Fig. 1

Phylogeny of selected chordates showing the variation of amino acid sequences in the region of interest of the β2 nAChR subunit. Scientific names are used for the frogs. The dot in the phylogeny represents the ancestor of the poison frogs (Dendrobatidae clade). The names of undefended species of poison frogs are in black, and those of defended species are in blue. Defense by sequestered alkaloids appears to have evolved three times, associated with the parallel evolution of S108C and the unique evolution of F106L in Epipedobates. Accession numbers and names of the species included in this figure can be found in Additional file 3. Photos of Ameerega bilinguis and Epipedobates anthonyi (from which epibatidine was first isolated) are shown in the lower left. Photos courtesy of David Cannatella