Hello to everyone. I ran into this issue that most likely is a simple one. But, when performing the Sørensen-Dice index, what happens when there's no shared species with lower abundance? I mean, I have these two communities with n number of shared species, but all of them has the same abundance, what next? is it possible to calculate this index anway? the formula goes as follows: S-D index=2pN/aN+bN
Where pN is the sum of the lower abundances of all the shared species between communities. aN is the total number of individuals from site A and bN is the total number of individuals from site B.
Thanks for your attention.
Hello Hiram; Here is a reference that provides a clear explanation of community similarity indices. It might help you.
Brower, Zar and von Ende. Field and laboratory methods for general ecology. McGraw Hill. Publ. Section 5C in the edition I'm looking at is the part that covers this topic. Good luck with the project.
My first reaction is that the two sites are VERY similar...maybe they are the same community. Or, is your sample size large enough?
Best regards, Jim Des Lauriers
Si los máximos y mínimos son iguales, utiliza cualquiera de ellos para los cálculos. Por ejemplo, tienes dos sitios y diez especies en total, que se distribuyen de esta forma:
Especies/sitios A B
Especie 1 10 10
Especie 2 9 9
Especie 3 8 8
Especie 4 7 7
Especie 5 6 0
Especie 6 0 6
Especie 7 5 0
Especie 8 0 4
Especie 9 3 0
Especie 10 0 2
pN = 34, aN = 48; bN = 46, S-D = 2*34/(48 + 46) = 0.7234
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