As nouns,
Ursus arctos middendorffi is a hyponym of
Ursus arctos; that is, Ursus arctos middendorffi is a
word with a more specific, narrower meaning than
Ursus arctos:
Ursus arctos: large ferocious bear of Eurasia
Ursus arctos middendorffi: brown bear of coastal Alaska and British Columbia