Carbohydrate supply limits invasion of natural communities by Argentine ants

Abstract

The ability of species to invade new habitats is often limited by various biotic and physical factors or interactions between the two. Invasive ants, frequently associated with human activities, flourish in disturbed urban and agricultural environments. However, their ability to invade and establish in natural habitats is more variable. This is particularly so for the invasive Argentine ant (Linepithema humile). While biotic resistance and low soil moisture limits their invasion of natural habitats in some instances, the effect of food availability has been poorly explored. We conducted field experiments to determine if resource availability limits the spread and persistence of Argentine ants in remnant natural forest in North Carolina. Replicated transects paired with and without sucrose solution feeding stations were run from invaded urban edges into forest remnants and compared over time using baits and direct counts at feeding stations. Repeated under different timing regimes in 2006 and 2007, access to sucrose increased local Argentine ant abundances (1.6-2.5 fold) and facilitated their progression into the forest up to 73 +/- 21% of 50-m transects. Resource removal caused an expected decrease in Argentine ant densities in 2006, in conjunction with their retreat to the urban/forest boundary. However, in 2007, Argentine ant numbers unexpectedly continued to increase in the absence of sugar stations, possibly through access to alternative resources or conditions not available the previous year such as honeydew-excreting Hemiptera. Our results showed that supplementing carbohydrate supply facilitates invasion of natural habitat by Argentine ants. This is particularly evident where Argentine ants continued to thrive following sugar station removal.

Contrasting effects of an invasive ant on a native and an invasive plant

“…Similarly, supercolony formation of Anoplolepis gracilipes and subsequent ecosystem collapse on Christmas Island is thought to be fuelled by honeydew obtained from scale insects (O'Dowd et al 2003). A strong association between ants and carbohydrate resources may be a common factor in areas where invasive ants have reached extraordinarily high abundances (Rowles and Silverman 2009;Savage et al 2009). Despite its potential to illuminate mechanisms of invasive ant success and impact, the quantification of ant benefits from facultative mutualisms remains an area in much need of further investigation.…”

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

“…Linepithema humile has been consistently linked to outbreaks in honeydew-producing Hemiptera (Bartlett 1961;Buckley 1987;Daane et al 2007;Lach 2003;Ness and Bronstein 2004;Way 1963) This ant is capable of invading open canopy woodland habitat in many parts of the world (Bond and Slingsby 1984;Espadaler and Gomez 2003;Rowles and O'Dowd 2007;Ward 1987), the degree of penetration usually limited by proximity to water (Menke and Holway 2006;Ward 1987). Linepithema humile have been unable to penetrate closed canopy forests in its introduced range (Ward and Harris 2005), possibly because these forests lack a readily available stable carbohydrate resource (Rowles and Silverman 2009).…”

Use of termites, Reticulitermes virginicus, as a springboard in the invasive success of a predatory ant, Pachycondyla (=Brachyponera) chinensis

“…Recent work suggests that many successful invasive ants rely on a mutualism with Hemiptera for their invasion success (Linepithema humile: Grover et al, 2007;Tillberg et al, 2007;Rowles and Silverman, 2009; Solenopsis invicta: Helms and Vinson, 2008). Phloem-feeding Hemiptera, such as aphids or scale insects, produce honeydew as a waste product.…”

“…Hemipteran honeydew is abundant and available throughout most of the year (yearround in some climates). This food source allows ants, such as L. humile, to grow massive colonies, and expand their territories (Morales, 2000;Helms and Vinson, 2002;Lach, 2005;Grover et al, 2007;Tillberg et al, 2007;Helms and Vinson, 2008;Rowles and Silverman, 2009). It has been suggested that one of the reasons that invasive ants tend to be dietary generalists is that such generalization makes them able to take advantage of hemipteran resources (Buckley and Gullan, 1991;Helms and Vinson, 2002;Lach, 2003).…”