How does mutation contribute to variety in a species

Genetic mutation can cause a different type within the species therefore more of a variety. 
For example; Dogs are a species, but there are breed within the dog species. The poodle was a breed within the dog species made by genetic mutation.
Also, genetic mutation could make some dogs better police dogs, other's better guard dog's etc so there is a certain dog that is perfect for every job.
For example; German Shepherds are a very common police dog, but many of them have been genetically mutated to best fit the job, to be able to stiff out all the drugs and follow commands perfectly.
There are many other species that benefit from genetic mutation but I just used dogs as my example :-)