Improving taxa and character sampling to support generic and infrageneric status of Alcantarea.
Historical difficulties encountered in defining species and generic units in Bromeliaceae was documented by Brown & Leme (2000)on the basis of sampling (i. e., "methodological") related problems: loss or modification of some important structures in herbarium specimens in post-collection preparation steps and under collection and the consequent poor documentation of morphological variation in wild populations. Other related problems are "historical": missing morphological data on most currently known species; "instrumental": reduced number of well documented living collections; "biological": high homoplasy in morphological characters; and "conservational": local and global species extinction.
Recent studies, however, using improved data mainly based on living specimens (e. g. Vieira, 1999; Forzza, 2001; Costa, 2002; Tatagiba, 2003; Souza, 2004; Faria et al., 2004; Leme & Siqueira-Filho, 2006) demonstrate that better taxon sampling combined with careful attention to character sampling can result in a much clearer understanding of taxonomic and phylogenetic relationships within Bromeliaceae.
A short-term investigation was conducted with the purpose of verifying how much improved morphological data based on living material may influence Alcantarea delimitation and its species circumscription in comparison to Vriesea. So, during 2004 and the first semester of 2005, in situ and ex situ observations were carried out with careful selection and documentation (i. e., descriptions, sketch drawings and photographs) of sub-utilized characters provided by living specimens only. The ex situ observations took place in the author's living collection, Refugio dos Gravatas, at Teresopolis, Rio de Janeiro, covering 15 of the 18 known species (Luther, 2006). Alcantarea hatschbachii (L. B. Sm. & Read) Leme is considered extinct and was excluded from this study, as were A. brasiliana (L. B. Sm.) Grant and A. regina (Vell.) Harms, both considered here to be dubious taxa. The results were presented in the Bromeliaceae Symposium, during the 17th International Botanical Congress, in Vienna, Austria, in July, 2005 (see Grant & Till, 2005).
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Alcantarea (E. Morren ex Mez) Harms was originally conceived in 1894 as Vriesea subg. Alcantarea E. Morren ex Mez. In 1929, Harms elevated it to generic status, but in 1935 Mez re-established its subgenus position, which was kept until 1995, when Jason R. Grant resurrected its genus status on the basis of the following highlighted characteristics: (1) geographical distribution restricted to southeastern and northeastern Brazil, in the states of Rio de Janeiro, Espirito Santo, Minas Gerais and Bahia; (2) plants with generally large habit with bulky compound inflorescence; (3) petals linear-long, spiraliscent, ephemeral, flaccidescent, 10-15 times longer than wide; (4) stigma convolute-bladed type, and (5) seeds bearing both basal and apical comas (Grant, 1995).
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After visiting large populations of Alcantarea in different areas, as well as examining many living flowering specimens, it was possible to confirm, improve and reevaluate some data mentioned by Grant (1995) to segregate Alcantarea from related genera.
The geographical distribution for the genus was confirmed and improved, extending its occurrence southward to the state of Sao Paulo, where Alcantarea edmundoi (Leme) J. R. Grant was found in Bertioga (Leme et al. # 3193), near seashore. The habit information was improved too: all members of the genus have a specialized rupicolous habit, living on vertical to nearly horizontal rocky surfaces and rocky outcrops, usually forming large populations associated with inselbergs in the domain of the Atlantic Forest and the Campos Rupestres, from near sea level to about 2,000 m elevation. They are never epiphytic, but can be accidentally terrestrial in the borders of rocky habitats.
Althought 12 of the 18 known species present large habit with bulky compound inflorescence as mentioned by Grant (1995), four taxa have a median habit [Alcantarea burlemarxii (Leme) J. R. Grant, A. duarteana (L. B. Sm.) J. G. Grant, A. hatschbachii and A. nevaresii Leme], and two are small-sized [A. benzingii Leme and A. farneyi (Martinelli & A. Costa) J. R. Grant]. Although the bulky compound inflorescence is a common feature in the genus, A. hatschbachii, A. benzingii, A. farneyi and another undescribed species (i.e. Leme et al. # 3658) have simple and sometimes comparatively short inflorescences, and so the character related to the presence of lateral branches can not be used to segregate Alcantarea from the related genera.
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One of the improved characters is related to the unique vegetative propagation of Alcantarea by means of numerous hairy adventitious offsets produced at the old elongated portion of stem not covered by leaves, like some Tillandsia species. These hairy offsets assure the vegetative propagation mainly for some species [e. g. Alcantarea imperialis (Carriere) Harms] that very often do not produce any regular rosette-offset at anthesis or afterwards and can be considered an example of "pseudo-monocarpy".
The data related to seed propagation was also confirmed and improved: Alcantarea seeds are fusiform, bearing both basal and apical plumose comas. However, the umbrella-like apical coma is relatively short and even shorter than the basal coma, which is responsible for its comparatively reduced flying capacity that may have important implications in the wind dispersal ability of their species and in the strategy for habitat colonization.
The unusual petal characters of Alcantarea was also confirmed: linear-long, recurved, spiraliscent, ephemeral, flaccidescent, 10-15 times longer than wide. But characters related to the delicate petals appendages that are hardly observed in herbarium specimens were improved: they are comparatively longer (to 4.8 cm long), equaling 3/4 of the corolla length to exceeding it (exserted) in a undescribed species from Minas Gerais (i.e., Leme et al. # 3658). The appendages are adnate to the petals for 2/3 to 4/5 of their length.
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Other difficult-to-observe structures in dried specimens are the anthers and stigma. However, in living specimens, these floral parts can be easily studied and improved. The anthers of the Alcantarea are narrowly linear, filiform and narrower than the filaments, subterete to slightly laterally complanate and sometimes spirally twisted at anthesis; the dehiscence line prevailing lateral (vs. prevailing frontal in Vriesea); margin of the opposed pollen sacs touching to slightly overlapping each other at anthesis and completely hiding the connective area (vs. connective area completely exposed in Vriesea), with pollen release-area covering the whole anther (vs. prevailing frontal in Vriesea). These characters are much closer related to those observed in Tillandsia and some Pitcairnia than in Vriesea.
The same is true about the stigma, as the convolute-bladed type reported by Grant (1995), typical of Vriesea species, was not confirmed. On the contrary, the stigma type observed in Alcantarea is conduplicate-spiral, bearing suberect to spreading blades, which is shared by many Tillandsia species, as well as by most members of Bromelioideae.
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The careful selection and documentation of sub-utilized characters provided by living specimens strengthened the generic status of the resurrected Alcantarea when compared to Vriesea and are potentially useful to segregate species and recognize new taxa. On the other hand, some of the improved characters (e.g., hairy adventitious offsets, anthers and stigma type) suggest in some unclear extent a closer relationship of Alcantarea to Tillandsia, which recommends a specific investigation. However, these results are not supported by the molecular study conducted by Barfuss et al. 2005), since Alcantarea (and Werauhia) was well-supported in Vriesea s. l., and the segregation of Alcantarea (and Werauhia) makes the remainder of Vriesea paraphyletic.
Besides all the advances provided by molecular systematic studies, improving taxa along with character sampling can be very useful for a morphological-based phylogenetic reconstruction within Bromeliaceae. Thus, the intensification of field activities and the establishment of well documented living collections have a strategic importance in the conduction of new taxonomic investigations in Bromeliaceae and to access and conserve biodiversity.
Barfuss, M. H. J., R. Samuel, et al. (2005). "Phylogenetic relationships in subfamily Tillandsioideae (Bromeliaceae) based on DNA sequence data from seven plastid regions." Am. J. Bot. 92: 337-351.
Brown, G. K. and E. M. C. Leme (2000). Cladistic Analysis in the Nidularioid Complex. Nidularium--Bromeliads of the Atlantic Forest. Rio de Janeiro, Sextante: 240-247.
Costa, A. F. d. (2002). Revisao Taxonomica do Complexo Vriesea paraibica Wawra (Bromeliaceae). Instituto de Biociencias Sao Paulo, Universidade de Sao Paulo. PhD: 187.
Faria, A. P. G., W. T, et al. (2004). "Cladistic Relationships of Aechmea (Bromeliaceae, Bromelioideae) and Allied Genera." Ann. MO. Bot. Gard. 91: 303-319.
Forzza, R. C. (2001). Filogenia da Tribo Puyeae Wittm. e Revisao Taxonomica do Genero Encholirium Mart. ex Schult. & Schult. f. (Pitcairnioideae--Bromeliaceae). Instituto de Biociencias Sao Paulo, Universidade de Sao Paulo. PhD: 208.
Grant, J. (1995). "Bromelienstudien. The resurrection of Alcantarea and Werauhia, a new genus." Trop. Subtrop. Pflanzenwelt 91: 1-57.
Grant, J. and W. H. Till (2005). "Report on the Bromeliaceae Symposium at the 17th International Botanical Congress." J. Bromeliad Soc. 55(5): 205-206.
Leme, E. M. C. and Siqueira-Filho (2006). Taxonomia das bromelias dos fragmentos de Mata Atlantica de Pernambuco e Alagoas. Fragmentos de Mata Atlantica do Nordeste, Biodiversidade, Conservacao e suas Bromelias. J. A. Siqueira-Filho and E. M. C. Leme. Rio de Janeiro, Andrea Jakobsson Estudio.
Luther, H. (2006). An alphabetical list of bromeliad binomials 10th edition. Sarasota, FL, Bromeliad Society International.
Souza, L. O. F. (2004). Revisao Taxonomica e Filogenia do Genero Lymania Read (Bromeliaceae: Bromelioideae). Rio de Janeiro, Universidade Federal do Rio de Janeiro. MSc thesis: 102.
Tatagiba, F. C. P. (2003). Revisao do Complexo Pitcairnia flammea Lindley (Bromeliaceae). Museu Nacional. Rio de Janeiro, Universidade Federal do Rio de Janeiro. MSc: 106.
Vieira, C. M. (1999). Quesnelia Gaudich. (Bromelioideae: Bromeliaceae) do estado do Rio de Janeiro, Brasil. Museu Nacional. Rio de Janeiro, Universidade Federal do Rio de Janeiro. MSc: 141.
Elton M. C. Leme (1) photographs by the author
(1) Herbarium Bradenum, Rio de Janeiro--RJ, email@example.com
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|Author:||Leme, Elton M.C.|
|Publication:||Journal of the Bromeliad Society|
|Date:||Sep 1, 2007|
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