Generic concepts in Styphelieae: resolving the limits of Leucopogon

Sequence data for the chloroplast-encoded atp beta -rbcL intergenic spacer were assembled for 43 representatives of Leucopogon R. Br., the largest gen us of Epacridaceae. Cladistic analysis rooted on Prionotes, and including r epresentatives of the sister Tribe Epacrideae and a range of other Stypheli eae, revealed Leucopogon in all senses to be polyphyletic. There is strong support for the placement of L. pluriloculatus (Leucopogon E) with Lissanth e, but the monophyly of the segregates Leucopogon A, C and D finds no suppo rt. Leucopogon hookeri and L. maccraei cluster strongly with Cyathodes and Leptecophylla, whereas the remainder of Leucopogon A form a separate well-s upported clade. Two clades defined by base chromosome numbers of x(2) = 6 a nd x(2) = 4 are resolved, the former including all representatives assigned to 'Gynoconus' (Leucopogon C) and some of 'Axonanthus' (Leucopogon D), the latter comprising the remainder of 'Axonanthus' as well as Styphelia virid is, Astroloma ciliatum and A. humifusum. The relationship of the monotypic Croninia (Leucopogon B) to these last two clades is unresolved. A data base of 41 non-molecular characters supported the association of L. plurilocula tus, L. hookeri and L. maccraei with Cyathodes, Leptecophylla and Lissanthe , and also resolved a clade containing the remaining Leucopogon A. When sup erimposed on the molecular tree, many non-molecular characters appeared hom oplastic. However, data for chromosome number and pollen morphology were hi ghly congruent with the molecular tree. Present generic concepts are clearl y inadequate. The analysis indicates that L. hookeri and L. maccraei should be removed from Leucopogon s.str. to a new genus; the remainder of Leucopo gon A constitute Leucopogon s.str. A sterile anther appendage characterises most species of Leucopogon s. str., but is neither a necessary nor suffici ent condition for membership. The genus can only be circumscribed using a c ombination of morphological features. Further data and more intensive sampl ing are needed before the limits of a more satisfactory set of genera for t he remaining segregates can be defined.