SYSTEMATICS OF FLAVERIA (FLAVERIINAE-ASTERACEAE)1 A. MICHIAEL POWELL' ABSTRACT Twenty-one species are recognized for Flaveria in this first revision of the genus since1915. Three new species are described. Morphological, cytological, chemical, and artificialhybridization approaches were used in the study. Interspecific crosses revealed both weakand strong reproductive barriers among various species of Flaveria, Sartwellia, and Haplo�s-thes. Flaveria includes both self-compatible and self-incompatible species, some of whichexhibit C( photosynthetic imetalolism, and ail of which produce sulfated flavonoids. Most of the 21 species of Flaveria are native to North America whrc the taxaoccur in Florida and adjacent statcs, in Kansas-Colorado, south through Texas,New Mexico, and Arizona in the United States, and throughout most of Mexicoto Yucattn. Three species also occur in the West Indies, Greater Antilles, andSouth America, with two weedy taxa extending to Africa and India. One speciesis restricted to Australia. The Flaverias have a strong preference for alkaline or gypseous soils, andfrcquently exist under disturbed conditions. The species in Florida occur only inalkaline soils at pH 7.2-8.2 (Long & Rhamstine, 1968). A fcw species, particularlythe weedy F. trinervia and F. bidentis, may occur in various soil types. In thearid southwestern United States and northern Mexico the species are commonlyfound in moderate to strong saline or gypseous soils close to permanent or ephem-eral water sources such as rivers, creeks, irrigation canals, fields, roadsides, ponds,and boisons. The distribution of most species consists of colonies that are some-what localized and spotty throughout the range. Seldom do Flaverias exist incontinuous populations, cxcept with coastal taxa where the habitats are continuous.Accordingly, most species are endemic, as though restrictcd by localized or re-gional edaphic and climatological features. This is the first comprehensive study of Flaveria since Rydberg (1915) recog-nized 16 species of the genus in his trcatment of Helenieae for the North AmericanFlora. The account by Rydberg is strikingly different from the original mono-I have deep appreciation for the curators of herbaria from which specimens were bor-rowed. The National Science Foundation kindly supported this work through grants GB-37674 and BMS 73-06851 A01. I thank B. L. Turner for having an interest in Flaveria, forhis informative discussions regarding relationships of the genus, and for providing seeds andbuds of several species. I thank Walter V. Brown for collecting and bringing to me livingplants of F. floridana, and for sharing provocative phylogenetic ideas based upon his investi-gations of C, photosynthesis and Kranz anatomy in Flaveria. I am grateful to R. M. King forassistance in gathering literature, and for helping to provide mounted specimens of my owncollections for study; to R. II. Ilartman for providing material of F. pubescens and F. pringlei;to Tom Mabry and Munira Al-Khubaizi for organizing and carrying out prcliminary chemicalstudies of Flaveriinae; to James F. Weedin for providing excellent and conscientious technicalassistance; to Marshall C. Johnston for the Latin translations; to Michael Theroux, Don Pin-kava, and David Keil for providing material for the propagation of F. nmcdotuallii; and toEmily Lott for reviewing the manuscript. Department of Biology, Sul Ross State University, Alpine, Texas 79830.ANN. MissoOmI BOT. C(;A. 65: 590-636. 1978. 0026-6493 78, 0590-0635/$04.75/0
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