Hippeastreae

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.[1][2]

Taxonomy

Meerow et al. (1999) provide a history of the treatment of the genera of Amaryllidaceae, including Hippeastreae, from the mid-twentieth century.[3] While morphological phylogeny has been frustrated by the perversive homoplasy typical of the Amaryllidaceae,[4] application of molecular phylogenetics to the Amaryllidaceae did not indicate clear tribal divisions but rather broad biogeographical clades. However the American clade resolved the Hippeastreae tribe.[3] 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),[lower-alpha 1] 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.[1] The tribe consists of 10–13 genera and about 180 species.[4]

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:[1]

Cladogram: Tribes of subfamily Amaryllidoideae
Subfamily Amaryllidoideae
Africa 

Tribe Amaryllideae

Africa 

Tribe Cyrtantheae
Africa 

Tribe Haemantheae


Australasia

Tribe Calostemmateae
Eurasian clade
Asia

Tribe Lycorideae


Mediterranean

Tribe Galantheae

Tribe Pancratieae

Tribe Narcisseae





American clade
Hippeastroid clade
Brazil

Tribe Griffineae

Tribe Hippeastreae



Andean clade


Tribe Eustephieae
Petiolate

Tribe Eucharideae/Stenomesseae


Tribe Clinantheae

Tribe Hymenocallideae










Subdivision

The genera of the Hippeastreae tribe have been treated in a number of different ways over the years. Traub (1963)[5] 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.[6] The concept of subtribes came from the Müller-Doblies' (1996), who had three subtribes, Griffinineae, Hippeastrinae and Zephyranthinae.[7]

Consequently, it has been customary to describe the Hippeastreae tribe as consisting of two subtribes:

In the study of Meerow et al. (2000) based on molecular markers Zephyranthinae (Zephyranthae of Traub)[5] 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.[1] Hippeastreae also include Haylockia, Rhodolirion and Tocantinia.[4]

A more focused study of Hippeastreae alone in 2014, resolved two major clades:[4]

However it also showed that of the 13 genera, two are monotypic (Haylockia and Traubia). Of the remaining 11 genera, based on Internal transcribed spacer (ITS) sequences the only monophyletic non-monotypic genera were Hippeastrum (about 60 species) and Sprekelia (2 species). But on chloroplast DNA (cpDNA) analysis, not even these genera were monophyletic. This brings into question the existing generic classification withi Hippeastreae. Consequently, the authors proposed the following nomenclature:[4]

Subtribes

Subtribe Traubiinae (Clade A) 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.[4]

Subtribe Hippeastrinae (Clade B), 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.[4]

Genera

Tribe Hippeastreae includes ten to thirteen genera and about 180 species. Two of the genera, Haylockia and Traubia are monotypic.[4]

Historical distribution of Hippeastreae (sensu Meerow 1999) genera by tribes and subtribes
Genus (alphabetical)Traub 1963[5]Dahlgren 1985[6]Müller-Doblies 1996[7] Meerow 1998[9]Garcia 2014[4]Species
Eithea
formerly Hippeastrum blumenavium		 Hippeastreae
Hippeastrinae 		1–2
Famatina
=Rhodophiala, Phycella		 4
GriffiniaEuchareae Hippeastreae
Griffiniinae		HippeastreaeGriffineae21
HabranthusZephyrantheaeHippeastreaeHippeastreae
Zephyranthinae		HippeastreaeHippeastreae
Hippeastrinae		40
HaylockiaZephyrantheae Hippeastreae
Zephyranthinae		=Zephyranthes=Zephyranthes1
Hippeastrum=AmaryllisHippeastreae Hippeastreae
Hippeastrinae		HippeastreaeHippeastreae
Hippeastrinae		60
PhycellaEustephieae HippeastreaeHippeastreae
Traubiinae		6
Placea AmarylleaeHippeastreae Hippeastreae
Hippeastrinae		HippeastreaeHippeastreae
Traubiinae		6
SprekeliaZephyrantheaeHippeastreaeHippeastreae
Zephyranthinae		HippeastreaeHippeastreae
Hippeastrinae		2
Rhodolirium=Rhodophiala Hippeastreae
Traubiinae		5
RhodophialaZephyrantheaeHippeastreaeHippeastreae
Hippeastrinae		HippeastreaeHippeastreae
Hippeastrinae		8
Tocantinia Hippeastreae
Hippeastrinae		1–2
TraubiaTraubieae Hippeastreae
Traubiinae		HippeastreaeHippeastreae
Traubiinae		1
WorsleyaAmarylleaeHippeastreae HippeastreaeGriffineae1
ZephyranthesZephyrantheaeHippeastreaeHippeastreae
Zephyranthinae		HippeastreaeHippeastreae
Hippeastrinae		50

Distribution and habitat

Hippeasteae have a major center of diversification in central Chile and western (Andean) 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 (Habranthus, Zephyranthes).[4]

Uses

The economic significance of the tribe lies in its horticultural usage.[4]

Notes

  1. ↑ Hippeastrum blumenavium, or Hippeastrum blumenavia, was earlier known as Griffinia blumenavia and is an unusual species more closely resembling Rhodophiala. Ultimately Meerow et al. recommended reassigning it to a monotypic genus, where it is now known as Eithea.

References

Bibliography

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