A systematic revision of Drimiopsis Lindl. & Paxt. (Hyacinthaceae)

Abstract

Drimiopsis Lindl. & Paxt. is one of many genera within the Hyacinthaceae that have not been comprehensively reviewed. In this study, a comprehensive systematic revision of Drimiopsis is accomplished through examination of the anatomy, morphology, phytochemistry, DNA and cytology with the express aim of establishing a phylogenetic classification. Results of the research include amongst others, character and taxa diversity, identification keys as well as the delimitation of the genus from the other closely related genera of the subtribe Ledebouriinae U. & D Miiller-Doblies. The phylogenetic species concept, a character-based approach inferring phylogeny via hierarchical distribution of characters, is preferred in elucidating the phylogenetic history of Drimiopsis and reviewing its taxonomy. To this end, both a phenetic and a cladistic analysis were done. This study also adopts a bifurcatus investigative approach encompassing generic concepts in the Ledebouriinae to enhance phylogenetic inference with respect to Drimiopsis. Ambiguities exist in the concept of Drimiopsis that cannot be fully understood in isolation. An analysis of the most immediate sister taxa namely, Resnova v. d. Merwe and Ledebouria Roth gives a better resolution of interspecific and intergeneric variation in characters and states as well as relationships. The leaf epidermis displays taxonomically significant cell arrangement, morphology and stomata characters. Anatomical characters confirm the morphological differentiation of epidermal cells. Phytochemical analysis of D. burkei Bak. extracts revealed six novel structured homoisoflavonoids and a scillascillin. The genus Drimiopsis has basic chromosome numbers x = 10 and x = 11. The former is predominant in Southern African taxa, the latter in tropical African taxa. There are distinctive intergeneric variations in the bulb, leaf, inflorescence, flower and pollen characters within the Ledebouriinae. The phenetic analysis of leaf, flower, pollen and phytochemical characters all demarcate Resnova, Ledebouria and Drimiopsis, clustering Resnova with Ledebouria throughout. The consensus cladogram of the cladistic analysis emphasises the monophyly of the three genera and supports the subtribe grouping of the Ledebouriinae. The total evidence analysis of morphological and available DNA data produced a well-supported and resolved tree similar in topology to the tree based on morphological characters alone. The nodes that were not resolved in DNA data analysis were resolved with the addition of morphological data to the matrix. The genus Drimiopsis, now consisting of 18 species, is endemic to Africa with disjunct distributions in southern and tropical Africa. Thirteen of these species are endemic to Southern Africa and five to tropical Africa. This study recognizes the current nine taxa endemic to Southern Africa. Of these two are elevated to species rank and four new species are described. The four taxa currently endemic to tropical Africa are recognized of which two are elevated to the rank of species. Two species are resurrected.