2004), making compilation of all species distributions a daunting task. Amazonia, the largest and least accessible part of the Neotropics, still harbors many regions where no plants have been collected at all; Schulman et al. (2007) reported 43% of Amazonia as devoid of botanical collections and an additional 28% as poorly collected. Species with limited or low occurrence are more likely to remain undiscovered, thus impeding the assessment of the distribution of narrow BEZ235 concentration endemic species. Given the fact that large areas generally are under-sampled, different techniques have been applied to map distribution patterns at large scale. The
first essential steps toward estimating plant biodiversity at the global scale have been made by Davis et al. (1997) and Barthlott et al. (1999, 2005) selleck inhibitor using inventory-based
data. These inventories are summary data for geographic units of varying size, mainly based on floras, regional species accounts, local checklists and plot-based data. Whereas Davis et al. (1997) collected information on all of their 234 priority sites and created sub-maps centered on these sites, Barthlott et al. (1999; 2005) estimated plant species richness for standardized units of area (10,000 km2) to derive global maps of plant species richness. In both studies, the Neotropics were indicated to be species-rich, VX-680 order but it was also noted that underlying collection data are lacking for vast parts of Amazonia (Kier et al. 2005; Kreft and Jetz 2007). As an alternative to inventory-based analyses of species richness, distribution patterns can also be obtained by overlaying maps of geographic ranges of individual species, henceforth referred to as species ranges. Basically, species ranges correspond to regions where occurrences of individuals of the species have been recorded (Gaston 1991), but various more sophisticated concepts of deriving species ranges from occurrence data
exist (Lomolino et al. 2006). For the Neotropics, two approaches to estimate angiosperm species ranges and species richness patterns have been applied. These are exclusively based on species occurrence records and do not rely on a summary of different data sources. Hopkins (2007) studied ranges Selleck Enzalutamide of 1,584 Amazonian species at 1° grid resolution. Here, species ranges were generated by extrapolating from point occurrence data sets, if neighbor occurrences were positioned within the maximum distance of roughly 500 km. The superposition of the thus derived species ranges yielded a species richness map of known species that recognized large parts of the Amazon basin as species-rich. At the same time it displayed a bias for better collected areas. In addition to this approach based on species ranges, Hopkins (2007) modeled species richness based on species numbers, using the same maximum distance of roughly 500 km. In both approaches, this predefined limit can lead to overestimation of species ranges and of species numbers.