Invasive Argentine ants reduce fitness of red maple via a mutualism with an endemic coccid

Abstract

Many invasive ant species form mutualisms with honeydew-producing Hemiptera and their aggressive presence deters the natural enemies of the Hemiptera. Invasive ant species like the Argentine ant have often been associated with hemipteran outbreaks in urban, agricultural and natural ecosystems. We investigated the effects of a mutualism between the invasive Argentine ant and the endemic terrapin scale on coccid density and the fitness of the host of this mutualism, the endemic red maple, situated in a commercial park. The terrapin scale has numerous natural enemies and we predicted that the high terrapin scale numbers associated with tending Argentine ants would collapse once Argentine ants were excluded from the host tree canopy. We predicted that excluding the Argentine ant from the tree canopy would result in an indirect net fitness benefit to the host. Terrapin scale numbers collapsed when Argentine ants were excluded from the host tree canopy. Red maples with Argentine ants excluded from their canopy had higher seed mass and larger early leaves indicating that this invasive ant-endemic scale mutualism imposed a net fitness cost to the host tree. The Argentine ant has yet to invade closedcanopy forest within its introduced range. The red maple is common in adjacent closed-canopy forest fragments and recent work has shown that invasion of these forest fragments by the Argentine ant is limited by a steady carbohydrate resource. We discuss the implications to forest invasion posed by a mutualism involving the Argentine ant and an endemic coccid.

Propagule Pressure and Climate Contribute to the Displacement of Linepithema humile by Pachycondyla chinensis

“…Spanning disturbed landscapes in six invaded continents, Argentine ants are on ISSG's “100 World's Worst Invasive Alien Species” list. Once established, Argentine ants are persistent and form large aggressive colonies, fostering hemipterans [34] and generally displacing native ants [35], [36], with cascading effects across many trophic levels [2], [37], [38].…”

Combined Effect of Hemipteran Control and Liquid Bait on Argentine Ant Populations

“…Red maple is extensively used as an ornamental tree within the site, with many of these red maples situated within the area infested by Argentine ants. The maples are heavily infested with the native terrapin scale Silverman 2009, Brightwell andSilverman 2010), a coccid known to excrete copious amounts of honeydew (Simanton 1916).…”

“…Banding ornamental trees with a sticky substance has been used to directly control ßightless pests such as ants (Phillips et al 1987), gypsy moths (Thorpe et al 1993), and ßightless weevils (e.g., Magarey et al 1992). Indirectly controlling phloem-feeding Hemiptera via ant exclusion is not often applied commercially and is mainly limited to scientiÞc study (Phillips et al 1987, Karhu 1998, Nagy et al 2007, Brightwell and Silverman 2010. Conventional hemipteran control strategies directly target the Hemiptera through horticultural oil sprays (e.g., Fernandez et al 2005), foliar sprays (Kanwar et al 2009), and systemic insecticides are the usual methods used (Hubbard and Potter 2006, Grafton-Cardwell et al 2008, Raupp et al 2008.…”

Ant–hemipteran association decreases parasitism of Phenacoccus solenopsis by endoparasitoid Aenasius bambawalei

“…Mutually beneficial interactions between ants and honeydew‐producing hemipterans have been well documented (Styrsky & Eubanks, ; Brightwell & Silverman, ; Powell & Silverman, ; Wilder et al ., ; Zhou et al ., ). Hemipterans benefit from ant tending as it can protect hemipterans from their natural enemies, which has been demonstrated in various ant–hemipteran mutualism systems (Kaplan & Eubanks, ; Daane et al ., ; Powell & Silverman, ; Zhou et al ., ).…”