Hylocereeae
The Hylocereeae are a tribe of cacti. Most are found in the tropical forests of Central and northern South America, and are climbers or epiphytes, unlike most cacti. The tribe includes between six and eight genera in different circumscriptions. The plants known as "epiphyllum hybrids" or "epiphyllums", widely grown for their flowers, are hybrids of species within this tribe, particularly Disocactus, Pseudorhipsalis and Selenicereus, less often Epiphyllum, in spite of the common name.
Description
The members of the tribe are very variable in their morphology, especially when the terrestrial Acanthocereus is included. Many species form aerial roots. The hylocereoid clade are mostly climbing or epiphytic, and have spiny ribbed stems. The phyllocactoid clade are mainly epiphytic, and have spineless flattened leaf-like stems. Flowers and pollination syndromes are equally diverse, ranging from large white nocturnal flowers to bright red flowers opening in the daytime.Taxonomy
The group was first identified by Britton and Rose in 1920 as the subtribe Hylocereinae of the tribe Cereeae. In 1958, Buxbaum revised the subtribe Hylocereinae, placing it in a newly created tribe Hylocereeae, which included four other subtribes, some containing genera removed from Hylocereinae, others containing different genera.The International Cactaceae Systematics Group classification, based on Barthlott & Hunt, recognized six genera within the tribe. Subsequent studies suggested a number of changes, for example including Acanthocereus in the tribe and excluding Strophocactus. It was also shown that Hylocereus was nested within Selenicereus. A major molecular phylogenetic study of the tribe was published in 2017. The lefthand cladogram below shows the relationships obtained. A 2020 phylogenetic study, which also included morphological features of the stem, produced the righthand cladogram below. This resolved the position of Aporocactus, placing it within the hyloceroid clade, but left relationships within the phyllocactoid clade unresolved.
The authors of the 2017 study proposed revised circumscriptions of some of the genera and of the tribe to make them monophyletic according to their molecular phylogeny:
- Acanthocereus, which had been included in Hylocereeae by some earlier authors, but also in Echinocereeae, Pachycereeae and Phyllocacteae, was expanded to include Peniocereus subg. Pseudoacanthocereus, and restored to Hylocereeae.
- Aporocactus was separated again from Disocactus.
- Selenicereus was expanded to include part of Weberocereus and the whole of Hylocereus, which was nested within it. Strophocactus wittii, which had been included in Selenicereus, was excluded from the Hylocereeae altogether, along with the genus Deamia, containing two species that had been placed in either Strophocactus or Selenicereus.
- To maintain the monophyly of Pseudorhipsalis, Pseudorhipsalis ramulosa was moved to a new genus, Kimnachia, as Kimnachia ramulosa.
| Barthlott & Hunt | Korotkova et al. |
| – | Acanthocereus |
| Disocactus | Aporocactus |
| Disocactus | Disocactus |
| Epiphyllum | Epiphyllum |
| Hylocereus | Selenicereus |
| Selenicereus | Selenicereus |
| Weberocereus s.l. | Selenicereus |
| Weberocereus s.s. | |
| Pseudorhipsalis | Pseudorhipsalis |
| Pseudorhipsalis | Kimnachia |
Genera
The tribe Hylocereeae includes eight genera in the 2017 classification by Korotkova et al.- Acanthocereus Britton & Rose
- Aporocactus Lem.
- Disocactus Lindl.
- Epiphyllum Haw.
- Kimnachia S.Arias & N.Korotkova
- Pseudorhipsalis Britton & Rose
- Selenicereus Britton & Rose
- Weberocereus Britton & Rose