Analysis of introduced and autochthonous populations of the red wood ant Formica paralugubris: ecological interactions and conservation issues

Abstract

Red wood ants (RWA) are ecologically important keystone species that affect a multitude of taxa at different trophic levels. In the past century, some RWA species were used as biological control agents and exported outside their native range. One of these species is Formica paralugubris, which was transplanted from the Italian Alps to the Apennines (Central Italy) but also to Quebec (Canada). Recently, it has been demonstrated that some of the introduced populations have acquired some invasivity features. This PhD thesis investigated the ecology of Formica paralugubris, aiming to assess its impact at multiple levels, from single taxa to the forest ecosystem as a whole. To do this, I combined different techniques, from direct observations to gas analysis and stable isotopes analysis. I started with assessing the effect of the presence of this species on epiphytic lichen communities, and I analyzed the myrmecophilous fauna inhabiting the nest mounds of introduced and autochthonous populations. I then compared the trophic position of native and introduced populations of this species, using Stable Isotopes Analysis (SIA) techniques. Finally, I characterized the microbial communities hosted within the nest mounds using molecular techniques and I measured the gas emissions from the mounds. To conclude, I have done an overview of the protection status of RWA throughout Europe. Overall, the results of this thesis confirm the ecological importance of F. paralugubris. This species was shown to affect the composition of lichen communities, both from a taxonomic and a functional point of view. Its nest mounds host a rich myrmecophilous fauna and diverse microbial communities. The species was also found to occupy key positions in the trophic web and to play an important role in the carbon dynamics at the forest scale. These results were also discussed in light of the nature of F. paralugubris as a peculiar invasive species. Finally, the complex status of RWA protection was highlighted, also pointing out paradoxical situations in which the introduced populations are protected whereas the native and sometimes declining ones are not.