Hippeastreae is a tribe of plants belonging to the subfamily Amaryllidoideae of the Amaryllis family (Amaryllidaceae). Species in this tribe are distributed in South America. Flowers are large and showy, zygomorphic, with the stamens in varying lengths, inflorescence bracts are often fused basally (along one side). The seeds are flattened, winged or D-shaped. Reported basic chromosome numbers are x= 8-13, 17, and higher. All the species in this tribe present a remarkable aesthetic interest and horticultural value.
Taxonomy
Meerow et al. (1999) provide a history of the treatment of the genera of Amaryllidaceae, including Hippeastreae, from the mid-twentieth century. While morphological phylogeny has been frustrated by the perversive homoplasy typical of the Amaryllidaceae, application of molecular phylogenetics to the Amaryllidaceae did not indicate clear tribal divisions but rather broad biogeographical clades. However the American clade resolved the tribe Hippeastreae. A later examination of the deeper relationships of the American genera suggested the two subclades, Andean and hippeastroid and within the latter separated the Brazilian Griffineae as sister to the remaining hippeastroids. The larger and more diverse grouping of hippeastroids formed two smaller monophyletic groups. The smaller contained Hippeastrum (with the exception of Hippeastrum blumenavium), but also a Rhodophiala. With the exception of Rodophilia (Brazil) all specimens were from Chile and Argentina. The second group corresponded to those genera variously included in tribe Zephyrantheae (Traub) or subtribe Zephyranthinae (Müller-Doblies), but only including some Zephyranthes species. The hippeastroid clade is predominantly diploid and extra-Andean by comparison to the Andean clade which is predominantly tetraploid, and contain those genera traditionally included in Hippeastreae. The precise position of Griffineae remained unresolved since its sister status to Hippeastrae was weak, leaving the possibility that it could be sister to the whole American clade. The tribe consists of 10–13 genera and about 180 species.
Phylogeny
The placement of Hippeastreae within subfamily Amaryllidoideae is shown in the
following cladogram, where this tribe is shown as a sister group to the Griffineae, forming the Hippeastroid subclade, of two American clades:
Subdivision
The genera of the tribe Hippeastreae have been treated in a number of different ways over the years. Traub (1963) in his monograph on the Amaryllidacea distributed those genera now considered in this tribe over a number of other tribes (see Table, below), while Dahlgren et al. included them all under Hippeastrae for the first time. The concept of subtribes came from the Müller-Doblies' (1996), who had three subtribes, Griffinineae, Hippeastrinae and Zephyranthinae.
Consequently, it has been customary to describe the tribe Hippeastreae as consisting of two subtribes: subtribe Hippeastrinae - includes species of medium height and often with many flowers in each inflorescence and inflorescence bracts are different in size and fused basally. Genera that have been placed in this subtribe include Placea, Hippeastrum, Phycella (includes Famatina), Eithea (=Griffiniopsis), Rhodophiala, and Traubia. (Some authors use the spelling Hippeastrineae) subtribe Zephyranthinae - includes species of small height with solitary flowers. Inflorescence bracts are fused forming a tube surrounding the pedicel of the flower. Genera in this subtribe are Sprekelia, Habranthus, Cooperia, and Zephyranthes. (Some authors use the spelling Zephyranthinea)
In the study of Meerow et al. (2000) based on molecular markers Zephyranthinae (Zephyranthae of Traub) were clearly polyphyletic, largely due to the polyphyly of Zephyranthes itself. This subgroup has been broadly characterised as having a chromosome number, x=6, but with considerable variation. Other polyphyletic genera included Rodophiala and Habranthus. Hippeastreae also include Haylockia, Rhodolirion and Tocantinia.
A more focused study of Hippeastreae alone in 2014, resolved two major clades: Clade A: Traubia, Placea, Phycella, Rhodolirium, and Famatina maulensis (now Phycella maulensis) Clade B: Rhodophiala, Habranthus, Haylockia, Hippeastrum, Sprekelia, Zephyranthes, and the remainder of Famatina.