the change in AM association in response to mite herbivory is a short-term response. 相似文献
13.
The presence of the exotic Argentine ant, Linepithema humile Mayr (Hymenoptera: Dolichoderinae), nitrogen enrichment, and early-season herbivory by the specialist beetle Trirhabda bacharidis (Coleoptera: Chrysomelidae) have been shown, through separate experiments, to affect the densities of insect herbivores of
the coastal shrub Baccharis halimifolia (Asteraceae), in Florida. Using a fully-factorial field experiment, we examined the relative importance of all three of these
factors to the six most common insect herbivore species utilizing this host plant in a West Central Florida coastal habitat.
The presence of ants affected more herbivore species than either early-season herbivory by larval T. bacharidis or nitrogen enrichment. Experimental reductions of L. humile resulted in reductions of an aphid, its coccinellid predators, and adult T. bacharidis, and increases of two species of leafminers and one species of stemborer. Due to the strong negative effects of stemborer
herbivory on host plant survival, the increase in stemborer abundance led to increased host plant mortality. Early-season
herbivory by larval T. bacharidis only affected the abundance of aphids and their predators, both of which were more abundant on trees with reduced early-season
herbivory. Nitrogen fertilization had the most limited effects and only T. bacharidis larvae achieved higher densities on fertilized trees. Our results indicate that aphid tending by the exotic L. humile affects other insects on B. halimifolia more so than herbivory by the exploitative competitor T. bacharidis or nitrogen as a limiting nutrient. 相似文献
14.
To examine plastic willow regrowth response to herbivory, we studied the effect of a boring insect, the swift moth Endoclita excrescens (Hepialidae: Lepidoptera), which does not remove apical meristems, on shoot growth in three willow species—Salix gilgiana, S. eriocarpa, and S. serissaefolia−by direct observations and experiments in the field. We hypothesized that the stem-boring could initiate new lateral bud
activation, and result in secondary shoot regrowth without the removal of the primary apical meristems. There were significantly
more lateral shoots on naturally attacked than unattacked stems, and a significant positive correlation between lateral shoot
density and the number of swift moth tunnels per tree was observed for all three willow species. Artificial boring, and larval
infestation, resulted in an increase in the number of lateral shoots, but did not affect growth of current-year shoots. The
length of lateral shoots differed between species, being significantly longer in S. gilgiana than S. eriocarpa and S. serissaefolia. The results of this study show that compensatory regrowth can result even if herbivory does not remove the apical meristem.
We argue that this type of plant compensatory response is probably widespread, given that the stem-boring is a common feeding
type of insect herbivores. 相似文献
15.
One explanation for the widespread absence of floral nectar in many orchids is that it causes pollinators to visit fewer flowers
on a plant, and thus reduces self-pollination. This, in turn, could increase fitness by reducing inbreeding depression in
progeny and promoting pollen export. The few previous investigations of this hypothesis have all involved bee-pollinated orchids
and some have given contradictory results. We studied the effects of adding artificial nectar (sucrose solution) to the spurs
of a non-rewarding long-proboscid fly-pollinated orchid, Disa pulchra. Addition of nectar significantly increased the number of flowers probed by flies (2.6-fold), the time spent on a flower
(5.4-fold), the number of pollinia removed per inflorescence (4.8-fold) and the proportion of removed pollen involved in self-pollination
(3.5-fold). The level of self-pollination increased dramatically with the number of flowers probed by flies. Experimental
self-pollination resulted in fruits with only half as many viable seeds as those arising from cross-pollination. Pollinators
were more likely to fly long distances (>40 cm) when departing from non-rewarding inflorescences than when departing from
rewarding ones. These findings provide support for the idea that floral deception serves to reduce pollinator-mediated self-pollination. 相似文献
16.
Pollination is a requisite for sexual reproduction in plants and its success may determine the reproductive output of individuals. Pollinator preference for some floral designs or displays that are lacking or poorly developed in focal plants may constrain the pollination process. Foliar herbivory may affect the expression of floral traits, thus reducing pollinator attraction. Natural populations of the Andean species Alstroemeria exerens (Alstromeriaceae) in central Chile show high levels of foliar herbivory, and floral traits show phenotypic variation. In the present field study, we addressed the attractive role of floral traits in A. exerens and the effect of foliar damage on them. Particularly, we posed the following questions: (1) Is there an association between floral display and design traits and the number and duration of pollinator visits? and (2) Does foliar damage affect the floral traits associated with pollinator visitation? To assess the attractiveness of floral traits for pollinators, we recorded the number and duration of visits in 101 focal plants. To evaluate the effects of foliar damage on floral traits, 100 plants of similar size were randomly assigned to control or damage groups during early bud development. Damaged plants were clipped using scissors (50% of leaf area) and control plants were manually excluded from natural herbivores (<5% of leaf area eaten). During the peak of flowering, we recorded the number of open flowers, and estimated corolla and nectar guide areas. The number and duration of pollinator visits was statistically associated with floral design and display traits. Plants with larger displays, corollas and nectar guide areas received more visits. Visits lasted longer as display increases. In addition, foliar damage affected attractive traits. Damaged plants had fewer open flowers and smaller nectar guide areas. We conclude that foliar damage affects plant attractiveness for pollinators and hence may indirectly affect plant fitness. 相似文献
17.
The evergreen dwarf shrub lingonberry (Vaccinium vitis-idaea L.) was subjected to microtine herbivory simulations to investigate its recovery in a boreal forest. Beside the control (A), the study included three levels of herbivory: clipping of half the annual branches from 50% of ramets (B), removal of 50% of ramets (C), and removal of 100% of ramets (D). Density, growth, and fecundity of the ramets were monitored during the study. New ramets emerged rapidly from dormant basal buds at the base of the removed ramets in groups C and D. After three growth seasons, 60–117% and 42–112% of density and biomass, respectively, had been regained in the groups damaged relative to the control, the difference being insignificant between the treated groups apparently because of the small sample size. Survival, fecundity and net growth of ramets were not affected by the treatment. Mean dry weight of annual branches in new ramets was lower in the damaged groups than the control. The recovery of the lingonberry was unexpectedly good. The results suggest that, since natural herbivory seldom is as heavy as in this work, the time between population density peaks of microtine rodents is usually long enough for the lingonberry to recover in boreal ecosystems. 相似文献
18.
Volatile phytohormones or other chemicals can affect processes in distal plant parts but may also influence neighboring plants,
and thereby function allelopathically. While this hypothesis has been widely discussed, rigorous tests are lacking. Transgenic
plants, silenced in the production of an emitted chemical, are ideal tools to test the hypothesis that the release of a chemical
can negatively influence the growth of neighbors (allelopathy). We used isogenic wild type (WT) and genetically transformed
plants that lacked the ability to produce ethylene (ir-aco), as both “emitters” and “receivers” of this volatile phytohormone in experiments where receiver plants were only exposed
to the headspace of WT or ir-aco emitters, in order to evaluate if natural ethylene releases can function allelopathically. Root growth (a proxy of plant
fitness) of WT receivers correlated negatively with the number of WT emitters and headspace ethylene concentrations. Reducing
ethylene concentrations in the headspace with the ethylene scrubber, KMnO4, and using ir-aco seedlings as emitters restored root growth of WT receiver seedlings. 1-Aminocyclopropane-1-carboxylic acid (ethylene biosynthesis
substrate) supplementation to WT but not ir-aco emitters inhibited root growth of ir-aco, but not WT receivers, suggesting increased sensitivity to exogenous ethylene of ir-aco seedlings. We conclude that plants genetically silenced in the production of a putative allelochemical are useful in determining
if the emitted chemical functions allelopathically.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Himanen SJ Nissinen A Auriola S Poppy GM Stewart CN Holopainen JK Nerg AM 《Planta》2008,227(2):427-437
Glucosinolates are plant secondary compounds involved in direct chemical defence by cruciferous plants against herbivores.
The glucosinolate profile can be affected by abiotic and biotic environmental stimuli. We studied changes in glucosinolate
patterns in leaves of non-transgenic oilseed rape (Brassica napus ssp. oleifera) under elevated atmospheric CO2 or ozone (O3) concentrations and compared them with those from transgenic for herbivore-resistance (Bacillus thuringiensis Cry1Ac endotoxin), to assess herbivory dynamics. Both elevated CO2 and O3 levels decreased indolic glucosinolate concentrations in transgenic and non-transgenic lines, whereas O3 specifically increased the concentration of an aromatic glucosinolate, 2-phenylethylglucosinolate. The herbivore-inducible
indolic glucosinolate response was reduced in elevated O3 whereas elevated CO2 altered the induction dynamics of indolic and aliphatic glucosinolates. Herbivore-resistant Bt plants experienced minimal
leaf damage after target herbivore Plutella xylostella feeding, but exhibited comparatively similar increase in glucosinolate concentrations after herbivory as non-transgenic plants,
indicating that the endogenous glucosinolate defence was not severely compromised by transgenic modifications. The observed
differences in constitutive and inducible glucosinolate concentrations of oilseed rape under elevated atmospheric CO2 and O3 might have implications for plant–herbivore interactions in Brassica crop-ecosystems in future climate scenarios. 相似文献
20.
The role of aquatic macrophytes in stimulating biodiversity and maintaining clear waters is currently undisputed. The management
of (eutrophic) shallow waters is therefore often directed at (re-)establishing macrophyte domination. In contrast, the role
of water birds has long been considered of minor importance for the functioning of fresh water ecosystems. Indeed, in terms
of biomass and production, water birds constitute only a minor part of these systems. However, water birds may graze heavily
on water plants under certain circumstances, and the question arises whether herbivorous water birds have an important indirect
effect on shallow fresh water systems. Mainly illustrated with the interaction between Bewick’s Swans and Fennel Pondweed,
we present data on the role that water plants may play in the life of water birds and how water birds may impact water plants’
fitness in terms of survival, production, dispersal and competitive ability. It appears that water plants may be crucial for
water birds during periods of high-energy requirements, such as migration. Despite the plants’ costs associated with water
bird grazing, the interaction between water birds and water plants varies in nature from an apparent predator–prey relationship
to a mutually beneficial interaction depending on the context and the perspective. For the case of the Bewick’s Swan–Fennel
Pondweed interaction, regular bird grazing is sustainable and may actually favour the plant’s dispersal. Thus, Bewick’s Swans
themselves may in fact play a crucial role in establishing and maintaining the Fennel Pondweed rich staging sites between
the swans’ wintering and breeding grounds, which are vital for the swans’ successful migration. 相似文献