Ecological dominance and community structure in Mediterranean ants following an environmental disaster

The recovery of ant communities at the Guadiamar River bank (SW Spain) was investigated following an environmental disaster caused by a spill of toxic sludge.  In 2005, seven years after the accident, the structure of ant communities in close damaged and non-damaged areas was studied using pitfall traps and baits (tuna, honey, and seeds).  The number of ant species was significantly lower in the damaged area, confirming earlier results, mostly due to fewer subordinate species.  Community structure differed in the proportion of dominant versus subordinate species, with a higher relative abundance of subordinates in the damaged sites, while equilibrium between abundance of dominants versus subordinates was found in non-damaged sites.  The frequency of aggressive interactions and the ecological dominance of ant species, measured as the relative abundant in traps and baits, were also lower in damaged sites.  This study showed a more relaxed competitive environment in damaged sites, even when food resources are scarce.  These results suggest that behavioral dominance is less important to community structure in highly disturbed habitats. The study of the restoration of these communities provides an ideal setting for generating and testing hypotheses in community ecology.