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Palavras-chave -beija-flores, biologia floral, Bromeliaceae, fenologia, Mata Atlântica IntroduçãoBromeliaceae está entre as poucas famílias em que a polinização por vertebrados predomina sobre a polinização por insetos (Sazima et al. 1989). Sick (1984) sugere que a diversificação das famílias Bromeliaceae e Trochilidae tenha se processado paralelamente, pois esta última contém os agentes polinizadores mais importantes para as bromélias. Essa idéia tem sido corroborada por diversos estudos que apontam os beijaflores como vetores de pólen de cerca de 85% das bromeliáceas nas diferentes comunidades investigadas, sendo as demais espécies visitadas por morcegos e, em menor quantidade, abelhas (Snow & Snow 1980, Snow & Teixeira 1982, Gardner 1986, Fischer & Araujo 1995, Sazima et al. 1995, 1996, Canela & Sazima 2003, Araujo et al. 2004.A fenologia e polinização de Bromeliaceae têm sido relativamente pouco investigadas. O padrão fenológico de uma comunidade vegetal é relevante no estudo da interação planta-animal, pois propicia importante ferramenta para o entendimento da reprodução das plantas e da organização espaço-temporal dos recursos disponíveis no ambiente aos animais associados

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We conducted an isozyme study in 22 populations of five Pleurothallis (Orchidaceae) species (12 loci in nine enzymatic systems). The genetic variability in all populations is surprisingly high (P = 58-83%, A = 2.1-3.8, H(e) = 0.25-0.43) in spite of the fact that the five species are pollinated by small flies whose behavior enables self-pollination. We suggest that self-incompatibility, inbreeding depression, and mechanical barriers that prevent self-pollination in these species are responsible for the maintainance of the high genetic variability. These traits are uncommon in Orchidaceae, but have been observed in these and some other species pollinated by flies or other pollinators with behavior that facilitates self-pollination. The genetic similarity among conspecific populations is also high for species with very short-range flying pollinators. Only one population of P. teres presented values of genetic similarity lower than usually observed in allopatric conspecific populations. Morphology, however, does not support its segregation as a new taxon. All species can be recognized by their enzymatic patterns, and the results agree with recently proposed taxonomic realignments. Conversely, the supposed affinities among these species based on floral morphology are not supported, and we hypothesize that it may be due to convergence in species with similar pollinators.

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Morphometric analyses of vegetative and floral characters were conducted in 21 populations of five Pleurothallis (Orchidaceae) species occurring in Brazilian 'campo rupestre' vegetation. A phylogenetic analysis of this species group was also carried out using nuclear ribosomal DNA internal transcribed spacers (ITS1 and ITS2). Results of the ordination and cluster analyses agree with species' delimitation revealed by taxonomic and allozyme studies. The groups formed in ordination analysis correspond to the pollinator groups determined in a previous pollination study. Relationships among the species in the cluster analysis using only vegetative characters are similar to those found in a previous allozyme study, but those indicated by cluster analysis using only floral characters differ. These results support the hypothesis that floral similarities are due to convergence driven by similar pollination mechanisms, and therefore floral traits may not be good indicators of phylogenetic relationships in this group. The results of the phylogenetic analysis support this conclusion to some extent. There is no correlation between genetic (allozyme) and morphological variability in the populations nor in the way this variability is distributed among conspecific populations. We describe a new subspecies of Pleurothallis ochreata based on differences in vegetative and chemical characters as well as geographic distribution. Absence of differentiation in floral characters, attraction of the same pollinator species, interfertility and genetic similarity support the argument for subspecific rather than specific status.