have you ever read the origin of species?
I would advise reading darwin’s words rather than commentary
then, observe for your self. Buy a good wild flower book. a good choice would be one of the Peterson’s Guides to wild flowers. then take it into the field and actually observe the possible wide variation that occurs within a single species and then the differences that are present within different species within a genus.
the mechanism of natural selection produces species
But where is the fossil evidence? Fossils are as common as mud, and the fossil record shows stasis in species, overwhelmingly.