His 1981 doctoral dissertation, supervised by Peter Raven, is entitled "A systematic and evolutionary study of the Oenothera caespitosa species group, Onagraceae".
[3] The previous flora (Hillebrand, 1888) was out of date, and subsequent contributions featured varied species concepts and were published in scattered places.
1999) was a major factor in permitting botanists to explore the amazing insular evolutionary phenomena that the Hawaiian flora contains.
Wagner’s work on islands continued with the Marquesas, where cladistic studies and contributions using DNA permitted an understanding of the biogeographic nature of the remote and neglected archipelago.
[3]Wagner ... worked with a husband-and-wife team of UC Irvine botanists, Ann Sakai and Stephen Weller, to study Schiedea, a genus of shrubs and vines that are in the carnation family.