Quercus texana vs oak tree

Quercus texana and oak tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Quercus texana	Yes	No	No	No
oak tree	Yes	No	No	No

As nouns, oak tree is a hypernym of Quercus texana; that is, oak tree is a word with a broader meaning than Quercus texana:

Quercus texana: small deciduous tree having the trunk branched almost from the base with spreading branches; Texas and southern Oklahoma
oak tree: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of Quercus texana include oak.

Quercus texana (noun)	oak tree (noun)
small deciduous tree having the trunk branched almost from the base with spreading branches; Texas and southern Oklahoma	a deciduous tree of the genus Quercus; has acorns and lobed leaves