Abstract

Micropalaeontologists often encounter select the appropriate number of individuals per sample based on the study objectives and consider the trade-offs between analysing more samples with fewer individuals and analysing a larger sample size with fewer samples. The relationship between a number of individuals and Shannon’s index using rarefaction is useful for finding this compromise. Here, we present a new empirical relationship between the specimen number and alpha diversity using the extant ostracod assemblage of Kumamoto Port, Kyushu, Japan. If we define a gradient of 0.002 or less as the rarefaction curve being sufficiently flat, then when Shannon’s index calculated from the number of individuals extracted is plotted in the area below the line with a gradient of 0.002, we can consider that a sufficient number of individuals have been picked up. This study presents a new method for determining the number of individuals required to estimate species diversity from rarefaction curves.