We use quantitative ethnobotanical data to compare the usefulness of six flortstically distinct forest types to mestizo people at Tambopat4g southeast Perg We aim to evaluate which forest types are most usefu~ arid why. Ethnobotanical data were collected with informants in inventory plots and analyzed using a new technique that uses a two-tier calculation process to derive an "informant indexed" estimate of each species" use value. Use values are estimated based on the degree of consistency between re. peated int~ of each informant and between different informant~ We show that (1) in 6 1 lgt 94% of woody stems are "useful" to mestizos. (2) Based on ~tages of useful plants per plog there is little difference between each forest type (3) Simply calculating the percent of useful plants is misleading h~, because most species have minor use~ and only a few are exceptionally useful (4) Using the informant indexing technique, we demonstrate significant differences between each forest type's utility. Mature forests of *DeceasegEtnobotMflca cuantitativa y la conservaci6n de la Amazonia Resumen: Se emple6 datos etnobotdnicos cuantitatlvos para comparar la uttlidad de seis tipos de bosques floristtcamente distinto~ con plantas usadas por la poblacidn mestiza en Tambopattg sureste de Pertt Datos etnobotdnicos fueron registrados de informantes en parcelas inventarlada~ usando una nueva t&'nica que constdera un procedimiento simple para obtener un estimado del valor de uso de cada especi~ Los valores de uso se basan en el grado de consistencla de entret~tas m4teradas con uno y ratios informantes (Phillips & Gentry, 1993a). Los resultados muestran que (1) en ~ 1 htg 9496 de individuos arb6reos son "~tiles" a la po-blaci6ft (2) Basados en el porcentaJe de plantas ~Hles por plog hay mtty escasa diferencia entre Hpos de bosqu~ (3) El porcentaJe de plantas t~tiles incluye sin embargo una mayorla de espectes alas que se ies da usos memm~ y son muy pocas las especies que brtndan mayor uttliddg pot" lo tan$o los calculos de porcentaje de plantas t~tiles son err6-nio¢ (4) Empleando la t~'nica del indice de utilida~ se encontraron di~ significativas entre la uHlidad de diferentes ttpos de bosqu~ Las dreas de bosque maduro en 225 Conservation Biology, Pages 225-*248 Volume 8, No. 1, March 1994226 Ethnobotany and Conservation Phillips et al. present and former floodplains are more useful than other forest type~ mostly due to their importance as sources of construction materials and fooa~ (5) Lower floodplain is more useful medicinally, swamp more important commercially, and terra trine sandy more important technologically; they are not easily substituted for some of these use~ (6) On averag¢ 80% of the value of forest plant products to mestizos is subsistence value; only 20% is commercial We conclude that (1) to maintain cultural autonomy, Amazonian people may need access to all local forest type~ and (2) present and former floodplain forests in western Amazonla should be a conservation priority. We make these broad conclustons on the...

While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant' species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region.

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water‐stress on the physiological processes of most tree species. This implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry‐tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance' hypothesis has broad applicability in the world's most species‐rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region.

The pantropical genus Begonia is the sixth-largest genus of flowering plants, including 1870 species. The sections of Begonia are used frequently as analogues to genera in other families but, despite their taxonomic utility, few of the current sections have been examined in the light of molecular phylogenetic analyses. We present herein the largest, most representative phylogeny of Begonia published to date and a subsequent provisional sectional classification of the genus. We utilised three plastid markers for 574 species and 809 accessions of Begonia and used Hillebrandia as an outgroup to produce a dated phylogeny. The relationships between some species and sections are poorly resolved, but many sections and deeper nodes receive strong support. We recognise 70 sections of Begonia including 5 new sections: Astrothrix, Ephemera, Jackia, Kollmannia, and Stellandrae; 4 sections are reinstated from synonymy: Australes, Exalabegonia, Latistigma and Pereira; and 5 sections are newly synonymised. The new sectional classification is discussed with reference to identifying characters and previous classifications.

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