Asphodelaceae is a family of flowering plants in the order Asparagales.[2] Such a family has been recognized by most taxonomists, but the circumscription has varied widely. In its current circumscription in the APG IV system, it includes about 40 genera and 900 known species.[3] The type genus is Asphodelus.
The family has a wide, but scattered, distribution throughout the tropics and temperate zones; for example, Xanthorrhoea is endemic to Australia, while the Aloes are unique to Africa and parts of the Arabian Peninsula. Many of the family's genera are cultivated as ornamentals, with some being highly collectible and sought-after, such as Haworthia and Gasteria, as well as their intergeneric hybrids with Aloe (x Gasteraloe, x Gastorthia, x Haworthaloe, etc.), while a few are grown commercially for cut flowers. Two species of Aloe, A. vera and A. maculata, are grown for their leaf sap, which contains digestive enzymes, and has medicinal and cosmetic applications.
Members of the Asphodelaceae are diverse, with few characters uniting the three subfamilies currently recognized. The presence of anthraquinones is one common character. The flowers (the inflorescence) are typically borne on a leafless stalk (scape) which arises from a basal rosette of leaves. The individual flowers have jointed stalks (pedicels). A disk of woody tissue (a hypostase) is present at the base of the ovule.[1]
The subfamily Xanthorrhoeoideae contains only the genus Xanthorrhoea, native to Australia. Plants typically develop thick woody stems; the flowers are arranged in a dense spike. Members of the subfamily Asphodeloideae are often leaf succulents, such as aloes and haworthias, although the subfamily also includes ornamental perennials such as red hot pokers (Kniphofia). Members of the subfamily Hemerocallidoideae are varied in habit. Daylilies (Hemerocallis) are one of the widely grown members of this subfamily.[1]
The order Asparagales can be divided into a basal paraphyletic group, the "lower Asparagales", which includes the Asphodelaceae as defined here,[4] and a well-supported monophyletic group of "core Asparagales", comprising Amaryllidaceae sensu lato and Asparagaceae sensu lato.[5] Three separate families were at one time recognized (e.g. in the first APG system of 1998): Asphodelaceae, Hemerocallidaceae and Xanthorrhoeaceae. Molecular phylogenetic studies have shown that the three are closely related,[1][6] although Rudall considered that the combination into a single clade was not supported by morphological analysis.[7] The most recent APG classification, the APG IV system of 2016, places the three former families into a single family, the Asphodelaceae sensu lato. The former families are treated as three subfamilies: Asphodeloideae, Hemerocallidoideae and Xanthorrhoeoideae.[8]
The following phylogenetic tree for Asphodelaceae sensu lato is based on a molecular phylogenetic analysis of the DNA sequences of the chloroplast genes rbcL, matK, and ndhF.[9] All branches have at least 70% bootstrap support. Of the 36 genera recognized by the authors, 29 were sampled. Eccremis was not sampled, but is added here because it is known to be closely related to Pasithea and is often combined with it. Hodgsoniola belongs somewhere in the grade from Tricoryne to Johnsonia. The unsampled genera, Astroloba, Chortolirion and Gasteria, belong to subfamily Asphodeloideae.[10]