Long-term dynamics of the distribution of the invasive Argentine ant, Linepithema humile, and native ant taxa in northern California

Abstract

Invasive species, where successful, can devastate native communities. We studied the dynamics of the invasive Argentine ant, Linepithema humile, for 7 years in Jasper Ridge, a biological preserve in northern California. We monitored the distributions at the hectare scale of native ant taxa and L. humile in the spring and fall from 1993 to 1999. We also studied the invasion dynamics at a finer resolution by searching for ants in 1-m plots. Our results are similar at both scales. The distributions of several native species are not random with regard to L. humile; the distributions of several epigeic species with similar habitat affinities overlap much less frequently than expected with the distribution of L. humile. We found that season had a significant influence on the distributions of L. humile and several native taxa. Over the 7-year period, L. humile has increased its range size in Jasper Ridge largely at the expense of native taxa, but there is seasonal and yearly variation in this rate of increase. Studies of invasions in progress which sample across seasons and years may help to predict the spread and effects of invasive species.

Linking Temporal and Spatial Scales in the Study of an Argentine Ant Invasion

“…The average rate of spread from 1993 to 1999 was about 5 ha/yr (Sanders et al 2001), but decreased from 2000 to 2004. Other studies from California report rates of spread along one dimension ranging from 0 to 300 m/yr (reviewed in Suarez et al 2001).…”

“…Each May and September, we visit about 250 permanently marked locations (sample plots) and record the ant species present (for details see Human and Gordon 1996;Human et al 1998;Sanders et al 2001;Sanders et al 2003).…”

“…Argentine ants are invading the preserve from the surrounding agricultural and residential areas (Human et al 1998;Sanders et al 2001), and have increased their range size at JRBP by 14 ha in 11 years, though there is considerable seasonal and yearly variation in this rate. The average rate of spread from 1993 to 1999 was about 5 ha/yr (Sanders et al 2001), but decreased from 2000 to 2004.…”

“…Because the ants tend homopterans, the Argentine ants are considered agricultural pests (Markin 1970). Wherever they become established, they reduce populations of native ants and other arthropods (Ward 1987;Cole et al 1992;Cammell et al 1996;Human and Gordon 1996;Human and Gordon 1997;Holway 1998;Suarez et al 1998;Sanders et al 2001Sanders et al , 2003. Despite the ubiquity and impact of Argentine ants, surprisingly little is known about their population ecology.…”

Mechanisms of Competitive Displacement of Native Ant Fauna by Invading <I>Myrmica rubra</I> (Hymenoptera: Formicidae) Populations

“…While a few "tramp ants" may be so closely associated with human activity and disturbance as to specialize largely on open niche habitat (Passera and Williams 1994), the superior competitive ability of many invasive species is demonstrated by their widespread ecological success and numerical dominance in habitats once occupied by rich and varied native ant communities (Human and Gordon 1996, Holway 1998, Holway and Case 2001, Holway et al 2002, Carpintero and Reyes-Lopez 2008. Although some evidence that such negative effects (i.e., virtual extirpation of native ant fauna) may be transient (Sanders et al 2001, Morrison 2002 and context-dependent (Menke andHolway 2006, Heller et al 2008), lasting changes in community structure appear to be the norm (Sanders et al 2003, Holway and Suarez 2006, Lessard et al 2009b). …”