What factor supports the theory that geographical size variations across the historical range might stem from grouping distinct species?

Answer

DNA studies have provisionally separated Australian and New Guinean populations.

DNA studies have provisionally separated Australian and New Guinean populations, now identified as Enhydrina zweifeli, from H. schistosus, supporting the idea that historical size variations included distinct but closely related species.

What factor supports the theory that geographical size variations across the historical range might stem from grouping distinct species?
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