Plant establishment was studied in a swamp forest in the lowland Atlantic rainforest in southeastern Brazil. A topographic gradient allowed a clear distinction between a periodically flooded and a permanently flooded site in the study area. Both sites were mosaics of patches: the former showed soil patches of varying sizes subject to distinct flooding durations (from 0 to 300 d per year) and in the latter, the tank bromeliads which densely occupied the understorey, trap litter and provided ‘suspended soil’ patches. In the periodically flooded site, the occurrence of regenerants (< 1.0 m tall) of the actively regenerating tree populations of Calophyllum brasiliense, Symphonia globulifera and Tovomitopsis paniculata (all Clusiaceae), originating from seed or vegetative organs, was recorded for 1 m2 quadrats placed in flooded (n = 82) and unflooded (n = 103) patches. In the permanently flooded site, dominated by Tabebuia cassinoides (Bignoniaceae), the presence of germinated seedlings was counted for 400 rosettes of the terrestrial tank bromeliad Nidularium procerum. The results showed that unflooded patches, including tank bromeliads, favoured seedling establishment. However, T. paniculata and T. cassinoides colonize patches where flooding lasts longer or is permanent mostly by reproducing vegetatively, while the seeds of C. brasiliense, which showed no form of vegetative reproduction, and S. globulifera are successful in colonizing flooded patches. Germination tests and field observations indicated that, for C. brasiliense, pre- and post-dispersal seed dormancy, a two-phase seed dispersal (water and bats) and seedling tolerance to flooding accounted for this pattern.

-(Species composition and biogeographic relations of the rock outcrop flora on the high plateau of Itatiaia, SE-Brazil). We studied the flora of vegetation islands on rock outcrops on the Itatiaia Plateau (22°21'S and 44°40'W), at 2,400 m.a.s.l. A total of 114 vascular plant species, which correspond to ca. 20%-25% of the currently inventoried flora of the plateau, were sampled in 197 small vegetation islands (total area of 0.034 ha). Xerophytes and hydrophytes were often found side by side due to environmental heterogeneity at a small scale, explaining in part the high species diversity. Rock outcrops may support floras quite distinct from those in neighbouring habitats, due to the action of strong environmental filters, but in Itatiaia the geographic distribution patterns among rupicolous plants appear to mimic those described for the whole flora around it, with 15.1% of narrow endemic species and six strictly rupicolous plants. Underlining the "temperate" nature of the high elevation climate in Itatiaia, the sampled flora was dominated by species of the families Asteraceae and Poaceae, and the number of CAM (crassulacean acid metabolism) species was very low. A few endemic species of tropical origin-Pleurostima gounelleana (Beauv.) Men. (Velloziaceae) and Fernseea itatiaiae (Wawra) Baker (Bromeliaceae)play a crucial role in this vegetation, as pioneer mat-formers facilitating later establishment of numerous other species. Hemicryptophytes prevail in the sampled flora, while therophytes are exceptionally rare and mainly consist of opportunistic species associated with disturbances. Numerous microhabitats and strong environmental gradients in these high elevation rock outcrops afford opportunities for establishment of a highly diversified flora. These island-like environments may represent an important refuge for grassland species from fire and other disturbances in the surrounding grasslands. Key words-Atlantic rain forest, biogeography, "campos de altitude", endemisms, rock outcrops, rupicolous plants RESUMO-(Composição de espécies e relações biogeográficas da flora sobre afloramentos rochosos no Planalto do Itatiaia, SE do Brasil). O objeto deste estudo foi a flora que se distribui em ilhas de vegetação isoladas sobre a superfície rochosa, no Planalto do Itatiaia (22°21'S e 44°40'W), a 2.400 m de altitude. Foi encontrado um total de 114 espécies vasculares, correspondendo a ca. 20%-25% da flora total atualmente inventariada do Planalto, em 197 pequenas ilhas de vegetação (área total de 0,034 ha). Xerófitas e hidrófitas com freqüência ocorrem lado a lado devido à forte heterogeneidade ambiental em pequena escala espacial, explicando em parte a alta diversidade local. Superfícies rochosas podem abrigar floras muito distintas do entorno em função de fortes filtros ambientais contrastantes, mas no Itatiaia os padrões de distribuição geográfica de plantas rupícolas assemelham-se aos dos campos no entorno, com 15,1% das espécies sendo endêmicas restritas e seis sendo estritamente rupícolas. Destacando a natureza "t...

available online at httpj//www.idealibrary.com on I BE bl 0 @ Four sites with contrasting environmental stress in southeastern Brazil: relations of species, life form diversity, and geographic distribution to ecophysiological parameters Some ecophysiological parameters related to plant performance and fitness (carbon and nitrogen isotope composition and total C and N concentrations; in situ chlorophyll fluorescence measurements) were determined for over 30 species in four habitats bordering the montane Atlantic rain forest of Brazil, along a gradient of altitude and rainfall: a dry coastal forest, two areas of sandy coastal plain vegetation (restingas), and a high altitude campo. There was a considerable diversity of ecophysiological behaviour within and between the functional groups we created based on plant life-forms. For instance, both crassulacean acid metabolism (CAM) and C3 species were found in most life-forms sampled and throughout all habitats. Despite the variation in rainfall regimes, average overall water-use efficiency was similar between sites, particularly for C., species, while no clear pattern regarding nitrogen-use emerged in this respect. Acute and chronic photoinhibition were found in many species across this gradient, even in CAM plants. However, on average, chronic photoinhibition and lower energy dissipation capacity were more characteristic of plants from the restinga habitats. This suggests that, although plants colonizing these habitats have evolved features to deal with water shortage, adaptation to high light levels has not been fully achieved yet. The ecophysiological performance of some individual species in distinct habitats and in distinct microhabitats within habitats is also discussed. ! C 2001 The Linnean Society of London ADDITIONAL KEY WORDS: Atlantic forest -carbon isotopes -chlorophyll a fluorescence -dry forest -high altitude vegetation -nitrogen isotopes -sandy coastal vegetation.

Plant establishment and growth on rocky outcrops in the Itatiaia massif (2400 m a.s.l.), southeastern Brazil, are limited by lack of soil and by freezing temperatures in winter nights. Mat‐forming species of different sizes and shapes on bare rock provide substrate for other plants to establish. The habitat preference of two geophytes, Stevia camporum (Asteraceae) and Alstroemeria foliosa (Alstroemeriaceae), was compared with regard to their association with the type of mat species and distinct rock topographies. The habitat preference of the mat species in regard to topography was also assessed. We found 1706 ramets of S. camporum and 1317 of A. foliosa in 253 vegetation islands ranging in size from 0.005 to 18.097 m2. Mat species in these islands were Fernseea itatiaiae, Vriesea itatiaiae (both Bromeliaceae), Pleurostima gounelleana (Velloziaceae) and/or Campylopus pilifer (Dicranaceae) and other mosses. Mat species were segregated by topography. Geophytes were similarly distributed across types of topography but showed negative interspecific association. S. camporum occurred mostly on the moss‐dominated islands, whereas A. foliosa was more common in P. gounelleana islands. We found geophyte co‐occurrence in larger vegetation islands containing both P. gounelleana and mosses as mat species. Thus, the effect of topography on geophyte segregation was indirect, since topography affects mat species distribution, and the geophyte preference for distinct mat species as substrate resulted in their segregation.

The Espinhaço Range, in eastern Brazil, has a peculiar landscape that has influenced the vegetation pattern of the region because of its valleys, canyons, ranges and disjunct rock outcrops found at high elevations. In this region, the vegetation type known as campos rupestres (rupestrian fields), which occurs in the disjunct outcrops, has high levels of species richness and endemism. Vellozia gigantea, a 6-m tall dracenoid monocot, is a vulnerable species endemic to this vegetation and has a narrow distribution that extends approximately 27 km. This region is located in a disturbed area, where populations are divided into three geographical groups, separated by a canyon and a valley. For this study, we used ISSR markers to measure the genetic diversity of the species and test the hypothesis that the canyon and the valley constitute geographical barriers to gene flow in V. gigantea. Nine populations and 173 individuals were analyzed using nine ISSR primers, which produced 89 fragments. In spite of being a vulnerable species with a narrow distribution, the populations of V. gigantea have high genetic diversity (mean percentage of polymorphic loci = 56.6%; mean Shannon's index of diversity = 0.278; mean expected heterozygosity = 0.183). Genetic divergence among populations was high (Φ(ST) = 0.28), and principal coordinate, neighborjoining and Bayesian analyses showed that only the canyon may constitute a partial barrier to gene flow in this species. Groups of populations separated by the canyon should be managed separately because they contain different gene pools.