The consequences of clustering by Aphis fabae foundresses on spring migrant production

Aphis fabae (Homoptera: Aphididae) foundresses were shown to have a clustered distribution on leaves of their primary host, Euonymus europaeus. Two field experiments were carried out to determine the costs or benefits of this clustering behaviour to aphid clones. The first experiment, in spring 1996, excluded predators from colonies formed by single fundatrices or clusters of three. No density-dependent effects on colony growth were observed early in the season, but the total production of migrants per foundress was significantly lower for clustered foundresses. This demonstrated that there was no synergistic effect of group feeding on clonal performance. All colonies were initiated on randomly selected leaves and all grew successfully, therefore clustering was not due to a shortage of feeding sites. The second experiment, in spring 1997, tested whether natural enemies cause selection for selfish herding by the foundress generation. Colonies were initiated by one or three foundresses, but half were left unbagged. If natural enemy attack is a selective force inducing clustering behaviour in foundresses, the costs of clustering should have been reduced or negated in unbagged colonies. Colonies grown from clusters produced significantly fewer migrants per foundress, irrespective of bagging treatment. Other potential factors causing clustering behaviour are discussed. Received: 19 August 1998 / Accepted: 16 November 1998     

寄主龄期对可疑柄瘤蚜茧蜂寄生及其后代适合度的影响

采用单选试验,观察了可疑柄瘤蚜茧蜂（Tysiphlebus anbiguus）对不同发育时期黑豆蚜的寄生选择及其后代生长发育适合度相关特征,以检验寄主大小与其质量是否存在正相关关系。结果表明,黑豆蚜（Aphis fabae）1～4龄和成蚜均被寄生,但对2龄若蚜的寄生率最高（35．25％）,对成蚜寄生率最低（14．75％）;寄生低龄蚜虫的羽化率显著高于高龄若蚜和成蚜。寄生2龄若蚜的发育历期（8．4d）最短,而寄生1龄若蚜最长（9．3d）;寄生2～4龄蚜虫的后代蜂体型显著大于寄生1龄和成蚜;寄生4龄若蚜的后代中,雌蜂比例（75．74％）显著高于1龄若蚜（62．89％）和成蚜（65．19％）,但与寄生2～3龄若蚜无显著差异。寄主黑豆蚜的质量从高至低依次为2龄〉3龄=4龄〉成蚜〉1龄,因此,对可疑柄瘤蚜茧蜂而言。寄主大小与其质量并非存在正相关性。     

Phenotypic plasticity as a state-dependent life-history decision

Summary A genotype is said to show phenotypic plasticity if it can produce a range of environmentally dependent phenotypes. Plasticity may or may not be adaptive. We consider plasticity as a genetically determined trait and thus find the optimal response of an animal to its environment. Various aspects of this optimal response are illustrated with examples based on reproductive effort. We investigate the selection pressure for plastic as opposed to fixed strategies. An example with spatial heterogeneity is used to compare our approach with that of Stearns and Koella (1986).     

Photoperiodic induction of winged females in the black bean aphid. Aphis fabae

Abstract. The Photoperiodic of winged females (alatae) in the black bean aphid, Aphis fabae Scop. (Homopetera: Aphididae), is investigated in detail with emphasis on the interaction of the maternal and embryonic/young larval photoperiodic clocks. Previous work had shown that in uncrowded conditions the induction of gynoparae (winged females that produce sexual females) requires both prenatal and postnatal exposure to long-night (12 h) Photoperidic cycles: present results show that sole postantal exposure to long nights of any lenght does not induce wing formation in early-born aphids.
When aphids were exposed to experimental light-dark cycles postanatally only, their daughters developed as alate in long nights and as apterae in short nights: the critical night lenght (CNL) was 11:1 h. Additional prenatal exposure to experimental regimes resulted in a significantly shorter CNL (10.6 h). This difference could be accounted for by the fact that more experimental light-dark cycles were experienced in the latter case.
Apterous aphids transferred from LD 16:8 h to LD 12:12 h as either third-or fourth-stadium larvae, or young adults, switched for aptera-production to alata-production. The transition form aptera- to alata-production was rather abrupt in third-stadium transfers but more gradual when transfers occurred as fourth-stadium larvae and adults. Moreover, s the number of days required for 50% of the aphids to become alata-producers increased from 7–8 in third-stadium transfers, to 9–10 and 11–12 in the later transfers.     

Photoperiodic regulation of the development of winged gynoparae in the aphid, Aphis fabae

ABSTRACT. In uncrowded rearing conditions, determination of the winged gynopara of the Aphis fabae Scopoli is dependent upon both pre- and postnatal short days (LD 12:12). Extension of the photophase to produce longday (LD 16:8) conditions localized on the head or abdominal region, showed that during the early larval instars of the parent generation (G1) there is a maternally-controlled induction of gynoparae. However, during later stages of embryonic development the presumptive gynoparae respond directly to photoperiod through the mother's abdominal wall. During early postnatal development, presumptive gynoparae (G2) remain sensitive to photoperiodic conditions; the photoperiodic receptors lie in the head. These results are discussed with respect to possible endocrine mediators of this photoperiodically controlled polymorphism.     

Antixenosis resistance to Aphis fabae Scopoli (Hemiptera:Aphididae) in bean cultivars

Aphis fabae Scopoli (Hemiptera: Aphididae) is heteroecious and polyphagous that is harmful on secondary hosts such as many important agricultural products like beet, common bean, faba bean, potato and other products. This aphid is the cause of more than 33 viral transition. One of the mechanisms of plant resistance is antixenosis. This mechanism influences on placement and nutrition of pests that result in less damage. In this study, antixenosis resistance mechanism of 12 varieties of bean was tested. Experiment was on completely randomised design with 12 treatments and 6 replications. Bean varieties include of white bean, kidney bean and wax bean, and each replication includes one pot, and then, pots were placed under the isolated room that were filled with winged adult aphids in circular form. After 24 and 48?h, aphids and level of nymph production were counted. The lowest number of adult aphids was observed on Sayad variety among 12 varieties (during 24?h). The least number of produced nymphs was in Daneshkade variety. In Sayad variety, the frequency of matured insects and produced nymphs was minimum.     

The effect of host plants on genotype variability in fitness and honeydew composition of Aphis fabae

Aphid species can be polyphagous, feeding on multiple host plants across genera. As host plant species can have large variation in their phloem composition, this can affect aphid fitness and honeydew composition. Previous research showed significant intraspecific genotype variation in the composition of the honeydew carbohydrates of the black bean aphid Aphis fabae, with the ant attractant trisaccharide melezitose showing especially large variation across different genotypes. In this study, we test if variation in melezitose and carbohydrate composition of aphid honeydew could be linked to the adaptation of specific aphid genotypes to particular host plants. To this end, 4 high and 5 low melezitose secreting genotypes of the black bean aphid Aphis fabae were reared on 4 common host plants: broad bean, goosefoot, beet, and poppy. The carbohydrate composition, and in particular melezitose secretion, showed important aphid genotype and host plant interactions, with some genotypes being high melezitose secreting on 1 host plant but not on another. However, the interaction effects were not paralleled in the fitness measurements, even though there were significant differences in the average fitness across the different host plants. On the whole, this study demonstrates that aphid honeydew composition is influenced by complex herbivore–plant interactions. We discuss the relevance of these findings in the context of ant–aphid mutualisms and adaptive specialization in aphids.     

Climate effects on life cycle variation and population genetic architecture of the black bean aphid, Aphis fabae

Aphid species may exhibit different reproductive modes ranging from cyclical to obligate parthenogenesis. The distribution of life cycle variation in aphids is generally determined by ecological forces, mainly climate, because only sexually produced diapausing eggs can survive harsh winters or periods of absence of suitable host plants. Aphids are thus interesting models to investigate intrinsic and environmental factors shaping the competition among sexual and asexual lineages. We conducted a Europe-wide sampling of black bean aphids, Aphis fabae, and combined population genetic analyses based on microsatellite data with an experimental determination of life cycle strategies. Aphids were collected from broad beans (Vicia faba) as well as some Chenopodiaceae, but we detected no genetic differentiation between aphids from different host plants. Consistent with model predictions, life cycle variation was related to climate, with aphids from areas with cold winters investing more in sexual reproduction than aphids from areas with mild winters. Accordingly, only populations from mild areas exhibited a clear genetic signature of clonal reproduction. These differences arise despite substantial gene flow over large distances, which was evident from a very low geographic population structure and a lack of isolation-by-distance among 18 sites across distances of more than 1000 km. There was virtually no genetic differentiation between aphids with different reproductive modes, suggesting that new asexual lineages are formed continuously. Indeed, a surprising number of A. fabae genotypes even from colder climates produced some parthenogenetic offspring under simulated winter conditions. From this we predict that a shift to predominantly asexual reproduction could take place rapidly under climate warming.     

Partial application of insecticide to broad bean (Vicia fabae) as a means of controlling bean aphid (Aphis fabae) and bean weevil (Sitona lineatus)

The effects upon the nature of insect pest attack of treating only a certain proportion (0%, 25%, 50%, 75% and 100%) of the plants in a field bean (Vicia fabae) stand, with a systemic insecticide (aldicarb as Temik 10G, Rhone Poulenc Drugs Ltd; 10% a.i.) were assessed. Numbers of both the black bean aphid (Aphis fabae) and the bean weevil (Sitona lineatus) were proportionally reduced on untreated plants in plots with an increasing proportion of insecticide treated plants. A similar response was also observed with bean weevil leaf damage scores.
It is postulated that the observed effects are due to a reduction in insect numbers per plot brought about by redistribution of insects after initial invasion. Insects initially alighting on untreated plants later migrate to treated plants and either die or leave the plot altogether. This resulted in proportionally fewer insects on the untreated plants than would be expected.     

温度对黑豆蚜体内共生菌胞数量及宿主体型大小的影响

为了明确饲养温度对黑豆蚜Aphis fabae 内共生菌和宿主蚜虫体型大小的影响,对在室内不同温度下饲养的黑豆蚜内共生菌胞数量和宿主蚜虫体型大小进行了观察和统计分析。结果表明,温度对同一发育时期蚜虫内共生菌胞数量的影响在不同温度范围内有所不同,1龄若蚜体内的菌胞数量除在25℃与35℃间有显著差异外,在其余各温度间没有显著差异; 其余时期的蚜虫内共生菌胞数量在高温（> 30℃）下显著低于较低温度下的菌胞数量,存在负直线相关性。温度对菌胞数量随宿主发育到产仔前的变化趋势有不同程度的影响,在较低温度（15℃、20℃和25℃）下,菌胞数量随虫体发育显著增加; 但在高温（30℃和35℃）下,蚜虫体内菌胞数逐渐增加直到3龄达到最高,然后略有下降（30℃）或显著下降（35℃）。除1龄若蚜外,蚜虫体型大小总体呈现随温度升高而降低的格局,但随其内共生菌数量增多而增大（35℃下除外）。据此认为,温度可能通过作用于蚜虫内共生菌胞数量而影响蚜虫体型的大小。     

'Bistability' experiments and photoperiodic morph determination in the aphid Aphis fabae

Abstract. Newly born larvae (presumptive gynoparae) of the aphid Aphis fabae were exposed to 'symmetrical skeleton' photoperiods, consisting of two equal pulses of light per 24 h. The general form of the photoperiods tested was LDLD 1:10:1:12 h. This regime is open to two 'interpretations', LDLD 1:10:1:12 h (PP_s12) and LDLD 1:12:1:10 h (PP_s14). As both light pulses are close to 12 h apart, it is expected that the interpretations result in two distinct steady state phase relationships, i.e. this regime would show bistability. If this is true and both interpretations could be adopted, PP_s12 is expected to result in a low and PP_s14 in a high percentage of 'apterized' insects.
Experiments undertaken with the aphid showed that bistability did not occur either at 15C or 20C, and the results could be entirely explained on the basis of an 'instantly' damping circadian oscillator clock.     

New polymorphic microsatellite loci,cross‐species amplification and PCR multiplexing in the black aphid,Aphis fabae Scopoli

Aphis fabae includes four morphological cryptic subspecies, which are mostly identified by their partially distinct secondary host range. To determine the extent of gene flow and isolation between these four taxa, we isolated and characterized 12 microsatellite loci from Aphis fabae fabae and tested cross‐species amplification of eight loci from the closely related species Aphis gossypii. Using eight previously described microsatellite loci, we have developed the polymerase chain reaction (PCR) multiplexing of 24 loci, which were separated in tree sets and five PCRs. These sets of microsatellite loci provide high throughput capacity for large‐scale population genetic studies at a minimum cost.     

Costs of ant attendance for aphids

1. Interactions between aphids and ants are considered to be mutualistic, with both partners benefiting. Costs associated with such interactions are likely to be less obvious, although they can be expected, especially if these associations are facultative.
2. It is demonstrated here that there are costs in several life-history parameters to individual aphids resulting from ant attendance. Over several generations Aphis fabae cirsiiacanthoides feeding on Cirsium arvense , at a range of developmental stages, suffered significant costs when tended by Lasius niger , e.g. in terms of a prolonged developmental time, delayed offspring production, proportionally smaller gonads, fewer well developed embryos and a reduced mean relative growth rate. These effects are similar to those observed when aphids feed on poor quality plants.
3. This is the first indication that there is a cost for aphids associated with ant attendance. The significance of this for the evolution of ant attendance in aphids is discussed.     

Interaction between plant resistance and predation of Aphis fabae (Homoptera: Aphididae) by Coccinella septempunctata (Coleoptera: Coccinellidae)

We investigated the compatibility of host plant resistance to the black bean aphid in the faba bean crop with the use of the predatory ladybird beetle for biological control under laboratory and greenhouse conditions. Greenhouse experiments indicated that apteriform Aphis fabae reproduced on Vicia faba major (susceptible) and on 79S4 (partially resistant) cultivars at different rates. During the entire experimental period, aphids built up higher populations on V. faba major than on 79S4 cultivar. Aphid numbers on 79S4 were about 37% of those on V. faba major after 14 days. Release of a newly hatched Coccinella septempunctata larva onto each plant significantly reduced aphid density to 32.8% and 57.2% on V. faba major and 79S4 on day 14, respectively. Partial resistance combined with predation was more effective in lessening aphid numbers on faba bean than either the predator or the plant resistance alone. Laboratory tests showed that prey, A.   fabae , raised on susceptible cultivar was more suitable for the predator as food source, enhancing the development rate and fecundity than aphids fed on the partially resistant cultivar. Consumption of aphids reared on susceptible cultivar significantly increased the female fecundity and fertility of C. septempunctata by 37.7% and 33.2%, respectively, more than those fed with aphids from partially resistant cultivar. Pre-oviposition time was shortened by 4.5 days, and oviposition period was extended by 11.4 days. Feeding the predator on aphids from the partially resistant cultivar prolonged the embryonic larval developmental time and the time required from egg laying to adult emergence by 19.8, 10.1 and 32.5 h, respectively. Adult longevity was not influenced by the aphid source. The results are discussed in relation to the compatible utilisation of host plant resistance and biological control in the integrated management of aphids.     

Provenance, experience and plant utilisation by the polyphagous aphid, Aphis fabae

Twenty-nine clones of Aphis fabae Scopoli (Aphididae: Homoptera) were isolated into laboratory culture from the primary host plants Euonymus europaeus and Viburnum opulus and the secondary host plants Arctium lappus, Impatiens glandulifera, Tropaeolum majus and Vicia faba. All clones performed well on either T. majus or V. faba, with mean intrinsic rates of increase (r_m) in the range 0.35–0.41 aphids aphid^{– 1} day^{– 1}, but none performed well on both plant species. Each clone could, therefore, be described as affiliated to either V. faba or T. majus. All of the 13 T. majus-affiliated clones and 15 of the 16 V. faba-affiliated clones could not be maintained beyond two parthenogenetic generations on the contrary plant. These results confirm that the performance of A. fabae on T. majus and V. faba is negatively correlated. Exceptionally, one V. faba-affiliated clone (clone AED95/119) persisted indefinitely on T. majus, exhibiting a progressive improvement in performance across four parthenogenetic generations: larval mortality dropped from 80% to <20%, mean adult weight almost doubled from 0.28 to 0.53 mg, and mean number of embryos per adult aphid increased threefold from 8.6 to 24.4 embryos. The mean r_m of clone AED95/119 that had been reared on T. majus for more than 4 generations was 0.17 aphids aphid^{– 1} day^{– 1}, significantly lower than the value of 0.34 aphids aphid^{– 1} day^{– 1} on V. faba. It was also shown that the r_m on V. faba did not differ significantly between aphids of clone AED95/119 that had been derived from long-term cultures on V. faba and T. majus. It is concluded that the negative correlation between performance on V. faba and T. majus is not genetically fixed, but may diminish with exposure to T. majus. The implication is that this clone may have a capacity to utilise T. majus that is independent of its capacity to utilise V. faba, and is expressed only on sustained exposure to T. majus. It is suggested that, although the latent capacity to utilise T. majus is probably not exhibited widely under natural conditions, aphids possessing it may be at a selective advantage when more suitable host plants are temporarily unavailable.     

Phenotypic plasticity in host choice behavior in black bean aphid, Aphis fabae (Homoptera: Aphididae)

The study of phenotypic plasticity in host choice behavior is crucial to predict evolutionary patterns of insect–plant interactions. The presence of sufficient variation in plasticity may facilitate host race formation and sympatric speciation. In this study, 13 Aphis fabae Scopoli genotypes reared both on broad bean and nasturtium exhibited statistically significant genotypic variability in host selection behavior. Some genotypes displayed increase in preference and acceptance in a novel host plant through generations. There are also strong conditioning effects of nasturtium as nasturtium reared genotypes are more willing to choose nasturtium over broad bean while broad bean reared genotypes do not show differences in choosing between the two host plants. There are also positive relationships between fitness and host choice behavior particularly for nasturtium. Results of the study supported the hypothesis that phenotypic plasticity in host choice behavior may be one of the major determinants of the evolutionary trajectory of a parasitic species, such as aphids.     

Polymorphic microsatellites loci in the black Aphid,Aphis fabae Scopoli, 1763 (Hemiptera,Aphididae)

Aphis fabae is a widespread pest in Europe. This species includes four morphological cryptic subspecies which are mostly identified by their partially distinct secondary host range. To determine the extent of gene flow and isolation between these four taxa, we isolated and characterized eight microsatellite loci from A. fabae fabae and tested them on the three other subspecies. Polymorphism ranged from five to 35 alleles on the 138 individuals collected. When analysing each taxon separately, significant deviations from Hardy‐Weinberg (HW) equilibrum were observed. This could have different explanations, including the presence of null alleles, or the Wahlund effect or the mating system.     

Effect of black bean aphid, Aphis fabae, on transpiration, stomatal conductance and crude protein content of faba bean

This study was initiated to investigate effects of damage by 0, 5 and 10 aphids/plant on the physiology of faba bean plants throughout different feeding periods and at two plant development stages. Immediately following removal of Aphis fabae, measurements showed 84–229% increase in transpiration rate. These changes were proportional to the number of aphids and infestation duration. Injury by A. fabae caused the stomatal conductance to be much higher in the leaves of infested plants. Leaf stomatal conductance of the infested plants increased significantly by 51–224% depending on initial aphid densities and feeding intervals. This increase was proportional to the infestation level for each date. Length of infestation period and plant growth stage seemed to have no clear effect on stomatal apertures. Aphid feeding caused a damage of about 7–33% of crude protein levels in the leaf tissue. This reduction increased with increasing infestation levels and time, except for 28‐day‐old plants on 28 days. The physiological effects of aphid feeding on water vapour and chemical composition of damaged leaves are particularly serious when the population is high.     

Counter-intuitive developmental plasticity induced by host quality

Adaptation to different hosts plays a central role in the evolution of specialization and speciation in phytophagous insects and parasites, and our ability to experimentally rank hosts by their quality is critical to research to understand these processes. Here we provide a counter-intuitive example in which growth is faster on poor quality hosts. The leaf beetles Oreina elongata and Oreina cacaliae share their host plant with the rust Uromyces cacaliae. Larvae reared on infected Adenostyles alliariae show reduced growth rate, reduced maximum weight and longer development time. However, they normally respond adaptively to the rust's mid-season arrival. When switched during development from healthy to infected leaves, larvae accelerate growth and reduce development time, but pupate at lower body weight. In this novel plant-insect-fungus interaction, infection forms the cue to trade off life-history traits in order to complete development within the brief alpine summer. It represents a novel mode of developmental plasticity, which is likely to be found in other host-parasite systems whenever host quality deteriorates due to multiple infection or ageing. This phenotypic plasticity would modify competition after co-infection and the mutual selection imposed by hosts and parasites, and creates a paradoxical negative correlation between growth rate and environmental quality.