Xiphidium Loefl., Iter Hispan.: 179. 1758.

Pellegrini, Marco O. O., Hickman, Ellen J., Guttierrez, Jorge E., Smith, Rhian J. & Hopper, Stephen D., 2020, Revisiting the taxonomy of the Neotropical Haemodoraceae (Commelinales), PhytoKeys 169, pp. 1-59 : 1

5. Xiphidium Loefl., Iter Hispan.: 179. 1758. Figs 22 , 23 , 24 , 26

Tonduzia Boeckeler ex Tonduz, Bull. Herb. Boissier 3: 464. 1895, nom. nud.

Durandia Boeckeler, Allg. Bot. Z. Syst. 2: 160, 173. 1896, Syn. nov. Type species. Durandia macrophylla Boeckeler (= Xiphidium caeruleum Aubl.).

Type species.

Xiphidium caeruleum Aubl.

Nomenclatural history.

It has been widely accepted that the original place of publication of the generic name Xiphidium is "Histoire des Plantes de la Guiane Françoise” by Aublet (1775). Nonetheless, Aublet never clearly states to be proposing a new genus. This seems to follow his publication’s formatting, where none of the new taxa present any explicit statement indicating that they are newly proposed. At the end of the Latin diagnosis and French comments, Aublet (1775: 35) mentions that his new species differs from the one described by Loefling (1758) due to its "fine stems and leaves furnished with hairs, blue flowers, and oval and acute petals". This statement makes it clear that Aublet had access to Loefling’s publication (1758) and knew of the description of his new genus Xiphidium . Finally, Dorr and Wiersema (2010) give the final support to our interpretation when they explain that in several instances, Loefling (1758) cited a genus published earlier by Linnaeus or P. Browne, followed by a full stop, (an) alternative generic name(s) and a description. The authors also point out that, on some occasions, this formatting has been misinterpreted as the proposal of species’ names (i.e., binary combinations), which they are not. That was the case of Xiphidium Loefl., which was misinterpreted as representing a new species, Ixia xiphidium Loefl. (e.g., Maas and Maas-van de Kamer 1993), instead of the publication of a new genus. Thus, the genus Xiphidium was originally described by Loefling (1758), without the inclusion of any species. The proposal of Xiphidium by Loefling (1758) is based on the author not agreeing on the inclusion of all elements/species by Linnaeus in his Ixia L.

The first species name to be validly published in Xiphidium was only proposed almost 20 years later, by Aublet (1775), as X. caeruleum Aubl. The publication of the generic name Xiphidium by Loefling (1758) makes it clear that the author recognised a sole species for that genus. The practice of not providing a specific epithet when describing monospecific new genera was common practice at the time. A similar situation, with the description of the type genus of Haemodoraceae - Haemodorum ( Smith 1798) -, supports this interpretation. When first described, Haemodorum was considered monospecific and, therefore, was not given a specific epithet, according to the standard practice of J.E. Smith (1798). Only seven years later, another author ( Vahl 1805) provided an epithet for Smith’s plant, as H. corymbosum Vahl. Thus, as the first species formally published and associated with Xiphidium , X. caeruleum automatically typifies this generic name.

Comments.

Xiphidium has traditionally been considered an ill-circumscribed genus, lacking any obvious synapomorphy ( Simpson 1990, 1993, 1998b). However, with the transfer of X. xanthorrhizon to Cubanicula , Xiphidium s.str. can be easily defined by its introrsely rimose, but functionally poricidal anthers (an adaptation to buzz-pollination; Buchmann 1980), the complete loss of septal nectaries (also an adaptation to buzz-pollination), capsules bright-coloured, indehiscent, lacking thickened septal ridges and somewhat fleshy at maturity (a possible adaptation to endozoochory) and cuboid seeds ( Hickman 2019; Pellegrini 2019). All these characters are unique in the family and observed on the two species of Xiphidium accepted by us in the present study. The anther morphology of Xiphidium and its floral biology are reminiscent of some species of Dichorisandra J.C. Mikan ( Commelinaceae , Commelinales ) that also possess introrsely rimose but functionally poricidal anthers ( Pellegrini and Faden 2017). However, studies on the reproductive biology of Xiphidium are non-existent, save that by Buchmann (1980). Further studies focusing on effective pollination and seed dispersal are necessary. The genus is well-documented as medicine for snakebite ( Odonne et al. 2013) and has antimalarial and leishmanicidal properties ( Valadeau et al. 2009). Xiphidium caeruleum also shows the most significant genetic divergence levels for any species of Haemodoraceae amongst populations across its wide Neotropical range ( Hopper et al., in prep.). A further detailed taxonomic study is recommended, combining extensive fieldwork, molecular data, and traditional taxonomy.

Figures

Figure 22. Xiphidium caeruleum Aubl. A specimen growing in a flooded forest B habit C inflorescence D cincinnus E, F flower: E flower with subequal, narrow, and pale apricot perianth lobes F flower with equal, broad, and white perianth lobes G flower with perianth removed showing androecium and gynoecium with ovary pubescent long the septal ridges H cincinnus with immature berries I mature berries. A, F by R. Aguilar, B by H. Medeiros, C-D, G, I by M. O. O. Pellegrini, E by A. Yakovlev, and H by R. Cumming.

Figure 23. Xiphidium caeruleum Aubl. Line drawing of the inflorescence. Illustration by E. J. Hickman. Scale bar: 1 cm.

Figure 24. Xiphidium caeruleum Aubl. A roots in cross-section B-D rhizome: B naked rhizome C longitudinal section D lateral branch E cincinnus F flower bud G hairs H, I flower: H frontal view I side view J flower with the perianth removed, showing the androecium and gynoecium K lateral stamen (frontal and dorsal view) L stigma M-P fruit: M immature berry N berry in cross-section O berry in longitudinal section P indehiscent and old berry Q-T seed: Q dorsal view R lateral view S ventral view T longitudinal section. Illustration by E. J. Hickman. Scale bars: 0.8 mm (A); 1.5 cm (B-D); 0.75 mm (E); 2 mm (F, H, I, M-P); 0.4 mm (G); 1.75 mm (J); 1 mm (K); 0.5 mm (L, Q-T).

Figure 26. Xiphidium pontederiiflorum M. Pell. et al. A-C habit: A vegetative habit B flowering habit with a young inflorescence C viviparous inflorescence with three axillary propagules D inflorescence with open flowers and apricot floral buds E floral buds and flowers at pre-anthesis F, G flower: F white flower with green ovary G pale apricot flower with vinaceous ovary H detail of the androecium and gynoecium, showing the ovary pubescence along the septal ridges I inflorescence with open flowers and mature berries J mature berry. C, E, J by A. R. Jonker, remaining photos by A. Kay.