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1.
Life history trade-offs should be detectable as negative correlations between the relevant traits (e.g. reproductive output
versus energy storage), but may be masked by variation in resource levels among individuals. One way to detect underlying
trade-offs, at least in organisms that rely on stored energy for reproduction (“capital breeders”), may be to monitor an individual's
energy stores before and after reproduction. We analysed energy stores and reproductive output in Eulamprus tympanum, a viviparous scincid lizard that stores energy for reproduction in its tail. One predicted trade-off (that between the size
and number of offspring in a litter) is consistently observed, and is detectable with minimal information. Another predicted
trade-off (that between offspring size and subsequent energy reserves) is not apparent in our data, perhaps because of constraints
imposed by correlations among other traits. Finally, trade-offs between reproductive output and subsequent energy stores are
evident in this species, but are only detectable with information on the extent of pre-reproductive as well as post-reproductive
energy stores. For “capital breeders”, non-destructive measurement of pre- and post-reproductive energy stores may greatly
enhance our ability to detect significant life history trade-offs.
Received: 10 July 1996 / Accepted: 16 January 1997 相似文献
2.
We studied the effects of host plant hybridization on the survival and mortality of the leaf-mining moth Phyllonorycter salicifoliella on hybrid and parental willow plants in the field and in a common garden experiment. P. salicifoliella survival differed significantly among three willow taxa in the field in 1994 but not in the field in 1995 or in the common
garden. Parasitism by eulophid wasps differed significantly among taxa in 1994 and appeared to account for the variation in
their survival. In the field in 1995, host feeding predation varied significant among taxa. The theory of tritrophic interactions
predicts that plant genotype can affect natural enemy impact, and this study supports this prediction. Significant variation
in survival and eulophid parasitism was also found among genotypes within taxa in the field in both years and in the common
garden experiment. The common garden results show that genetic differences in plants affect the herbivore-parasitoid interaction.
Variation among years in the patterns of survival and causes of mortality among field plants suggest that genotype by environment
interactions may be important.
Received: 1 March 1996 / Accepted: 4 November 1996 相似文献
3.
Stephen F. Matter 《Oecologia》1997,110(4):533-538
The relationship between population density and the size of host plant patches was investigated for the red milkweed beetle
Tetraopestetraophthalmus inhabiting unmanipulated patches of Asclepias syriaca. The resource concentration hypothesis proposes that density-area patterns, specifically that of increasing herbivore density
with patch size, are primarily a function of movement between host plant patches. This research investigated the degree to
which movement accounted for density-area patterns. Poisson regression analysis of beetle abundance versus milkweed patch
size revealed that beetle density tended to increase with patch size. The pattern of density and patch size resulted from
local reproduction and residence time. The density of emerging beetles tended to increase with patch size while emigration
rates were unrelated to patch size. Immigration rates were constant with patch size for male beetles, and decreased with patch
size for female beetles. Net flux of beetles (immigration – emigration) did not vary with patch size for male beetles and
decreased with patch size for female beetles. Comparisons are made between this system and previously studied systems where
movement plays a significant role in forming density area patterns. Additionally, several hypotheses are presented which may
account for greater in situ recruitment and residence time in large patches.
Received: 23 February 1996 / Accepted: 8 January 1997 相似文献
4.
Inger Åhman 《Oecologia》1997,111(1):61-68
Many species of dioecious plants show sex-related differences in growth rate and rates of attack by various herbivores and
diseases. The common pattern is for males to grow faster than females and to be less well defended against herbivores. In
willows (Salix spp.), the predominance of female-biased sex ratios has been ascribed in part to differential feeding by herbivores. In this
study of Salix viminalis, seven families grown on agricultural land showed no gender-related variation in shoot biomass or rates of herbivory by insects
(lepidopterans and cecidomyiids). However, Melampsora rust disease was found to be more severe on females than on males when the plants were in a non-reproductive stage. After
flowering and seed-set females tended to be more affected in some families but less affected in others. Although, on average,
there was a female bias in the sex ratio of S. viminalis, sex ratios differed significantly between families. These ratios were not related to any of the recorded biotic agents,
but rather to relationships between families. These results are interpreted in terms of resource allocation between reproduction,
growth and defence, and causes for divergence from the expected patterns are discussed. The results may have implications
for S. viminalis breeding strategies where the aim is to produce biofuel. For instance, these findings suggest that gender can be ignored
when selecting for a high growth rate and resistance to Melampsora and certain insect pests.
Received: 2 November 1996 / Accepted: 8 February 1997 相似文献
5.
David L. Boose 《Oecologia》1997,110(4):493-500
Sources of variation in floral nectar production were investigated in a natural population of Epilobium canum (Onagraceae), a hummingbird-pollinated herbaceous shrub. Field measurements showed significant phenotypic variation among
plants in floral nectar production rates. Average variance among flowers within plants was approximately one-third to one-half
as great as variance among plants, with coefficients of variation among flowers ranging from 6.5% to 116.7%. A greenhouse
experiment using clonally propagated ramets from field plants showed significant genetic variation for nectar production rates;
broad sense heritability was estimated to have a maximum value of 0.64. In the greenhouse, plants grown under low water or
low light conditions produced approximately 25% less nectar on average than those grown under control conditions. However,
significant genotype-environment interactions indicated that genets differed in their responses to the changes in conditions.
Rank correlations for genet mean nectar production rates across environmental conditions were low, and in two out of three
comparisons were not different from zero. It is concluded that although the opportunity for natural selection on nectar production
rates exits in this population, the response to selection will likely be slow, and the opportunity for selection of a narrow-optimum
nectar production phenotype may be limited.
Received: 9 January 1996 / Accepted: 18 December 1996 相似文献
6.
Shade-induced changes in the branching pattern of a stoloniferous herb: functional response or allometric effect? 总被引:10,自引:1,他引:9
Shade-induced changes in the branching pattern of clonal plants can lead to conspicuous modifications of their growth form
and architecture. It has been hypothesized that reduced branching in shade may be an adaptive trait, enabling clonal plants
to escape from unfavourable patches in a heterogeneous environment by allocating resources preferentially to the growth of
the main axis (i.e. linear expansion), rather than to local proliferation by branching. However, such an adaptionist interpretation
may be unjustified if (1) branching frequency is a function of the ontogenetic stage of plants, and if (2) shading slows down
the ontogenetic development of plants, thereby delaying branch formation. In this case, architectural differences between
sun- and shade-grown individuals, harvested at the same chronological age, may not represent a functional response to changes
in light conditions, but may be a by-product of effects of shade on the rate of plant development. To distinguish between
these two alternatives, individuals of the stoloniferous herb Potentilla reptans were subjected to three experimental light conditions: a control treatment providing full daylight, and two shade treatments:
neutral shade (13% of ambient PPFD; no changes in light spectral composition) and simulated canopy shade (13% PPFD and a reduced
red:far-red ratio). Plant development was followed throughout the experiment by daily monitoring primary stolon growth as
well as branch and leaf initiation. Biomass and clonal offspring production were measured when plants were harvested. At the
end of the experiment shaded plants had produced significantly fewer branches than clones grown in full daylight. In all three
treatments, however, initiation of secondary stolons occurred at the same developmental stage of individual ramets. Shading
significantly slowed down the ontogenetic development of plants and this resulted in the observed differences in branching
patterns between sun- and shade-grown individuals, when compared at the same chronological age. These results hence provide
evidence that shade-induced changes in the branching pattern of clonal plants can be due to purely allometric effects. Implications
for interpreting architectural changes in terms of functional shade-avoidance responses are discussed.
Received: 16 August 1996 / Accepted: December 1996 相似文献
7.
Sexual reproduction of Daphnia pulex in a temporary habitat 总被引:1,自引:0,他引:1
David J. Innes 《Oecologia》1997,111(1):53-60
Species of Daphnia (Crustacea: Cladocera) typically reproduce by cyclical parthenogenesis, in which a period of all-female parthenogenetic reproduction
is followed by sexual reproduction. Sex in Daphnia is determined by the environment, with factors such as temperature, photoperiod and crowding stimulating the production of
males and sexual females. Previous studies on Daphnia pulex from temporary pond habitats demonstrated the coexistence of male-producing and non-male-producing (NMP) females, as determined
under crowding in the laboratory. A strong genetic component to this sex allocation variation suggested that sex expression
in D. pulex is better described as a result of genotype-environment interaction. The present study examined the switch from parthenogenetic
to sexual reproduction in two temporary-pond populations of D. pulex. Both populations showed a very early investment in sexual reproduction, independent of population density, by producing
males very soon after the populations were reestablished from resting eggs in the early spring. Approximately 40% of the initial
broods were male. Additional evidence for gender specialization was obtained by observing the sex of two or three successive
broods for 85 individual females. Fifty-eight females produced successive broods of females, 13 females produced successive
broods of males and 14 females produced successive broods which included both male and female broods. Females that produced
successive female broods under natural conditions included a higher frequency of NMP females compared to a random sample of
females, confirming the existence of NMP females. Sexual females were observed in both populations after the first appearence
of males, suggesting that the presence of males may stimulate the production of sexual females. For D. pulex populations in a temporary environment, there appears to be an increased emphasis on sexual reproduction and a decreased
influence of the environment on sex determination, compared to Daphnia populations in more permanent habitats.
Received: 19 February 1996 / Accepted: 20 January 1997 相似文献
8.
In dioecious clonal plants, the reproductive effort required to set seeds will be responsible for the larger investment in sexual reproduction by females. If there will be a trade-off in resource allocation between sexual and clonal reproduction, this differential sexual reproduction will lead to sexual differentiation in the relative amount of clonal reproduction. To test this prediction, we studied differences between the sexes in their phenologies and investments in sexual and vegetative reproduction (clonal reproduction by means of bulbils) with respect to ramet size in a dioecious clonal plant, Dioscorea japonica Thunb. The period of bulbil production overlapped the period during which infructescences developed. Females flowered later, produced heavier inflorescences, and fewer flowers per inflorescence than did males. Regression analysis using the size of the individual plants demonstrated that large females made smaller investments in inflorescences and larger investments in sexual reproduction than did large males. In contrast, females invested fewer resources in vegetative reproduction than did males. However, the total investments in sexual and vegetative reproduction did not differ between the sexes. These results supported our hypothesis on the sexual differentiation in sexual and clonal reproduction. 相似文献
9.
Kathleen Donohue 《Oecologia》1997,110(4):520-527
A factorial design of three densities of siblings at three local distances from seed parents was employed to distinguish
effects of density from effects of dispersal distance on lifespan and fruit production of Cakile edentula var. lacustris, a plant with heteromorphic seeds. The segmented fruits produce two seed types: proximal and distal, with distal seeds having
greater mass and greater dispersibility. Effects of longer distances (0.5 km and 30 km) on lifespan and fruit production were
investigated using plants at low density. The prediction was tested that the greater seed mass of distal seeds increases fitness
when seeds are dispersed into sites of unknown quality away from the home site or when seeds are dispersed to low density.
High density caused earlier mortality and lower probability of reproduction. Distance from the maternal plant did not influence
lifespan or reproduction at distances of 15 m or less, but lifespan was longer 0.5 km from the home site. No interaction was
detected between the effects of density and distance on either lifespan or total fitness. Environmental conditions that influence
fitness did not vary as a function of dispersal distance in this system, and favorable conditions at the home site did not
persist between generations. Therefore, selection on dispersion patterns in natural conditions is likely to be through effects
of density rather than dispersal distance. Proximal seeds had greater reproduction than distal seeds at the home site, and
distal seeds had greater reproduction at the more distant sites (but not the most distant site), as expected, but these performance
differences could not be attributed to differences in mass between the two seed types. Reduced seed mass was favored at the
most distant site, but larger seed mass was favored most strongly at low density. Seeds that are dispersed to low density
are larger, suggesting that although kin selection may limit the effectiveness of individual selection to increase seed mass
under conditions of sibling competition, density-dependent individual selection on seed mass, rather than distant-dependent
selection, also contributes to the observed associations among seed type, seed mass and dispersal ability.
Received: 21 October 1996 / Accepted: 4 December 1996 相似文献
10.
Storage forms of N were studied in below-ground structures of nine boreal forest understorey plants. The ericaceous shrubs
Vacciniumvitis-idaea and V.myrtillus, the fern Gymnocarpium dryopteris, the grass Deschampsia flexuosa, and the herbs Epilobium angustifolium, Maianthemum bifolium, Solidago virgaurea, Geranium sylvaticum and Trientalis europaea were sampled in early summer and late autumn from plots fertilised with a complete mixture of nutrients and from non-fertilised
control plots. Concentrations of total nitrogen, insoluble and soluble proteins, free amino acids and nitrate were measured,
and changes in absolute and relative concentrations of these N fractions between early summer and late autumn were used to
identify the forms in which the plants store N. In all species studied, the concentration of free amino acids increased both
between summer and autumn and in response to fertilisation, while the concentration of protein N increased only in response
to fertilisation. Thus, free amino acids appear to have a central role in N storage. In all of the species except G. dryopteris, D. flexuosa and S. virgaurea, arginine dominated the pool of free amino acids and thus arginine was the major form of stored N in most species. In D. flexuosa and S. virgurea, however, asparagine and arginine together were the major forms of stored N, while glutamine was the major free amino acid,
and N storage form, in G. dryopteris.
Received: 10 March 1996 / Accepted: 22 December 1996 相似文献
11.
S. Ohshima M. Murata W. Sakamoto Y. Ogura F. Motoyoshi 《Molecular & general genetics : MGG》1997,254(2):186-194
The Arabidopsis gene Terminal Flower 1 (TFL1) controls inflorescence meristem identity. A terminal flower (tfl1) mutant, which develops a terminal flower at the apex of the inflorescence, was induced by transformation with T-DNA. Using
a plant DNA fragment flanking the integrated T-DNA as a probe, a clone was selected from a wild-type genomic library. Comparative
sequence analysis of this clone with an EST clone (129D7T7) suggested the existence of a gene encoding a protein similar to
that encoded by the cen gene which controls inflorescence meristem identity in Antirrhinum. Nucleotide sequences of the region homologous to this putative TFL1 gene were compared between five chemically induced tfl1 mutants and their parental wild-type ecotypes. Every mutant was found to have a nucleotide substitution which could be responsible
for the tfl1 phenotype. This result confirmed that the cloned gene is TFL1 itself. In our tfl1 mutant, no nucleotide substitution was found in the transcribed region of the gene, and the T-DNA-insertion site was located
at 458 bp downstream of the putative polyadenylation signal, suggesting that an element important for expression of the TFL1 gene exists in this area.
Received: 14 November 1996 / Accepted: 29 November 1996 相似文献
12.
Using 18 years of census data from permanent quadrats, we examined the interactions between spatially coexisting but temporally
segregated winter and summer ephemeral plant communities in the Chihuahuan Desert. The ability of winter and summer annuals
to achieve nearly complete temporal segregation by partitioning the bimodal annual rainfall permits the coexistence of a diverse
flora of annual (and perennial) plants in this unproductive arid environment. Despite the differences in their biogeographical
affinities and temporal segregation, long-term data indicated that at the scales of both the entire 20-ha study site and small
0.25-m2 sample quadrats, abundances of plants were never high in two successive growing seasons, suggesting a negative interaction
between winter and summer annuals. We evaluate alternative hypotheses for this phenomenon.
Received: 22 February 1996 / Accepted: 16 September 1996 相似文献
13.
水蓼花大小在花序和个体上的变化及其与数量权衡关系研究 总被引:1,自引:0,他引:1
探讨一年生植物水蓼花大小在花序上和个体上的变化及花大小与花数量的权衡关系。在54株植物个体上随机选取一花序,在花序的基部、中部和顶部各选取1~2朵花,花大小(生物量)以基部最大(0.851mg),顶部最小(0.715mg),可能是由结构效应引起的。在每个体上随机采集4~20朵花,以其均值表示植物个体的花大小,花大小不随植物个体大小变化而变化。花朵展示和总花数均随个体增大而增加。在控制植物个体大小(地上部分营养器官生物量)后,没有发现花朵展示或花数量与花大小之间的权衡关系,表明个体资源水平的差异可能掩盖了花数量与大小间的权衡关系。 相似文献
14.
How symbiotic bacteria influence plant utilisation by the polyphagous aphid, Aphis fabae 总被引:1,自引:0,他引:1
To explore the effect of rearing-plant species on the contribution of the symbiotic bacterium, Buchnera, to aphid performance, larvae of Aphis fabae that contained the bacteria (symbiotic aphids) and larvae experimentally deprived of the bacteria (aposymbiotic aphids) were
reared on 16 plant species. Mortality of aphids was low on most plant species. The relative growth rate (RGR) of the larvae
varied with plant species, and was generally depressed by elimination of the bacteria; the mean values of RGR varied between
0 and 0.29 μg μg−1 day−1 for symbiotic aphids and 0 and 0.17 μg μg−1 day−1 for aposymbiotic aphids. The extent to which RGR was depressed by aposymbiosis varied significantly between plant species,
suggesting that aphid host plant may influence the contribution of the bacteria to plant utilisation. It is proposed that
the bacteria may be particularly important on plants with phloem sap of high amino acid content of low quality, i.e. low concentrations
of essential amino acids.
Received: 18 August 1996 / Accepted: 13 January 1997 相似文献
15.
Ulf Sperens 《Oecologia》1997,109(3):368-373
Variation in fruit production and pre-dispersal seed predation by Argyresthia conjugella was studied in␣four populations of Sorbus aucuparia in northern Sweden.␣The number of infructescences, fruits per infructescence, consumed seeds and developed unattacked seeds
per fruit were scored in marked trees from 1984 to 1990. The results showed that the number of fruits produced in each population
determined the number of seed predators occurring in the host population, as the yearly number of seed predators was significantly
and positively correlated with yearly number of fruits, in all but one population. The seed predators showed a delay in response
to variation in number of fruits produced. This lag in response resulted in a large proportion of fruits being attacked and
seeds consumed in a bad fruiting year that followed a good fruiting year, and vice versa. The proportion of fruits attacked
and seeds consumed was largest in the population showing the greatest between-year variation in fruit production and lowest
in the population showing the lowest between-year variation in fruit production. Furthermore, the individuals within the former
population were synchronised, while they were not in the latter population. These results contradict one of the possible explanations
of mast-seeding, where large synchronised between-year variation is supposed to reduce pre-dispersal seed predation. Instead,
differences in attraction of the seed predator to differences in fruit crop size could explain the observed difference in
seed predation between the two populations with opposite fruiting patterns. Within each population, irrespective of year,
the proportion of fruits attacked and seeds consumed was independent of a tree's fruiting display. Therefore, trees with high
fruit production, despite harbouring the largest number of seed predators, produced the largest number of developed seeds
in absolute numbers, compared to trees that produced few fruits.
Received: 25 February 1996 / Accepted: 30 November 1996 相似文献
16.
新疆郁金香营养生长、个体大小和开花次序对繁殖分配的影响 总被引:2,自引:0,他引:2
植物有性繁殖与资源分配的关系研究对于揭示植物生活史特征及繁育系统进化具有重要意义。新疆郁金香(Tulipa sinkiangensis)是新疆天山北坡荒漠带特有的一种多年生早春短命植物。在自然生境中,该物种仅以有性繁殖产生后代,每株能产生1-8朵花,且不同植株上的花数及果实数以及花序不同位置上的花与果实大小明显不同。本文通过对新疆郁金香有性繁殖与营养生长及植株大小的关系以及花序中不同位置花及果实间的资源分配研究,旨在揭示营养生长、个体大小及开花次序对其繁殖分配的影响。结果表明:在开花和果实成熟阶段,新疆郁金香植株分配给营养器官(鳞茎和地上营养器官)与繁殖器官的资源间均存在极显著的负相关关系(P<0.01),说明其植株的营养生长与生殖生长间存在权衡关系。多花是新疆郁金香的一个稳定性状,其植株上花数目、花生物量、果实生物量和种子数量与植株生物量间均呈极显著的正相关关系(P<0.01),说明新疆郁金香植株的繁殖分配存在大小依赖性。在具2-5朵花的新疆郁金香植株中,花序内各花的生物量、花粉数和胚珠数、结实率、果实生物量、结籽数、结籽率及种子百粒重按其开花顺序依次递减,说明花序内各花和果实的资源分配符合资源竞争假说。植株通过减少晚发育的花或果实获得的资源来保障早发育的花或果实获得较多的资源,从而达到繁殖成功。 相似文献
17.
Shizuo Suzuki 《Oecologia》1998,117(1-2):169-176
Leaf demography, seasonal changes in leaf quality and leaf-beetle herbivory of a herbaceous perennial plant, Sanguisorba tenuifolia, were compared between low- and high-elevation sites. Leaf nitrogen concentration was higher and leaf mass per area (LMA)
was lower at the higher site than at the lower one. At the lower site, with a long growth period, plants produced many leaf
cohorts and leaves emerged throughout the growing season. At the higher site, with a short growth period, however, leaf emergence
was concentrated early in the growing season. The improvement of leaf quality and acceleration of leaf emergence at higher
altitude are seen as adaptations to a short growing season. Results of a feeding trial suggested that leaf quality for the
leaf-beetle Galerucella grisescens was higher at the higher site, but plants at the higher site showed less damage. Oviposition of G. grisescens was seasonal and unimodal at both altitudes, but the period of oviposition was shorter and its density lower at the higher
site. The low temperature and short growth period at the higher site appear to reduce the activity of the leaf-beetles, resulting
in a decrease in damage by herbivory, despite better leaf quality.
Received: 11 December 1997 / Accepted: 24 July 1998 相似文献
18.
Carbohydrate storage and use in an alpine population of the perennial herb, Oxytropis sericea 总被引:2,自引:2,他引:0
Tomasz Wyka 《Oecologia》1999,120(2):198-208
I tested hypotheses for ecological roles of storage carbohydrates in perennating organs (roots and branches) of alpine Oxytropis sericea, a leguminous herb. In naturally growing plants, total nonstructural carbohydrates achieved their maximal concentration in
the fall, declined during winter, and reached minimal levels immediately after growth initiation in the spring. Experimental
manipulation of carbon sink-source relations through shading of leaves of reproductive plants revealed that the normally unused
portion of these carbohydrates is largely available for withdrawal. In another experiment, plants subjected to carbohydrate
depletion through shading suffered decreased leaf growth after winter dormancy and had a lower probability of flowering and
decreased inflorescence biomass. The dependence of reproductive growth on stored carbohydrates, however, was limited to its
initial stages, because accumulation of storage carbohydrates occurred simultaneously with inflorescence expansion, flowering,
and fruiting. Moreover, the whole-plant photosynthetic rate, estimated from gas exchange measurements also peaked at the time
of inflorescence growth. To address whether stored reserves allow compensatory regrowth following defoliation, plants were
subjected to experimental removal of leaves and inflorescences. Defoliated O. sericea partly regrew the lost leaves but withdrawal of stored carbohydrates was limited. Similarly, in a second defoliation experiment
where infructescences were left intact, the plants used little stored carbohydrate and only partly compensated for fruit growth.
However, carbohydrate accumulation was negatively affected by defoliation. While the ecological importance of stored nonstructural
carbohydrates cannot be attributed to any function in isolation, winter respiration, leaf regrowth after winter, and early
reproductive growth in O. sericea all depend to a significant extent on stored reserves. Maintaining a large storage pool may protect these functions in years
when carbon status is less favorable than during this study.
Received: 13 May 1998 / Accepted: 24 November 1998 相似文献
19.
Interference competition by aggressive foraging often explains resource partitioning, but mechanisms contributing to partitioning
have rarely been studied in Asian social bee guilds. Foraging of social bees at canopy flowers of Santiria laevigata (Burseraceae) and honey-water feeders was studied in a lowland mixed-dipterocarp forest in Sarawak, Malaysia. Four stingless
bee species (Apidae, Meliponinae), Trigona canifrons, T.␣fimbriata, T. apicalis and T. melina, aggressively defended flower patches and feeders. At the flowers, T.␣canifrons excluded other bees only in the morning when nectar flow peaked. At the feeders, the aggression resulted in asymmetric interference
competition, which produced a dominance hierarchy among seven social bee species. Interspecific partitioning of the feeders
was detected in time and height but not quality. Only time of the first arrival after feeder presentation was negatively correlated
with the dominance hierarchy: more aggressive species arrived at the feeders later than less aggressive species. This result
suggests that a trade-off between searching ability and defensive ability at flower patches gives rise to resource partitioning
in the social bee guild.
Received: 22 June 1996 / Accepted: 22 November 1996 相似文献
20.
Effects of changes in atmospheric carbon dioxide on the location of hosts by the moth, Cactoblastis cactorum 总被引:3,自引:0,他引:3
Gert Stange 《Oecologia》1997,110(4):539-545
Sensory organs that detect CO2 are common in herbivorous moths and butterflies, but their function has been unclear until now. As the CO2 gradients in the vicinity of a host plant depend on its physiological condition, CO2 could provide a sensory cue for the suitability of the plant as a larval food source. This study investigated whether changing
the atmospheric CO2 concentration affected oviposition by Cactoblastis cactorum on its host, the cactus Opuntia stricta. On host plants exposed to rapid fluctuations in CO2 concentration, the frequency of oviposition was reduced by a factor of 3.2 compared to the control. As the fluctuations mask
the much smaller CO2 signals generated by the plants, this suggests that those signals constitute an important component of the host identification
process. On host plants exposed to a constant background of doubled CO2, oviposition was also reduced, by a factor of 1.8. An increased background reduces host signal detectability, partially as
a consequence of a general principle of sensory physiology (Weber-Fechner's law), and partially due to other factors specific
to CO2-receptor neurons.
Received: 4 October 1996 / Accepted: 16 January 1997 相似文献