Hybridization & introgression among HeliconiusHybridization is widespread among closely-related Heliconius species and we are using molecular genetics to quantify the extent and timing of interspecific gene flow among sympatric species. Our work in Costa Rica has shown appreciable introgression among the closely-related species H. cydnoH. pachinus, and H. melpomene. Furthermore, we have found evidence for on-going gene flow between the melpomene/cydno clade and H. hecale, a member of the silvaniform clade, groups that diverged almost 2.5 million years ago. Currently, we are following up on this work by examining hybridization and gene flow among melpomene/cydno/silvaniform species in west Ecuador.