Variation and Subspeciation in the Common Sunflower, Helianthus Annuus

Abstract

An understanding of the origin of our cultivated plants obviously requires a knowledge of the plant's wild ancestors. Unfortunately the wild ancestors of many of our cultivated crop plants are not known and in all likelihood are extinct. The sunflower, however, is a significant exception, for the common sunflower is a wide ranging species throughout much of North America. In cultivation it is known throughout the world. It has long been recognized as a highly variable species and previously three main taxa have been recognized (Heiser, 1951c) -H. annuus var. lenticularis, the so-called wild form of western North America; H. annuus var. arnnuus, the ruderal sunflower primarily of the central United States; and H. annuus var. macrocarpus, the forms cultivated for their oily seeds. In the present paper an attempt will be made to analyze some of the wild and weed forms of the sunflower with emphasis being placed upon their variation, taxonomy, and probable evolution. A number of cultivated strains have been examined previously and preliminary remarks concerning the origin of the cultivated sunflower have been published (Heiser, 1951c). Archaeological material of the sunflower has been studied but these data have not as yet been published. After detailed considerations of the archaeological sunflowers, the cultivated races in existence today, and the wild and weed forms, we should have a fairly complete knowledge of the origin of the cultivated sunflower. ACKNOWLEDGMENTS