Least-biased Extrapolation of a Partial Inventory of Butterfly Fauna in Manas Range (Royal Manas National Park, Bhutan)

Abstract

As a rule, most biodiversity inventories at local scales remain more or less incomplete, when dealing with relatively speciose taxonomic groups, such as butterflies in tropical regions. It remains yet possible to take maximum additional advantage of partial inventories and to develop reliable predictions by extrapolating, as accurately as possible, the species accumulation curve beyond the already achieved sampling-size. For this purpose, selecting for the less-biased estimator of the number of missing species (among the wide diversity of currently available solutions) and for the corresponding expression of the species accumulation curve is desirable. Accordingly, implementing the recently derived “least-biased extrapolation procedure” is recommended in this respect. Least-biased extrapolation procedure was applied to an incomplete inventory of butterfly fauna (91 observed species) carried on by Tshering Nidup and coworkers in the Manas Range (Royal Manas National Park, Bhutan). The estimated total species richness of butterflies for the set of investigated ecosystems reaches around 120 species; accordingly the achieved-sampling completeness is estimated around 76%. Alternative estimations, based on six empirical models of species accumulation curves (namely: Clench, Negative Exponential, Exponential, Logarithmic B, Power and Margalef) prove markedly less accurate than the selected least-biased extrapolation, with Clench model being the less worst, however.