ANOVA two-way with interaction missing in R

Question

I have a data-set where my response variable is clutch size (TCL), and two predictors that are factors: location (TYPE2) and year (AN). I did a two-way ANOVA analysis with interaction. However, in my results I am not able to see results for the interaction. The data looks like this (an example):

TCL
8
6
5
3
2
3
3
3
NA
4

LOC
N
S
S
N
N
N
N
S
N
N

AN
2000
2005
2005
2010
2010
2000
2010
2008
2000
2000

Is it because AN is independent from LOC? (ie if AN=2000 belongs to LOC=N, this means it is never in LOC=S). Every AN can be only in one category, either N or S.

This is my model and my result:

INIcrp <- aov(INI ~ TYPE2 * AN,data=todos)
summary(INIcrp)

#              Df Sum Sq Mean Sq F value Pr(>F)  
#TYPE2          1   3437    3437   380.9 <2e-16 *** 
#AN            14  29713    2122   235.2 <2e-16 ***

#Residuals   5168  46628       9    

Answer 1

I'm not sure why the interaction term is missing, but there are ways to add it in explicitly, such as :

aov(INI ~ TYPE2 * AN + I(TYPE2*AN),data=todos)

or

todos$TYPE2_AN <- with(todos,TYPE2*AN)
aov(INI ~ TYPE2 + AN + TYPE2_AN,data=todos)