A major challenge remains to understand the relative contributions of history, dispersal, and environmental filtering to the assembly of hyperdiverse communities across spatial scales. Here, we ...examine the extent to which biogeographical history and habitat specialization have generated turnover among and within lineages of Amazonian trees across broad geographic and environmental gradients. We replicated standardized tree inventories in 102 0.1-ha plots located in two distant regions—the western Amazon and the eastern Guiana shield. Within each region, we used a nested design to replicate plots on contrasted habitats: white-sand, terra firme, and seasonally flooded forests. Our plot network encompassed 26,386 trees that together represented 2,745 distinct taxa, which we standardized across all plots and regions. We combined taxonomic and phylogenetic data with detailed soil measurements and climatic data to: (1) test whether patterns of taxonomic and phylogenetic composition are consistent with recent or historical processes, (2) disentangle the relative effects of habitat, environment, and geographic distance on taxonomic and phylogenetic turnover among plots, and (3) contrast the proportion of habitat specialists among species from each region. We found substantial species turnover between Peru and French Guiana, with only 8.8% of species shared across regions; genus composition remained differentiated across habitats and regions, whereas turnover at higher taxonomic levels (family, order) was much lower. Species turnover across plots was explained primarily by regions, but also substantially by habitat differences and to a lesser extent by spatial distance within regions. Conversely, the composition of higher taxonomic levels was better explained by habitats (especially comparing white-sand forests to other habitats) than spatial distance. White-sand forests harbored most of the habitat specialists in both regions, with stronger habitat specialization in Peru than in French Guiana. Our results suggest that recent diversification events have resulted in extremely high turnover in species and genus composition with relatively little change in the composition of higher lineages. Our results also emphasize the contributions of rare habitats, such as white-sand forests, to the extraordinary diversity of the Amazon and underline their importance as conservation priorities.
Little is known about the mechanisms promoting or limiting the coexistence of functionally divergent species in hyperdiverse tropical tree genera. Density-dependent enemy attacks have been proposed ...to be a major driver for the local coexistence of chemically divergent congeneric species. At the same time, we expect local soil conditions to favor the coexistence of species sharing similar functional traits related to resource use strategies, while environmental heterogeneity would promote the diversity of these traits at both local and large spatial scales. To test how these traits mediate species coexistence, we used functional trait data for 29 species from the tree genus
(Burseraceae), collected in 19 plots (2 ha each) in the Peruvian Amazon. We characterized the presence-absence of 189 plant secondary metabolites (SM) for 27 of these species, and 14 functional traits associated with resource use strategies (RUT) for 16 species. Based on these data, we found that SM were significantly more dissimilar than null expectations for species co-occurring within plots, whereas RUT were significantly more similar. These results were consistent with the hypothesis that density-dependent enemy attacks contribute to the local coexistence of congeneric species displaying divergent chemical defenses, whereas local habitat conditions filter species with similar RUT. Using measurements of nine soil properties in each plot, we also found a significant turnover of RUT traits with increasing dissimilarity of soil texture and nutrient availabilities, providing support for the hypothesis that soil heterogeneity maintains functional diversity at larger spatial scales (from 500 m up to ca. 200 km) in
communities. Our study provides new evidence suggesting that density-dependent enemy attacks and soil heterogeneity both contribute to maintaining high species richness in diverse tropical forests.
The new species Platycarpum vriesendorpiae N. Dávila (Rubiaceae, Henriquezieae) is described from Peru, where it is restricted to white‐sand forests and peatlands in the Tapiche and Blanco River ...watersheds in southeastern Loreto Region. The new species is generally similar to P. acreanum Rogers of western Brazil in its phyllotaxy, leaf pubescence, and fruit shape and size. However, P. vriesendorpiae differs in its triangular stipules that are 2‐ or 3‐angled at the base and in its smaller corolla.
Understanding how biotic interactions and environmental filtering mediated by soil properties shape plant community assembly is a major challenge in ecology, especially when studying complex and ...hyperdiverse ecosystems like tropical forests. To shed light on the influence of both factors, we examined how the edaphic optimum of species (their niche position) related to their edaphic range (their niche breadth) along different environmental gradients and how this translates into functional strategies. Here we tested four scenarios describing the shape of the niche breadth—niche position relationship, including one neutral scenario and three scenarios proposing different relative influences of abiotic and biotic factors on community assembly along a soil resource gradient. To do so, we used soil concentration data for five key nutrients (N, P, Ca, Mg, and K), along with accurate measurements of 14 leaf, stem, and root traits for 246 tree species inventoried in 101 plots located across Eastern (French Guiana) and Western (Peru) Amazonia. We found that species niche breadth increased linearly with species niche position along each soil nutrient gradient. This increase was associated with more resource acquisitive traits in the leaves and the roots for soil N, Ca, Mg, and K concentration, while it was negatively associated with wood density for soil P concentration. These observations agreed with one of our hypothetical scenarios in which species with resource conservation traits are confined to the most nutrient‐depleted soils (abiotic filter), but they are outperformed by faster‐growing species in more fertile conditions (biotic filter). Our results refine and strengthen support for niche theories of species assembly while providing an integrated approach to improving forest management policies.
Abstract This study defines and characterizes the species of Linaceae occurring in Reserva Ducke. We analyzed material collected mainly during the Project Flora of Reserva Ducke. Two genera, each ...with one species, are recorded: Hebepetalum humiriifolium and Roucheria columbiana. We present species descriptions, taxonomic comments, illustrations, habitat information, geographic distribution and an identification key to species of Linaceae.
Resumo Este estudo define e caracteriza as espécies de Linaceae que ocorrem na Reserva Ducke. Analisamos materiais coletados principalmente durante o Projeto Flora da Reserva Ducke. Dois gêneros, cada um com uma espécie, são registrados: Hebepetalum humiriifolium e Roucheria columbiana. Apresentamos descrições das espécies, comentários taxonômicos, ilustrações, informações sobre habitat, distribuição geográfica e uma chave de identificação para as espécies.
Resumo O presente trabalho tem como objetivo contribuir para o conhecimento das espécies de Metteniusaceae ocorrentes na Reserva Ducke. O estudo tem por base a análise morfológica de materiais ...depositados em herbários e revisão de literatura. Cinco espécies foram registradas: Dendrobangia boliviana, Emmotum acuminatum, E. amazonicum, Poraqueiba guianensis e P. sericea. Chave para identificação, descrições, ilustrações, dados sobre habitat, fenologia e distribuição geográfica das espécies são apresentados.
Abstract The present work aims to improve the knowledge of the Metteniusaceae species found in Reserva Ducke. The study is based on morphological analysis of material deposited in herbaria and literature revision. Five species were recorded: Dendrobangia boliviana, Emmotum acuminatum, E. amazonicum, Poraqueiba guianensis and P. sericea. An identification key, descriptions, illustrations, data on habitat, phenology, and species geographic distribution are provided.
Abstract
Peatland pole forest is the most carbon-dense ecosystem in Amazonia, but its spatial distribution and species composition are poorly known. To address this knowledge gap, we quantified ...variation in the floristic composition, peat thickness, and the amount of carbon stored above and below ground of 102 forest plots and 53 transects in northern Peruvian Amazonia. This large dataset includes 571 ground reference points of peat thickness measurements across six ecosystem types. These field data were also used to generate a new land-cover classification based on multiple satellite products using a random forest classification. Peatland pole forests are floristically distinctive and dominated by thin-stemmed woody species such as
Pachira nitida
(Malvaceae),
Platycarpum loretense
(Rubiaceae), and
Hevea guianensis
(Euphorbiaceae). In contrast, palm swamps and open peatlands are dominated by
Mauritia flexuosa
(Arecaceae). Peatland pole forests have high peat thickness (274 ± 22 cm, mean ± 95% CI,
n
= 184) similar to open peatlands (282 ± 46 cm,
n
= 46), but greater than palm swamps (161 ± 17 cm,
n
= 220) and seasonally-flooded forest, terra firme, and white-sand forest where peat is rare or absent. As a result, peatland pole forest has exceptional carbon density (1,133 ± 93 Mg C ha
−1
). The new sites expand the known distribution of peatland pole forest by 61% within the Pastaza-Marañón Foreland basin, mainly alongside the Tigre river, to cover a total of 7540 km
2
in northern Peruvian Amazonia. However, only 15% of the pole forest area is within a protected area, whilst an additional 26% lies within indigenous territories. The current low levels of protection and forest degradation but high threat from road paving projects makes the Tigre river basin a priority for conservation. The long-term conservation of peatland pole forests has the potential to make a large contribution towards international commitments to mitigate climate change.
Resumo O presente trabalho tem como objetivo contribuir para o conhecimento das espécies de Icacinaceae ocorrentes na Reserva Ducke. O estudo tem por base a análise morfológica de materiais ...depositados em herbários e revisão de literatura. Três espécies pertencentes a dois gêneros foram registradas: Casimirella rupestris, Pleurisanthes emarginata e P. parviflora. Casimirella rupestris é falcilmente diferenciada das espécies de Pleurisanthes por apresentar ramos cobertos por tricomas estrelados e inflorescência em panícula (vs. ramos glabros ou puberulentos em Pleurisanthes), enquantos as espécies de Pleurisanthes se diferenciam entre si pela margem da folhas (denticulada em P. emarginata vs. inteira em P. parviflora) e ápice da folha (rotunda em P. emarginata vs. acuminada-unguiculada em P. parviflora). Chave para identificação, descrições, ilustrações, dados sobre habitat, fenologia e distribuição geográfica das espécies são apresentados.
Abstract This study aims to improve the knowledge of the Icacinaceae species found in Reserva Ducke. It is based on morphological analysis of herbaria collections and literature compilation. Three species which belongs to two genera were recorded: Casimirella rupestris, Pleurisanthes emarginata and P. parviflora. Casimirella rupestris differs from Pleurisanthes by its stems with stellate trichomes and paniculate inflorescence (vs. globrous or puberulent stems and “spigate” inflorescente in Pleurisanthes), while Pleurisanthes species differs from each other by the leaf margin (denticulate in P. emarginata vs. entire in P. parviflora) and leaf apex (rotund in P. emarginata vs. acuminate-unguiculate in P. parviflora). An identification key, descriptions, illustrations, habitat information, phenology, and species distribution are also provided.
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