Location map of Southeast Asia illustrating the 37 rivers sampled in this study. Black dots along rivers represent the sampling sites as identified in Table 1 and Table . Dark grey shading illustrates the extent of the emerging Sunda Shelf at sea levels 75 m below present day levels; light grey denotes emerging shelf at sea levels 120 m below present day levels (as illustrated by Voris 2000). Rivers illustrated on the Sunda Shelf represent drowned Pleistocene river drainage systems, according to Voris (2000).