They do not have so much impact on southern beech ( Nothofagus ) .
Their presence tends to reduce the species diversity of southern beech forest , since they eat many of the other species that would naturally be present .
They do not have so much impact on southern beech ( Nothofagus ) , but their presence tends to reduce the species diversity of Nothofagus forest , since they eat many of the other species that would naturally be present .