I just read @DavidLowry 's excellent 2012 review of the evolution of the #ecotype concept, from Turesson and Clausen, Keck and Hiesey through Stebbins, Grant, Raven, Levin, Wu, Mallet, Schemske, and the early genomic era.
A good reference if you are interested in how #biosystematics connects to modern studies of plant #speciation and #species concepts.