Fig. 2.

Schematic representation of data used in the probabilistic model for a single hypothetical species. Black circles (●), years in which the species was found; open circles (○), years when searches were undertaken but the species was not found; dashes, years in which there were no searches. The year in which the species was last seen is designated t*, and the year of the last survey is T. Extinction can happen only after year S (year of extinction rate shift), and after the last successful search. The extinction year (E) is unknown. Given the sampling effort before and after the last collection (number of searches, successful or not), the model assesses whether not finding a species is due to extinction or to insufficient sampling.