[R] TukeyHSD not working

[Michael Eisenring]

Dear r-help members.
I would like to compare species numbers of moths between eight different forests (each sampled for six nights). I would like to do a nested anova to compare species numbers between forests and nights.
For more site specific details I wanted to do a Tukey test (TukeyHSD). Unfortunately this test is not working (message:  "nicht anwendbare Methode für 'TukeyHSD' auf Objekt der Klasse "c('anova', 'data.frame" ) /(message: "method not appropriate for TukeyHSD for objects of the class "anova", "data.frame").
I tried it also with the "aov" instead of the "anova" function but neither the "aov" nor the "anova" approach is working.
Could anyone help me with this  problem?
Attached you can find the txt.file and the r-script.
I'm working with a MAC OSX snow leopard, with R-Studio 0.96 316.

Thank you very much.
Michael