Thereby, quadrats with high observed species richness acquire few

Thereby, quadrats with high observed species richness acquire fewer additional species from interpolation while quadrats with a low number of observed species could acquire a larger fraction

of additional species—if the unadjusted interpolation results predict additional species. We accepted overestimating species richness in some quadrats, knowing that vast areas of the Neotropics are under-sampled (Prance et al. 2000; Ruokolainen et al. 2002; Tobler et al. 2007). Although detailed maps of botanical sampling effort are available for some areas within the Neotropics (e.g. for Amazonia by Schulman et al. 2007), Sorafenib they are not available everywhere and therefore not used in the present work. Also, the procedure to adjust for sampling effort proposed here has the advantage of only requiring information inherent in the available point-to-grid data. Species richness Areas of elevated levels of species richness are the result of multiple overlapping species ranges. Most species occupy small ranges (Fig. 2a). Weighting of the species ranges (Eq. 3) demonstrates that the range sizes increase when applying our interpolation approach (Fig. 2f), but with a lower skewness and a lower maximum number of species compared

to a medium interpolation distance of five quadrats (Fig. 2c), thus avoiding overestimation of ranges of widespread species. The ‘smoothed’ increase of the range sizes due to the interpolation approach is reflected in the species richness maps (Fig. 3b, c). Whereas the inclusion of 340 more species (Fig. 3a) showed no major differences to the point-to-grid

species richness map presented in Morawetz and Raedig (2007), considerable distinctions are evident in both maps of species richness (Fig. 3b, c). For the weighted interpolation, these differences are plotted in Fig. 4. For all centers of diversity as well as for the unassigned quadrats, interpolated species richness is above the equity line. Edoxaban The different effect of interpolation on the species richness according to diversity center is particularly revealing for Amazonia. Even for small distances, the interpolation of species ranges here is consistently high. Comparison of maps 3b and 3c reveals the effect of adjusting species richness for sampling effort: the range of species richness is reduced, whereas the peaks of species richness found in Fig. 3b are retained in Fig. 3c. This effect is also apparent in the lower mean and standard deviation values for the centers of adjusted species richness, and in their closer range (Table 1). The Andean species richness center (Fig. 3c, polygon 2) shows the lowest standard deviation relative to the mean values (Table 1), suggesting more equal species richness and sampling effort of these Andean quadrats. The most obvious difference is that the Amazonian species richness center is by far the largest.

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