2016-12-23T18:52:10

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ABSTRACT-(Plant species and habitat structure in a sand dune field in the Brazilian Caatinga: a homogeneous habitat harbouring an endemic biota). One dune habitat in the semi-arid Caatinga Biome, rich in endemisms, is described based on plant species composition, woody plant density, mean height and phenology and a multivariate analysis of the micro-habitats generated by variables associated to plants and topography. The local flora is composed mainly by typically sand-dweller species of Caatinga, suggesting the existence of a phytogeographic unity related to the sandy areas in the Caatinga biome, which seems to be corroborated by faunal distribution. Moreover, some species are probably endemic from the dunes, a pattern also found in vertebrates. The plant distribution is patchy, there is no conspicuous herbaceous layer and almost 50% of the ground represents exposed sand. Phenology is not synchronized among species, occurring leaves budding and shedding, flowers development and anthesis, fruits production and dispersion both in rainy and dry seasons. Leaf shedding is low compared to the level usually observed in Caatinga areas and about 50% of the woody individuals were producing leaves in both seasons. Spectrum of dispersal syndromes shows an unexpected higher proportion of zoochorous species among the phanerophytes, accounting for 31.3% of the species, 78.7% of the total frequency and 78.6% of the total density. The habitat of the dunes is very simple and homogeneous in structure and most of environmental variance in the area is explained by one gradient of woody plants density and another of increase of Bromelia antiacantha Bertol. (Bromeliaceae) and Tacinga inamoena (K. Schum.) N.P. Taylor & Stuppy (Cactaceae) toward valleys, which seem to determine two kinds of protected micro-habitats for the small cursorial fauna.Key words -density, endemic species, phenology, phytogeography, semiarid RESUMO -(Espécies vegetais e estrutura do hábitat em um campo de dunas arenosas na Caatinga brasileira: um hábitat homogêneo portando uma biota endêmica). Um ambiente de dunas no bioma Caatinga, rico em endemismos, é descrito a partir da composição florística, da densidade, altura média e fenologia das espécies lenhosas e de uma análise multivariada dos microhábitats criados por variáveis associadas às plantas e à topografia. A flora local é composta principalmente por espécies típicas de áreas arenosas da caatinga, sugerindo a existência de uma unidade fitogeográfica na caatinga relacionada a áreas arenosas, o que parece ser corroborado por dados faunísticos. Além disso, algumas espécies são provavelmente endêmicas das dunas, padrão também observado nos vertebrados. A vegetação possui distribuição agregada, não há estrato herbáceo conspícuo e quase 50% do solo representa areia nua. A fenologia das espécies não é sincronizada, ocorrendo brotamento e queda de folhas, desenvolvimento e antese de flores e produção e dispersão de frutos nas estações seca e chuvosa. A caducifolia é particularmente baixa em comparação com outras ...

Aim We aimed to assess the generality of existing models of late Quaternary biodiversity refugia in the Brazilian Atlantic forest by testing whether taxonomic identity and range descriptors influence the extent by which previously proposed models of forest (habitat) refugia successfully predict species' inferred refugial areas. Location Brazilian rain forest. Methods We compiled and filtered records of 14 animal species that belong to distantly related groups (spiders, harvestmen, scorpions, amphibians, birds, lizards and mammals) and show distinct distribution patterns within the Atlantic rain forest. Using MAXENT, we generated three distribution models for each species under different climatic scenarios (current, 6000 and 21,000 years ago). Species‐specific historically stable areas (refugia) were identified through the intersection of the three models. We then measured the amount of ‘inclusion’ of species‐specific refugia within published forest refugia, and quantified ‘filling’ of the biome refugia by species‐specific refugia. The influence of taxonomic distance between species and range descriptors were analysed. Results Current distribution models generated for the 14 species had high accuracy (AUC > 0.9). Inclusion and filling, two uncorrelated metrics, varied among species and were not influenced by taxonomic identity. Species range characteristics influenced forest model filling only, with higher values found in widely distributed species (i.e. occurring from Northeastern to Southeastern Brazil). Main conclusions Species‐specific and forest refugial areas are not necessarily the same. The power of forest refugial models to predict species‐specific refugial area differs among species and may be influenced by range attributes. Species data suggests the existence of a large refugium in Southeast of Brazil, a result at odds with the currently available forest‐wide models. The predictive power of forest refugial models is narrowed; we now better understand their applicability limits.

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