Sycamore Aphid Research Articles

The genome sequence of the Common Sycamore Aphid, Drepanosiphum platanoidis (Schrank, 1801).

We present a genome assembly from an individual female Drepanosiphum platanoidis (the Common Sycamore Aphid; Arthropoda; Insecta; Hemiptera; Aphididae). The genome sequence is 284.5 megabases in span. Most of the assembly is scaffolded into 15 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 19.45 kilobases in length. Gene annotation of this assembly on Ensembl identified 13,286 protein coding genes.

Phenological responses in a sycamore-aphid-parasitoid system and consequences for aphid population dynamics: A 20year case study.

Species interactions have a spatiotemporal component driven by environmental cues, which if altered by climate change can drive shifts in community dynamics. There is insufficient understanding of the precise time windows during which inter-annual variation in weather drives phenological shifts and the consequences for mismatches between interacting species and resultant population dynamics-particularly for insects. We use a 20year study on a tri-trophic system: sycamore Acer pseudoplatanus, two associated aphid species Drepanosiphum platanoidis and Periphyllus testudinaceus and their hymenopteran parasitoids. Using a sliding window approach, we assess climatic drivers of phenology in all three trophic levels. We quantify the magnitude of resultant trophic mismatches between aphids and their plant hosts and parasitoids, and then model the impacts of these mismatches, direct weather effects and density dependence on local-scale aphid population dynamics. Warmer temperatures in mid-March to late-April were associated with advanced sycamore budburst, parasitoid attack and (marginally) D. platanoidis emergence. The precise time window during which spring weather advances phenology varies considerably across each species. Crucially, warmer temperatures in late winter delayed the emergence of both aphid species. Seasonal variation in warming rates thus generates marked shifts in the relative timing of spring events across trophic levels and mismatches in the phenology of interacting species. Despite this, we found no evidence that aphid population growth rates were adversely impacted by the magnitude of mismatch with their host plants or parasitoids, or direct impacts of temperature and precipitation. Strong density dependence effects occurred in both aphid species and probably buffered populations, through density-dependent compensation, from adverse impacts of the marked inter-annual climatic variation that occurred during the study period. These findings explain the resilience of aphid populations to climate change and uncover a key mechanism, warmer winter temperatures delaying insect phenology, by which climate change drives asynchronous shifts between interacting species.

Exploring Pattern Analysis with Sycamore Aphids

Many students enjoy biology as a qualitative science but struggle with its quantitative aspects. Yet the detection of patterns and testing hypotheses about their causes is a central aim of biological inquiry. That is the goal of the laboratory analysis described in this article. This exercise involves the students right away in collecting data from living organisms, calculation of some basic statistics, and the formal test of a hypothesis. This fall will be the 10th year I've used this exercise at the college freshman level, but I believe this lab could be used on almost any campus and adapted to any class size. The equipment requirements are minimal and the protocol is simple to follow. The real value lies in empowering students to work with their own data and to see that patterns in biology can be approached quantitatively (requiring only algebra), all critical tools for inquiry-based learning. The aphid of study, likely to be found on practically any sycamore tree in North America, is Drepanosiphum platanoides (Schrank), a relatively large pale or dark green or reddish yellow species with the wing veins slightly dusky (Essig, 1958, p.234). A few other aphids may be found on sycamore leaves (Drepanaphis spp., Periphyllus spp.) and may be used instead. The point is to illustrate how individuals in a population may be distributed and to test a null hypothesis of randomness that, if rejected, suggests a host of possible biotic or abiotic causes. To activate student interest in the project, solicit their own ideas for causes, after a brief discussion of aphid biology. What follows is the handout I give to the students on the first day; they have a week to complete the lab. After the handout discussion is a section for the instructor on implementation of the techniques used and some possible extensions. Purpose In this lab you will practice important aspects of biological inquiry: observation, data collection, data analysis, and scientific writing. You will work in pairs and do the lab on your own time. The objectives of this laboratory are: 1. to become familiar with how to calculate a sample mean and variance 2. to become familiar with population sampling and data analysis 3. to collect your own data from live organisms and puzzle over a real biological pattern. Ecology has been defined as the study of the distribution and abundance of organisms (Andrewartha & Burch, 1954). This is because patterns we see may reflect and reveal unseen ecological relationships. Thus the analysis of spatial pattern can lead to a better understanding of the biotic and abiotic forces that affect organisms. Our null hypothesis may be that individuals of a species are distributed at random, implying no particular interactions with each other or the environment. For example, when cottonwood seeds drift down onto a newly-formed Platte River sandbar, they may land randomly (that is, any chosen square meter of sandbar has an equal probability of receiving a seed). Later, the emerging seedlings may not show a random pattern. Pattern analysis might reveal a population of organisms to be aggregated (clumped) or evenly-distributed (regular). Both terms refer to a deviation from randomness that can be quantified. One must use care in selecting a technique for sampling organisms that will not bias one's results. Also, different techniques and scales will have different powers of detection. For example, consider that a newspaper photo represents an image at a distance but only dots of various sizes on very close inspection. What we choose to measure, count, etc. has a great influence on the pattern we detect. In some cases, sampling units (SUs) present themselves naturally (i.e., leaves on a plant). In other cases we may choose the size, shape, and location of the SUs. Over a century ago, two University of Nebraska graduate students (Roscoe Pound & Frederick Clements, 1898) championed the use of the quadrat in plant community analysis. …

Exploring Pattern Analysis with Sycamore Aphids

Exploring Pattern Analysis with Sycamore Aphids

Thermal requirements for development and resource partitioning in aphidophagous guilds

The duration of the increase, peak and decline in abundance of the immature stages of sycamore and cereal aphids each year is ephemeral. These temporary resources are exploited by a sequence of aphidophagous insect predators. The temporal sequence in the appearance of the immature stages of coccinellids and syrphids in the sycamore and cereal aphid systems is defined. In spring in the sycamore aphid system and early summer in the cereal aphid system the immature stages of syrphids consistently appeared before those of coccinellids. In the case of the sycamore aphid the autumnal peak in abundance was on average larger than the spring peak, and although attacked by more syrphids, it was not exploited by coccinellids. These temporal patterns in the attack sequence are associated with a difference in the lower developmental thresholds (LDT) of these two groups of predators. The LDT of syrphids (4°C) enables them to be active at lower temperatures and to develop faster between 10° and 27°C than coccinellids, whose LDT is 10°C. As a consequence, early in the year, when temperatures are low but increasing, syrphids appear before and complete their development more quickly than coccinellids, and in the latter half of the year, when temperatures are generally lower and decreasing, only syrphids are likely to be able to complete their development before the aphids disappear. Thus, the niche shift between syrphids and coccinellids is possibly more a consequence of a phylogenetic constraint than a response to competition and or intraguild predation. The relevance of these findings for the ecology of intraguild predation is discussed.

Plant quality, progeny sequence, and the sex ratio of the sycamore aphid, Drepanosiphum platanoidis

AbstractThe reproductive sequence of sexuparae of the sycamore aphid, Drepanosiphum platanoidis (Schrank) (Homoptera: Callaphididae), observed in the field and glasshouse was examined to elucidate the relationship between host nutrition and sex ratio. The observations were made in autumn when the transition from parthenogenetic to sexual reproduction occurred. A switch occurred in the reproductive sequence of the sexuparae. The production of apterous sexual females (oviparae) was followed by alate males, after a brief reproductive pause lasting 2.5–4.0 days. The switchover period was relatively constant across treatments and years. On poor hosts, the first appearance of the oviparae was a day later, whereas the first appearance of males was a day earlier than those on good nutrition. The primary sex ratio (i.e., proportion of males) was numerically female biased. Under semi‐natural field conditions it was 0.22, but altered to 0.18 and 0.29, respectively, under poor and good host nutrition in the glasshouse. In both the field and glasshouse, nymphal development time was significantly longer in oviparae (ca. 22 days) than in males (ca. 18 days). The time from birth to adult was significantly shorter on good hosts (oviparae: 20 days; males: 17 days) than on poor hosts (oviparae: 23 days; males: 19 days). The proportion of nymphs surviving to the adult moult was not dependent on sex in both the field and glasshouse, but the chances of survival were slightly enhanced under good (88%) compared with poor (82%) host nutritive status. In conclusion, the order of morph production and differences in maturation times ensured the synchronisation of the sexes so that mating and oviposition opportunities were optimised before the onset of winter. The female‐bias in the sex ratio maximised the fitness of sexuparae, and reduced the chances of local mate competition by economising in members of the competing sex.

Overwintering of the sycamore aphid, Drepanosiphum platanoidis

AbstractSpatial and temporal aspects of overwintering in the holocyclic sycamore aphid Drepanosiphum platanoidis (Schrank) (Homoptera: Callaphididae) were investigated. Eggs of D. platanoidis were principally laid on trunks and branches of Acer pseudoplatanus L., at considerable distances from the buds. Trunks with rough bark, followed by branches with moderate roughness supported more overwintering eggs than the relatively exposed smooth surfaces of twigs and terminal buds. Eggs were aggregated on rough bark. Aspect had no effect on the number of eggs laid. Experimental manipulations varying ovipara densities showed intra‐specific competition among oviparae for optimal oviposition sites. Overwintering egg mortality was a function of time, with the greatest mortality rate occurring in late winter. Egg mortality varied from 80.4% to 76.9% on trunks and 83.0% to 65.9% on branches in 1996 and 1997.

Reproductive diapause and the bacterial symbiosis in the sycamore aphid Drepanosiphum platanoidis

Summary1. Parthenogenetic adults of the sycamore aphid Drepanosiphum platanoidis exhibited reproductive diapause for 4–6 weeks in the summer.2. The diapausing aphids had small gonads (accounting for just 13% of the total aphid protein content) bearing small (< 0.5 mm long) and developmentally immature embryos. There was no evidence of embryo resorption.3. The diapausing aphids had significantly depressed essential amino acid content and elevated glutamine content, relative to reproductively active D. platanoidis.4. The reproductive characteristics and amino acid titres of the diapausing aphids resemble those of aphids lacking functional symbiotic bacteria. Uncoupling of maternal and embryo growth and suppression of bacterial function are proposed as key elements in the diapause of D. platanoidis.

Herbivory, phenology, morphology and the expression of sex in trees: who is in the driver's seat?

Herbivores, whether sucking such as aphids or chewers such as lepidopterans, impose an important drain on plant resources (Dixon 1971, Leather 1988). Plants have evolved a number of responses to minimise the effects of such parasites, although the herbivores have fought back in a variety of ingenious ways. For example, it is well known that individual trees within a species show significant variation in budburst date (Jones 1959, Leather 1996a) and it is traditionally assumed that early flushing trees suffer higher rates of herbivory from leaf chewing insects than those that flush later (Varley and Gradwell 1968). There is, however, conflicting evidence to support this assumption (Crawley and Akhteruzzaman 1988, Watt and MacFarlane 1991, Hunter 1992). These and other studies (e.g. Watt 1987, Hunter 1990) although recognizing the importance of synchrony between herbivore and host plant have not considered either within-tree variability or the fact that plant phenology may be altered by, or in response to, insect attack. Although sycamore and other trees show consistent variability in herbivore loads from year to year, i.e. a good tree for herbivores one year is a good tree for herbivores the following year (Leather 1986, Crawley and Akhteruzzaman 1988), the intra-tree distribution of these herbivores is not uniform (Leather 1996b). For example, in sycamore, Acer pseudoplatanus, some branches support much higher populations of the sycamore aphid, Drepanosiphum platanoidis, than others. Field observations suggest that those branches that supported high aphid populations in the preceding year, have an accelerated budburst compared to those branches that had few aphids on them the preceding year (Leather 1996b) and as a consequence escape the aphids hatching from the overwintering eggs. The tree thus ensures, that although aphid numbers may be high on the tree as a whole, not all branches suffer equally damaging levels of aphids. Losses due to aphid feeding, which can exceed 15% reductions in volume increment (Dixon 1971) are thus minimised. Is this a widespread phenomenon or does it apply only to phloem feeding herbivores and/or sycamores in particular? The important and puzzling question is how does the tree engineer accelerated budburst in those particular branches?

Positive Effects of Endophyte Infection on Sycamore Aphids

In this study, I examined the effects of infection of leaves by an endophytic fungus (Rhytisma acerinum) on the populations and individual performance of two species of aphid (Drepanosiphum platanoidis and Periphyllus acericola), living on Acer pseudoplatanus. Populations of aphids were followed through one season and numbers compared on infected and uninfected leaves. Both species of aphid aestivated during the summer. D. platanoidis aestivated as non-reproducing adults, while P. acericola did so as nymphs. Fungal abundance, as measured by stromata number, was very low compared with previous studies in the UK. Nevertheless, in contrast to other studies of arboreal endophytes and insects, fungal presence affected aphid numbers in a positive manner, and in late summer, aphid numbers were higher on infected leaves. In D. platanoidis, higher aphid numbers resulted from an increased nymphal production by adults, but in P. acericola there was an accumulation of dispersing nymphs on infected leaves. Field rearing experiments with both aphid species demonstrated an increase in adult weight and potential fecundity in two autumnal generations. The infected leaves had higher soluble and total nitrogen and total carbon contents and the increases in aphid performance are attributed to the increase in soluble nitrogen. The numbers of sycamore aphids in one year can influence the dynamics of the population in the following season. It is suggested that increased numbers of aphids, resulting from endophytic infection, may therefore alter the between- as well as the within-year population dynamics of the species. In addition, the data appear to provide support for the hypothesis that endophyte presence may determine seasonal patterns of herbivory. The hypothesis may be interpreted with an endophyte-induced change in food quality, but other possibilities are discussed.

The role of food quality and competition in shaping the seasonal cycle in the reproductive activity of the sycamore aphid.

The hypothesis that seasonal changes in sycamore aphid,Drepanosiphum platanoidis (Schr.), recruitment are determined by changes in food quality and aphid population density was tested. There was no clear association between the reproductive activity of the sycamore aphid and the seasonal changes in specific amino acids or groups of amino acids in extracts of sycamore,Acer pseudoplatanus L., leaves. Seasonal changes in reproductive activity tracked the changes in total amino acids of the leaf tissue of the host, but with a short time delay. High numbers of adult aphids appeared to depress reproductive activity. A regression analysis of the results revealed that total amino acids the previous week and current numbers of adult aphids significantly affected sycamore aphid reproductive activity. The results of this analysis support the above hypothesis, that the marked seasonal changes in the total quantity of amino acids in sycamore leaves and intraspecific competition for this resource, through its effect on adult weight, shape the seasonal cycle in the reproductive activity of the sycamore aphid.

The nutritional quality of phloem sap utilized by natural aphid populations

Abstract. The amino acid content of phloem exudates from leaves and of aphid honeydew were adopted as indices of the nutritional quality of phloem sap for aphids. Four plant species and associated leaf‐dwelling aphids were investigated: the sycamore Acer pseudoplanatus and sycamore aphid Drepanosiphum platanoides; Prunus domestica (victoria plum) and the mealy plum aphid Hyalopterus pruni; and the spindle tree Euonymus europaeus and broad‐bean Vicia faba, both hosts of the black bean aphid Aphis fabae. The concentration of amino acids in the phloem exudates varied with: (a) plant species (greater in the herb Vicia than in the tree species), (b) season (greater in the autumn than summer for Acer and Euonymus), and (c) position (greater in flush leaves than mature leaves of Prunus). For Acer and Prunus and their aphids, the concentration of amino acids in phloem exudates was significantly correlated with the amino acid content of the aphid honeydew. The amino acids in all exudates and honeydew were dominated by non‐essential amino acids (glutamic acid, glutamine, asparagine or serine, varying with season and between plant species). The sole major discrepancy between the amino acid profiles of exudates and honeydew was the production of asparagine‐rich honeydew by aphids feeding on leaves, whose exudates were dominated by glutamic acid; this applied to both H.pruni on mature Prunus leaves and Drepanosiphum platanoides on summer‐leaves of Acer. It is suggested that EDTA‐exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary plant hosts.

An evolutionary interpretation of the “motivation to oviposit”

AbstractThe ovipositional behavior of parasitoids and other insects is often described by phrases such as “motivation to oviposit” or “ovipositional drive”. This paper shows how an evolutionary (i.e. functional) interpretation can be given to such phrases. A detailed model for the parasitisation of Sycamore aphids by M. pseudoplatani is developed, using experiments by Collins and Dixon (1986). Two models are developed: i) one in which egg complement is the only state variable and ii) one in which egg complement and information concerning host densities are state variables. Comparisons of the behaviour of simulated parasitoids, using the decisions associated with the models, and the experiments suggest that both egg complement and information are important for the parasitoid's decision making. Accepting previously parasitized hosts may be optimal, and not simply an error in parasitoid perception. A number of other detailed predictions are made, such as the relative fitness of first and second eggs in superparasitized hosts and the nature of the memory of the parasitoid.

Chemical control of sycamore aphid, Drepanosiphum platanoidis (Schr.), with organophosphorous and soap insecticides

The three organophosphorous insecticides dimethoate, fenitrothion and malathion were more toxic than any of the soaps to the sycamore aphid, D. platanoidis, but their high mammalian toxicity makes them unsuitable for use in enclosed and public areas. Of the soaps, potassium (K) caprate, K oleate, K linoleate and Safer's insecticidal soap (SIS) were more toxic than K caproate, K caprylate, K laurate and K myristate. Of three aphid morphs present during the summer and autumn, the viviparae were the most susceptible to SIS, with the males less and the oviparae least susceptible. Alate recolonization of leaves cleared of aphids by spraying with selected soaps or organophosphorous formulations was delayed by up to 1 week after treatment with K caprylate, K linoleate, and K oleate. These three compounds were actively avoided by male D. platanoidis in laboratory choice-chamber tests; malathion and dimethoate, which also delayed leaf recolonization to some extent, were similarly avoided. Viviparae actively avoided only leaf surfaces treated with K caprylate and K linoleate. It was concluded that all of the four most toxic soap formulations merited consideration for aphid control in enclosed or public situations, SIS having the minor disadvantage that it would not delay recolonization by aphids from untreated areas. This would be particularly important for male recolonization where possible decreases in numbers of oviparae fertilized in the autumn could decrease egg production and hence aphid populations in subsequent springs.

Sycamore Aphid Numbers and Population Density. III. The Role of Aphid-Induced Changes in Plant Quality

Sycamore Aphid Numbers and Population Density. III. The Role of Aphid-Induced Changes in Plant Quality

Sycamore Aphid Numbers and Population Density: II. Some Processes

Comparaison de la variation saisonniere de la densite de population de Drepanosiphum platanoidis au laboratoire et sur le terrain. La croissance et la vitesse de developpement des aphides prises individuellement sont influencees par la valeur nutritive de leur plante-hote et par l'entassement; ce dernier effet est precise. Role des divers processus etudies sur la regulation du nombre d'aphides sur sycomore

Sycamore Aphid Numbers and Population Density: I. Some Patterns

Etude sur 9 ans menee dans diverses regions de Grande-Bretagne. Dynamique saisonniere de la population de Drepanosiphum platanoidis et regulation de celle-ci en rapport avec la densite. Productivite de la population et synchronisation; recrutement; certaines associations entre l'aphide et son hote sont notees

Maternal Experience of Crowding and Duration of Aestivation in the Sycamore Aphid

When reared in crowded conditions, second generation individuals of the sycamore aphid were smaller and had a longer aestivation than when reared in isolation. The duration of the aestivation was further lengthened if their mothers were reared in crowds, but the influence of maternal crowding was not mediated by a plant factor since the two generations were reared on different sets of plants. The importance of maternal crowding and aestivation in the population dynamics of the sycamore aphid is discussed.

The effect of temperature on the growth and reproduction of two closely related aphid species on sycamore

Abstract. 1. Egg hatch in the two species of sycamore aphid was temporally separated: the median time to hatch was 30 days later in Drepanosiphum acerinum than in D.platanoidis.2. D.platanoidis was larger at egg hatch than D.acerinum. Progeny of D.platanoidis adults were also larger than those of D.acerinum.3. D.platanoidis was the larger of the two species as an adult, as a consequence of its greater birth weight.4. Over a range of temperatures, development rates in the two species were the same, while the growth rate in D.acerinum was significantly higher at high temperatures.5. The reproductive rate of the two species was significantly different at 6d̀C and 20d̀C.

Factors determining the distribution of sycamore aphids on sycamore leaves during summer

Abstract In summer the sycamore aphid's responses to gravity, light direction and intensity and unidentified features of a leaf's surface result in the aphid settling and feeding on the undersurface of leaves. At this time the petioles are a poor source of food and are not colonized. Removal of leaf laminae results in premature abscission of the petioles. Prior to abscission the petioles become senescent and a richer food source than the laminae of mature leaves, and are colonized by aphids.