It all depends what you believe. Does speciation actually occur? There are different species, but we may never know if one changed into another. Endemism definitely does occur though :)
The speciation if plants can dépends or non of phytogeographical influence.
In same country the level of plant endemism is very big, for exemple, in mountain part or in the différente côtes of river. See the study of N.I.Vavilov
Occurrence of a complex of plant species in any geographic location is an indication of the adaptability of the species in that complex to the prevalent conditions in the location being studied. Adaptability, in turn, is an expression of genes for survival and reproduction in the location. Initial lot of plants in this population might have come from diverse locations by way of dispersal or migration through various means available. Together, migration and survival make-up the adaptive radiation. At this stage, the change in genes in any species in the complex may not be much different from those prevailing in the parent populations from which they are derived. With advancing time and concurrent changes in climate, the genes for adaptation may change by way of recombining with related species in the vicinity, by mutation or by both. This results in a significant change in the expression of these genes in the next generation that may lead one to consider that new species are emerging. Sometimes, related species may interbreed and the resulting hybrids may tetraploidize as happened in the evolution of several crop species like coffee, wheat etc. In these cases speciation events are more clearly discernible.