Classification, biodiversity and conservation: compare question

Two populations of frogs, Rana cantans and Rana silens, are found in separate but adjacent regions. They are indistinguishable in external morphology (size, colour, body shape) and occupy similar pond habitats. However, their mating calls are distinct, and when individuals from different populations are placed together in a laboratory, no fertile offspring are produced.

Compare how the biological species concept and the morphological species concept would classify these two populations. In your answer, explain the reasoning for each classification.