Fig. 1. Bathymetric map of our Indo-Pacific study region with Carcharhinus amblyrhynchos sampling location information.

Sampling locations are indicated by red circles, and the number of specimens collected at each location is indicated in parentheses. Grey shading denotes land area above mean sea level; light blue denotes area no deeper than 200 m; darker blue shading denotes area deeper than 200 m. Inset (a) is a bathymetric profile of southern Indonesia, New Guinea, and northern Australia during the last glacial maximum. Area that is currently below sea level but was exposed (i.e., land) during the last glacial maximum is coloured green. Inset (b) shows the wider Indian and Pacific Oceans and inset (c) shows the New Caledonia area in more detail.