Identification of Trillium ovatum

Trillium ovatum is a white-flowered pedicellate trillium native to western North America. For decades, botanists have recognized two taxa, but based on unpublished data circulated in 2019, Plants of the World Online (and therefore iNaturalist) came to recognize four taxa. An identification key for this group of trilliums appeared in a journal article in March 2024, but since the article is not easily accessible, the key has been reproduced in the following document: