Assessing the completeness of bat biodiversity inventories using species accumulation curves

1. In this study we used species accumulation models to solve one of the most ser-ious problems encountered when comparing species richness between di?erent com-munities. The problem is how to compare data among inventories in whichdi?erent methodologies or measures of sampling e?ort have been employed. Themethods used here for bats may be applied to any other biological group. We ttwo asymptotic models to species accumulation curves for bat inventories to evalu-ate local or within-community diversity (alpha) and landscape diversity (gamma) incentral Veracruz, Mexico.2. Species accumulation models allow us to: (i) measure within-inventory ecacyand completeness; (ii) obtain an estimate of species richness that is based on a stan-dardized measure of sampling e?ort, which makes valid comparisons betweeninventories possible; and (iii) estimate the minimum sampling e?ort required toreach a satisfactory level of completeness.3. The applied models t well in all cases (r2 > 095). The linear dependence modelpredicted lower asymptotes and the Clench model predicted higher asymptotes thanthe observed species richness. These models are useful as predictors representing thelower and upper limits between which the true species richness value should lie.4. Alpha diversity for bats in all vegetation communities (1118 species) was lowerthan the gamma diversity (20 species), suggesting that species richness and the sam-pling e?ort required are related to environmental heterogeneity.5. We propose that 90% of the total fauna predicted by either of the models is anacceptable standardized value for comparing species richness between communities.6. We assessed the within-inventory completeness as the proportion of the models'asymptote, where 90% is the desired minimum level of completeness. Except in palmstands, all bat inventories had an acceptable level of completeness, at least for thelinear dependence model.7. For conditions similar to those of our study area, the minimum e?ort required toobtain a satisfactory level of completeness is 518 nights for plant communities and18 nights for more heterogeneous landscapes.8. We make recommendations for improving the ecacy and completeness of batsurveys based on the application of species accumulation models.