Epiphyllum, Haworth, 1812

Korotkova, Nadja, Borsch, Thomas & Arias, Salvador, 2017, A phylogenetic framework for the Hylocereeae (Cactaceae) and implications for the circumscription of the genera, Phytotaxa 327 (1), pp. 1-46 : 11-12

The Epiphyllum clade

A clade corresponding to Epiphyllum and including the type E. phyllanthus (Linnaeus) Haworth is supported with 1 PP, 94% MLBS, 98% JK, while three former species [ E. crenatum (Lindley) G. Don , E. anguliger (Lemaire) H.P. Kelsey & Dayton and E. lepidocarpum Britton & Rose are part of Disocactus . Our results are thus consistent with those obtained by Cruz et al. (2016) to exclude these three species. Epiphyllum chrysocardium Alexander is resolved as sister to the rest of Epiphyllum . It is a remarkable species with large white flowers and broad stems resembling fern leaves, known only from few collections from Chiapas and Tabasco, Mexico ( Figs. 1G , 3A ). It was originally described as a member of Epiphyllum , subsequently Backeberg (1959) placed it in his genus Marniera Backeberg , emphasizing that Marniera has hairy or bristly pericarpels while Epiphyllum has naked pericarpels. Marniera as a genus was later no longer accepted because its type M. macroptera (Lemaire) Backeberg cannot be satisfactorily identified ( Kimnach 1991), although the generic name as such was never formally rejected. Until recently E. chrysocardium was treated under Selenicereus because it has spiny fruits, which is untypical for Epiphyllum ( Bauer 2003 a, Kimnach 1991). Our data and those obtained by ( Cruz et al. 2016) confirm this species to be part of Epiphyllum .

The rest of Epiphyllum consists of two well supported clades. The Oxypetalum clade (1 PP, 77% MLBS, 79% JK) is characterized by stamens in two series. The Phyllanthus clade (1 PP, 68% MLBS, 72% JK) includes E. baueri R. Dorsch and E. cartagense (F.A.C. Weber) Britton & Rose and a subclade (1 PP, 85% MLBS, 62% JK) of species that have been regarded as taxonomically difficult within Epiphyllum . Numerous subspecies were described within this complex, but in the other extreme, they have been all treated under the name E. phyllanthus ( Dodson & Gentry 1977, Kimnach 1964). Currently two species are recognized within this complex ( Bauer 2003a): E. hookeri Haworth with three subspecies [ subsp. columbiense (F.A.C. Weber) Ralf Bauer , subsp. guatemalense (Britton & Rose) Ralf Bauer and subsp. pittieri ], and E. phyllanthus with one subspecies [ subsp. rubrocoronatum (Kimnach) Ralf Bauer ]. Our data show all E. phyllanthus accessions forming a clade (1 PP, 63% MLBS, 62% JK) while E. phyllanthus subsp. rubrocoronatum is not part of that clade but resolved as sister to E. hookeri (1 PP, 89% MLBS, 88% JK). The two subspecies of E. hookeri that were sampled are found as sisters to each other, but do not cluster with the third E. hookeri accession. Therefore, a more comprehensive evolutionary analysis including morphological and molecular characters and all known taxa related to the E. phyllanthus / E. hookeri complex is required to understand species limits (our study did not include E. grandilobum , E. hookeri subsp. pittieri or E. laui ).

Epiphyllum , as it is currently circumscribed, is a morphologically distinct genus and easily recognisable by flattened stems with often crenate or lobed stem margins and large, white nocturnal flowers with a well-developed floral tube. Its confusing classification history has been reviewed several times ( Backeberg 1959, Britton & Rose 1923, Buxbaum 1969).

Figures

FIGURE 1. Stem and flower morphology of the Hylocereeae.A) Acanthocereus chiapensis (Arias 1021); B) A. tetragonus (Arias 2166); C) Disocactus quezaltecus (Veliz 42515); D) D. phyllanthoides (Arias 1432); E) Aporocactus flagelliformis (Arias 1236); F) Epiphyllum cartagense (Hammel 19793); G) E. chrysocardium (cultivated, Botanical Garden UNAM); H) E. hookeri subsp. hookeri (Arias 1560); I) E. thomasianum (Hammel 22020); J) Pseudorhipsalis himantoclada (Hammel 20806); K) P. ramulosa (Ferrufino 718); L) Hylocereus monacanthus (Hammel 26600); M) H.undatus (cultivated, Botanical Garden UNAM); N) Selenicereus anthonyanus (Hammel, cultivated); O) S. dorschianus (Arias 2221); P) S. pteranthus (Garcia 874); Q) Weberocereus glaber (Bravo s.n.) [photos by S. Arias (A–H, K, M, O–Q), and B. Hammel (I, J, L, N)].

FIGURE 3. Convergent fern-like flattened stems in A) Epiphyllum chrysocardium, B) Weberocereus imitans, C) Epiphyllum anguliger, D) Selenicereus (Cryptocereus) anthonyanus (photos by W. Barthlott, Lotus-Salvinia.de).