s), 101697-701. _Panama_: 2 km WSW
Chepo, KU 101680-8; 6 km WSW Chepo, KU 77324-27; El Cangrejo (Panama),
KU 101676-8; Nueva Gorgona, AMNH 69991, 69798; 1.5 km W Pacora, KU
77328-32; 2 km N Tocumen, KU 101689-95; 8 km NE Tocumen, KU 101696.

EVOLUTIONARY HISTORY

My assumptions regarding the evolutionary history of the _Hyla rubra_
group in Central America were derived partly from interpretations of the
evolutionary history of other animal groups (Simpson, 1943, 1965; Dunn,
1931b; Stuart, 1950; Duellman, 1958, 1960, 1963, 1965; and Duellman and
Trueb, 1966). The origin and early evolution of the group probably
occurred prior to the Mid-Pliocene in the lowlands of South America,
because the greatest diversity of the group is in Brazil. Differentiation
into two or more subgroups took place in South America prior to the late
Pliocene. At the end of the Pliocene, shortly after the closure of the
Colombian Portal, many South American animals migrated into Central
America (Simpson, 1943, Maldonado-Koerdell, 1964, and Savage, 1966). It
is likely that the _Hyla rubra_ group entered Central America at that
time; apparently two stocks (_rubra-elaeochroa-staufferi_ stock and
_boulengeri-foliamorta_ stock) migrated into Central America.

_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 Panama 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