Chlorophytum Comosum - Taxonomy

Taxonomy

There are three described varieties of the species: the autonym C. comosum var. comosum has strap-shaped narrow leaves and is found along forest margins, C. comosum var. bipindense has broader, petiolate leaves with stripes on the underside and the inflorescences are 2-3 times the length of the leaves, and C. comosum var. sparsiflorum also has broader leaves that narrow to the base and usually lacks a petiole and the striping on the underside of the leaf and the inflorescences are up to two times the length of the leaves. The latter two are rain forest-dwelling taxa that had earlier been described as separate species, but botanists Axel Dalberg Poulsen and Inger Nordal reduced the taxa to varieties of C. comosum in 2005.

Delimitation of species boundaries within the genus Chlorophytum is reported to be difficult, possibly because of several evolutionary radiations into forest environments that led to morphological aspects that are too similar to reliably distinguish separate species. The evidence given to support this is the widespread distribution of most taxa in the genus and poor seed dispersal, leading to the conclusion of deeper evolutionary divergence among the taxa. The three described varieties in C. comosum could be an example of this convergent evolution of leaf shape among the forest-dwelling varieties from species of disparate origin, leading to the species C. comosum being polyphyletic, instead of the traditional view of morphological divergence among the varieties within the species with the assumption of a common origin (monophyly). The widespread C. comosum var. comosum has slender, near linear leaves that lack a petiole similar to plants found in cultivation and is only found growing at the margins of the rain forest. The two other varieties, C. comosum var. sparsiflorum and C. comosum var. bipindense, possess petioles and have broader leaves necessary for collecting more light in the shady Guineo-Congolean rain forest. A study published in 2005 used 16 morphological characters and was unable to delimit species boundaries among these three taxa, so they were relegated to varietal status. A follow-up study published in 2008 provided preliminary evidence from phylogenetic analysis of plastid and nuclear DNA sequences that established samples from disparate collections sites identified as C. comosum were polyphyletic.