Spatial distribution and range expansion of the Tawny Coster butterfly, Acraea terpsicore (Linnaeus, 1758) (Lepidoptera: Nymphalidae), in South-East Asia and Australia MICHAEL F. BRABY, 1,2 CL  EO BERTELSMEIER, 3 CHRIS SANDERSON 4 and BRIAN M. THISTLETON 5 1 Department of Land Resource Management, Palmerston, NT, Australia, 2 School of Biological Sciences, The Australian National University, Canberra, ACT, Australia, 3 Ecologie, Syst ematique & Evolution, UMR CNRS 8079, Universit e Paris Sud XI, Orsa, France, 4 Environmental Resources Management Australia, Canberra, ACT, Australia and 5 Plant Industries, Department of Primary Industry and Fisheries, Darwin, NT, Australia Abstract. 1. Documenting the range size and range boundaries of species, and understanding the factors determining changes in these spatial components, is crucial given current rates of anthropogenic climate change and habitat loss. Here, we document the establishment of the acraeine butterfly, Acraea terpsi- core, in South-East Asia (Indonesian islands south of Malay Peninsula, and Ti- mor) and Australia for the first time. We estimate its rate of colonisation and potential for further range expansion in the Indo-Australian region according to bioclimatic niche models. 2. We modelled the potential distribution of the species in the Indo-Austra- lian region under current climatic conditions and in 2050 following climate change. The bioclimatic niche models were based on five different modelling techniques, three global circulation models (GCMs) and two CO 2 emission sce- narios (SRES), yielding 30 individual models that were combined in a consensus model. 3. Acraea terpsicore became established in Indo-China (Thailand) during the 1980s and since that time it has spread to other parts of South-East Asia. It was first recorded on the Australian mainland in the Northern Territory in April 2012 and within a few months of detection was found to occur at six locations, with an estimated extent of occurrence of 4000 km 2 . Thus, the range size of A. terpsicore has expanded by approximately 6000 km across the equator (c. 32 degrees latitude) in 28 years, with an average rate of colonisation (from Thailand to Australia) of 200 km year À1 (range: 170–230 km year À1 ). 4. The bioclimatic niche models identified additional regions with favourable climatic conditions, and within Australia it is likely to occupy coastal and sub- coastal savannah woodlands of the entire monsoon tropics, indicating potential for further range expansion. Moreover, the species’ potential range is likely to increase with climate change. 5. We hypothesise that habitat modification, particularly rapid deforestation of tropical forest in South-East during the past three decades, is a major factor accounting for the range expansion given the species’ habitat preference for dis- Correspondence: Michael F. Braby, Department of Land Resource Management, PO Box 496, Palmerston NT 0831, Aus- tralia. E-mail michael.braby@nt.gov.au Ó 2013 The Royal Entomological Society 1 Insect Conservation and Diversity (2013) doi: 10.1111/icad.12038