The idea that many species are redundant (di Castri and Youni%, 1990) in soil has been
long implicitly accepted by those scientists who proposed diverse functional
classifications for most zoological groups (Gisin, 1943 for Collembola; Grass& 1984
for termites; Lee, 1958 and Bouché, 1977 for earthworms). However, there is almost
immediate feedback between the effect an organism has on its environment and the
consequences for its future conditions of life. Therefore, if we can admit in a fnst
instance Andren's (1995) remark that organisms have evolved through selection to
maximize their contribution to future generations .... not to serve functions in the
ecosystem, we have to add that the effect of a dominant species on soil processes is
likely to affect their resource base in the future. Selection may have operated on the long
term consequences of function of a species on its life condition.