Diversification of the red-eyed tree frog around a focal barrier in Costa Rica and Panama. A: Phylogenetic relationships suggest diversification along the Atlantic and Pacific slopes of the barrier (major clades) followed by limited gene flow across parapatric boundaries (different symbols within clades). Currently allopatric populations in the northwestern portion of the species' range share mitochondrial haplotypes (dashed arrows) suggesting ancestral gene flow. The most genetically divergent taxa occur at the southeastern end of the known range (adapted from ). Bayesian consensus phylogram based on 1,149 base pairs of the NADH1 mitochondrial DNA gene fragment; rooted with the outgroup taxon Agalychnis saltator; thick branches are supported by > 0.95 posterior probability. B: Morphologic intergradation in flank stripe patterns and color pattern linking different ecomorphotypes [22, 36]. C: Patterns of population structure suggesting ongoing gene flow as inferred from six microsatellite loci . Bayesian assignment probabilities were inferred in the program Structure  identifying eight genetic demes with ongoing introgression among neighboring demes (solid arrows on map). The other two arrows represent current barriers to gene flow around the ring between the most phenotypically divergent taxa (dashed arrow), where mitochondrial data suggest ancestral gene flow, and the phylogenetically most divergent taxa (dotted arrow), where, based on current sampling, there is no such evidence and taxa seem to be separated by ecologically unsuitable habitat.