There are either two or four closely-related species in the darter family, Anhingidae. The Anhinga of the Americas (Anhinga anhinga) is clearly individual, the Indian, African, and Australian darters can be regarded as either three very similar species, or a single species with three widely separated subspecies (A. melanogaster melanogaster, A. melanogaster rufa and A. melanogaster novaehollandiae). In either case, all four share very similar behaviour and habitat.
This group is related to other Pelecaniformes as below:
The Anhinga is native to the Americas. The Indian Darter is widespread in the Indian sub-continent, and differs in appearance from African and American darters most recognisably by its white lateral neck stripe. The African Darter occurs in tropical sub-Saharan Africa, and differs in appearance from Indian and American Darter most recognisably by its thin white lateral neck stripe against a rufous background colour.