. Bonn zoological bulletin. Zoology. 6 Johan van Rooijen et al. is the number of observed species represented by exact- ly two specimens. RESULTS Figure 3 depicts the deviations of the fitted functions from the sample-based rarefaction curve (residuals) for reptiles. As expected, the NE exhibits a very poor goodness-of-fit. At first, the fitted curve is situated beneath the rarefaction curve, then above and finally drops beneath the rarefac- tion curve again. The suboptimal fit of the NE as well as the pattern of residuals are in agreement with results ob- tained with regard to avian diversity
. Bonn zoological bulletin. Zoology. 6 Johan van Rooijen et al. is the number of observed species represented by exact- ly two specimens. RESULTS Figure 3 depicts the deviations of the fitted functions from the sample-based rarefaction curve (residuals) for reptiles. As expected, the NE exhibits a very poor goodness-of-fit. At first, the fitted curve is situated beneath the rarefaction curve, then above and finally drops beneath the rarefac- tion curve again. The suboptimal fit of the NE as well as the pattern of residuals are in agreement with results ob- tained with regard to avian diversity (Flather 1996) as well as snake diversity (Van Rooijen 2009). Although the RC and 3pW fit substantially better than the NE, they exhib- it a similar pattern of residuals. The 4pW function obvi- ously exhibits a superior, near-perfect, fit. 46. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 cumulative nunihei of search days Fig. 4. Reptile species sample-based rarefaction curve with fitted 4-parameter Weibull function. ~^ji~> "1 9 11 13 15 17. ^^T^*— negative exponential 3-parameter Weibull - - - 4-parameter Weibull Chapman-Richards search days Fig. 3. Deviations of the fitted models from the sample-based rarefaction curve (residuals). has reached a more or less stable level. A similar result (unpublished) was obtained on the basis of a dataset that underlies a study of Bornean snakes (Van Rooijen 2009): the 4pW-based estimate reached an approximately stable plateau rather early with the CR- and 3pW-based estimates approaching the 4pW-based estimate with increasing search days. On the basis of these results, the 4pW-based estimate, 69, is assumed to be the least biased. Finally, the estimate based on the nonparametric Chao I estimator, 62, agrees reasonably well with the 4pW-based estimate. Taking the average, 65 reptile species are expected to inhabit Pangkor Island. As for amphibians species richness, the fitted 4pW and Chao I estimator both resulted in
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