pairwise comparisons with multcomp package

Hi,
I've got this model and following Hothorn et al advices, I used glht for a
post hoc comparison

modezqM<-glm(rojos~estacion*zona3,quasipoisson,subset=(edadysexo=="M"))
anova(modezqM,test="F") 

Df      Deviance      Resid. Df     Resid.
Dev       F                   Pr(>F)    
NULL                    293         41148                      
estacion                  1         3647.0           292             37501       
23.6250          1.927e-06 ***
zona3                      2           931.4           290             36569         
3.0167           0.050510.  
estacion:zona3      2         2421.7           288            34148         
7.8438            0.000482 ***

summary(glht(modezqM,linfct=mcp(zona3="Tukey",interaction_average=T))) 

Estimate       Std. Error      z-value      
Pr(>|z|)  
norte - turist == 0     -0.05182    0.23701      -0.219             0.9727  
occid - turist == 0     -1.05970    0.41618      -2.546             0.0271 *
occid - norte == 0     -1.00788    0.45830      -2.199             0.0665 .

I'm trying to understanding the way this command made pairwise comparisons,
but, where does this z-value comes from?  
I'm suspected this not come from Tukey's test, but i don't know it's Wald or
something i've never use
I know it is not an habitual doubt.
Sorry and thanks in advance

I suspect it


-----
Mario Garrido Escudero
PhD student
Dpto. de Biolog?a Animal, Ecolog?a, Parasitolog?a, Edafolog?a y Qca. Agr?cola
Universidad de Salamanca
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