Rudbeckia heterophylla, a species in the southeastern clade of subgenus Macrocline, is restricted to Levy County Florida where it is locally abundant. Although originally described as a distinct species, it has been treated for the past 50 or more years as a variety of the widespread, common R. laciniata based largely on their sharing deeply lobed to pinnately compound cauline leaves. Spontaneous garden hybrids between R. auriculata, a species restricted to Alabama and the panhandle of Florida, and R. laciniata resemble R. heterophylla in having simple basal and upper cauline leaves –characters used to separate this taxon from other entities of R. laciniata. ETS sequences of R. auriculata and R. laciniata are complemented in the garden hybrid and clearly show at least 12 polymorphic sites. ETS sequences for several individuals of R. heterophylla from Levy County show a similar degree of polymorphism indicating their possible hybrid nature. The polymorphisms, however, are not the same as seen in the garden samples. In order to determine more precisely the origin and nature of R. heterophylla, ETS sequence variation is being explored further in R. mohrii and R. nitida which are also members to the southeastern Macrocline clade. The fact that R. heterophylla is completely allopatric from its sister taxa suggests that the probable hybridization event had taken place in the distant past, and that geographic distributions for these taxa or their ancestors differ dramatically from the present.

Key words: Asteraceae, DNA sequence data, ETS, Heliantheae, phylogeny, Rudbeckia