Verification of Argentine ant defensive compounds and their behavioral effects on heterospecific competitors and conspecific nestmates

Abstract

The invasive Argentine ant (Linepithema humile) has become established worldwide in regions with Mediterranean or subtropical climates. The species typically disrupts the balance of natural ecosystems by competitively displacing some native ant species via strong exploitation and interference competition. Here we report that Argentine ants utilize glandular secretions for inter and intra-specific communications during aggressive interactions with a heterospecific competitor, California harvester ant (Pogonomyrmex californicus). Chemical analyses indicated that Argentine ants deploy glandular secretions containing two major volatile iridoids, dolichodial and iridomyrmecin, on the competitor’s cuticular surface during aggressive interactions. Bioassays indicated that the glandular secretions function as a defensive allomone, causing high levels of irritation in the heterospecific. Furthermore, the same glandular secretions elicited alarm and attraction of conspecific nestmates, potentially enabling more rapid/coordinated defense by the Argentine ants. Two major volatile constituents of the glandular secretion, dolichodial and iridomyrmecin, were sufficient to elicit these responses in conspecifics (as a mixture or individual compounds). The current study suggests that invasive Argentine ants’ superior exploitation and interference competition may rely on the species’ effective semiochemical parsimony.

Corpse management of the invasive Argentine ant inhibits growth of pathogenic fungi

“…Argentine ants start carrying dead nestmates to refuse piles when cuticular “life-associated” chemicals, dolichodial and iridomyrmecin, have disappeared 22 . These volatiles are secreted from pygidial gland and Argentine ants use them also as defensive compounds 23 and trail pheromones 24 . Argentine ants have four distinct anal endocrine glands: Pavan’s, Dufour’s, venom, and pygidial gland 25 , from which the pygidial gland is the largest 25 .…”

“…Argentine ants have four distinct anal endocrine glands: Pavan’s, Dufour’s, venom, and pygidial gland 25 , from which the pygidial gland is the largest 25 . Iridomyrmecin is major product of pygidial gland 23 and it has been shown to be weakly antibacterial 26 . Beetle pygidial gland secretion has been described to inhibit fungal growth 27–29 .…”

“…We cannot separate in our experiments faeces and pygidial gland-derived staining, since the food-derived dye was able to cross to pygidial gland content as well. However, as pygidial gland secretion has been shown to attract nestmates as a trail pheromone 24 and defence substance 23 , its application on corpses could create virtuous cycle, whereby more ants gather to the site, which leads to increased pygidial gland secretion and thus more efficient fungal growth inhibition.…”

Effects of the Argentine ant venom on terrestrial amphibians

“…Welzel et al. (2018) established that it deploys its defensive compounds against native ants. Although indirect effects on vertebrates are also known, such as contributing to the decline of the horned lizard ( Phrynosoma coronatum ) (Suarez & Case 2002) and the spatial shift in habitat use of amphibians (Alvarez‐Blanco et al.…”

Volatile Terpenes and Terpenoids from Workers and Queens of Monomorium chinense (Hymenoptera: Formicidae)

“…In the subfamily Ectatomminae, isogeraniol, a monoterpene might function as a recruitment signal in ant Rhytidoponera metallica [ 11 ]. In addition to the pheromonal role, terpenes and terpenoids are used as defensive compounds, such as iridomyrmecin (cyclopentanoid monoterpenes) and iridodials in some ant species in the subfamily Dolichoderinae [ 12 , 13 ]. However, functions of many terpenes have not been elucidated, such as ( E )-β-ocimene and geranylgeraniol in Labidus praedator of subfamily Ecitoninae and Aenictus rotundatus of subfamily Dorylinae, respectively [ 14 , 15 ].…”