Species delimitations in plants： lessons learned from potato taxonomy by a practicing taxonomist

Solanum section Petota has been the subject of intensive taxonomic work since the description of the cultivated potato in 1753. In total, there are 494 epithets for wild taxa and 626 epithets for cultivated taxa. Different taxonomists applied various taxonomic philosophfes and species concepts to the section. Hypotheses of the number of species and their interrelationships have differed greatly among authors. A taxonomic treatment of section Petota by Jack Hawkes in 1990 recognized 228 wild species and seven cultivated species, divided into 21 taxonomic series. In 2014 Spooner and collaborators more than halved this number to 107 wild species and four cultivated species, partitioned into four clades; not using series. The purpose of this paper is to provide a retrospective of the methods and philosophies that have resulted in this drastic decrease in the number of species and their infrasectional classification.