Microbial activity and functional diversity in the mounds of three different ant species

Activity and functional diversity of the soil microflora in the mounds of M yrmica scabrinodis, Lasius niger and L. flavus were investigated. These thr ee ant species strongly differ in foraging strategy and in the mode of moun d construction. To take account of changing microbial performances during t he cycle of mound building, immature mounds of L. flavus were compared to w ell established ones. The study was carried out with substrate sampled in t he rural district of Hohenahr-Erda (Lahn-Dill Bergland, Central Hesse, Germ any). Nest abundance as well as mound size and architecture were recorded f or all three species. Microbial activity was quantified by determining the C mineralization rate (C-min). Functional diversity of the microflora was m easured by means of the Biolog method. Additional factors were substrate mo isture and pH. Substrate moisture and pH value were not different in the mounds from that in the control. High C-min values in all mound types indicate that the moun ds of the three ant species investigated form a mosaic of microbial hot spo ts at the study site. Substrate diversify and evenness were higher in the m ounds of both M. scabrinodis and L. niger than in the control soil, but low er in the two mound types of L. flavus. The results of the Biolog measureme nts suggest that different components of the microbial community were activ ated in the different mounds. The increase of C-min in L. flavus mounds see ms to be based on the stimulation of a comparatively small and specialized microbial community. The high microbial activity in the mounds of L. niger and M. scabrinodis, in contrast, is accompanied by an increase in functiona l diversity. Investigations on the developing L. flavus mounds show that ty pical features characterizing the microflora in the mounds of this species need a considerable time to develop. It is concluded that ants have an impo rtant role as soil engineers and that species specific differences in the e ffect on the soil microflora are related to feeding strategy and nest archi tecture. Methodological difficulties arising from the application of the Bi olog approach are discussed. (C) 2000 Elsevier Science Ltd. All rights rese rved.