Aphid Interactions Research Articles

Should aphids attract or repel ants? Effect of rival aphids and extrafloral nectaries on ant–aphid interactions

AbstractAmong plants and herbivores, two types of conflicts occur in relation to mutualism with ants: one is competition for ant mutualism among myrmecophilous herbivores and plants, and the other is the conflict whether to attract or repel ants between myrmecophiles and nonmyrmecophiles that are damaged by ants. We investigated the extent to which two species of aphids (Megoura crassicauda and Aphis craccivora) and extrafloral nectaries on their host plant (Vicia faba var. minor) interact with one another for their relationships with ants. We designed an experiment where ants can choose to visit seedlings colonized by (1) M. crassicauda, (2) A. cracivora, (3) both aphid species, or (4) neither aphid species. Ants preferred A. craccivora to extrafloral nectaries and avoided tending M. crassicauda. We also analyzed the population growth of each aphid when it coexists with (1) ants, (2) the other aphid species, (3) ants and the other aphid species, or (4) neither of them. Under ant‐free conditions, we detected an exploitative competition between the two aphid species. The ants had no significant effect on the population of A. craccivora, whereas they had negative effects on the population growth of M. crassicauda by attacking some individuals. When both aphids coexisted, M. crassicauda suffered ant attack more intensely because A. craccivora attracted more ants than extrafloral nectaries despite ant‐repelling by M. crassicauda. On the other hand, the ants benefited A. craccivora by eliminating its competitor. To avoid ant attack, aphids may have been selected either to be more attractive to ants than other sympatric sugar sources or to repel the ants attracted to them. We hypothesize that competition among sympatric sugar sources including rival aphids and extrafloral nectaries is a factor restricting aphids to be myrmecophilous.

Responses of spruce seedlings ( Picea abies) to exhaust gas under laboratory conditions— I plant–insect interactions

The effects of motor vehicle exhaust gas on Norway spruce seedlings ( Picea abies (L.) Karst) and plant–insect interaction of spruce shoot aphid ( Cinara pilicornis Hartig) was studied. The exhaust gas concentrations in the fumigation chambers were monitored and controlled by measuring the concentration of nitrogen oxides (NO x) with a computer aided feedback system. The concentrations of major exhaust gas components (black carbon [BC], fine particles, VOCs and carbonyl compounds) in the chamber air were also measured. Reponses of Norway spruce seedlings to a 2 and 3-week exhaust gas exposure and subsequent performance of spruce shoot aphid were studied using realistic exposure regimes; 50, 100 and 200 ppb NO x. The feedback control system based on NO x concentrations proved an adequate and practical means for controlling the concentration of exhaust gases and studying plant responses in controlled environment chambers. The exhaust exposure resulted in increased concentrations of proline, glutamine, threonine, aspartic acid, glycine and phenylalanine and decreased concentration of arginine, serine, alanine and glycine in young needles. No changes in soluble N concentrations were observed. The results are interpreted as a stress response rather than use of NO x as a nitrogen source. No changes in total phenolics and only transient changes in some individual terpene concentrations were detected. The exhaust gas exposure stressed the exposed seedlings, but had no significant effect on N metabolism or the production of defence chemicals. Aphid performance was not significantly affected. Soluble N, secondary metabolism and aphid performance were not sensitive to exhaust gas exposure during shoot elongation in Norway spruce.

Erratum

The interaction of green spruce aphid and fertilizer applications on the growth of Sitka spruce by R. C. Thomas and H. G. Miller, Forestry 67, 329–342, 1994.

The Interaction of Green Spruce Aphid and Fertilizer Applications on the Growth of Sitka Spruce

The Interaction of Green Spruce Aphid and Fertilizer Applications on the Growth of Sitka Spruce

Habitat suitability and herbivore dynamics

We derive a dynamic model for a plant herbivore system describing the interaction of a gall-forming aphid and a single plant. We compare the behavior of our model with experimental observations obtained from an aphid plant system studied by Whitham (Whitham, T.G. 1978, Habitat selection of Pemphigus aphids in response to resource limitation and competition. Ecology 59, 1164–1176). A simple parameter estimation shows a close correlation between the predicted and observed results.

Survival of Yellow Pecan Aphids and Black Pecan Aphids (Homoptera: Aphididae) at Different Temperature Regimes

Constant high temperature regime (30, 34, 37, and 40°C) for 1–5 h decreased mean survival of nymphal and adult stages of Monelliopsis pecanis Bissell and Melanocallis caryaefoliae (Davis) with increasing temperature and time of exposure. Constant low-temperature regime (0, 6, 12, and 15°C) decreased aphid survival with decreasing temperatures and increasing time of exposure. A temperature by aphid interaction was observed, with the greatest mortality being at the extreme high (37 and 40°C) and low (0 and 6°C) temperatures. Aphid stages showed differences in tolerance to all temperature levels. Third and fourth ins tars and adults of both species withstood a wide range of temperatures better than first and second instars under either regime. M. pecanis tolerated low temperatures better than M. caryaefoliae , but at high temperatures, M. caryaefoliae was more tolerant. Air temperature fluctuations within a pecan tree were measured during July with temperature probes. Air temperature was slightly higher at the edge of the tree crown than near the trunk, otherwise temperatures were very uniform within the tree crown for a given hour of the day.

Effect of Selected Pests and Multiple Pest Complexes on Alfalfa Productivity and Stand Persistence

The effects of Egyptian alfalfa weevil, Hypera brunneipennis (Boheman); the aphids, Acyrthosiphon pisum (Harris) and A. kondoi Shinji; and larval Lepidoptera, alfalfa caterpillar, Colias eurytheme Boisduval , beet armyworm, Spodoptera exigua (Hubner) , and western yellowstriped armyworm S. praefica (Grote), individually and in combination, on alfalfa .(Medicago sativa L. cv. Moapa 69) yield and stand persistence were evaluated in a field study from 1980 to 1983. H. brunneipennis had the greatest effect on yield with the major reduction occurring in the first cutting. Injury caused by H. brunneipennis feeding before the first harvest also affected yields for an additional 2-3 cuttings. Yield loss caused by aphids was generally confined to the specific harvest in which aphid density reached damaging levels and did not carry over into succeeding cuttings. Repeated subeconomic aphid populations over several cuttings, however, resulted in reduced yields late in the season. Lepidoptera populations encountered in this study were relatively low and produced effects that resulted in yield increases. Significant aphid and weevil interactions were obtained in 1981 and 1982 and occurred in harvests made 30-60 d after peak insect populations, indicating a significant lag between actual damage and yield loss. None of the pests or pest complexes had a long-term effect on stand density. Whereas some plant death can possibly be attributed to insect herbivores during the seedling year, the pests encountered in this study had an insignificant role in overall plant mortality.

Parameter estimation techniques for interaction and redistribution models: a predator-prey example.

The use of parameter estimation techniques for partial differential equations is illustrated using a predatorprey model. Whereas ecologists have often estimated parameters in models, they have not previously been able to do so for models that describe interactions in heterogeneous environments. The techniques we describe for partial differential equations will be generally useful for models of interacting species in spatially complex environments and for models that include the movement of organisms. We demonstrate our methods using field data from a ladybird beetle (Coccinella septempunctata) and aphid (Uroleucon nigrotuberculatum) interaction. Our parameter estimation algorithms can be employed to identify models that explain better than 80% of the observed variance in aphid and ladybird densities. Such parameter estimation techniques can bridge the gap between detail-rich experimental studies and abstract mathematical models. By relating the particular bestfit models identified from our experimental data to other information on Coccinella behavior, we conclude that a term describing local taxis of ladybirds towards prey (aphids in this case) is needed in the model.