_Hyla elaeochroa_ is closely related to _rubra_ and probably differentiated from _rubra_ through spatial isolation. Thus, we have _elaeochroa_ in Central America and _rubra_ in South America; most likely only in relatively recent times has _rubra_ migrated into eastern Panamá from northern South America. The differentiation and dispersal of _elaeochroa_ and _staufferi_ took place in Central America after the Pliocene. Probably the events of the Pleistocene resulted in the isolation of populations. One of these (_Hyla staufferi_ stock) was restricted in the subhumid Pacific lowlands, whereas the _Hyla elaeochroa_ stock occupied the tropical wet forests of the Caribbean lowlands. _Hyla elaeochroa_ apparently more closely resembled the parental stock by being restricted to the tropical rain forests, whereas _staufferi_ adapted to subhumid environments and thereby was able to disperse throughout most of the subhumid regions of Central America. After geographical separation took place the initial genetic divergence between the two populations was maintained by means of ecological and ethological isolating mechanisms. Under these circumstances it can be supposed that the different ecological preferences of _elaeochroa_ and _staufferi_ depend on the climatic changes that took place during the Pleistocene. On this basis it may be proposed that when the original prototype broke up into the two incipient species, the _staufferi_ stock became physiologically and behaviorally adapted to subhumid conditions and dispersed into dry areas of the lowlands of Middle America. The tropical evergreen forests on the Caribbean side of lower Central America and the uplift of the Talamanca range in the Pliocene were barriers to the dispersal of _staufferi_. Consequently, this frog dispersed along the Pacific lowlands. At the present time _staufferi_ occupies the length of the Pacific lowlands in Central America, except in the rainforest of the Golfo Duce region, which apparently is a relict stand and now separates the ranges of two subspecies of _Hyla staufferi_. This species crossed the central Nicaraguan lowlands and reached the Caribbean lowlands of Nicaragua and nuclear Central America. The species migrated through the subhumid corridor in northern Honduras and eastern Guatemala (Comayagua Valley in Honduras and the Motagua Valley of Guatemala) to the Isthmus of Tehuantepec. Duellman (1960) hypothesized "that during the times of glacial advances (Pleistocene) the lowlands of the Isthmus probably were more extensive and had more semiarid tropical environments than at the present" and that when semiarid environments were continuous from the Pacific slope across the isthmus to the Gulf lowlands _staufferi_ and other amphibians migrated northward to southeastern Tamaulipas, México.