It has been suggested that the Allosyncarpia ternata forests of western Arnhemland, Northern Territory, may be relictual and may be biotic refugia from Tertiary times. To explore the hypothesis, a study of the entire beetle fauna was made in an A. ternata forest in Podocarpus Canyon, a small, isolated refugial forest containing the richest recorded plant diversity in NT. At least 508 beetle species were found, belonging to 58 families and at least 318 genera. Only 47 could be named to species; new species and new records for NT were found; and most species are probably not described. Of the named species limited to rainforest, more have disjunct distributions shared with Queensland than with Western Australia. These range disjunctions can be interpreted as evidence of either long distance dispersal or fragmentation of broader former distributions. No taxa were found which seemed to be phylogenetic relicts. A total diversity of more than 2000 species of insects is calculated for the forest. It is concluded that the beetle fauna assembled itself by dispersal in Holocene times. It is not a relict (ancient) assemblage. Beetles and insects in general may be able to contribute more towards reconstructing the biogeographic history of Australia and the forest history of NT, but only when their taxonomy and distributions become better known.

Memoirs of the Queensland Museum
Department of Biology

Peck, S. (2002). Australian rainforest biogeography: Is there a relictual beetle fauna in an Allosyncarpia rainforest refugium, Arnhemland, Northern Territory?. Memoirs of the Queensland Museum, 48(1), 181–192.