Recovery of ground ant (Hymenoptera: Formicidae) communities six years after a major environmental disaster.

The recovery of ant communities at the Guadiamar River bank (southwest Spain) was studied across 5 yr, after an environmental disaster caused by the spill of toxic sludge over the river caused by a mine accident. Three affected and three control sites were sampled from 2000 to 2004 using pitfall traps. The last year of study, a more exhaustive sampling was conducted at the affected area (eight sampling sites). Additionally, four adjacent study sites not affected by the toxic spill were also studied. Ants showed clear responses to the restoration of the area. Mean ant species richness in spillage affected sites showed a significant increase over the 5 yr. Moreover, multivariate analysis showed distinct changes of ant community composition of the affected area over the years that were not observed in control sites. Six years after the disaster, one half of the species recorded in control sites were also present in the affected area, with only one species exclusive to this area, Cardiocondyla mauritanica Forel (tramp species). However, not only habitat specialist species but also some generalist and conspicuous species within the river basin are not present along the affected area, including species of the genera Camponotus, Messor, Cataglyphis, and Aphaenogaster. This study shows an incipient recovery of ant communities 6 yr after a major environmental disturbance, highlighting the absence of any invasive ant species in the restored area.

The distribution and density of a lycaenid butterfly in relation to Lasius ants.

Larvae and pupae of lycaenid butteflies are often associated with ants: this is usually a mutualism in which ants guard the lycaenids from natural enemies, and the lycaenid larvae and pupae provide sugars and amino acids for the ants. A possible consequence of the interaction is spatially correlated ant and lycaenid distributions, but the phenomenon is poorly documented. We examined the lycaenid Plebejus argus, which is tended by Lasius ants. Within habitat patches, P. argus eggs, larvae and pupae were all spatially associated with Lasius. On a larger scale, the densities of butterflies in different habitat patches and populations, and whether the butterfly was present or not, were correlated with Lasius ant densities. The association of P. argus with Lasius ants is consistent among populations, and occurs at several spatial scales. Other aspects of the ecology of P. argus are more variable.