Maternal age as a source of variation in the ability of an aphid to produce dispersing forms

Apterous parthenogentic females of the pea aphid, Acyrthosiphon pisum (Harris ), begin to produce alate offspring soon after they have been subjected to crowding. Females which were born early in their own parent's reproductive period respond most strongly to crowding, producing much larger numbers of alatae than their late-born sisters. In contrast, the early-born daughters of most alate females do not produce winged offspring after being crowded. Some of their later-born sisters may produce a few winged individuals, resembling in this respect the late-born daughters of the apterous females. Control of the production of alatae thus begins in the grandparental generation. Risk-spreading by means of differential dispersal becomes a less uncertain venture when local populations can modify their responses to environmental changes by utilizing past as well as present signals from their surroundings.     

Maternal age as a source of variation in the ability of an aphid to produce dispersing forms

Summary Apterous parthenogentic females of the pea aphid,Acyrthosiphon pisum (Harris), begin to produce alate offspring soon after they have been subjected to crowding. Females which were born early in their own parent’s reproductive period respond most strongly to crowding, producing much larger numbers of alatae than their late-born sisters. In contrast, the early-born daughters of most alate females do not produce winged offspring after being crowded. Some of their later-born sisters may produce a few winged individuals, resembling in this respect the late-born daughters of the apterous females. Control of the production of alatae thus begins in the grandparental generation. Risk-spreading by means of differential dispersal becomes a less uncertain venture when local populations can modify their responses to environmental changes by utilizing past as well as present signals from their surroundings.     

Geographical variation in wing polymorphism of the waterstrider Aquarius najas (Heteroptera,Gerridae)

The waterstrider Aquarius najas is wingless in Northern Europe, while winged individuals occur frequently in Central and Southern Europe. To test if the latitudinal difference is genetically controlled, we collected mature individuals from 10 different populations and raised their offspring in ‘common garden’ laboratory conditions. Half of these populations were from southern and the other half from central Finland. Daylength and temperature do influence wing development among other species of waterstriders, and thus we maintained a similar short daylength and warm conditions for all populations. These conditions should be favourable for wing development in general. Among laboratory-bred individuals several winged individuals appeared, and their proportion varied between populations. The relative frequency of winged individuals was highest in the southern populations. Thus, apart from phenotypic plasticity there seems to be some genetic control over the occurrence of wings, and the latitudinal trend coincides with the direction in natural populations over a larger European scale. Overwinter survival in our laboratory conditions was higher among the wingless individuals. The survival cost may explain why the proportion of winged individuals was lower in the northern populations with more extreme overwintering conditions than in the southern ones.     

Genetic variation for an aphid wing polyphenism is genetically linked to a naturally occurring wing polymorphism

Many polyphenisms are examples of adaptive phenotypic plasticity where a single genotype produces distinct phenotypes in response to environmental cues. Such alternative phenotypes occur as winged and wingless parthenogenetic females in the pea aphid (Acyrthosiphon pisum). However, the proportion of winged females produced in response to a given environmental cue varies between clonal genotypes. Winged and wingless phenotypes also occur in males of the sexual generation. In contrast to parthenogenetic females, wing production in males is environmentally insensitive and controlled by the sex-linked, biallelic locus, aphicarus (api). Hence, environmental or genetic cues induce development of winged and wingless phenotypes at different stages of the pea aphid life cycle. We have tested whether allelic variation at the api locus explains genetic variation in the propensity to produce winged females. We assayed clones from an F2 cross that were heterozygous or homozygous for alternative api alleles for their propensity to produce winged offspring. We found that clones with different api genotypes differed in their propensity to produce winged offspring. The results indicate genetic linkage of factors controlling the female wing polyphenism and male wing polymorphism. This finding is consistent with the hypothesis that genotype by environment interaction at the api locus explains genetic variation in the environmentally cued wing polyphenism.     

Variation in wing dimorphism of oriental mole cricket Gryllotalpa orientalis: Comparative study in Okinawa and Hyogo populations

The oriental mole cricket Gryllotalpa orientalis exhibits variation in wing dimorphism. In an Okinawa population, no short‐winged individuals were observed, and wing dimorphism has not been detected. Flight behavior of G. orientalis was observed from April to October in Okinawa. In contrast, a Hyogo population exhibited seasonal wing dimorphism and long‐winged individuals appear from June to September. The flight period of the long‐winged morph coincided with this period. Short‐winged individuals appeared from September to the following June and they never fly. Both populations showed univoltine life cycles. Considering the possible flight period, wing pattern and life cycle of mole crickets in these two areas, it is presumed that flightlessness is expected to arise when adults can not experience suitable temperatures for flight activity.     

Evidence for a quiet revolution: seasonal variation in colonies of the specialist tansy aphid, Macrosiphoniella tanacetaria (Kaltenbach) (Hemiptera: Aphididae) studied using microsatellite markers

In cyclical parthenogens, clonal diversity is expected to decrease due to selection and drift during the asexual phase per number of asexual generations. The decrease in diversity may be counteracted by immigration of new genotypes. We analysed temporal variation in clonal diversity in colonies of the monophagous tansy aphid, Macrosiphoniella tanacetaria (Kaltenbach), sampled four times over the course of a growing season. In a related field study, we recorded aphid colony sizes and the occurrence of winged dispersers throughout the season. The number of colonies increased from April, when asexual stem mothers hatched from the sexually produced eggs, to the end of June. The proportion of colonies with winged individuals also increased over this period. After a severe reduction in colony sizes in late summer, a second expansion phase occurred in October when sexuals were produced. At the season's end, the only winged forms were males. A linked genetic study showed that the number of microsatellite multilocus genotypes and genetic variability assessed at three polymorphic loci per colony decreased from June to October. Overall, the relatedness of wingless to winged individuals within colonies was lower than average relatedness among wingless individuals, suggesting that winged forms mainly originated in different colonies. The results demonstrate that patterns of genetic diversity within colonies can be explained by the antagonistic forces of clonal selection, migration and genetic drift (largely due to midsummer population bottlenecks). We further suggest that the males emigrate over comparatively longer distances than winged asexual females.     

Body colour and genetic variation in winged morph production in the pea aphid

Aphids (Homoptera: Aphidoidea) produce a number of different phenotypes in their life-cycle, among which are winged (alate) and wingless (apterous) morphs. Lowe & Taylor (1964) and Sutherland (1969a, b) were the first to suggest that aphid clones differ in their propensity to produce the winged morph and that in the pea aphid (Acyrthosiphon pisum Harris), this propensity is linked to the colour of the phenotype. We tested for the occurrence of genetic variation in winged morph production by rearing individuals from red and green clones of pea aphid under wing-inducing (crowding) and control conditions, and scored the phenotypes of their offspring. Clones differed significantly in alate production and red clones produced on average a higher proportion of winged morphs than green clones. Importantly, however, there was considerable variation between clones of the same colour. Broad-sense heritabilities of winged morph production were 0.69 (crowding treatment) and 0.63 (control). Clones also differed in the number of offspring they produced. When exposed to the crowding stimulus, aphids deferred offspring production, resulting in a higher number of offspring produced in the crowding treatment than in the control.     

Inter-Individual Variation and Consistency in Walking Behavior of the Rose Aphid, <Emphasis Type="Italic">Macrosiphum rosae</Emphasis> (Hemiptera: Aphididae)

Variations in morphological and behavioral properties of animals are generally considered as evolutionary adaptations to unpredictable environments. At the same time, individuals may present a strong consistency in their expressed behavior. In this study, we investigated inter-individual variations and consistency in walking behavior of both apterous and winged morphs of the rose aphid, Macrosiphum rosae (L.) (Hemiptera: Aphididae). Adult apterous and winged aphids were released three times on the surface of a corn leaf cut (40 cm × 5 mm) and the time elapsed and the numbers of steps walked by individuals to go through it were recorded. Although, our results revealed a strong consistency in walking speed of both apterous and winged individual aphids, we found a wide variation in walking speed of different individuals for these morphs. These variations were predominantly associated with the differences in the number of steps walked by individual aphids, and less importantly, to their walking speed. Altogether, winged aphids walked with a higher average speed than apterous ones (42.42 vs. 38.92 cm min^?1, respectively) (P < 0.01). This may be an evolutionary adaptation of winged aphids where they should walk actively to find a suitable site for establishment after an unpredictable air-borne flight. We measured the wet body weight of apterous and winged adults to find a correlation between body weight and walking speed. Although, the winged aphids were significantly lighter than apterous ones (P < 0.01), we found no reliable data to correlate the observed variations in walking behavior of rose aphids to their body weight. The importance of this inter-individual variation in the evolutionary biology of clonal aphids has been discussed.     

有翅和无翅豌豆蚜中翅型分化信号通路相关微小RNA及其靶基因的表达差异

【目的】前期研究发现麦长管蚜Sitobion avenae孤雌蚜有翅和无翅个体中存在很多差异表达的微小RNA(microRNA, miRNA),本研究旨在进一步明确这些miRNA在豌豆蚜Acyrthosiphon pisum中发挥作用的发育阶段,探索miRNA调控孤雌蚜翅两型性分化的机制。【方法】选择在麦长管蚜有翅蚜和无翅蚜中显著差异表达,且靶基因为蜕皮激素、胰岛素信号通路及翅型发育关键基因的5个miRNA(Let-7,miR-92a, miR-92b, miR-92a-1-p5和miR-277),利用qPCR检测这些miRNA及其靶标基因在豌豆蚜3-4龄若蚜和成虫有翅和无翅个体中的表达谱;同时利用双荧光素酶活性检测法对上述miRNA的靶基因进行验证。【结果】表达谱分析发现,这5个miRNA在豌豆蚜成虫中表达量均高于其在若蚜中的表达量,而其预测的靶基因在4龄若蚜中的表达量均高于其在成虫中的表达量,表明miRNA对其靶基因的调控作用可能集中在成虫阶段。分析豌豆蚜有翅和无翅个体中5个miRNA的表达情况发现,在成虫有翅个体中5个miRNA的表达量均高于无翅个体中的,其中miR-277表达差异最显著,成虫有翅个体中的表达量是无翅个体中表达量的7.5倍;其次为Let-7,表达差异达3倍。而Let-7在3龄有翅若蚜和无翅若蚜中表达差异最显著,有翅个体中的表达量是无翅个体中的37.8倍;其次为miR-277,表达差异达7.6倍。比较5个miRNA与其靶基因在豌豆蚜3-4龄若蚜及成虫有翅和无翅个体中的表达发现,miRNA Let-7和miR-92b的表达趋势分别与其靶基因abrupt和Foxo的基本相反。荧光素酶活性检测结果显示,Let-7的真实靶标为abrupt,共转染Let-7模拟物后与对照相比,荧光素酶活性下降53%,达极显著水平。其他miRNA与靶标基因的互作不显著。【结论】首次发现miRNA对豌豆蚜孤雌蚜翅型分化相关基因的调控可能发生在成虫阶段。Let-7可能通过调控abrupt基因参与孤雌蚜翅型分化。该研究为进一步探索miRNA参与孤雌蚜翅两型性分化的机制奠定了基础。     

Multiple Cues for Winged Morph Production in an Aphid Metacommunity

Environmental factors can lead individuals down different developmental pathways giving rise to distinct phenotypes (phenotypic plasticity). The production of winged or unwinged morphs in aphids is an example of two alternative developmental pathways. Dispersal is paramount in aphids that often have a metapopulation structure, where local subpopulations frequently go extinct, such as the specialized aphids on tansy (Tanacetum vulgare). We conducted various experiments to further understand the cues involved in the production of winged dispersal morphs by the two dominant species of the tansy aphid metacommunity, Metopeurum fuscoviride and Macrosiphoniella tanacetaria. We found that the ant-tended M. fuscoviride produced winged individuals predominantly at the beginning of the season while the untended M. tanacetaria produced winged individuals throughout the season. Winged mothers of both species produced winged offspring, although in both species winged offspring were mainly produced by unwinged females. Crowding and the presence of predators, effects already known to influence wing production in other aphid species, increased the percentage of winged offspring in M. tanacetaria, but not in M. fuscoviride. We find there are also other factors (i.e. temporal effects) inducing the production of winged offspring for natural aphid populations. Our results show that the responses of each aphid species are due to multiple wing induction cues.     

Juvenile hormone titres and winged offspring production do not correlate in the pea aphid, Acyrthosiphon pisum

Pea aphids, Acyrthosiphon pisum, reproduce parthenogenetically and are wing-dimorphic such that offspring can develop into winged (alate) or unwinged (apterous) adults. Alate induction is maternal and offspring phenotype is entirely determined by changes in the physiology and environment of the mother. Juvenile hormones (JHs) have been implicated in playing a role in wing differentiation in aphids, however until recently, methods were not available to accurately quantify these insect hormones in small insects such as aphids. Using a novel LC-MS approach we were able to quantify JH III in pea aphids that were either producing a high proportion of winged morphs among their offspring or mainly unwinged offspring. We measured JH III titres by pooling the hemolymph of 12 or fewer individuals (1 μL hemolymph) treated identically. Levels of JH ranged from 30 to 163 pg/μL. While aphids in the two treatments strongly differed in the proportion of winged morphs among their offspring, their JH III titres did not differ significantly. There was also no correlation between JH III titre and the proportion of winged offspring in induced aphids. This supports earlier findings that wing dimorphism in aphids may be regulated by other physiological mechanisms.     

Variation in singing behaviour among morphs of the sand field cricket,Gryllus firmus

1. Trade‐offs play a fundamental role in the evolution of many traits. 2. In wing‐polymorphic field crickets, the long‐winged morph can disperse from unfavourable environments, but has lower reproductive success than the short‐winged morph, because of costs associated with flight capability. 3. However, long‐winged individuals may minimise costs in favourable environments by histolysing their flight muscles and becoming flightless. 4. Few studies have examined how flight‐muscle histolysis affects male signalling and mate attraction. 5. We examined differences in singing activity and song characteristics among the flightless (short‐winged and histolysed long‐winged) and the flight‐capable male morphs, and female preferences for male song, in the sand field cricket. 6. We found: (i) both flightless morphs sang more than the flight‐capable morph, (ii) song characteristics varied among the three morphs, and (iii) females preferred songs characteristic of the long‐winged morphs. 7. Histolysis should increase mating success of long‐winged males because it increases singing activity. 8. Histolysed long‐winged males may have higher mating success than short‐winged males as they sing as frequently but produce more attractive songs. 9. Therefore, plasticity within the long‐winged morph may reduce costs of maturing in environments from which dispersal is not advantageous; non‐flying morphs may be pursuing different reproductive tactics.     

Alternative life histories in the water strider Gerris lacustris: time constraint on wing morph and voltinism

The wing dimorphic water strider Gerris lacustris L. (Heteroptera: Gerridae) switches to a bivoltine life cycle under favorable climatic conditions. The switch in voltinism is accompanied by a reduction of wing development in the directly reproducing midsummer generation, while the diapausing generation has a high fraction of long‐winged individuals. We investigated whether the thermal energy (degree‐days) available in natural habitats constrains the combination of developmental pathway and wing morph. Offspring of G. lacustris were reared under quasi‐natural conditions at two temperature regimes to determine the thermal constant k required to complete adult development in either wing morph. The thermal constant for egg‐to‐adult development of the short‐winged morph was about 20% lower than of the long‐winged morph. Based on the results from the outdoor laboratory experiment, we calculated the total degree‐days necessary to complete the possible combinations of wing morph pattern and voltinism. Comparison of these estimates with the thermal energy actually available during the reproductive season of 2004 for various natural habitats (sun‐exposed field ponds and shaded forest ponds) suggests that voltinism as well as wing morph pattern is strongly limited by the number of degree‐days available in these habitats. On forest ponds, only univoltine life cycles were possible, whereas on field ponds temperature allowed bivoltine life cycles. However, only the eggs laid at the very beginning of the season had the potential to accumulate enough degree‐days to complete a bivoltine life cycle with both generations long‐winged. We conclude that thermal energy is the main environmental constraint limiting voltinism of populations in the two habitat types. Furthermore, the available thermal energy also seems to influence the determination of the seasonal wing pattern in G. lacustris.     

Occurrence and genetics of black‐eyed migratory locusts,Locusta migratoria (Orthoptera: Acrididae)

Black‐eyed Locusta migratoria appeared in albino locusts as a result of crossing between a short‐winged strain originating from Tsushima Island, Japan, and an albino strain originating from Okinawa Island. The black eye trait was recessive to the white eye trait because the crosses between black‐ and white‐eyed albino locusts produced only individuals with white eyes in the F₁ generation. In the F₂ generation, black‐ and white‐eyed individuals appeared in a ratio of 1:3, indicating that the black eye trait was controlled by a simple Mendelian unit. The black eye trait showed no genetic association with other traits including wing morph, adult body dimensions and classical morphometric ratios such as hind femur length / head width and forewing length / hind femur length.     

Alarm pheromone mediates production of winged dispersal morphs in aphids

The aphid alarm pheromone ( E )- β -farnesene (EBF) is the major example of defence communication in the insect world. Released when aphids are attacked by predators such as ladybirds or lacewing larvae, aphid alarm pheromone causes behavioural reactions such as walking or dropping off the host plant. In this paper, we show that the exposure to alarm pheromone also induces aphids to give birth to winged dispersal morphs that leave their host plants. We first demonstrate that the alarm pheromone is the only volatile compound emitted from aphid colonies under predator attack and that emission is proportional to predator activity. We then show that artificial alarm pheromone induces groups of aphids but not single individuals to produce a higher proportion of winged morphs among their offspring. Furthermore, aphids react more strongly to the frequency of pheromone release than the amount of pheromone delivered. We suggest that EBF leads to a 'pseudo crowding' effect whereby alarm pheromone perception causes increased walking behaviour in aphids resulting in an increase in the number of physical contacts between individuals, similar to what happens when aphids are crowded. As many plants also produce EBF, our finding suggests that aphids could be manipulated by plants into leaving their hosts, but they also show that the context-dependence of EBF-induced wing formation may hinder such an exploitation of intraspecific signalling by plants.     

A transgenerational interval timer inhibits unseasonal sexual morph production in damson-hop aphid, Phorodon humuli

Abstract.  The induction of sexual and parthenogenetic morphs of the damson-hop aphid, Phorodon humuli , on hops is controlled by daylength. The ability of P. humuli , to produce winged pre-sexual females (gynoparae) in the short-day conditions of spring is inhibited by an interval timer present in generations immediately after hatching of the overwintering egg. The inhibition expires after three generations when nymphs are born and reared in short days (LD 12 : 12 h), irrespective of whether their parents are reared in short or long days (LD 18 : 6 h). No gynoparae are produced by aphids maintained for 13 generations in long days. Two wingless aphids from 35 survive transfer from Prunus spinosa to hops. No winged females are produced during nine generations among their progeny maintained in long days on hops, but gynoparae, followed by males, are produced one generation after these aphids are transferred to short days.     

不同小麦品种对有翅与无翅型禾谷缢管蚜生长发育与繁殖的影响

室内采用水培小麦法饲养禾谷缢管蚜Rhopolosiphum padi(L.),比较了有翅与无翅型禾谷缢管蚜若虫发育历期、成虫寿命、繁殖力和日均体重增长量.结果表明,不同小麦品种上有翅型和无翅型若虫发育历期均存在显著差异;同时产若蚜数量、每代产若蚜数和腹中胚胎数均存在显著差异,而成蚜寿命、产若蚜历期和产若蚜代数差异不显著...     

Effects of wing polyphenism, aphid genotype and host plant chemistry on energy metabolism of the grain aphid, Sitobion avenae

Wing dimorphism has been proposed as a strategy to face trade-offs between flight capability and fecundity. In aphids, individuals with functional wings have slower development and lower fecundity compared with wingless individuals. However, differential maintenance costs between winged and wingless aphids have not been deeply investigated. In the current study, we studied the combined effect of wing dimorphism with the effects of aphid genotypes and of wheat hosts having different levels of chemical defences (hydroxamic acids, Hx) on adult body mass and standard metabolic rates (SMR) of winged and wingless morphs of the grain aphid, Sitobion avenae. We found that wingless aphids had higher body mass than winged aphids and that body mass also increased towards host with high Hx levels. Furthermore, winged aphids showed a plastic SMR in terms of Hx levels, whereas wingless aphids displayed a rigid reaction norm (significant interaction between morph condition and wheat host). These findings suggest that winged aphids have reduced adult size compared to wingless aphids, likely due to costs associated to the development of flight structure in early-life stages. These costs contrast with the absence of detectable metabolic costs related to fuelling and maintenance of the flight apparatus in adults.     

Analysis of differential proteins in two different wing‐types of female Nilaparvata lugens

Nilaparvata lugens (stal) is a rice pest and contains long‐winged and short‐winged varieties, called the wing differentiation. This study compared the protein profiles of the two wing‐types in females and two wing‐disc types 5th‐instar females by two‐dimensional electrophoresis analysis. We detected 172 and 174 protein spots in adults and 5th‐instar nymphs, respectively. The number of proteins with higher content in the long‐winged (disc) individuals is much more than that in the short‐winged (disc) individuals. A total of 32 differential protein spots were found, of which 20 were successfully identified. Their main function is about catabolic process, fiber and nucleoside binding, and they constitute 52 protein–protein interactions, which is around the glycolysis as the core. These results enrich the research on the protein Level in wing development, and provide more references for future studies.     

Wing Dimorphisms and the Evolution of Migratory Polymorphisms among the Insecta

Many species of insects exhibit wing dimorphism, one morph havingfully developed wings and the other morph having reduced wingsand being incapable of flight. These wing dimorphisms providevisible manifestations of migratory polymorphisms. Since wingedindividuals do not, in principle, have to fly, the existenceof forms with reduced wings suggests that there is a tradeoffbetween flight capability and other fitness components. Comparisonsof the life histories of the fully winged and wing reduced morphsdemonstrate that this tradeoff is most commonly expressed asa decrease in the age of first reproduction and increased fecundityin the morph with reduced wings. Given these tradeoffs, theevolution of wing dimorphism will depend upon its genetic basis,including correlations with other life history components. Areview of the recent literature suggests that the heritabilityof wing morphology is high, and we suggest that this high heritabilitycould be maintained, in part, by antagonistic pleiotropy. In dimorphic species, the winged morph is generally consideredto be the migrant form. However, there are significant correlations,both within and among species, between the proportion of wingedindividuals, the proportion of winged individuals with functionalflight muscles, and the flight propensity of those individuals.This suggests that the proportion of winged individuals andthe propensity of the winged morph to migrate are intimatelyconnected at both the physiological and population level. Therefore,the study of the evolution of wing dimorphism is important notonly in its own right but also as a model of how migratory propensityevolves in monomorphically winged species.