A new exception to the dominance-discovery trade-off rule in ant communities

Interspecific competition is one of the main factor shaping ant community structure. The “dominance-discovery trade-off’’, an inverse relationship between interference and exploitative competitive ability, is thought to be a fundamental mechanism facilitating coexistence of ants. Despite its widely acceptance in literature, this trade-off appears to be broken in several cases and needs further investigations. Thus, the aim of the present study was to detect the presence/absence of the dominance-discovery trade-off in Mediterranean ant communities. Samplings were conducted inside the Presidential Estate of Castelporziano (Rome, Italy) and seven sampling sites were selected according to their vegetation structure. In each site, baiting was conducted to assess two behavioural indices for each species: the monopolization index and the discovery ability index. Correlation analyses showed no evidence for the existence of a dominance-discovery trade-off. Furthermore, a positive correlation between the two indices was detected in some of the sampling sites. The dominance-discovery trade-off seems therefore to be just one of the possible mechanisms facilitating species coexistence in ant communities

Gall-Colonizing Ants and Their Role as Plant Defenders: From ’Bad Job’ to ’Useful Service’

Galls are neoformed structures on host plant tissues caused by the attack of insects or other organisms. They support different communities of specialized parasitic insects (the gall inducers), and can also provide refuge to other insects, such as moths, beetles and ants, referred to as secondary occupants. This study focuses on galls induced by the oak gall wasp Andricus quercustozae and secondarily colonized by ants in a mixed oak forest. A field survey and two experiments were carried out to a) study ant (species-specific) preferences for different features of the galls, b) describe differences in gall architecture due to ant activity, c) analyse the effects of the presence of gall-dwelling ants on plant health. The results show that there are differences between ant species in gall colonization and in the alteration of gall opening and inner structure. We verified that gall-dwelling ants protect their host plants efficiently, offering them an indirect defence mechanism against enemies (predators and pathogens). The data suggest a new paradigm in ant–plant relationships mediated by the presence of galls on the plants whose ecological and evolutionary implications are discusse

A new exception to the dominance-discovery trade-off rule in ant communities

Interspecific competition is one of the main factor shaping ant community structure. The "dominance-discovery trade-off", an inverse relationship between interference and exploitative competitive ability, is thought to be a fundamental mechanism facilitating coexistence of ants. Despite its widely acceptance in literature, this trade-off appears to be broken in several cases and needs further investigations. Thus, the aim of the present study was to detect the presence/absence of the dominance-discovery trade-off in Mediterranean ant communities. Samplings were conducted inside the Presidential Estate of Castelporziano (Rome, Italy) and seven sampling sites were selected according to their vegetation structure. In each site, baiting was conducted to assess two behavioural indices for each species: the monopolization index and the discovery ability index. Correlation analyses showed no evidence for the existence of a dominance-discovery trade-off. Furthermore, a positive correlation between the two indices was detected in some of the sampling sites. The dominance-discovery trade-off seems therefore to be just one of the possible mechanisms facilitating species coexistence in ant communitie

First Report on the Acrobat Ant <i>Crematogaster scutellaris</i> Storing Live Aphids in Its Oak-Gall Nests

This study provides new data about the role of ants in mutualistic interactions with aphids mediated by galls. We focused our investigation on galls induced by the cynipid Andricus kollari by conducting a survey and a subsequent experiment in an Italian oak forest. The ants Crematogaster scutellaris, Colobopsis truncata and Temnothorax italicus frequently used the galls as nests: Crematogaster scutellaris occupied galls which were located higher on the oak trees, while C. truncata and T. italicus were located at lower positions. In addition, galls occupied by C. scutellaris showed varied internal architecture in relation to the colony composition. Importantly, field surveys revealed for the first time that C. scutellaris nest galls also contained live individuals of the non-galligenous aphid Panaphis juglandis. Field experiments suggested that the ants actively seek, collect and stock live aphids. No signs of predation and injuries were detected on the stored aphids, which were probably kept for safe overwintering, though we cannot exclude a possible occasional use as food. This report reveals a possible novel relationship which could have important consequences on the phenology and presence of aphids on the host plant

Predatory ability of the ant Crematogaster scutellaris on the brown marmorated stink bug Halyomorpha halys

The pest Halyomorpha halys is a recent example of severe worldwide biological invasion. In Italy, after the first detection in 2012, it has rapidly spread and economic damage has already been reported in commercial fruit orchards, eliciting enormous concern for Italian agricultural production. As a long-term solution, biological control investigations are focusing on the potential of natural antagonists, such as generalist predators, in the invaded areas. Due to their biology, ecology and behavior, ants represent one such generalist predator potentially suitable for inflicting mortality on H. halys. In this research, Crematogaster scutellaris was used as a study model. Specifically, the effect of ant predatory behavior on the survival of all H. halys pre-imaginal stages was tested in the laboratory environment. The results suggest that C. scutellaris has a significant predatory impact on all H. halys pre-imaginal stages except for eggs. The reduction of survivorship is between 95 and 85% for instars 1 and 2 and between 38 and 52% for instars 3, 4 and 5. The different levels of predation success suggest that these ants could act as useful generalist predators when associated with other antagonists and/or other control strategies. Although further field investigations are needed, the potential of ants as biocontrol agents of invasive species in agroecosystems deserves consideration in integrated pest management programs

Ants as mealybug detectors: a novel tool for monitoring Planococcus ficus infestation based on ant behaviour

Vineyards are economically valuable agroecosystems that have spread to all continents. As such, sustainable management of their pests is an important goal. Mealybugs are serious pests of vines with Planococcus ficus (VMB) being the most problematic worldwide. Mealybugs are attended by different ant species, whose trophobiotic relationship is often considered damaging since some ant species may offer effective protection from natural enemies in exchange for honeydew. We tested whether this trophobiosis can be used as a VMB monitoring tool, developing a protocol to evaluate infestation on the plants based on ant behaviour (Ant method). We compared this new protocol with the conventional one, consisting in visual counting of VMBs on infested leaves (Leaf method). Our results demonstrated that the Ant method yielded significant advantages over the Leaf method by: (i) allowing to detect VMB infestation on individual plants much earlier; and (ii) allowing to keep track of VMB presence after pest treatments. The Ant method is proposed as a valid complementary tool for integrated pest management in vineyards and its successful achievement encourage searching for further agricultural contexts in which ants may be revaluated as a monitoring tool

Do It by Yourself: Larval Locomotion in the Black Soldier Fly Hermetia illucens, with a Novel "Self-Harvesting" Method to Separate Prepupae

Simple Summary The black soldier fly Hermetia illucens is a widespread species of fly of American origins, which is increasingly used to develop sustainable waste recycling processes as it is able to develop by consuming a wide variety of wastes as food, while both its body and the residuals of its feeding activity can be re-used in a variety of processes. However, many aspects of its larval biology remain unknown. Among these, there is larval movement and its variation in response to external stimuli and environmental conditions. Larvae of the black soldier fly eventually reach the prepupal stage, during which they stop feeding and seek a shelter to pupate. Sorting prepupae from the younger larvae and feeding substratum can be important in rearing processes, since they are used to obtain adults but are also particularly rich in protein and lipids. We focused our study on behavioural differences between prepupae and younger larvae, describing tonic immobility as an anti-predatory response of both, but also their very different ways of locomotion and reactions to stress. Finally, we developed a practical system to exploit these differences, inducing prepupae to move away from the substratum and other larvae to be efficiently collected. The neotropical insect Hermetia illucens has become a cosmopolite species, and it is considered a highly promising insect in circular and sustainable economic processes. Being able to feed on a wide variety of organic substrates, it represents a source of lipids and proteins for many uses and produces recyclable waste. We investigated the characteristics and differences in the poorly-known locomotory behaviour of larvae of different instars, paying particular attention to the unique characteristics of the prepupal stage, key to farming and industrial processes. Moreover, we attempted to develop a "self-harvesting" system relying on the behavioural traits of prepupae to obtain their separation from younger larvae under rearing condition with minimum effort. Prepupae differ from younger larvae in their response to physical disturbance in the form of tonic immobility and significantly differ in their locomotory movements. Both prepupae and younger larvae reacted similarly to heat or light-induced stress, but low light and high moisture induced only prepupae to migrate away, which resulted in the development of a highly efficient separation methodology. The new data on the behaviour of H. illucens not only shed new light on some unexplored aspects of its biology, but also led to develop an inexpensive self-harvesting system that can be implemented in small-scale and industrial farming