dorsal view. The nasal comprises about 40 per cent of the total length
of the skull. Anteromedially the two nasals converge; posteriorly they
overlap the sphenethmoid. The nasals lack a concavity in the midlateral
surface. Dorsally, the sphenethmoid is wider than long, roughly
pentagonal in shape; the frontoparietal is elongate, narrow, and
smooth, with a small supraorbital process anteriorly. The
frontoparietal fontanelle is narrow anteriorly and wide posteriorly.
TABLE 7.--Geographic Variation in Size and Color in Males of _Hyla
staufferi_. (Means in parentheses below observed ranges.)
=================================================================
| | |Complete dorsal|
| |Snout-vent | stripes |Barred shanks
Locality | N |length (mm.)| (per cent) | (per cent)
---------------+-----+------------+---------------+--------------
Veracruz | 47 | 23.0-27.3 | 0.0 | 100
| | (25.4) | |
| | | |
Campeche | 20 | 24.6-27.5 | 0.0 | 100
| | (25.5) | |
| | | |
Oaxaca | 75 | 24.0-28.7 | 9.3 | 100
| | (26.4) | |
| | | |
Chiapas | 20 | 23.2-27.8 | 10.0 | 100
| | (25.5) | |
| | | |
Guatemala | 22 | 25.0-29.0 | 10.9 | 100
| | (26.9) | |
| | | |
El Salvador | 21 | 24.7-28.6 | 0.0 | 100
| | (27.0) | |
| | | |
Honduras | 34 | 20.6-27.0 | 3.3 | 100
| | (24.9) | |
| | | |
Nicaragua | 67 | 21.5-26.8 | 3.0 | 92.7
| | (24.9) | |
| | | |
Costa Rica | 54 | 20.7-26.6 | 5.5 | 98.1
| | (24.2) | |
| | | |
Total | 360 | 20.7-29.0 | 5.4 | 98.3
Non-Panamanian | | (25.9) | |
| | | |
Panama | 72 | 21.7-26.0 | 94.5 | 0.0
| | (23.6) | |
Only a narrow connection exists between the posterior, pointed arm of
the squamosal and the lateral edge of the prooetic. The crista parotica
is visible dorsally along the lateral edge of the bony prooetic. The
squamosal is narrow anteriorly and posteriorly.
The prevomers are short and separated anteriorly by partly ossified
cartilage of the overlying solum nasi. The prevomer is joined to the
premaxillary by cartilage. The posterior margin of the prevomer
articulates directly with the sphenethmoid. The anterolateral and
posterolateral processes of the prevomers form the incomplete bony
internal margin of the choanae. Each prevomer bears three to six teeth.
The palatine is absent. The anterior part of the parasphenoid is narrow
and ends in a point. The pterygoid is slender and weakly developed.
_Natural History._--Throughout its range _Hyla staufferi_ occurs in
subhumid forests and savannas; consequently, the breeding activities
are limited by the seasonal occurrence of rainfall, which accumulates
in temporary ponds where this species breeds. Clasping pairs and gravid
females have been found mostly from June to August throughout its
range. This species was observed calling at Finca Taboga, Guanacaste
Province, Costa Rica, in mid-July. The males were calling from
temporary grassy and weedy ponds in which _Hyla microcephala_ also was
calling, but the two species had different calling sites. _Hyla
staufferi_ called at stations at heights of five to 80 cm. near the
edge of the pond, whereas _Hyla microcephala_ called from emergent
vegetation in the middle of the pond. Charles W. Myers informed me that
at Penonome, Cocle, Panama, he found _staufferi_ calling from grass in
puddles where _microcephala_ was absent, and at El Cano, Cocle, Panama,
_staufferi_ was calling from higher sites ("several inches to a few
feet above water") than _microcephala_.
Stuart (1948:34) reported breeding individuals from La Libertad,
Guatemala, after rainfall in late May, and Schmidt and Stuart
(1941:239) reported _staufferi_ breeding in July in the Salama basin,
Alta Verapaz, Guatemala. Stuart (1935:38) and Duellman (1960:63 and
1963:226) agreed that this species breeds early in the rainy season.
However, Rand (1957:519) stated that in El Salvador "these frogs did
not begin to call until almost a month and a half after the beginning
of the rains." Blair (1960:133) reported that males call in June and
July in Chiapas, Oaxaca, Veracruz, and Tamaulipas, Mexico.
The mating call of this species is a series of closely spaced notes
having a fundamental frequency of about 100 cycles per second. Each
note has a duration of 0.13 to 0.23 second, repeated at intervals that
are longer than the duration of the call. The notes are moderately
low-pitched and have a dominant frequency of more than 3,000 cycles per
second and about 120 pulses per second (Table 2).
_Tadpoles._--Measurements of the 33 tadpoles that are available are
given in Table 8. The largest tadpole examined is in stage 38 and has a
total length of 29.5 mm.
A typical tadpole in stage 38 of development (KU 104162, 5 km ESE
Cordoba, Veracruz, Mexico) has a body length of 10 mm., tail length of
19.5 mm., and a total length of 29.5 mm. Other characters are as
follows: body as deep as wide, depressed anteriorly; body as long as
depth of tail; interorbital space greater than distance between eye and
snout but equal to internarial space; nostril equidistant between eye
and tip of snout; distance between spiracle and eye less than distance
between eye and snout; eyes large, situated dorsolaterally; mouth
anteroventral, approximately triangular in outline; one row of papillae
covering lower lip and all except median fourth of upper lip; scattered
papillae at corners of mouth; tooth rows 2/3; first upper row entire,
second row interrupted medially, shorter than first; lower rows shorter
than upper rows; beak weak; spiracle short and nearer eyes than anus;
anal opening not reaching edge of ventral fin; dorsal fin barely
extending onto body; caudal musculature pointed distally.
TABLE 8.--Sizes of Tadpoles of _Hyla s. staufferi_ in Relation to
Developmental Stages. (Means in parentheses below observed ranges;
measurements in mm.)
======================================================
Stage | N | Body length| Tail length | Total length
--------+---+------------+-------------+--------------
25 | 3 | 6.0-7.0 | 12.0-13.0 | 18.0-20.0
| | (6.7) | (12.5) | (19.2)
| | | |
26 | 2 | 7.0-7.5 | 14.0-15.0 | 21.5-22.0
| | (7.3) | (14.5) | (21.8)
| | | |
27 | 9 | 7.0-8.0 | 13.0-17.0 | 21.0-25.0
| | (7.6) | (14.5) | (22.0)
| | | |
32 | 1 | 8.5 | 15.5 | 24.0
| | | |
36 | 2 | 8.0-10.0 | 16.5-17.0 | 25.0-26.5
| | (9.0) | (16.8) | (25.8)
| | | |
38 | 6 | 9.0-10.0 | 19.0-20.5 | 28.0-29.5
| | (9.6) | (19.5) | (29.1)
| | | |
41 | 1 | 10.0 | 14.0 | 24.0
| | | |
42 | 6 | 11.0-14.0 | 10.0-13.0 | 20.0-29.0
| | (11.8) | (11.9) | (24.8)
| | | |
45 | 1 | 12.5 | 0.5 | 13.0
| | | |
46 | 1 | 13.0 | -- | --
In life, body pale olive-tan, belly silvery white with pinkish-orange
reticulations in some specimens; tail creamy white with silvery flecks
and black or brown reticulations. In preservative, tan and
pinkish-orange coloration lost; body transparent, reticulations on tail
present.
_Remarks._--_Hyla staufferi_ was described by Cope (1865:195) on the
basis of specimens from Orizaba, Veracruz, Mexico. He described the
color pattern as "color above dark olive, with a short black bar over
each scapula, and one from eye to eye, with a trace along the coccyx."
Cope (1887:14) placed _staufferi_ as a subspecies of _Hyla eximia_, but
he did not justify his action. Guenther (1901:262) also considered
_staufferi_ to be conspecific with _eximia_ without making any
qualifying statement. Dunn and Emlen (1932:24) named _Hyla culex_ from
Tela, Honduras, on the basis of a male (MCZ 16098) having a snout-vent
length of 25.1 mm., and a female (USNM 20267) from Patuca, Honduras.
They diagnosed the species as having "discs larger than tympanum ...
black interorbital triangle, traces of black dorsal marking; three
black bars on anterior and posterior face of thighs, two black bars on
tibia, on tarsus and on forearm." The holotype now is faded but has
some of the pattern described. Dunn and Emlen did not compare _culex_
with _staufferi_ but did compare it with _boulengeri_ and _rubra_.
Dunn (1933:61) named _Hyla altae_ from Summit, Canal Zone. His
description was based on a male (MCZ 17972) having a snout-vent length
of 25.1 mm., the color pattern was described as "gray with four darker
dorsal stripes ... a faint trace of mid-dorsal striping...." Dunn
defined the _Hyla rubra_ group and recognized _boulengeri_, _altae_,
_culex_, and _rubra_ as members. _Hyla elaeochroa_ and _staufferi_ were
omitted from his key to the group in Central America.
Kellogg (1932:174) compared _staufferi_ with _eximia_ and concluded
that the two were probably distinct species. Stuart (1935:38)
considered _altae_ to be a synonym of _culex_. Gaige (1936:293)
considered _altae_ and _culex_ to be conspecific but regarded
_staufferi_ as a different species. She also suggested that _staufferi_
was not related to _eximia_ but belonged to the _rubra_ group. Taylor
(1952:865) and Duellman (1966a:274) considered _altae_ and _culex_ to
be synonyms of _staufferi_.
The only other worker besides Cope and Guenther to consider _Hyla
staufferi_ as a member of the _eximia_ group was Blair (1960:129), who
suggested the relationship on the basis of similarities in the
structure of the calls of _eximia_ and _staufferi_. Taylor (1938:421)
and Smith and Taylor (1948:78) excluded _staufferi_ from the _eximia_
group on the basis of morphological characteristics. I consider _culex_
to be inseparable from _staufferi_, whereas _altae_ is recognizable as
a Panamanian subspecies of _staufferi_.
_Hyla staufferi staufferi_ Cope, New Combination
_Hyla staufferi_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 17:195,
October 1865 [Holotype.--USNM 15317, Orizaba, Veracruz, Mexico;
Francis Sumichrast collector], Brocchi, Mission Scientifique au
Mexique et dans L'Amerique Centrale, 1881, p. 36. Boulenger,
Catalogue, of the Bratrachia Salientia s. Ecaudata, p. 400,
February 1, 1882. Kellogg, Bull. U.S. Natl. Mus., 160:173, March
31, 1932. Smith and Taylor, Bull. U.S. Natl. Mus., 194:88, 1948.
Taylor, Univ. Kansas Sci. Bull., 35:862, July 1, 1952. Rand,
Fieldiana Zool. Chicago Nat. Hist. Mus., 34:518, April 18, 1957.
Duellman, Univ. Kansas Publ, Mus. Nat. Hist., 17:274, June 17,
1966.
_Hyla eximia staufferi_ Cope, Bull. U.S. Natl. Mus., 32:14, January
16, 1887.
_Hyla eximia_ (part): Guenther, Biologia Centrali-Americana,
Reptilia and Batrachia, p. 261, June 1901. Nieden, Das Tierreich,
Anura I, p. 245, June 1923.
_Hyla culex_ Dunn and Emlen, Proc. Acad. Nat. Sci. Philadelphia,
84:24, March 22, 1932 [Holotype.--MCZ 16098, Tela Honduras; Raymond
A. Stadelman collector]. Stuart, Misc. Publ., Univ. Michigan Mus.
Zool., 29:38, October 1935. Gaige, Carnegie Inst. Washington Publ.,
457:293, 1936.
_Diagnosis._--Small frogs (Male to 29 mm., Female to 31.6 mm.);
dorsolateral stripes irregular; paravertebral stripes usually broken;
two or three transverse bars on shanks; thighs spotted or not; arms
usually barred; interorbital bar usually present; toes about three
fourths webbed; color brown, tan, or olive-green.
_Variation._--Three hundred and sixty males chosen at random from
throughout the range have snout-vent lengths of 20.7 to 29 mm. (25.9
mm.). The smallest individuals are from Costa Rica and Nicaragua (means
24.2 and 24.4 mm., respectively). The largest individuals are from
Guatemala and El Salvador (mean of each 27.0 mm.). The ratio of the
diameter of the tympanum to that of the eye is more than 60 per cent in
most samples, but in those from Costa Rica and British Honduras it is
smaller. The color pattern is highly variable. Some specimens are dark
brown or pale brown in color. Incomplete dorsal stripes are present in
94.6 per cent of the specimens, and transverse bars are present on the
shanks in 98.3 per cent of the specimens. The interorbital spot varies
from transverse to longitudinal in position, and an irregular white
line extends from the upper jaw to the arm in some specimens (Table 7).
_Distribution._--_Hyla staufferi staufferi_ inhabits savanna and
subhumid and xeric forests in the lowlands and moderate elevations from
southern Tamaulipas southward to Nicaragua on the Caribbean versant and
from Guerrero, Mexico to northwestern Costa Rica on the Pacific
lowlands (Fig. 7). Duellman (1963:226) commented that a specimen from
Chinaja, Guatemala, possibly was transported there in the cargo from
Toocog, because with this one exception the species is unknown in
tropical rainforest in Guatemala.
[Illustration: Fig. 7. Map showing locality records for _Hyla
staufferi staufferi_ (circles) and _H. staufferi altae_ (dots).]
_Specimens Examined._--Mexico: _Campeche_: 5 km S Champoton KU 71296-7;
7 km W Escarcega, KU 71298-308; 13 km W, 1 km N Escarcega, KU 71309-10,
75090-4. _Chiapas_: 32 km S Arriaga, KU 57789-92; 4 km N Ixtapa, KU
5776-81; 3.6 km SW Las Cruces, KU 37740; 17 km S Las Cruces, KU
57793-4; 24 km S Las Cruces, KU 104160 (tadpoles); 11 km S Tapachula,
KU 57782-8, 60000 (young). _Guerrero_: El Limoncito, near La Venta, KU
31392-401; Mexcala, near Balsa River, KU 31391; Organos, S El Trienta,
KU 31390. _Oaxaca_: 26 km N Matias Romero, KU 33878-82; 2.5 km S
Pochutla, KU 59924-7 (skeletons); 5 km S Pochutla, KU 57795-801; 3.2 km
E Tapanatepec, KU 37877-902; 17.6 km WNW Tapanatepec, KU 65033-4;
Temascal, USC 8243 (8); 3.2 km S Tolocita, KU 39657-8; 0.5 km Tuxtepec,
KU 87073-81, 87610 (tadpoles); 17 km S Tuxtepec, KU 65035-7; 1 km W
Zanatepec, KU 104161 (tadpoles). _Quintana Roo_: Isla Cozumel, 3.5 km N
San Miguel, KU 71710-11 (young). _San Luis Potosi_: Valles, KU 31490.
_Tabasco_: Teapa, UMMZ 118887 (3), 119203 (13); 9.6 km N Teapa, UMMZ
119202; 24 km N Teapa, UMMZ 119961 (5); 29 km N Teapa, UMMZ 119960; 3.5
km S Villahermosa, UMMZ 119201 (2); 17.6 km S Villahermosa, UMMZ 119200
(8). _Tamaulipas_: 1 km E Chamal, UMMZ 110706; Gomez Farias, UMMZ
110701 (3); 5 km SE Gomez Farias, UMMZ 110705; 8 km NE Gomez Farias,
UMMZ 11282 (2), 11283 (3); Kilometer 615 between Rio Limon and Llera,
UMMZ 80455 (2); 5 km W San Geraldo, UMMZ 110702 (4), 110703 (3); 8 km W
San Geraldo, near Rio Frio, UMMZ 110704 (5). _Veracruz_: 3 km SW Boca
del Rio, KU 10494-8; 5 km SW Boca del Rio, KU 23701; 5 km ESE Cordoba,
KU 104162 (tadpoles); Cuautlapan, KU 57098-102, 26787; Hacienda
Tamiahua, Cabo Rojo, KU 62871; 2 km ENE Mata Oscura, KU 105627; 5 km SE
Paso del Toro, KU 40144; Portrero Viejo, KU 23911-2, 26786, 27413,
57094-7.
Guatemala: _Alta Verapaz_: Chinaja, KU 57769; Finca La Cubilquitz, UMMZ
90871, 90872 (5), 91379 (2). _Baja Verapaz_: 1 km S San Jeronimo, UMMZ
84077 (7), 84078 (14). _Chiquimula_: 1.6 km SE Chiquimula, UMMZ 98114
(2); Esquipulas, UMMZ 106784 (4), 106785 (14). _El Peten_: No specific
locality, USNM 25143, 24825-6; La Libertad, FMNH 27096-7, KU 57770,
UMMZ 75339 (15), 75340 (15), UMMZ 94341-2. _Esquintla_: 20 km N San
Jose, AMNH 74369-76. _Guatamala_: 16 km NE Guatamala, KU 43539. Izabal:
Puerto Barrios, TCWC 16671-73, 16646-56; 2.5 km NE Rio Blanco, KU
57774-5. _Jalapa_: Jalapa, UMMZ 106788 (44). _Jutiapa_: Finca La
Trinidad, UMMZ 107730 (12), 107731 (16); Jutiapa, UMMZ 106786 (2).
_Zacapa_: 14 km ENE Mayuelas, KU 57773; 7 km ENE Rio Hondo, KU 57771-2,
59999 (young).
British Honduras: BELIZE: Belize, FMNH 4406. _El Cayo_: San Agustin,
UMMZ 80741 (8). _Stann Creek_: 10 km S Stann Creek on Hummingbird
Highway, UMMZ 125720-1.
El Salvador: _Cuscatlan_: 7 km WNW Cojutepeque, TNHC 32004-10. _La
Libertad_: 16 km NW Santa Tecla, KU 43540-1. _La Union_: 2.5 km Santa
Rosa, TCWC 16669-70. _Morazan_: Dividendero, USNM 73288-92. _San
Salvador_: San Salvador, FMNH 65101-06, KU 61932-44, 61989-92, 62152
(eggs), USNM 117588, 118391 (3), 118394; 1.6 km NW San Salvador, KU
43162-3.
Honduras: _Atlantidad_: Ceiba, USNM 117592. _Choluteca_: Choluteca, KU
85361-6; 2 km E Choluteca, UMMZ 118395 (7); 3.2 km NE Choluteca, KU
100500-01; 6.2 km E Choluteca, KU 65046-56; 10 km E Choluteca, KU
65045: 5 km S Choluteca, USC 2700 (4). _Colon_: Isla Guanaja (Islas de
la Bahia), TCWC 21551, TNHC 32011. _Cortes_: Agua Azul, TCWC 19178-9;
East side Lago Yojoa, KU 65038-44. _El Paraiso_: Valle de Jamastran,
AMNH 54800-04. _Francisco Morazan_: Escuela Agricola Panamericana, AMNH
54963-73; 14.5 km NW Comayaguela, KU 100499; El Zamorano, KU 103224; 29
km N Tegucigalpa, TNHC 32003, 32012.
Nicaragua: _Chinandega_: Finca San Isidro, 10 km S Chinandega, KU
85311-33. _Managua_: 13 km E Managua, KU 85339; 2 km S Tipitapa, KU
85334-8. _Rivas_: 9.5 km SE Rivas, KU 85355-6; 18 km SE Rivas, KU
85354; 7.7 km NE San Juan del Sur, KU 85346-53; 16.5 km NE San Juan del
Sur, KU 85340-5; 5 km SE San Pablo, KU 43151-61. _Zelaya_: Isla Grande
del Maiz, KU 85357-60.
Costa Rica: _Alajuela_: _Los Chiles_, USC 7215 (2), 7217. _Guanacaste_:
4 km W Bagaces, USC 7019 (5); Finca Taboga, KU 102265-5; 12 km S La
Cruz, USC 8091; Las Canas, KU 41113 (skeleton); 27 km N Las Canas, USC
8171 (5); Guardia, Rio Tempisque, USC 8214; 10 km N Guardia, KU
102266-7; 1.6 km N Guayabo de Bagaces, USC 7023 (3); Liberia, KU
36510-22; 4 km W Liberia, KU 36449-64, USC 102 (10), 103 (9), 104 (7),
105; 6 km N Liberia. USC 8096; 8 km NNW Liberia, KU 65032; 14.5 km N
Liberia, USC 8079, 8138 (2); 14.5 km S Liberia, USC 8238 (5); 6 km N
Nicoya, USC 8229 (11); 4 km S Nicoya, USC 8230, 8231; Penas Blancas, KU
102263; 8.6 km ESE Playa del Coco, USC 8137 (14); 21 km E Playa del
Coco, USC 8138 (2); Santa Cruz, USC 8232 (2); 3 km E Santa Rosa, TCWC
16663-68; Tenorio, KU 32159; Tilaran, KU 36509. _Puntarenas_: 10 km WNW
Esparta, KU 65022-9, 68614 (skeleton); 4.5 km WNW Esparta, KU 65030; 12
km WNW Esparta, KU 65031; 6 km E Esparta, KU 86477; Hotel Maribella, KU
32157-8; 3 km W Puntarenas, TCWC 16657-62.
_Hyla staufferi altae_ Dunn, New Combination
_Hyla altae_ Dunn, Occas. Papers Boston Soc. Nat. Hist., 8:61, June
7, 1933 [Holotype.--MCZ 17972, Summit, Canal Zone, Panama; Emmett
R. Dunn collector].
_Hyla culex_: Stuart, Misc. Publ. Univ. Michigan Mus. Zool., 29:38,
October 1, 1935. Gaige, Carnegie Inst. Washington Publ., 457:293,
1936.
_Hyla staufferi_: Taylor, Univ. Kansas Sci. Bull., 35:862, July 1,
1952. Duellman, Univ. Kansas Publ., Mus. Nat. Hist., 17:274, June
17, 1966.
_Diagnosis._--Small frogs (Male to 26 mm., Female to 27 mm.);
dorsolateral and paravertebral stripes complete; longitudinal dark gray
stripe on shank; thighs unmarked; interorbital bar usually absent; toes
about three fifths webbed; gray to brownish gray above.
_Variation._--_Hyla staufferi altae_ is less variable in size,
proportions, and color pattern than is _H. s. staufferi_. The size
varies from 21.7 to 26 mm. (23.6) in 72 males. The ratio of tibia to
snout-vent length is 0.42 to 0.50 (0.45), slightly less than in the
northern subspecies. In color pattern 94.5 per cent of the individuals
have complete dorsal stripes, and all have a longitudinal stripe on the
shank (Table 7).
_Distribution._--This subspecies is restricted to subhumid forests and
savannas on the Pacific lowlands of Panama. _Hyla s. altae_ is
presently known to occur from Chepo in east-central Panama through the
Azuero Peninsula to Concepcion, Chiriqui, in western Panama (Fig. 7).
_Specimens Examined._--Panama: _Canal Zone_: No specific locality, TNHC
24406; 2.8 km SW Fort Kobbe, KU 101679. _Chiriqui_: 14.4 km E
Concepcion, AMNH 69799-801; 6.6 km N David, TNHC 32013-4; 2 km S David,
AMNH 68802. _Cocle_: 1 km NE El Cano, KU 101662-75; El Valle de Anton,
AMNH 59601-5, KU 77333-47; 7 km SSW Penonome, KU 101654-61. _Los
Santos_: Tonosi, KU 101246 (tadpoles), 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 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,
Mexico.
_Hyla elaeochroa_ dispersed along Caribbean lowland routes. This
species not only occurs in the wet forests of the Golfo Dulce region
but also in Guanacaste. It is possible that _elaeochroa_ entered
Guanacaste and moved to the Golfo Dulce region when the intervening
area was less xeric than now (Duellman, 1966b). _Hyla elaeochroa_
extended its range to eastern Nicaragua, but even though northeastern
Nicaragua has over 2,000 mm. of precipitation annually (Vivo Escoto,
1964), this species has not spread into Honduras and Guatemala.