THE FLAVONOIDS OF ONAGRACEAE, TRIBE EPILOBIEAE: EPILOBIUM SECT. EPILOBIUM

An analysis of about 100 populations of 39 taxa of Epilobium sect. Epilobium showed quercetin 3-0-rhamnoside and glucoside and myricetin 3-0-rhamnoside and glucoside to be present in most species, with the arabinosides present in some and in much smaller quantities. Kaempferol 3-0-rhamnoside was also present in some populations of some entities in small quantities. Variability, particularly in the presence of myricetin 3-0-rhamnoside and quercetin 3-0-glucoside, was characteristic of some species, especially those of Australia and New Zealand. FOLLOWING the studies of Baptisia by Alston and Turner (1962, 1963) and Turner and Alston (1959), flavonoids have been widely employed in systematic studies. Most studies have involved the analysis of hybridization or the delimitation of closely related taxa. Flavonoids have been used to some extent in phylogenetic interpretations but, generally, little consideration has been given to the evolution of the various compounds present. Further, although extensive chemosystematic studies of particular groups have been completed, a synthesis of these data with those from biological characters has yet to be completed (Harborne, 1975). As a part of a comprehensive survey of the flavonoids of the Onagraceae in which structural modifications and changes in substitution patterns will be correlated with a phylogeny firmly based on other systematic data, we are reporting the flavonoids of Epilobium sect. Epilobium. Epilobium is a genus of some 200 species, all but 15 of which are included in section Epilobium (Raven, 1976). Most of the species of the genus are found at relatively high latitudes or altitudes, and in the tropics are confined to the mountains. Within these confines, the distribution of Epilobium is worldwide. Approximately 70 species are found in Eurasia, 46 in Australasia, 40 in North America, 30 in South America, and 10 in Africa. Excepting the very distinctive sect. Chamaenerion (7 species) which is centered in western Eurasia, other sections are primarily North American. The greatest morphological and chromosomal diversity in Epilobium is found in 1 Received for publication 14 December 1977; revision accepted 9 March 1978. Research supported by individual grants from the U.S. National Science Foundation to J. E. A. and P. H. R. The assistance of D. E. Boufford and P. C. Hoch is gratefully acknowledged. western North America and, from present distributions, one might predict that the genus originated there and radiated with the expansion of the plant communities related to the Madro-Tertiary Geoflora. An alternative possibility would be the origin of the genus in western Eurasia (Raven and Raven, 1976). Experimental hybridization has revealed that within sect. Epilobium a particular chromosome arrangement known as the BB arrangement is the original one (Seavey and Raven, 1977a, b, c, 1978). This is the most frequent arrangement in Eurasia and the only one in Australasia and Africa (except for E. atlanticum Litard. & Maire of the Grand Atlas of Morocco and the Sierra Nevada of Spain). It is well represented in North America and characterizes E. obcordatum A. Gray, one of the two most primitive species of the section (Raven, 1976; Seavey, Magill, and Raven, 1977). The chromosomes of the other, E. rigidum Hausskn., do not associate with those of other species of sect. Epilobium in interspecific hybrids (Seavey and Raven, 1977b, 1978), and its chromosome arrangement is therefore unknown. The BB arrangement likewise occurs in South America, possibly in species that have been dispersed via the prevailing westerlies from Australasia (Seavey and Raven, 1977b). The AA chromosome arrangement characterizes five North American species, including the widespread and polymorphic E. ciliatum Raf., as well as an unknown number of South American species (Seavey and Raven, 1977b), and three unrelated species of Europe (Seavey and Raven, 1977a). This arrangement differs from BB by a single reciprocal translocation, and was evidently derived from it, probably in western North America, where the most primitive species with the AA chromosome arrangement, and the only one with a four-lobed stigma, E. oreganum