Disentangling regional and local tree diversity in the Amazon
Stropp, J. et al. Ecography 32: 46-54.
We analyzed the most extensive data set of tree inventory plots spread over the complete Amazon basin and Guiana shield. We aimed to separate the regional and local tree alpha-diversity to investigate the drivers of diversity at the relevant scale. Our results are consistent with the partitioning of total tree alpha-diversity into regional and local components, which are controlled by evolutionary- and ecological processes, respectively. Regional diversity is correlated with palaeoclimatic stability (31%), and long-term large-scale ecosystem dynamics (14%), as represented by the age of the geological formation. Both mechanisms contribute to high diversity in the central to western Amazon. Actual rainfall seasonality is correlated with regional tree diversity to a certain extent (19%), but we argue that this is of little consequence for the evolutionary drivers of the regional species pool. Frequency of disturbance is the main process driving local diversity, although its explanatory power is relatively small (17%).
Paddy Haripersaud, PhD thesis, Utrecht University
There are major concerns about the use of primary species occurrence data that are rapidly becoming available on the internet for ecological studies. To this end, this research assessed the extent of biases associated with a herbarium dataset based is based on specimens collected in Guyana, Suriname and French Guiana. After getting an understanding of the biases, the database was used to: (a) develop a model to simulate relative abundance distributions in the herbarium; (b) to assess the roles of dispersal and environmental constraints in shaping the floristic composition of the Guianas; and (c) determine species richness and endemism patterns across the study area. More than 7,000 species and about 190,000 specimens were collected over the 2000 years period. The herbarium database showed historical, taxonomic, geographical and seasonal bias in collecting and these were demonstrated to have serious consequences when the database was used in a number of ecological applications. The model with the main strategy of “never collect the same species twice” generated species abundance distribution patterns comparable to those in the herbarium. Dispersal limitation rather than environmental constrains better describe the floristic composition across the study area. The species richness patterns modelled did not quite meet the expectations. Key words: herbarium database, bias, the Guianas, collector behavior, floristic composition,species richness maps.
ATDN were also used in:
Phillips, O.L. et al. Drought sensitivity of the Amazon rainforest. Science. 323: 1344-1347.
Malhado, A.C.M. et al. Spatial trends in leaf size of Amazonian rainforest trees. Biogeosciences 6: 1563-1576.
Malhado, A.C.M. et al. Spatial distribution and functional significance of leaf lamina shape in Amazonian forest trees. Biogeosciences 6: 1577-1590.
Gloor, M., Does the disturbance hypothesis explain the biomass increase in basin-wide Amazon forest plot data? Global Change Biology 5: 2418-2430.