Measuring the species occurrence and relative abundance in faunal studies: a case study of Finnish butterflies (Lepidoptera: Hesperioidea, Papilionoidea)

Any faunal study in addition to the list of species assumes an evaluation of their occurrence and abundance. These estimates are usually subjective. We propose to unify the methods, using 10-point logarithmic scale. As an example, the results of day butterfly counts in Finland (1991–2011) were used. All the species were differentiated according to the occurrence in 10x10 km squares and relative abundance. Stochasticity in the distribution of the empirical frequencies can be reduced by fitting to a theoretical model.