Summary

1
Feeding preferences of nectarivorous ants for sugars and amino acids were studied in an Australian tropical rain forest using artificial nectar solutions. Fifty-one ant species were recorded feeding on the solutions.

2
Preferences among carbohydrates were principally concordant between ant species. In paired tests, sucrose was often preferred over fructose, glucose, maltose, melezitose, raffinose and xylose, respectively. Attractiveness of sucrose baits increased with concentration.

3
Many ant species preferred sugar solutions containing mixtures of amino acids over pure sugar solutions. However, preferences among seven pairs of single amino acids in sugar solutions differed substantially between ant species, including several cases where different ant species displayed significant opposite choices.

4
Ant selectivity between solutions was significantly reduced when different ant species co-occurred on the same bait. Preferences for single amino acids were also reduced when colonies fed extensively on the same compound prior to the experiment for 2 days.

5
Our results indicate that both interspecific variability in gustatory preferences and conditional effects such as competition and colony requirements affect resource selection in multispecies communities. These processes may be crucial in niche partitioning of species-rich nectarivore assemblages.

Further studies of ant-aphid interaction

Preferences for sugars and amino acids and their conditionality in a diverse nectar-feeding ant community

Publisher Summary Ants, plants, and homoptera interact in a wide variety of ways. Each participant in these interactions can affect the other two either directly or indirectly by affecting the third participant. The outcome of a particular interaction may also be affected by other species interacting with one or more of the participants and by abiotic factors such as fire, soil, and climate. The quantitative significance and the degree of specificity, obligacy, and specialization for each participant vary widely between interactions. There are many interactions between ants and plants that do not involve Homoptera at all, the direct twofold ant-plant components of ant-plant-homopteran interactions are generally negligible unless the plants also possess extrafloral nectaries or ant-attractant food bodies. In direct interactions between Homoptera and plants, the homopterans gain food, habitat, and sometimes allelochemicals from the plants, while the plants suffer tissue damage, loss of metabolites, and most importantly, increased incidence of infection by homopteran-transmitted microbial pathogens: plants therefore employ a range of physical and chemical defenses against Homoptera. The direct interactions between ants and Homoptera fall into two main classes: either the ants prey on the homopterans, or they tend and/or defend them against predators and parasites. Some ants may prey on some species of homopteran and tend others. In either case, the homopterans provide food for the ants, either as prey or by exuding honeydew, which the ants collect. The indirect components of the overall threefold interaction may be as or more significant to the participants than the direct twofold components.

Ant-Plant-Homopteran Interactions

Do oligosaccharides reduce the suitability of honeydew for predators and parasitoids? A further facet to the function of insect-synthesized honeydew sugars

. 1. Subterranean aphids in old pasture were found to show extremely clumped distributions with about 3000 aphids (omitting first instars) per ant nest throughout the year.



2. They were generally distributed in and away from the nest mounds, but within the ant's foraging territories.



3. At summer temperatures, more than 3000 first instars are lost from the aphid population per ant nest per day and it is concluded that these are eaten by the ants in addition to some older aphids and the honeydew produced.



4. The aphids may therefore provide enough food to maintain the ants with very little extra needed in the form of other prey.

The numbers and distribution of subterranean aphids and their exploitation by the ant Lasius flavus (Fabr.)

Melezitose is a trisaccharide found only in the honeydew of homopterous insects (and in honey produced from honeydew). It is not present in the phloem sap and is apparently specifically synthesized in the homopteran gut, but the reasons for its production are unknown. Owen and Wiegert (1976) suggested that its significance lay in a mutualistic interaction in which melezitose, falling upon the ground in the immediate vicinity of the insect's host plant, stimulates non-symbiotic nitrogen fixation in the soil to the benefit of the plant (and, ultimately, the insect). Petelle (1980) disputed this hypothesis on the basis of his findings that fructose, common both in phloem sap and in honeydew, stimulates nitrogen fixation at a much higher rate than does melezitose (although he also raised the possibility that mixtures of sugars, perhaps including melezitose, may be more effective than any single sugar). Petelle suggested that the significance of melezitose may lie in decreasing the rate of absorption of sugars through the homopteran gut wall. I propose another (not necessarily exclusive) hypothesis concerning the selective significance of melezitose synthesis. The work of Duckett (1974) demonstrated that the ant Lasius niger, which feeds extensively on honeydew, shows a highly significant preference for melezitose and, to a lesser degree, glucosucrose (another aphid-synthesized trisaccharide) over a wide variety of monoand disaccharides. Sucrose was preferred over all sugars tested with the exception of melezitose and glucosucrose. Because it has been shown in numerous studies that honeydew-collecting ants provide a significant benefit to homopterans (largely through protection from predators and parasites), it is reasonable to hypothesize that the synthesis of these trisaccharides in the guts of homopterous insects may have evolved in the context of attracting attendant ants.

Further studies of ant-aphid interaction

Citations

Preferences for sugars and amino acids and their conditionality in a diverse nectar-feeding ant community

Ant-Plant-Homopteran Interactions

Do oligosaccharides reduce the suitability of honeydew for predators and parasitoids? A further facet to the function of insect-synthesized honeydew sugars

The numbers and distribution of subterranean aphids and their exploitation by the ant Lasius flavus (Fabr.)

Melezitose, Aphids and Ants

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