Gaylussacia includes 49 species of understory shrubs in the heath family (Ericaceae) with a disjunct distribution in North and South America. Little is known about evolutionary relationships among the species. To investigate phylogenetic and biogeographic relationships in Gaylussacia, three data sets were constructed and analyzed cladistically using parsimony: morphology, nuclear ribosomal internal transcribed spacer DNA sequences, and chloroplast trnL intron-trnF spacer DNA sequences. Molecular data sets were analyzed in two ways to determine the phylogenetic informativeness of insertion/deletion events. Comparison of results from separate analyses of each data set showed some incongruencies between the nuclear and chloroplast data sets, indicating possible past hybridization or lineage sorting. Combined analyses were conducted for ITS and morphology, and for trnL-trnF and morphology. The monophyly of the genus including G. brachycera was not strongly supported. In addition, the traditional sectional divisions of Gaylussacia were not supported in the morphological and nuclear DNA analyses. Finally, a broader perspective on the disjunct distribution of Gaylussacia includes the possibility of a North American origin for the genus, rather than a South American origin as previously hypothesized.

Communicating Editor: Matt Lavin