Browsing by Author "Pereira, Henrique M."
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- Dispersal ability determines the scaling properties of species abundance distributions : a case study using arthropods from the AzoresPublication . Borda-de-Água, Luis; Whittaker, Robert J.; Cardoso, Pedro; Rigal, François; Santos, Ana M. C.; Amorim, Isabel R.; Parmakelis, Aristeidis; Triantis, Kostas A.; Pereira, Henrique M.; Borges, Paulo A. V.Species abundance distributions (SAD) are central to the description of diversity and have played a major role in the development of theories of biodiversity and biogeography. However, most work on species abundance distributions has focused on one single spatial scale. Here we used data on arthropods to test predictions obtained with computer simulations on whether dispersal ability influences the rate of change of SADs as a function of sample size. To characterize the change of the shape of the SADs we use the moments of the distributions: the skewness and the raw moments. In agreement with computer simulations, low dispersal ability species generate a hump for intermediate abundance classes earlier than the distributions of high dispersal ability species. Importantly, when plotted as function of sample size, the raw moments of the SADs of arthropods have a power law pattern similar to that observed for the SAD of tropical tree species, thus we conjecture that this might be a general pattern in ecology. The existence of this pattern allows us to extrapolate the moments and thus reconstruct the SAD for larger sample sizes using a procedure borrowed from the field of image analysis based on scaled discrete Tchebichef moments and polynomials.
- Response of Common and Rare Beetle Species to Tree Species and Vertical Stratification in a Floodplain ForestPublication . Haack, Nora; Borges, Paulo A. V.; Grimm-Seyfarth, Annegret; Schlegel, Martin; Wirth, Christian; Bernhard, Detlef; Brunk, Ingo; Henle, Klaus; Pereira, Henrique M.Vertical stratification and host tree species are factors with a high influence on the structure of communities of xylobiont beetles. However, little is known about how this influence varies between common and rare species. Based on estimated species richness, we compared alpha and beta diversity patterns of common and rare species in the canopy of the Leipzig floodplain forest to assess their response to vertical stratification and tree species. We used two measures of rarity: threat level in red lists and abundance based on octaves. The understory displayed a significantly higher number of common species than the canopy strata. Conversely, the canopy strata harbored a higher number of rare species. Turnover was always dominant over richness differences in beta diversity partitions. Using Raup–Crick null models and non-metric multidimensional scaling, we found that the vertical strata accounted for 19% of the overall beta diversity of common species and for 15% of the overall beta diversity of rare species. The tree species accounted for 7% of the overall beta diversity of the common species and 3% of the beta diversity of the rare species. Our results indicate that studies carried out in the understory alone do not allow drawing conclusions regarding the biodiversity in the canopy strata, and thus regarding the overall community structure of xylobiont beetles in the canopy.
- Spatial scaling of species abundance distributionsPublication . Borda-de-Água, Luís; Borges, Paulo A. V.; Hubbell, Stephen P.; Pereira, Henrique M.Species abundance distributions are an essential tool in describing the biodiversity of ecological communities. We now know that their shape changes as a function of the size of area sampled. Here we analyze the scaling properties of species abundance distributions by using the moments of the logarithmically transformed number of individuals. We find that the moments as a function of area size are well fitted by power laws and we use this pattern to estimate the species abundance distribution for areas larger than those sampled. To reconstruct the species abundance distribution from its moments, we use discrete Tchebichef polynomials. We exemplify the method with data on tree and shrub species from a 50 ha plot of tropical rain forest on Barro Colorado Island, Panama. We test the method within the 50 ha plot, and then we extrapolate the species abundance distribution for areas up to 5 km2. Our results project that for areas above 50 ha the species abundance distributions have a bimodal shape with a local maximum occurring for the singleton classes and that this maximum increases with sampled area size.
- Species accumulation curves and extreme value theoryPublication . Borda-de-Água, Luís; Alirezazadeh, Saeid; Neves, Manuela; Hubbell, Stephen P.; Borges, Paulo A. V.; Cardoso, Pedro; Dionísio, Francisco; Pereira, Henrique M.The species–area relationship (SAR) has been described as one of the few general patterns in ecology. Although there are many types of SAR, here we are concerned solely with the so-called species accumulation curve (SAC). The theoretical basis of this relationship is not well established. Here, we suggest that extreme value theory, also known as the statistics of extremes, provides a theoretical foundation for, as well as functions to fit, empirical species accumulation curves. Among the several procedures in extreme value theory, the appropriate way to deal with the species accumulation curve is the so-called block minima procedure. We first provide a brief description of this approach and the relevant formulas. We then illustrate the application of the block minima approach using data on tree species from a 50 ha plot in Barro Colorado Island, Panama. We conclude by discussing the extent to which the assumptions under which the extreme types theorem occurs are confirmed by the data. Although we recognize limitations to the present application of extreme value theory, we predict that it will provide fertile ground for future work on the theory of SARs and its application in the fields of ecology, biogeography and conservation.