A comparative study of the fauna associated with nest mounds of native and introduced populations of the red wood ant Formica paralugubris

In the second half of the twentieth century, many red wood ant populations were transferred from the Alps to the Apennines as biological control agents. Since the introduction involved the relocation of entire nest mounds, it is presumable that the associated fauna was also relocated. While the introduction of these ants has raised several concerns about their ecological impact, there has been no attempt to investigate the introduction of other nest associated species. In this study, we collected samples of soil and nest material from three populations of the red wood ant Formica paralugubris, one Alpine native and two imported into the Apennines. We aimed to confirm that nest mounds are hotspots for soil fauna, detect the occurrence of new myrmecophilous species, and compare the nest-associated fauna among sites, to test the hypothesis of mass species relocation. We focused our analyses mainly on two taxa, springtails and oribatid mites, two highly representative groups of the mesofauna inhabiting nest mounds. The results showed higher richness and diversity in nests than soil for oribatids but not for springtails. We found 17 myrmecophilous oribatid species, but only two springtail species. Finally, native and imported sites shared only a few oribatid and springtail species, suggesting that massive relocation did not occur with nest transplants or it was likely limited. Additionally, we found some species never before collected in Italy.