Complex sentence: Isolated on the islands, the St Kilda house mouse diverged from relatives, it became larger than the mainland varieties, although it had a number of traits in common with a subspecies found on Mykines in the Faroe Islands, "Mus musculus mykinessiensis".
Split into simpler sentences: Isolated on the islands, the St Kilda house mouse diverged from relatives. It became larger than the mainland varieties, although it had a number of traits in common with a subspecies found on Mykines in the Faroe Islands, "Mus musculus mykinessiensis".