Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 10. 1981. (Budapest, 1981)
c: the number of the common spécii a: the species number of the first flora/fauna b: the species number of the second flora Besides the comparison of two assemblages it is also possible to give one common index for several floras. This has significance if floras/faunas of different formations belonging to the same stage are compared, and the individual formations contain several fossil-assemblages. In this case the Koch-index can be applied (in ZHILIN 1974): = 100 (T-S) k (n-1) S I^: the Koch-index n: the number of the floras/faunas compared S: the global species number in the floras/faunas being compared T: B1+S2+S3+ +s n = the species numbers of the fl or as/faun as . The other group of indices characterizing floras and faunas differs basically from the abovementioned ones. While it is sufficient to consider the species number in connection with the Jaccard-, S<$rensen-, Koch-indices, with the following ones the specimen-number and the quantity are important. A very important character of a biocoenose is the diversity, the quantitative analysis of which can be made with the best result by means of the Shannon diversity-index (SHANNON & WEAVER 1949). This is very sensitive but It is independent from external (testing, sampling) circumstantes. s nj nj H " " - f =1 TT • log 2 "nH' ' : the Shannon diversity-index nj: the specimen number of the i-th species in the flora N: the global specimen number of the flora s: the species-number In the flora ni — : the relative frequency of the 1-th species O S H" € log 2 s The diversity is closely related to equitability. This demonstrates the relationship between specimen-numbers and species-numbers . Til » J" = -r o ^ j" $ 1 log2S J* ' : equitability H* ' : Shannon' s diversity index loggS: the highest number of the diversity-Index (binary log of specie s-number) If we substitue species numbers in the equation, the result will be species diversity. It is possible to calculate diversity with higher taxonomic categories; even in case of relatively rough calculations (genus and familia level) good results can be obtained. For comparison - besides the comparison of H' ' -values obtained independently of each other - the equation of diversity difference (Hdjff) can be applied. The higher its value is the farther the two floras are from each other with regards to diversity. H diff * H t" H- + H»' H diff dlversitv difference Hj': the diversity index of the first flora Hg' : the diversity index of the second flora P i + P i , P l H t = - r -^- . iog 2 s
