Onoclea is a genus of plants in the Onocleaceae family, native to moist habitats in eastern Asia and eastern North America. They are deciduous ferns with sterile fronds arising from creeping rhizomes in spring, dying down at first frost. Fertile fronds appear in late summer. Depending on the authority, the genus contains one to five species.
The Onocleaceae family is recognized as having more than one species by every authority.
If this were true it would state there were 2-5 species (or 3-5, etc). Since 1 is included, it must be represented. This as a nuanced issue that the AI doesn't understand.