Natural enemy spectrum ofAphis spiraephaga (Hom.: Aphididae), an exotic immigrant aphid in Central Europe

Aphis spiraephaga Müller, an aphid of Central Asian origin, dispersed west-wards and reached Central Europe probably before 1956. It now occurs in most European countries. Research undertaken in the Czech Republic mainly in 1991–1993, revealed that the aphid is attacked by a variety of natural enemies, including both parasitoids (Aphelinidae, Aphidiidae) and predators (Anthocoridae, Chrysopidae, Hemerobiidae, Cantharidae, Coccinellidae, Chamaemyidae, Itonididae, Syrphidae). All the natural enemies were identified to species. Attendance by ants (Lasius sp.) was common.A. spiraephaga was also successfully utilised as a new alternate host of two newly introduced parasitoid biocontrol agents (Aphidius colemani Viereck,Lysiphlebus testaceipes (Cresson).     

PHYLOGENETIC PLACEMENT OF AN UNUSUAL CORAL MUSHROOM CHALLENGES THE CLASSIC HYPOTHESIS OF STRICT COEVOLUTION IN THE APTEROSTIGMA PILOSUM GROUP ANT–FUNGUS MUTUALISM

The ∼50 million-year-old fungus-farming ant mutualism is a classic example of coevolution , involving ants that subsist on asexual, fungal biomass, in turn propagating the fungus clonally through nest-to-nest transmission. Most mutualistic ants cultivate two closely related groups of gilled mushrooms, whereas one small group of ants in the genus Apterostigma cultivates a distantly related lineage comprised of the G2 and G4 groups. The G2 and G4 fungi were previously shown to form a monophyletic group sister to the thread-like coral mushroom family Pterulaceae. Here, we identify an enigmatic coral mushroom that produces both fertile and sterile fruiting structures as the closest free-living relative of the G4 fungi, challenging the monophyly of the Apterostigma -cultivated fungi for the first time. Both nonparametric bootstrap and Bayesian posterior probability support the node leading to the G4 cultivars and a free-living Pterula mushroom. These data suggest three scenarios that contradict the hypothesis of strict coevolution: (1) multiple domestications, (2) escape from domestication, (3) selection of single cultivar lineages from an ancestral mixed-fungus garden. These results illustrate how incomplete phylogenies for coevolved symbionts impede our understanding of the patterns and processes of coevolution.     

Changes in food selection by workers of the pharaoh''s ant, Monomorium pharaonis

The results from simple choice test experiments with laboratory and field colonies of pharaoh's ants have revealed two behavioural traits that influence the way in which foraging worker ants respond to foods. Initially, worker ants from laboratory colonies showed a distinct preference for certain foods (e.g. honey and peanut butter). However, when given only these 'preferred' foods continuously for several weeks, workers showed a marked preference for other foods when offered a choice. This 'satiation' response occurred even though the initial diet was originally highly attractive to foraging workers. In addition, workers show a marked tendency to alternate between carbohydrate foods and protein foods. Thus, workers from colonies fed predominantly on proteins, subsequently showed a marked preference for carbohydrates, and vice versa. The 'satiation' and 'alternation' responses to foods ensure that colonies receive a diet that is both varied and balanced. In addition, these aspects of feeding behaviour have important consequences for the use of food-based baits in control measures against Monomorium pharaonis (L.).     

Ant–Acacia interaction: Chemical or physical defense?

Two different ant–Acacia ecosystems at two different sites were investigated for comparing their lifestyles. One ecosystem is at St. Katherine's Protectorate and the other at Ismailia Province, Egypt. The defense mechanisms that each Acacia tree use against browsers were investigated. Seasonal and daily abundances of ants and other herbivores on two Acacia trees were studied. The study indicated different defense mechanisms used by these two Acacia species: Acacia use both physical and chemical defense mechanisms. The efficiency of both mechanisms in defending Acacia against herbivores and why Acacia trees preferred one mechanism to the other are discussed.     

Microsatellite loci for the weaver ant Oecophylla smaragdina

We developed 13 microsatellite loci in Oecophylla smaragdina from random amplified polymorphic DNA (RAPD) fragments. These loci showed two to 14 alleles in O. smaragdina with expected heterozygosity of each locus from 0.10 to 0.89, and six were also polymorphic in the related species, O. longinoda. The results suggested that the loci will be useful to analyse the genetic structure of Oecophylla species at both the colony and population levels.     

Influence of macronutrient imbalance on native ant foraging and interspecific interactions in the field

1. Ants interact with a diversity of organisms. These interactions, coupled with their abundance, cause ants to have ecologically important effects across multiple trophic levels. 2. Empirical study of ant nutritional ecology has led to the prediction that a macronutrient imbalance will affect ant behaviour and interspecific interactions that underlie these broad‐scale effects. Excess carbohydrate relative to protein is predicted to increase ant aggressiveness, predatory tendency and foraging activity, and to decrease collection of hemipteran honeydew and plant nectar. 3. In field experiments conducted in 2009 and 2010, captive colony fragments of a native ant, Formica podzolica (Hymenoptera: Formicidae), were provided with either simulated prey or carbohydrate solution ad libitum. Foraging behaviours and interactions with flowers, myrmecophilous aphids and aphid natural enemies on wild‐grown plants were documented. 4. Strong effects of macronutrient imbalance on foraging manifested quickly and consistently across colonies; in accordance with predictions, prey‐fed foragers collected both honeydew and floral nectar, whereas carbohydrate‐fed ants ceased collecting these resources. Counter to predictions, carbohydrate‐fed ants dramatically lowered their activity levels and did not prey upon aphids. 5. Ants had no effect on aphid enemies in 2009, when the latter were relatively rare, but decreased their abundance in 2010. Despite this protection, the net effect of ants on aphids was negative (measured only in 2009). Prey‐fed ants demonstrated a strong preference for honeydew over floral nectar, thus demonstrating that a macronutrient imbalance may lead to different interactions with similar resources. 6. This study links ant nutrition and community ecology by demonstrating the rapid, asymmetric and multitrophic consequences of nutritionally mediated behaviour.     

Cuticular spectra and inter-individual recognition in the slave-making ant Polyergus rufescens and the slave species Formica rufibarbis

Abstract. The relationship between behavioural tests and relative proportions of cuticular components were studied in the slave-making species Polyergus rufescens and the slave and Formica rufibarbis living in either monospecific or mixed colonies. A correlation between the relative proportions of the cuticular products and interindividual recognition exists in each of the two species Polyergus and Formica: Polyergus are fiercely aggressive towards individuals which have different cuticular spectra and originate from a geographically isolated nest. This seems to be true also in the case of Formica living in monospecific colonies. A similar correlation also exists between the two species, which have different cuticular spectra: encounters arranged between them show that free-living Formica are always fiercely aggressive towards Polyergus. The reason why no such correlation seems to exist, however, between Polyergus and Formica when the latter are enslaved and the two species coexist peacefully at the same nest is discussed.     

Cuticular spectra in the slave-making ant Polyergus rufescens and the slave species Formica rufibarbis

Abstract. The relative proportions of cuticular components having the same retention times were compared between the slave-making ant Polyergus rufescens and the slave ant Formica rufibarbis living in monospecific or mixed colonies. The two species were found to present different spectra. The Formica workers, when enslaved by Polyergus , tend to lose their colony characteristics but they do not seem to adopt the characteristics of Polyergus.