Red list of algae in Hungary

The algological investigations in the protected landscape areas have started at the end of the 19th century. As a result of the intensive floristical and taxonomic research a large number of records were accumulated over a period of last century, which were summarised in a monograph (Németh 2004). In the book mentioned above the occurrence data of 3,724 algal species and intraspecific taxa were processed. The red list of algae in Hungary was also elaborated as an aim to reveal the algological state of the water bodies in these areas. The algal taxa are listed into threatened categories using quantitative criteria for classification. The quantitative criteria considered in the present study are based on and only on the occurrence data of algae. The occurrence data is to be considered as the number of localities in which a given taxon was found, without any consideration how many times and how many authors it has been published by. Three criteria and six categories were used for create the red list. The measure of the first criterion (a) was calculated from the date of the publication of the last occurrence of a given taxon. The second and third criteria (r and v) express the rarity of the taxa and the value of the locality respectively. The numeric values of the last two criteria were calculated from the rows and columns of the data matrix contained the occurrence data using the Rényi's generalised entropy functions of order a = 1 and a= 2. The original values of the three quantitative criteria were then converted to the values of a logarithmic interval scale and were given as a three-digit code number. For classification the 504 threatened algal taxa observed in Hungarian protected landscape areas six categories were used as follows: Extinct (EX), Critically endangered (CR), Endangered (EN), Vulnerable (VU), Low risk (LR), Presumably threatened (PR).