Secondary invasion by European fire ants following buckthorn removal alters arthropod communities

Invasive species management often focuses on the removal of dominant
non-native flora, yet these interventions can unintentionally facilitate
secondary invasions. This study evaluates the ecological consequences of
removing the invasive shrub Rhamnus cathartica (common buckthorn) on the
abundance of the invasive ant Myrmica rubra (European fire ant) and
associated pollinator communities in a post-industrial preserve. Contrary
to expectations, M. rubra abundance was higher in restored plots, a
pattern linked more strongly to increased leaf litter thickness than to
decreased canopy cover. Whereas cavity-nesting bee abundance increased
following buckthorn removal, ground-nesting bees exhibited reduced
abundance in areas with high M. rubra presence, suggesting direct or
indirect antagonistic interactions. Diptera abundance also increased with
restoration but remained unaffected by ant presence. These results
underscore the potential for invasive species removal to create ecological
conditions favorable to secondary invaders, thereby complicating
restoration outcomes. The study emphasizes the need for integrated
management approaches that anticipate secondary invasions and include
ongoing monitoring to safeguard native biodiversity.