Complex sentence: Further, some clades of brown bear, as assessed by their mtDNA, are more closely related to polar bears than to other brown bears, meaning that the polar bear would not be a true species according to some species concepts.
Split into simpler sentences: Further, some clades of brown bear, as assessed by their mtDNA, are more closely related to polar bears than to other brown bears,. The polar bear is not be a true species according to some species concepts.