The impact of invasive species on island faunas
can be of major local consequence, while their control is an
important part of island ecosystem restoration. Among
these invasive species are ants, of which some have a
disruptive impact on indigenous arthropod populations.
Here, we study the impact of the invasive African bigheaded
ant, Pheidole megacephala, on a small Seychelles
island, Cousine, and assess the impact of this ant, and its
chemical control, using the commercially available
hydramethylnon-based bait, Siege, on the endemic keystone
Seychelles giant millipede species, Sechelleptus
seychellarum. We found no significant correlations in
landscape-scale spatial overlap and abundance between the
ant and the millipede. Furthermore, the ant did not attack
healthy millipedes, but fed only on dying and dead individuals.
The chemical defences of the millipede protected
it from ant predation. Ingestion of the bait at standard
concentration had no obvious impact on the millipede. The
most significant threat to the Seychelles giant millipede in
terms of P. megacephala invasion is from possible catastrophic
shifts in ecosystem function through ant hemipteran
mutualisms which can lead to tree mortality, resulting
in alteration of the millipede’s habitat.
