Why Wallace drew the line: A re-analysis of Wallace's bird collections in the Malay Archipelago and the origins of biogeography

The significance of Wallace’s Line is often misrepresented in modem scientific literature. Many assume that it was a demarcation between Australian and Asian faunas. However, Wallace drew his line to illustrate that the distribution of animals reflects underlying geological history. Arguments over biogeographic boundaries are rarely relevant to Wallace’s hypothesis. His work is also often assumed to lack empirical support. We reassess Wallace’s Line using 2,517 bird specimens he collected from the Malay Archipelago, as well as modem avifaunal lists. We classified families as Asian, Australian or cosmopolitan and calculated the proportion of Asian to Australian species for each island. The islands fall into three groups, separated by Wallace’s Line and Lydekker’s Line. Our results suggest that Wallace’s Line is supported by the data collected and that it demarcates a major faunal break for birds, concordant with modem geological evidence on the origin of the region.