Fig. 2.

Trophic ecology of Argentine ants at an active invasion front. (A) Mean (±SE) δ¹⁵N values for Argentine ants invading Rice Canyon from 1996 to 2003. For each year, δ¹⁵N values are averaged over sampling stations at which Argentine ants were present. (B) For each of the nine sampling stations in Rice Canyon, the δ¹⁵N value for the first year that L. humile was recorded at a sampling station (i.e., at the leading edge of the invasion front) vs. the mean δ¹⁵N value for that station in all subsequent years (i.e., after the displacement of native ants). The solid line and closed circles represent the mean (±SE) values across all sample stations.