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1.
    
Adaptation to human‐induced environmental change has the potential to profoundly influence the genomic architecture of affected species. This is particularly true in agricultural ecosystems, where anthropogenic selection pressure is strong. Heliothis virescens primarily feeds on cotton in its larval stages, and US populations have been declining since the widespread planting of transgenic cotton, which endogenously expresses proteins derived from Bacillus thuringiensis (Bt). No physiological adaptation to Bt toxin has been found in the field, so adaptation in this altered environment could involve (i) shifts in host plant selection mechanisms to avoid cotton, (ii) changes in detoxification mechanisms required for cotton‐feeding vs. feeding on other hosts or (iii) loss of resistance to previously used management practices including insecticides. Here, we begin to address whether such changes occurred in H. virescens populations between 1997 and 2012, as Bt‐cotton cultivation spread through the agricultural landscape. For our study, we produced an H. virescens genome assembly and used this in concert with a ddRAD‐seq‐enabled genome scan to identify loci with significant allele frequency changes over the 15‐year period. Genetic changes at a previously described H. virescens insecticide target of selection were detectable in our genome scan and increased our confidence in this methodology. Additional loci were also detected as being under selection, and we quantified the selection strength required to elicit observed allele frequency changes at each locus. Potential contributions of genes near loci under selection to adaptive phenotypes in the H. virescens cotton system are discussed.  相似文献   

2.
    
In moth species, females emit a species‐specific sex pheromone that is perceived over long distance by conspecific males. The species‐specificity in the chemical communication channel is achieved by a combination of unique components in specific ratios and sometimes also by interspecific behavioural antagonists to deter sympatrically occurring heterospecific males. In this study, we determined possible antagonistic effects in Helicoverpa gelotopoeon Dyar (Lepidoptera: Noctuidae) males to the major sex pheromone component of sympatrically occurring heliothine moths, Z11‐16:Ald, as well as to the sex pheromone of the sympatrically occurring Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) (Z11‐16:Ald and Z9‐14:Ald). We also explored whether other co‐occurring species are attracted to these pheromone blends. Our field experiments showed that the addition of Z11‐16:Ald alone or in combination with Z9‐14:Ald inhibited trap catches of H. gelotopoeon males and that this inhibition depended on the concentration of these compounds. In addition, other moth species were attracted to the blends. Together, our results confirm the antagonistic effect of heterospecific sex pheromone compounds of H. virescens to H. gelotopoeon.  相似文献   

3.
    
Parasitoids use odor cues from infested plants and herbivore hosts to locate their hosts. Specialist parasitoids of generalist herbivores are predicted to rely more on herbivorederived cues than plant-derived cues. Microplitis croceipes (Cresson)(Hymenoptera: Braconidae) is a relatively specialized larval endoparasitoid of Heliothis virescens (F.)(Lepidoptera: Noctuidae), which is a generalist herbivore on several crops including cotton and soybean. Using M. croceipes/H. virescens as a model system, we tested the following predictions about specialist parasitoids of generalist herbivores:(i) naive parasitoids will show innate responses to herbivore-emitted kairomones, regardless of host plant identity and (ii) herbivore-related experience will have a greater influence on intraspecific oviposition preference than plant-related experience. Inexperienced (naive) female M. croceipes did not discriminate between cotton-fed and soybean-fed H. virescens in oviposition choice tests, supporting our first prediction. Oviposition experience alone with either host group influenced subsequent oviposition preference while experience with infested plants alone did not elicit preference in M. croceipes, supporting our second prediction. Furthermore, associative learning of oviposition with host-damaged plants facilitated host location. I terestingly, naive parasitoids attacked more soybeathan cotton-fed host larvae in two-choice tests when a background of host-infested cotton odor was supplied, and vice versa. This suggests that plant volatiles may have created an olfactory contrast effect. We discussed ecological significance of the results and concluded that both plant- and herbivore-related experiences play important role in parasitoid host foraging.  相似文献   

4.
    
Plants can detect cues associated with the risk of future herbivory and modify defence phenotypes accordingly; however, our current understanding is limited both with respect to the range of early warning cues to which plants respond and the nature of the responses. Here we report that exposure to volatile emissions from plant tissues infested with herbivore eggs promotes stronger defence responses to subsequent herbivory in two Brassica species. Furthermore, exposure to these volatile cues elicited an apparent shift from growth to reproduction in Brassica nigra, with exposed plants exhibiting increased flower and seed production, but reduced leaf production, relative to unexposed controls. Our results thus document plant defence priming in response to a novel environmental cue, oviposition‐induced plant volatiles, while also showing that plant responses to early warning cues can include changes in both defence and life‐history traits.  相似文献   

5.
    
  1. The survival of eggs and larvae is dependent on the oviposition site selection of their mothers. In obligate myrmecophilic butterflies, both host plant phenology and host ant presence are expected to affect the decision where to deposit eggs. The importance of ant nest presence in the oviposition site selection of Phengaris butterflies is, however, highly debated.
  2. We studied oviposition in the largest Phengaris (Maculinea) alcon population in Portugal, exploiting Gentiana pneumonanthe as the host plant and Myrmica aloba as host ant. We collected phenological plant data and recorded the presence and number of eggs on plants with and without Myrmica ants nearby during the flight period of the butterfly.
  3. Females oviposited on tall plants with many tall buds, while the presence of host ant nests weakly affected oviposition on plants where the probability of finding ants at close range was high. Moreover, larger plants with many tall buds close to host ant nests received more eggs.
  4. A density‐dependent shift in oviposition was not found as the proportion of buds not infected with eggs did not differ between plants with or without ants, whereas plant characteristics did have an effect. Tall plants with many large buds were associated with earlier oviposition.
  5. Our results suggest that females of P. alcon in Portugal choose gentian plants for oviposition mainly based on plant characteristics whereas the vicinity of ants had a weak effect. Moreover, our study shows that testing the ant‐mediated oviposition hypothesis requires baiting ants more than once.
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6.
    
The loss of grasslands in southeastern South America has negatively affected grassland birds, leading to marked declines in their populations. However, the extent to which habitat transformation impacts on their reproductive performance, and whether the magnitude of these effects may be modulated by landscape matrices, is unknown. We assessed the effect of fragmentation on grassland bird reproduction by comparing the combined influence of fragmentation and landscape matrix on nesting success, brood parasitism and productivity of the Spectacled Tyrant Hymenops perspicillatus and the Brown‐and‐yellow Marshbird Pseudoleistes virescens. Surveys were undertaken in small grassland patches embedded within different landscape matrices (urban and agro‐ecosystem) and in a large patch within a reserve. Reproductive performance was adversely affected by fragmentation. However, these effects were conditioned by matrix type, and the response was not the same for the two species. For Brown‐and‐yellow Marshbird, fragmentation resulted in higher rates of brood parasitism and lower productivity regardless of the matrix type, whereas for Spectacled Tyrant, we found a negative effect only in an agricultural matrix. The lack of extensive grasslands makes small patches important; however, knowing the effects of different matrix types is critical to predicting the conservation value of grassland patches, and the response of different species is not uniform.  相似文献   

7.
    
Phytophagous insects use a wide range of indicators or associated cues to avoid laying eggs in sites where offspring survival is low. For insects that lay eggs in flowers, these unsuitable sites may be created by the host plant's resource allocation to flowers. In the sequentially flowering host plant, Yucca glauca, late‐opening distal flowers are more likely to be aborted in the presence of already‐initiated basal fruits because they are strong resource sinks. If flowers are aborted, all eggs of the phytophagous insect, Tegeticula yuccasella, within the flower die. We used the phytophagous insect T. yuccasella that lays eggs in and pollinates host plant Y. glauca flowers to test the hypothesis that phytophagous insect females are less likely to invest eggs in host plant flowers if basal fruits are present because they are more likely to be aborted. We also investigated potential predictors of arrival of T. yuccasella at inflorescences at the onset of flowering. These factors may influence a phytophagous insect's decisions to select oviposition sites. We carried out a behavioral experiment using wild‐caught T. yuccasella females on manipulated inflorescences with distal flowers with basal fruits and without fruits. As potential predictors of T. yuccasella arriving at inflorescences, we used floral display size and day of onset of flowering. In support of our hypothesis, our experimental results showed that T. yuccasella was significantly less likely to oviposit in distal flowers on inflorescences with basal fruits. We also found that T. yuccasella arrival was higher at inflorescences with larger floral display size and earlier in the flowering season. These findings uncover a novel indicator of unsuitable oviposition sites—the presence of basal fruits, that phytophagous insects use to make oviposition decisions. Further, our study contributes to the growing body of evidence that shows that females prefer sites that increase the probability of survival of their offspring.  相似文献   

8.
    
An insect species that shows variation in host species association across its geographical range may do so either because of local adaptation in host plant preference of the insect or through environmentally or genetically induced differences in the plants, causing variation in host plant suitability between regions. In the present study, we experimentally investigate the host plant preference of Anthocharis cardamines (orange tip butterfly) in two populations from the UK and two from Sweden. Previous reports indicate that A. cardamines larvae are found on different host plant species in different regions of the UK, and some variation has been reported in Sweden. Host plant choice trials showed that females prefer to oviposit on plants in an earlier phenological stage, as well as on larger plants. When controlling for plant phenological stage and size, the host species had no statistically significant effect on the choice of the females. Moreover, there were no differences in host plant species preference among the four butterfly populations. Based on our experiment, the oviposition choice by A. cardamines mainly depends on the phenological stage and the size of the host plant. This finding supports the idea that the geographical patterns of host–plant association of A. cardamines in the UK and Sweden are consequences of the phenology and availability of the local hosts, rather than regional genetic differences in the host species preference of the butterfly.  相似文献   

9.
    
The cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae), is a new invasive pest of cereals in western Canada. Host plant resistance is a potential option in the integrated management of this insect. Wheat (Triticum aestivum L.) genotypes are known to possess antixenosis against O. melanopus; however, mechanisms involving antibiosis are relatively less explored. We present results of an investigation exploring antibiotic resistance in wheat germplasm of Central Asian origin with putative resistance to O. melanopus. Our laboratory assessment of development and survivorship of O. melanopus on test genotypes indicated antibiotic properties in four of the six genotypes evaluated. Antibiosis effects were reflected through lower survivorship, extended developmental periods and low adult fitness. However, two genotypes were excellent hosts, and beetles had higher survivorship and fitness on them. The performance of O. melanopus on these two genotypes was comparable to that on the susceptible genotype CDC GO included as a check. The genotypes with antibiotic resistance identified by this research can now serve as sources of genetic resistance for breeding cultivars adapted to western Canadian conditions.  相似文献   

10.
In this study, we developed an oviposition model of Neoseiulus californicus (McGregor) with Tetranychus urticae Koch as prey. To obtain data for the model, we investigated the longevity, fecundity and survivorship of adult female N. californicus at six constant temperatures (16, 20, 24, 28, 32 and 36°C), 60–70% RH and a photoperiod of 16 : 8 (L : D) h. Longevity (average ± SE) decreased as temperature increased and was longest at 16°C (46.7 ± 5.25 days) and shortest at 36°C (12.8 ± 0.75 days). Adult developmental rate (1/average longevity) was described by the Lactin 1 model (r2 = 0.95). The oviposition period (average±SE) was also longest at 16°C (29.8 ± 2.93 days) and shortest at 36°C (6.7 ± 0.54 days). Fecundity (average±SE) was greatest at 24°C (43.8 ± 3.23 eggs) and lowest at 36°C (15.9 ± 1.50 eggs). The oviposition model comprised temperature‐dependent fecundity, age‐specific cumulative oviposition rate and age‐specific survival rate functions. The temperature‐dependent fecundity was best described by an exponential equation (r2 = 0.81). The age‐specific cumulative oviposition rate was best described by the three‐parameter Weibull function (r2 = 0.96). The age‐specific survival rate was best described by a reverse sigmoid function (r2 = 0.85).  相似文献   

11.
    
Mutations are the ultimate source of all genetic variations. New mutations are expected to affect quantitative traits differently depending on the extent to which traits contribute to fitness and the environment in which they are tested. The dogma is that the preponderance of mutations affecting fitness will be skewed toward deleterious while their effects on nonfitness traits will be bidirectionally distributed. There are mixed views on the role of stress in modulating these effects. We quantify mutation effects by inducing mutations in Arabidopsis thaliana (Columbia accession) using the chemical ethylmethane sulfonate. We measured the effects of new mutations relative to a premutation founder for fitness components under both natural (field) and artificial (growth room) conditions. Additionally, we measured three other quantitative traits, not expected to contribute directly to fitness, under artificial conditions. We found that induced mutations were equally as likely to increase as decrease a trait when that trait was not closely related to fitness (traits that were neither survivorship nor reproduction). We also found that new mutations were more likely to decrease fitness or fitness‐related traits under more stressful field conditions than under relatively benign artificial conditions. In the benign condition, the effect of new mutations on fitness components was similar to traits not as closely related to fitness. These results highlight the importance of measuring the effects of new mutations on fitness and other traits under a range of conditions.  相似文献   

12.
    
When future reproductive potential is threatened, for example following infection, the terminal investment hypothesis predicts that individuals will respond by investing preferentially in current reproduction. Terminal investment involves reallocating resources to current reproductive effort, so it is likely to be influenced by the quantity and quality of resources acquired through diet. Dietary protein specifically has been shown to impact both immunity and reproduction in a range of organisms, but its impact on terminal investment is unclear. We challenged females from ten naturally derived fruit fly (Drosophila melanogaster) genotypes with the bacterial pathogen Pseudomonas aeruginosa. We then placed these on either a standard or isocaloric high‐protein diet, and measured multiple components of reproductive investment. As oogenesis requires protein, and flies increase egg production with protein intake, we hypothesized that terminal investment would be easier to observe if protein was not already limiting. Oral exposure to the pathogen triggered an increase in reproductive investment. However, whereas flies feeding on a high‐protein diet increased the number of eggs laid when exposed to P. aeruginosa, those fed the standard diet did not increase the number of eggs laid but increased egg‐to‐adult viability following infection. This suggests that the specific routes through which flies terminally invest are influenced by the protein content of the maternal diet. We discuss the importance of considering diet and natural routes of infection when measuring nonimmunological defences.  相似文献   

13.
    
The box‐tree pyralid Cydalima perspectalis (Walker 1859) (Lepidoptera: Pyralidae), native to Eastern Asia, is a newly introduced species causing severe damage to box‐trees (Buxus sp.) in private and public gardens as well as in semi‐natural box‐tree forests in Central Europe. It is so far not known whether different box‐tree subspecies (or varieties) are similarly affected by this invasive moth. In a choice experiment offering branches of five different box‐tree varieties as oviposition sites, we found a preference of female moths for laying their egg clusters on the variety ‘Rotundifolia’, while other varieties were less frequently considered. The preference for ‘Rotundifolia’, the variety with the largest leaves in the tests, remained when intervariety differences in foliar area (mean leaf size × number of leaves) were taken into account. Feeding larvae on leaves of either of the five box‐tree varieties revealed a significant effect of the seasonal generation of C. perspectalis on the growth rate of individuals but no influence of the box‐tree variety. Larvae from the spring generation show the highest growth rate, those from the summer generation a moderate and those from the autumn generation the lowest growth rate. The moths used in the experiments may belong to the 10th to 12th generation present in Europe. The time elapsed since their introduction may be too short for an optimal adaptation to the partly novel diet encountered by the invasive moth.  相似文献   

14.
    
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15.
    
We conducted a field investigation and evaluation of 13C natural abundance to determine the growth habit and propagation strategy of Acer catalpifolium Rehd., a tree species native to China that is highly endangered. The results showed that A. catalpifolium is a K‐selected strategist and pioneer species. Its narrow ecological range limits its geographical distribution, and poor fecundity limits its population size. The analysis of 13C natural abundance showed that A. catalpifolium does not use organic matter for reproduction when its stand volume is less than 1.08 × 106 cm3 or it is less than 18.6 m tall, but it does use this strategy when it has a sufficient 1.08 × 106 cm3 stand volume or more or is taller than 18.6 m. If environmental conditions are not conducive (e.g., severe human disturbance, cliff edges, or fierce interspecific competition) to the continued growth of the tree, A. catalpifolium may allocate organic matter for reproduction. Human disturbance seems to promote the population expansion of A. catalpifolium. We provide our suggestions for the promotion and protection of A. catalpifolium as a species.  相似文献   

16.
    
  1. Species composition and abundance of larval insects can vary significantly between similar channel units (riffles) on the same stream as well as between similar streams. The source of this variation is largely unexplained, but important because such spatial variations can influence population and community dynamics and the design of sampling programmes. The maternal and oviposition behaviours of some aquatic insects are specialised, such that eggs are laid in particular locations, and this could influence the spatial distribution of eggs and larvae within a stream.
  2. In a relatively short length of stream (1 km), we tested whether the number of oviposition sites influenced the number of larvae of different instars in whole riffles that ranged in area from 80 to 460 m2. We examined two species, a mayfly Baetis rhodani and a caddisfly Rhyacophila dorsalis, with larvae that are riffle specialists and adults that oviposit exclusively on emergent rocks in riffles. For comparison, we also examined a control species, blackflies Simulium spp., with larvae that are also riffle specialists, but adults that oviposit on trailing vegetation. As an alternative hypothesis, we tested whether the numbers of larvae per riffle were associated with habitat availability, as measured by riffle area.
  3. Numbers of early‐instar B. rhodani and R. dorsalis were positively associated with the numbers of oviposition sites per riffle, but not riffle areas. In contrast, numbers of early‐instar Simulium per riffle (the control species) were not associated with either predictor variable. For later instars, riffle area was a good predictor of larval numbers per riffle for all species, even though the number of oviposition sites still explained much variation for B. rhodani and R. dorsalis. This ontogenetic shift in distribution patterns suggests an adjustment of densities during larval life, and the evidence points to density‐dependent mortality of early‐instar larvae.
  4. Contrary to the prevailing view that riffle‐to‐riffle variations in the numbers of aquatic insect larvae can be explained by larval habitat, this study demonstrates a strong influence of adult behaviour, and oviposition site availability can explain significant amounts of this variation for some species. These results challenge traditional views about aquatic insect populations, which may have more complex and interesting dynamics than considered previously.
  相似文献   

17.
    
In just a few years, the Asian fly Drosophila suzukii has invaded several continents and has become a very serious pest of many fruit crops worldwide. Current control methods rely on chemical insecticides or expensive and labour‐intensive cultural practices. Classical biological control through the introduction of Asian parasitoids that have co‐evolved with the pest may provide a sustainable solution on condition that they are sufficiently specific to avoid non‐target effects on local biodiversity. Here, we present the first study on the development of three larval parasitoids from China and Japan, the Braconidae Asobara japonica and the Figitidae Leptopilina japonica and Ganaspis sp., on D. suzukii. The Asian parasitoids were compared with Leptopilina heterotoma, a common parasitoid of several Drosophilidae worldwide. The three Asian species were successfully reared on D. suzukii larvae in both, blueberry and artificial diet, in contrast to L. heterotoma whose eggs and larvae were encapsulated by the host larvae. All parasitoids were able to oviposit one day after emergence. Asobara japonica laid as many eggs in larvae feeding in blueberry as in artificial diet, whereas L. heterotoma oviposited more in larvae on the artificial diet and the Asian Figitidae oviposited more in larvae feeding on blueberry. Ganaspis sp. laid very few eggs in larvae in the artificial diet, suggesting that it may be specialized in Drosophila species living in fresh fruits. These data will be used for the development of a host range testing to assess the suitability of Asian parasitoids as biological control agents in invaded regions.  相似文献   

18.
    
Plant‐emitted volatile organic compounds (VOCs) mediate interactions within a plant community. Typically, receiving a signal from a damaged neighbour enhances the defensive attributes of a receiver plant. The mechanisms underlying plant–plant interactions may be divided into active and passive processes, both of which involve transit of VOCs between plants and are vulnerable to environmental perturbation. Numerous studies have documented between‐plant interactions, but the specific effects on a receiver plant's interactions with herbivores have received little attention. Moreover, the relative contributions of active and passive processes to plant defence and the effects of environmental pollutants on the processes have been largely unexplored. We used a system comprising Brassica oleracea var. italica (broccoli) and the specialist herbivore Plutella xylostella to test whether plants previously exposed to herbivore‐damaged neighbours differed from nonexposed plants in their susceptibility to oviposition. We then investigated the roles of active and passive mechanisms in our observations and whether differences in susceptibility remained under elevated ozone concentrations. Plants exposed to herbivore‐damaged neighbours were more susceptible to oviposition than plants exposed to undamaged neighbours, which indicates associational susceptibility. Mechanistically, active and passive volatile‐mediated processes occurred in tandem with the passive process – involving adsorption of sesquiterpenes to receiver plants – appearing to structure the oviposition response. Exposure to ozone rapidly degraded the sesquiterpenes and eliminated the associational susceptibility. Plant volatiles have typically been thought to play roles in between‐plant interactions and to promote receiver plant defence. Here, we show that receiver plants may also become more susceptible to oviposition and thus more likely to be damaged. Extensive disruption of volatile‐mediated interactions by an atmospheric pollutant highlights the need to consider the pervading environment and changes therein when assessing their ecological significance.  相似文献   

19.
    
Understanding the impact of spontaneous mutations on fitness has many theoretical and practical applications in biology. Although mutational effects on individual morphological or life‐history characters have been measured in several classic genetic model systems, there are few estimates of the rate of decline due to mutation for complex fitness traits. Here, we estimate the effects of mutation on competitive ability, an important complex fitness trait, in a model system for ecological and evolutionary genomics, Daphnia. Competition assays were performed to compare fitness between mutation‐accumulation (MA) lines and control lines from eight different genotypes from two populations of Daphnia pulicaria after 30 and 65 generations of mutation accumulation. Our results show a fitness decline among MA lines relative to controls as expected, but highlight the influence of genomic background on this effect. In addition, in some assays, MA lines outperform controls providing insight into the frequency of beneficial mutations.  相似文献   

20.
    
Species of Lasiodiplodia are important pathogens of a wide variety of plants covering a wide geographical distribution. These fungi can be associated with different symptoms such as stem cankers, shoot blights, fruit rots, dieback and gummosis. Diseases caused by Lasiodiplodia were surveyed on Eucalyptus urophylla × grandis, Polyscias balfouriana and Bougainvillea spectabilis in a nursery in southern China. Based on morphology characteristics and phylogenetic analyses of ITS rDNA sequences and translation elongation factor 1‐alpha (TEF‐1α) gene regions, four species of Lasiodiplodia were identified. Lasiodiplodia theobromae was identified from E. urophylla × grandis, P. balfouriana and B. spectabilis. L. hormozganensis, L. iraniensis and L. pseudotheobromae were identified from B. spectabilis. To our knowledge, with the exception of L. theobromae on E. urophylla × grandis, this study represents the first report of these fungi on the host plants. Pathogenicity tests showed that all Lasiodiplodia spp. obtained in this study are virulent to E. urophylla × grandis and B. spectabilis, and L. theobromae was virulent to P. balfouriana.  相似文献   

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