Hippeastreae


Hippeastreae is a tribe of plants belonging to the subfamily Amaryllidoideae of the Amaryllis family. 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. 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. 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, but also a Rhodophiala. With the exception of Rodophilia all specimens were from Chile and Argentina. The second group corresponded to those genera variously included in tribe Zephyrantheae or subtribe Zephyranthinae, 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 in his monograph on the Amaryllidacea distributed those genera now considered in this tribe over a number of other tribes, while Dahlgren et al. included them all under Hippeastrae for the first time. The concept of subtribes came from the Müller-Doblies', who had three subtribes, Griffinineae, Hippeastrinae and Zephyranthinae.
Consequently, it has been customary to describe the tribe Hippeastreae as consisting of two subtribes:
In the study of Meerow et al. based on molecular markers Zephyranthinae 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:
However it also showed that of the 13 genera, two are monotypic. Of the remaining 11 genera, based on Internal transcribed spacer sequences the only monophyletic non-monotypic genera were Hippeastrum and Sprekelia. But on chloroplast DNA analysis, not even these genera were monophyletic. This brings into question the existing generic classification within Hippeastreae.
Consequently, the authors proposed the following nomenclature:
Subtribe Traubiinae includes about 20 endemic Chilean taxa, but only about 10% of the species within tribe Hippeastreae. Characterisation includes a haploid chromosome number, x=8, lack of polyploidy and a capitate stigma.
Subtribe Hippeastrinae, by contrast has a variable chromosome number, x=6–11, with frequent aneuploidy and polyploidy. Although there are no unique synapomorphies, most taxa exhibit a trifid or trilobed stigma, although in a few it is capitate.

Genera

Tribe Hippeastreae includes ten to thirteen genera and about 180 species. Two of the genera, Haylockia and Traubia are monotypic.
Genus Traub 1963Dahlgren 1985Müller-Doblies 1996Meerow 1998Garcia 2014Species
Eithea
formerly Hippeastrum blumenavium		Hippeastreae
Hippeastrinae		1–2
Famatina
=Rhodophiala, Phycella		4
GriffiniaEuchareaeHippeastreae
Griffiniinae		HippeastreaeGriffineae21
HabranthusZephyrantheaeHippeastreaeHippeastreae
Zephyranthinae		HippeastreaeHippeastreae
Hippeastrinae		40
HaylockiaZephyrantheaeHippeastreae
Zephyranthinae		=Zephyranthes=Zephyranthes1
Hippeastrum=AmaryllisHippeastreaeHippeastreae
Hippeastrinae		HippeastreaeHippeastreae
Hippeastrinae		60
PhycellaEustephieaeHippeastreaeHippeastreae
Traubiinae		6
PlaceaAmarylleaeHippeastreaeHippeastreae
Hippeastrinae		HippeastreaeHippeastreae
Traubiinae		6
SprekeliaZephyrantheaeHippeastreaeHippeastreae
Zephyranthinae		HippeastreaeHippeastreae
Hippeastrinae		2
Rhodolirium=RhodophialaHippeastreae
Traubiinae		5
RhodophialaZephyrantheaeHippeastreaeHippeastreae
Hippeastrinae		HippeastreaeHippeastreae
Hippeastrinae		8
TocantiniaHippeastreae
Hippeastrinae		1–2
TraubiaTraubieaeHippeastreae
Traubiinae		HippeastreaeHippeastreae
Traubiinae		1
WorsleyaAmarylleaeHippeastreaeHippeastreaeGriffineae1
ZephyranthesZephyrantheaeHippeastreaeHippeastreae
Zephyranthinae		HippeastreaeHippeastreae
Hippeastrinae		50

Distribution and habitat

Hippeasteae have a major center of diversification in central Chile and western Argentina, together with minor centres in eastern Brazil, the north east of Argentina and with more distant centers in Mexico, the Greater Antilles and southern United States.

Uses

The economic significance of the tribe lies in its horticultural usage.