Phylogenetic relationships and the diversification of floral form in Achimenes (Gesneriaceae)

Achimenes is a genus in the Gesneriaceae, subfamily Gesnerioideae, tribe Gloxinieae that shows remarkable variation in floral form and possibly floral pollination syndrome. This includes flowers that are salverform, tubular, or infundibuliform, white, yellow, pink, purple, and red, and with or without corolla spurs. Previous classifications of Achimenes have relied heavily on floral form as a measure of relationship. This study explores phylogenetic relationships in Achimenes and addresses questions of proper supraspecific classification, evolution of floral forms and pollination syndromes, the origins of floral spurs, chromosome evolution, and biogeographic patterns using nrDNA ITS and cpDNA trnL-F spacer sequences analyzed using maximum parsimony and maximum likelihood methodologies. Phylogenetic hypotheses support the non-monophyly of most of the supraspecific classification units currently recognized in Achimenes, multiple origins of each of the pollination syndromes and the major morphological characteristics used to define these syndromes, multiple origins of floral spurs, multiple tetraploid events, and sympatric distributions of many closely related species.