Alcantarea (Bromeliaceae) leaf anatomical characterization and its systematic implications Leonardo M. Versieux, Paula Maria Elbl, Maria das Grac ¸as Lapa Wanderley and Nanuza Luiza de Menezes L. M. Versieux (lversieux@yahoo.com.br), Depto de Bota ˆnica, Ecologia e Zoologia, Univ. Federal do Rio Grande do Norte, Natal, RN, 59072- 970, Brazil.  P. M. Elbl and N. Luiza de Menezes, Depto de Bota ˆnica, Inst. de Biocieˆncias, Univ. de Sa ˜o Paulo, Rua do Mata ˜o, trav. 14, n. 321, Sa ˜o Paulo, SP, 05508-090, Brazil.  M. das Grac ¸as Lapa Wanderley, Inst. de Bota ˆnica, Caixa Postal 3005, Sa ˜o Paulo, SP, 01061- 970, Brazil. Alcantarea (Bromeliaceae) has 26 species that are endemic to eastern Brazil, occurring mainly on gneissgranitic rock outcrops (‘inselbergs’). Alcantarea has great ornamental potential and several species are cultivated in gardens. Limited data is available in the literature regarding the leaf anatomical features of the genus, though it has been shown that it may provide valuable information for characterizing of Bromeliaceae taxa. In the present work, we employed leaf anatomy to better characterize the genus and understand its radiation into harsh environments, such as inselbergs. We also searched for characteristics potentially useful in phylogenetic analyses and in delimiting Alcantarea and Vriesea. The anatomical features of the leaves, observed for various Alcantarea species, are in accordance with the general pattern shown by other Bromeliaceae members. However, some features are notable for their importance for sustaining life on rock outcrops, such as: small epidermal thick-walled cells, uneven sinuous epidermal walls, hypodermis often differentiated into lignified layers with thick-walled cells, aquiferous hypodermis bearing collapsible cells, and the presence of well developed epicuticular stratum. Alcantarea leaves tend to show different shapes in the spongy parenchyma, and have chlorenchymatous palisade parenchyma arranged in more well-defined arches, when compared to Vriesea species from the same habitat. The monocot family Bromeliaceae is almost exclusive of the New World but exhibits a great morphological and ecophy- siological versatility (Smith and Downs 1974, Benzing 2000a). Including 58 genera and 3172 species (Luther 2008), Bromeliaceae can be seen in a wide variety of habitats across tropical and subtropical Americas, ranging from coastal sandy plains  like the Brazilian ‘restingas’  to humid tropical forests to deserts and high altitudes vegetation in the Andes (Smith 1934, Pittendrigh 1948, Rundel and Dillon 1998). Currently, Bromeliaceae is considered to be the first lineage to emerge within the Poales order, and is close to Typhaceae and Rapateaceae (Soltis et al. 2005, Chase et al. 2006). Several bromeliad species are key elements in stressful environments (e.g. restingas, swamps, high altitude fields, rock outcrops inside the Atlantic rainforest domain), usually providing more favorable conditions for the establishment (germination and growth) of other species, thus being known as ‘nurse plants’ (Scarano 2002). The Atlantic rainforest of eastern Brazil has been considered a center of diversity for Bromeliaceae. A pattern of decreasing numbers of genera and species when approach- ing the drier inland territory with its associated vegetation has been an observed (Smith 1934, Reitz 1983, Versieux and Wendt 2007). Most bromeliads, however, present adapta- tions to save water, such as the rosettes formed by the spirally distributed leaves. In this case, the overlapping bases form a cavity that can be filled up with rain water (Pittendrigh 1948) forming a reservoir. A second key characteristic is the presence of peltate foliar trichomes, also referred to as lepidote, stellate, or multi-cellular hairs considered to be the most distinguishing feature of the family (Tomlinson 1969). Their functions include e.g. retarding transpiration, redu- cing heat load, and photo-injury to absorbing water and nutrients (Benzing 1976, 2000b). Concomitant to the evolution of absorptive trichomes, there was a progressive structural and functional reduction of the root system, formation of parenchyma and support structures, all important for the transition to epiphytic and rupiculous life forms (Braga 1977). Due to these adaptations and others, like endurance to drought and impoverished sub- strates (such as xeromorphic leaf structure, ‘crassulacean acid metabolism’ (CAM) photosynthesis, and heterophylly), Bromeliaceae are able to occupy exceptional habitats and become the most exclusive and dominant plant in a particular environment (Reinert and Meirelles 1993, Por- embski et al. 1998, Benzing 2000a). Along eastern Brazil, a type of habitat that can be considered stressful for plant communities are the inselbergs Nordic Journal of Botany 28: 385397, 2010 doi: 10.1111/j.1756-1051.2010.00727.x, # The Authors. Journal compilation # Nordic Journal of Botany 2010 Subject Editors: Guido Grimm and Thomas Denk. Accepted 26 April 2010 385