South Asian river dolphin display the variances needed to support their classification as separate species. Thus, at present, a single species with two subspecies is recognized in the genus "Platanista", "P. g. gangetica" (Ganges river dolphin) and "P. g. minor" (Indus river dolphin). An assessment of divergence rates in mitochondrial DNA of the two subspecies indicates that they diverged from a common ancestor around 550,000 years ago. This ancestor is thought to have been a marine Platanistid inhabiting the epi-continental seas in South Asia during the sea level rises in the middle Miocene. The earliest fossil identified as belonging to the species is only
Asystasia gangetica it has become naturalized. Both subspecies of this plant have been introduced to Australia where "A. g. micrantha" is on the National Environmental Alert List and must be reported when found. The original range of the subspecies is unclear, but it is likely that "A. g. gangetica" was limited to Asia, and "A. g. micrantha" was limited to Africa. Ernest Akamine (1947) found that there were no apparent dormancy mechanisms operating in the seeds, which germinated freely 135 days after being expelled from parent plants. Flower production can begin as early as 40 days after germination, with seed development beginning