South East Asia (SEA)is geologically active, with three tectonic plates. Each plate could be expected to correspond to a faunistic province with different species. There is, for exampled, a known and deep divide in species identities between Asia and Australasia. A divide long recognized and named the Wallace line.

However, this divide is not necessarily true for small insect species because these might be easily wind-transported across plate boundaries. These species may show other faunistic structures related to other causes.

I therefore used DrosWLD, a database of Drosophila species, to compile species lists for identifiable regions of SEA. I then created a faunistic network for SEA. The nodes in this network are the regions and the links between nodes represent faunistic similarity greater than the average across all regions. There are many useful tools in network analysis for identifying structure within the network. I applied several of these to the Drosophila faunistic network. My analyzes demonstrated that network tools are very useful in biogeographic faunistics and that they can extract information otherwise hidden in simple species occurrence lists.

The network analyzes revealed that the SEA Drosophila fauna does have structure but that this structure is probably climatically induced and not the result of plate tectonics. In particular, the analyzes show no evidence for a Wallace line.