The Systematics of the Frogs of the Hyla Rubra Group in Middle America Part 4

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. Gunther (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, Ca.n.a.l 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 Gunther to consider _Hyla staufferi_ as a member of the _eximia_ group was Blair (1960:129), who suggested the relations.h.i.+p 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): Gunther, 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. Was.h.i.+ngton 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.

[Ill.u.s.tration: 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, Ca.n.a.l Zone, Panama; Emmett R. Dunn collector].

_Hyla culex_: Stuart, Misc. Publ. Univ. Michigan Mus. Zool., 29:38, October 1, 1935. Gaige, Carnegie Inst. Was.h.i.+ngton 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: _Ca.n.a.l 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 Toc.u.men, KU 101689-95; 8 km NE Toc.u.men, KU 101696.

EVOLUTIONARY HISTORY

My a.s.sumptions 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 circ.u.mstances 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.

_Hyla boulengeri_ is widespread in Amazonian and northern South America, whereas _foliamorta_ occurs only in eastern Panama and in north-central Colombia. The ancestral _boulengeri-foliamorta_ stock probably invaded Central America in the late Pliocene and dispersed through humid forested environments to Nicaragua. Apparently a peripheral population established itself in the dry Pacific lowlands of Panama. This population differentiated from _boulengeri_ of the humid Caribbean lowlands and evolved into _foliamorta_, which subsequently expanded its range into Colombia.

LITERATURE CITED

BLAIR, W. F.

1960. Mating call as evidence of relations in the _Hyla eximia_ group.

Southwestern Nat., 5(3):129-135. November 1.