Hohenbergia mesoamericana I.Ramírez, Carnevali et Cetzal[as Hohenbergia mesoamericana I Ramirez, G Carnevali & W Cetzal]

Diagnose: —Species haec H. spinulosae Mez similis sed infl orescentia proportione longiore, multo laxiore, 1-pinnata (vs. 2-pinnata), ramis cylindricis 3.2-4.9 cm longis (vs. fusiformibus, 1.8-2.2 cm longis), pedicellatis (vs. plerumque sessilibus), bracteis primariis proportione brevioribus et sepalis brevioribus (11.4 vs. 7.5 mm longis) differt.

Observations: —Hohenbergia mesoamericana appears to be most similar to H. spinulosa Mez, from Jamaica (portrayed in Baensch and Baensch, 1994: 111), with which it shares the general habit, the relatively short infl orescence, the extremely long bracts subtending the primary spikes, and the fl owers with green petals. These 2 are apparently the only species of Hohenbergia subgenus Wittmackiopsis Mez with truly green petals; all others display white petals (or apparently blue in H. caymanensis). However, H. mesoamericana is readily distinguished from H. spinulosa by means of several infl orescence and fl oral characters. In H. mesoamericana the infl orescences are relatively longer, conspicuously laxer, and with the bracts subtending the primary spikes relatively shorter. In H. mesoamericana the bracts subtending the lowermost spikes are 2.5-3 times longer than the spikes, whereas in H. spinulosa they are at least 6-7 times longer. The spikes are 20-22 in number, 3.2-4.9 cm long, and cylindrical in H. mesoamericana while they exceed 40 in number, are 1.8-2.2 cm long, and fusiform in the Jamaican taxon. In H. mesoamericana the fl oral bracts are 12 mm long while they exceed 15 mm in H. spinulosa. The sepals in Hohenbergia spinulosa are ca. 7.5 mm long, but 11.4 mm long in H.mesoamericana. Furthermore, the foliar spines are shorter in H. mesoamericana (1 vs. 2 mm long). This is the fi rst record of the genus Hohenbergia from Mesoamerica or elsewhere in the American mainland north of Colombia and Venezuela. Whether its mainland distribution is due to vicariance from an ancestral distribution or is due to a long-range dispersal event remains to be investigated. The emerged portions of the Antillean Plate have apparently never been in contact with the emerged portions of modern-day Mesoamerica (Coney, 1982). This fact apparently precludes vicariance as an explanation for the current disjunct distribution of Hohenbergia subg. Wittmackiopsis. The Antillean Plate was closest (probably ca. 300 km) to the then-emerged eastern portion of the current day Yucatán Peninsula during its SW-NE migration at the Paleogene-Eocene border (40- 50 my). The emerged portion of the Antillean Plate then diverged westward. Based on fl oristic similarities it has been concluded that the fl oristic relationships of the Yucatán Peninsula are closer to northern Mesoamerica (Estrada-Loera, 1991, Carnevali et al., 2003) than to the Antilles, despite the fact that the westernmost tip of Cuba is only ca. 200 km from the easternmost tip of the Yucatán Peninsula. The most striking feature of the Yucatán Peninsula and the Antillean fl oras is not what elements they share, but those that are missing from each area. In the Bromeliaceae, very few species are shared between the Antilles and the Mesoamerican mainland (Smith and Downs, 1979). In another large and mainly epiphytic family, the Orchidaceae, there are several endemic genera in the Antilles that are totally absent from the Mesoamerican mainland (Broughtonia R. Br., Tolumnia Raf., Tetramicra Lindl., Quisqueya Dod, Dilomilis Raf., Psychilis Raf., etc.). Similarly, many Mesoamerican orchid genera are absent from the Antilles. This evidence strongly suggests a long history of isolation between the 2 areas. However, there is a small but distinct Antillean element in the fl ora of current day Yucatán Peninsula, which requires an explanation. A “stepping stone” migration through the several small islands that constituted the emerged portions of the Antillean Plate into the Yucatán Peninsula at various times during the eastward drift of the Antillean plate is a likely explanation for this small but conspicuous Antillean element. Thus, H. mesoamericana or its common ancestor with other species of Hohenbergia subg. Wittmackiopsis, most likely arrived into the Mesoamerican mainland in this fashion. The apparently small phenetical divergence between the Mesoamerican taxon and the rest of the subgenus is, however, noteworthy, suggesting a recent invasion of the mainland by this bromeliad group. Today’s Jamaica is located more than a thousand kilometers from the only known locality of H. mesoamericana, thus making highly unlikely recent long range dispersal. An alternative explanation could be the frequent hurricanes occurring in the Caribbean, which could have been a factor in the dispersal of the Antillean elements found in the Yucatán Peninsula (and other areas of Mesoamerica), allowing for the transportation of propagules (wind-borne seeds) or of stray birds carrying the seeds of Hohenbergia in their guts. Examples of this kind of dispersal in other plant groups occurring in the Yucatán Peninsula are taxa such as Jacquinia arborea Vahl (Theophrastaceae), Canella winterana (L.) Gaertn. (Canellaceae), and Senna polyphylla (Jacq.) H. S. Irwin et Barneby (Fabaceae), among several others. A phylogenetic analysis of the genus Hohenbergia, coupled with a molecular-clock hypothesis would be required to test these alternative biogeographical scenarios as explanations for the disjunct distribution of Hohenbergia subg. Wittmackiopsis. According to the IUCN (2001), Hohenbergia mesoamericana would be classifi ed as critically endangered (CR) since it meets criterion D. The species is known from a single population consisting of probably only 2-3 plants/ genotypes. Furthermore, the habitat where it grows, a lowstature, thorn forest or arid tropical scrub that is associated with rocky outcrops close to the sea along the eastern coast of the Yucatán Peninsula, is severely fragmented due to human activities, particularly tourist developments. The lone population known was discovered during a vegetation assessment required by federal law prior to the construction of a series of condominiums and other tourist developments. Since no measures were taken at the time to protect the few plants located, this population may already be extinct. Hohenbergia mesoamericana remains to be rediscovered in 1 or more of a series of isolated patches of this severely fragmented habitat, all of them bound to disappear given that they lie within the so-called “Riviera Maya”. With any luck, populations of this species will be discovered within the boundaries of the Sian Ka’an Biosphere Reserve, which lies 50 km to the south, where extensive tracts of suitable habitat still exist in relatively good condition. Fortunately, a small cutting of the plant was brought into cultivation and vegetatively reproduced; these propagules now survive in several plant collections, at CICY’s Jardín Botánico Regional “Xíitbal’neek” (Mérida, Yucatán), and at the Jardín Botánico “Dr. Alfredo Barrera Marín” (Chetumal, Quintana Roo). Once the plants are brought into fl ower, we will attempt to reproduce Hohenbergia mesoamericana by seeds.

Edited from : Ramirez et al. 2010. (protologue) Hohenbergia mesoamericana (Bromeliaceae), first record of the genus for 0Mesoamerica .