The coloration of the tadpoles is not distinctive, except for the presence of dorsal blotches on the tails of _S. sila_ and _sordida_. However, the similarity in pattern cannot be interpreted as indicating close relationships because nearly identical patterns are present in _Hyla legleri_ and some species of _Prostherapis_. This disruptive coloration seems to be directly associated with the pebble-bottom, stream-inhabiting tadpoles.
In the _baudini_ group, _S. phaeota_ and _cyanosticta_ are allopatric, whereas _S. baudini_ occurs sympatrically with both of those species. The call of _S. baudini_ differs notably from the calls of _S. phaeota_ and _cyanosticta_, which are more nearly alike. Although in the phylogenetic scheme proposed here _S. sila_ is considered to be more distantly related to _S. puma_ than is _S. sordida_, the calls of _S. sila_ and _puma_ more closely resemble one another than either resembles that of _S. sordida_. _Smilisca sila_ and _puma_ are allopatric, whereas _S. sordida_ is broadly sympatric with both of those species. We assume that in their respective phyletic lines the differentiation of both _S. baudini_ and _sordida_ was the result of genetic changes in geographically isolated populations. Subsequently, each species dispersed into areas inhabited by other members of their respective groups. Selection for differences in the breeding calls helped to reinforce other differences in the populations and thereby aided in maintaining specificity.
With respect to temporal and spatial aspects of evolution in _Smilisca_, we have tried to correlate the phylogenetic evidence on _Smilisca_ with the geologic data on Middle America presented by Lloyd (1963), Vinson and Brineman (1963), Guzmán and Cserna (1963), Maldonado-Koerdell (1964), and Whitmore and Stewart (1965). Likewise, we have borne in mind the evidence for, and ideas about, the evolution of the Middle American herpetofauna given by Dunn (1931b), Schmidt (1943), Stuart (1950, 1964) Duellman (1958, MS), and Savage (MS).
According to Stuart's (1950) historical arrangement of the herpetofauna, _Smilisca_ is a member of the Autochthonous Middle American Faunal Element, and according to Savage's (MS) arrangement the genus belongs to the Middle American Element, a fauna which was derived from a generalized tropical American unit that was isolated in tropical North America by the inundation of the Isthmian Link in early Tertiary, that developed _in situ_ in tropical North America, and that was restricted to Middle America by climatic change in the late Cenozoic.