This species was treated as the most widespread and morphologically variable species of Danais by Puff & Buchner (1994), with a range in Mauritius, Reunion, and throughout Madagascar. This species varies morphologically in particular in leaf size and shape and inflorescence size. Puff & Buchner (1994) characterized this species by its small triangular stipules, small to rather large leaves that are usually quite stiff to leathery in texture, rather short cymose inflorescences with the flowers and fruits all pedicellate, calyx limb with a short tubular portion and broadly triangular lobes generally about as long as the tubular portion, rather small corollas, and medium-sized fruits. In practice, they gave significant weight for identifying and circumscribing this species to the calyx limb. Puff & Buchner (1994) considered this species closely related to Danais cernua, which they distinguished mainly by seed morphology. 

Danais was subsequently studied with molecular data by Razafimandimbison et al. (2012), who found the plants of Mauritus and those of Madagascar were separated as two distinct lineages in their phylogram. They included all of these plants in this analysis as "Danais fragrans", but noted in their discussion comments that the Malagasy plants seem distinct and probably should be separated and called Danais lyallii. They later adopted that name in another analysis (Razafimandimbison et al., 2022), but have not yet published a formal taxonomic statement about the separation and names for these so this change has not yet been widely adopted. A formal new taxonomy for these plants is expected to be presented soon (S. Razafmindimbison, pers. comm., I 2023), and this web page taxonomy will be updated when that is published. 

For geographic and ecological information on this species, see the Madagascar Catalogue Project. (To access that data, in the upper right of this web screen, click on "Choose Project", and then the corresponding database from that list.)