Interactions Between Introduced and Native Millipede Species in South Australia

Abstract

The Portugese millipede Ommaroiulus moreleti (Lucas) (Diplopoda:Julidae) has recently been introduced to South Australia where it has reached very high densities. In parts of the Adelaide Hills it now co-occurs with two native millipedes, Oncocladosoma clavigerum Jeekel (Diplopoda: Paradoxosomatidae) and Dimerogonus orophilus (Attems) (Diplopoda: Cambalidae). We attempted to show whether the introduced species, which has successfully invaded the detrivore community, has affected the ecology or behaviour of the native millipede members of that community. Experiments in laboratory and field arenas showed that the three species overlap broadly in activity time and microhabitat. The two native species showed no significant difference in habitat choice or aggregating behaviour when alone or mixed with the introduced O. moreleti, and the natives commonly aggregated with the introduced species. Although D. orophilus had reduced feeding activity in the presence of O. moreleti, neither native species rejected food that had been in contact with O. moreleti. We conclude that direct interactions between the introduced invader and the native species cause few behavioural or ecological changes within the detrivorous millipede community.