The Systematics of the Frogs of the Hyla Rubra Group in Middle America Part 3

Living _Hyla:_ (A) _H. elaeochroa_ (KU 91688), (B) _H. staufferi staufferi_ (KU 57791), and (C) _H. staufferi altae_ (KU 101688), 2.]

[Ill.u.s.tration: PLATE 3

Audiospectrograms and sections of mating calls of (A) _Hyla boulengeri_ (KU Tape No. 511) and (B) _H. foliamorta_ (KU Tape No.

511) and (B) _H. foliamorta_ (KU Tape No. 288).]

[Ill.u.s.tration: PLATE 4

Audiospectrograms and sections of mating calls of (A) _Hyla elaeochroa_ (KU Tape No. 97), (B) _H. s. staufferi_ (KU Tape No.

93), and (C) _H. staufferi altae_ (KU Tape No. 502).]

The prevomer is short, and broadest anteriorly. The prevomer is joined to the premaxillary by ossification. The posterior margin of the prevomer bears a narrow cartilaginous articulation with the sphenethmoid. The anterolateral and posterolateral processes of the prevomer form an incomplete bony margin to the small choanae; each prevomer bears four to seven teeth. The palatine is small, curved anteriorly and edentate. The anterior part of the parasphenoid is robust and ends in a point. The pterygoid is slender and weakly developed.

_Natural History._--_Hyla elaeochroa_ inhabits humid lowland tropical forests in lower Central America and breeds in temporary ponds.

Clasping pairs, gravid females, and calling males have been found mostly in June, July, and August. William E. Duellman informed me that he also found males calling in mid-February, late April, and May.

Duellman (1967) reported detailed observations of the social organization in the mating call of _Hyla elaeochroa_. The choruses in this species are initially organized, but when many individuals call, the chorus loses organization. I observed this species breeding in a temporary pond at Puerto Viejo, Heredia Province, Cost Rica, in late June. Calling males and clasping pairs were extremely abundant within a few hours after a heavy rain. Males were mostly found calling from low emergent herbs in the pond and less commonly from bushes and trees to heights of six meters above the water. Calling males were also observed at Ricon de Osa, Puntarenas Province, Costa Rica, in late July. These breeding individuals were found in a shallow pond at the edge of a wet forest. Calling stations were less than two meters in height. John D.

Lynch informed me that after a heavy rain in early August, he found several hundred individuals congregated in a small gra.s.sy pond less than a foot deep, at Rincon de Osa. Males were calling from sites on gra.s.s stems a few centimeters above the water.

The mating call of _Hyla elaeochroa_ consists of short notes, repeated at intervals of about 0.40 second. Each note has a duration of 0.12 to 0.24 second. The fundamental frequency varies from 48 to 65 cycles per second, and the notes have 40-50 pulses per second; the dominant frequency is at about 2,900 cycles per second (Table 2, Pl. 4A).

The eggs are deposited in a ma.s.s in the water near floating vegetation.

William E. Duellman informed me that he observed hatchlings oriented vertically with the tip of the mouth at the surface of the water. They gradually sank to bottom, but swam back to surface again. No additional information is available concerning early development. Tadpoles have been found in shallow gra.s.sy ponds in clearings and in temporary woodland ponds.

_Tadpoles._--Three hundred and thirty-one tadpoles in various stages of development are available. Thirty-five tadpoles in stage 35 have a mean body length of 8.1 mm. (8.0-9.0 mm.), tail length of 17.7 mm.

(15.0-19.5 mm.), and total length of 25.9 mm. (23.0-27.5 mm.). The largest tadpole examined is in stage 40 and has a total length of 34.5 mm. (Table 6).

A typical tadpole, stage 35 of development (KU 104134, from Puerto Viejo, Heredia Province, Costa Rica), has a body length of 9.1 mm., tail length of 17.7 mm., and a total length of 26.8 mm. Other characters are as follows: body depressed anteriorly; body length greater than depth of tail; internarial s.p.a.ce as broad as interorbital distance; nostril equidistant between eye and tip of snout; eyes moderately large; mouth anteroventral and triangular; median fourth of upper lip bare; rest of lip bordered by one row of papillae; clumps of small papillae at corners of mouth; tooth rows 2/3; upper rows equal in length; second row interrupted medially; lower rows shorter than upper rows, diminis.h.i.+ng in length; beak rather weak with small serrations; spiracle short and nearer eyes than a.n.u.s; a.n.a.l opening not reaching edge of ventral fin; caudal musculature attenuated distally (Figs. 2B and 3B).

TABLE 6.--Sizes of Tadpoles of _Hyla elaeochroa_ in Relation to Developmental Stages. (Means in parentheses below observed ranges; measurements in mm.)

------+---+-------------+-------------+-------------- Stage | N | Body length | Tail length | Total length ------+---+-------------+-------------+-------------- 24 | 2 | 4.0-4.0 | 8.5-9.0 | 12.5-13.0 | | (4.0) | (8.8) | (12.8) | | | | 25 |64 | 5.0-6.5 | 8.5-15.0 | 13.5-21.5 | | (5.7) | (11.8) | (17.6) | | | | 27 |30 | 7.0-7.5 | 13.0-16.0 | 20.0-23.0 | | (7.1) | (14.2) | (21.3) | | | | 30 |15 | 7.0-8.0 | 13.0-16.5 | 20.0-24.0 | | (7.3) | (15.0) | (22.4) | | | | 32 |30 | 7.5-8.5 | 15.0-17.0 | 22.5-25.0 | | (7.8) | (16.1) | (23.8) | | | | 35 |35 | 8.0-9.0 | 15.0-19.5 | 23.0-27.5 | | (8.1) | (17.7) | (25.9) | | | | 37 |22 | 8.5-9.5 | 16.0-22.0 | 25.0-31.0 | | (9.0) | (18.8) | (27.8) | | | | 39 |14 | 9.5-10.5 | 19.0-24.9 | 28.5-33.5 | | (9.9) | (21.1) | (31.0) | | | | 40 |27 | 7.0-11.5 | 15.0-23.0 | 23.0-34.5 | | (9.1) | (22.0) | (31.2) | | | | 43 |10 | 8.0-12.0 | 11.0-17.0 | 20.0-26.0 | | (10.2) | (13.5) | (23.7) | | | | 45 |16 | 10.0-12.0 | 1.0-7.0 | 12.0-17.0 | | (11.2) | (3.4) | (14.6) | | | | 46 |45 | 11.0-13.0 | | | | (11.8) | |

In life, dorsum yellowish tan with gray-brown mottling; belly and ventrolateral surfaces silvery-gold or white; black stripe from tip of snout to eye; two black blotches below eye, another blotch extending from eye to base of caudal musculature; caudal musculature and fins gray-brown. In preservative, yellowish tan and silvery-gold colors lost; black reticulations present on tail.

_Remarks._--Cope (1876:105) described _Hyla elaeochroa_ from Sipurio, Limon Province, Costa Rica. He based his description on a small specimen, 26.0 mm. in snout-vent length, having a dorsum uniformly colored and lacking an interorbital triangle and blotches on the thighs. Cope (1887) described pigmented specimens from Nicaragua as _Hyla quinquevittata_, which he diagnosed as having dark brown bars on the hind limbs and five dark brown longitudinal stripes on the dorsum, the median one of which was expanded anteriorly so as to form a large triangular spot between the eyes. He thought this species was related to _Hyla eximia_ Baird and noted that "the hinder legs are much larger; the muzzle is more ac.u.minate and the color bands are much wider" than in _eximia_. Cope did not compare _quinquevittata_ with _elaeochroa_, which he had described ten years before. Gunther (1901:268), n.o.ble (1918:340), and Nieden (1923:251) regarded both _elaeochroa_ and _quinquevittata_ as valid species. Dunn and Emlen (1932:25) regarded both as synonyms of _Hyla rubra_, but they made no qualifying statements. Taylor (1952:859) placed _quinquevittata_ as a synonym of _elaeochroa_ and indicated that _rubra_ was another species.

Taylor (1958:37) described _Hyla dulcensis_ from the humid tropical forests of Golfo Dulce, Puntarenas Province, Costa Rica. He thought this species was "related to _H. elaeochroa_ but differs in its somewhat larger size, smaller finger and toe discs, the obsolete canthus rostralis; the loreal region concave and the choanae larger."

Duellman (1966a:270) compared adults, tadpoles, and mating calls of _dulcensis_ and _elaeochroa_ and concluded that a single species was involved.

_Hyla elaeochroa_ can be easily confused with the closely related _Hyla staufferi_. Although the durations of the calls are similar, the call of _elaeochroa_ has only about one third the number of pulses per second, a much lower fundamental frequency, and a lower dominant frequency than that of _staufferi_. _Hyla elaeochroa_ is larger and has a less pointed snout than does _staufferi_. Although the skulls of the two species are similar, that of _elaeochroa_ differs in having broad palatines and comparatively larger nasals that are truncate anteriorly.

In _staufferi_ the nasal is rounded anteriorly and the palatine is absent.

_Distribution._--_Hyla elaeochroa_ occurs on the Caribbean lowlands from western Panama through Costa Rica to eastern Nicaragua, and on the Pacific lowlands of southeastern Costa Rica and extreme western Panama.

Most localities where it has been collected are below 800 meters, but the species has been found at two localities above 1000 meters (El Silencio and Pacuare, Cartago Province) on the Caribbean slopes of the Cordillera de Talamanca, Costa Rica (Fig. 6).

_Specimens Examined._--Nicaragua: _Zelaya_: El Recreo, UMMZ 79721 (9).

Costa Rica: _Alajuela_: Laguna Monte Alegre, KU 64499. _Cartago_: 2 km E Chitaria, KU 107058; El Silencio, 14.4 km NE Turrialba, KU 107059-60; 4.6 km ENE Pacuare, KU 64451-75, 64628-37; 4 km S Pavones, KU 64500; Turrialba (Inst.i.tuto Interamericano de Ciencias Agricolas), KU 30305-26, 24616-57, 30337-54, 31776-91, 31803, 31807-15, 64413-50, 68283-87 (skeletons), 68390-1 (young), 35042 (eggs), 25207-8 (skeletons), 25221 (skeleton), 41073-83 (skeletons). _Guanacaste_: 2 km E Tilaran, KU 86356-77, 87667-8 (young). _Heredia_: Puerto Viejo, KU 36696, 46466, 64501-17, 68288-91, 68387, 68388-9 (young), 91803 (young), 91688-9, 104134 (tadpoles), 104135 (young), 104354-6 (skeletons); 1.5 km N Puerto Viejo, KU 64518-23, 68386 (tadpoles); 1 km S Puerto Viejo, KU 84985-6 (skeletons), 87669 (young), 87772-3 (skeletons). _Limon_: Bataan, KU 30327-36; La Lola, KU 64478-98, 68281-2 (skeletons); Los Diamantes, KU 31800-02, 64476-7; Peralta, KU 31816-21; Puerto Limon, KU 31792-99; Suretka, KU 36467-79, 36697, 41084. _Puntarenas_: 5 km NW Buenos Aires, KU 107057; 10 km E Esparta, KU 87666 (tadpoles); Golfito, KU 32166-8; 8 km E Palmer Norte KU 93939; 10.7 km SE Palmar Sur, KU 93938 (skeleton), 93940-51, 93952 (eggs), 93953-6 (tadpoles); Piedras Blancas, KU 103646-59; 4.5 km W Rincon de Osa, KU 102208-41, 104298 (tadpoles).

[Ill.u.s.tration: Fig. 6. Map showing locality records for _Hyla elaeochroa_ (circles) and _H. rubra_ (dots).]

Panama: _Bocas del Toro_: Almirante, KU 80079; Isla Bastimentos, KU 96008-11; Rio Cricamola, 3.7 km from coast, KU 96012. _Chiriqui_: Rio Gariche, 8.3 km ESE Paso de Canoas, KU 101571-2.

_Hyla staufferi_ Cope

_Hyla staufferi_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 17:165, October 1, 1865 [Holotype.--USNM 15317, Orizaba, Veracruz, Mexico; Francis Sumichrast collector].

_Diagnosis._--Small frogs (Male to 29 mm., Female to 31.6 mm.); skull longer than wide; palatine absent; large cartilaginous crista parotica present; snout flat, elongate and protruding; dark interorbital bar and dorsal stripes usually present.

_Description._--Head flat, especially in females, longer than wide; snout long, protruding beyond mouth; loreal region concave; canthus ill-defined; length of eye greater than internarial distance or width of eyelid; length of eye less than interorbital s.p.a.ce; tympanum distinct; interorbital spot irregular; supratympanic fold faint; arms short; fingers free of webs; discs on third and fourth fingers equal to diameter of tympanum; inner metatarsal tubercle on base of first finger distinct; first finger shorter than second; palmar tubercle distinct (Fig. 1C); legs short (usually less than 50 per cent of snout-vent length); tarsal fold absent; metatarsal tubercles small, outer tubercle smaller than inner; subarticular tubercles small, simple, distinct; toes less than half webbed (Fig. 1D); skin smooth above with a few small pustules on head, scapular region, flanks, and supratympanic region; arms and legs smooth; skin of belly coa.r.s.ely granular; posteroventral surfaces of thighs finely granular; tongue small, rounded, longer than wide, slightly free and notched posteriorly; vocal slits small, lateral to tongue; choanae moderate in size.

_Variation._--The largest males of _Hyla staufferi_ are from Jalapa, Guatemala, and from San Salvador, El Salvador. In these samples the average snout-vent length is 27 mm. In Panamanian specimens the average snout-vent length is 23.6 mm. Slight variation in the ratio of tibia length to snout-vent length exists throughout the range; more variation exists in the ratio of the diameter of the tympanum to that of the eye; the tympanum is proportionately larger in northern populations (Table 7). The primary differences between Panamanian and more northern populations are in size, color pattern on the dorsum and shanks, amount of webbing between the toes, and duration of notes in the mating call (Table 2, Pl. 4).

The color in Panamanian _staufferi_ is gray or gray-brown with a pair of distinct, complete, dark brown dorsolateral stripes, a pair of entire paravertebral stripes, and in some specimens a vertebral stripe.

About five per cent of the individuals have interrupted stripes on the dorsum, whereas in the more northern populations complete paravertebral stripes are present in less ten per cent of the specimens; when complete stripes are present, they are irregular. The dorsal ground color in non-Panamanian specimens is brown, olive-brown, or dark brown.

Transverse bars are present on the shanks in _Hyla staufferi_ from Costa Rica northward to Mexico, whereas in Panama all the individuals have a longitudinal stripe on the shank (Table 7, Pl. 2). The interorbital spot or bar is more noticeable in northern populations than in specimens from Panama. Frogs from Costa Rica and northward have the toes about three fourths webbed, whereas in Panama the toes are about two fifths webbed. The mating calls of the northern and Panamanian populations are similar, but the notes have a longer duration in the northern populations and a higher dominant frequency in Panamanian populations.

_Hyla staufferi_ is the most variable member of the _Hyla rubra_ group in Central America. The Panamanian populations are geographically separated from the Costa Rican and more northern populations by an area of tropical rainforest in the Golfo Dulce region in southeastern Costa Rica and adjacent Panama. _Hyla staufferi_ does not occur on the Caribbean versant of Costa Rica and Panama. The Golfo Dulce region and the Caribbean versant are humid and inhabited by _Hyla elaeochroa_.

_Hyla staufferi_ is an inhabitant of subhumid and xeric areas.

On the basis of the discontinuous variation in several characters which correlate with the disjunct distribution of the two populations, two subspecies of _Hyla staufferi_ are recognized. The accounts that follow apply equally to each.

_Cranial Osteology._--The skull of _Hyla staufferi_ is flat and longer than wide. The premaxillary is small and bears 9 to 13 teeth (mean for 5 specimens, 11.3). The alary process of the premaxillary is small, concave posteriorly and vertical. Ventrally, the premaxillary is united to the prevomers by partially ossified cartilage. The maxillary is slender and usually bears 49 to 70 teeth (mean for 5 specimens, 60.7).

The pars facialis of the maxillary is convex and less than twice the height of the pars dentalis.

The nasal is large, rounded anteriorly, and pointed posteriorly in 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 prootic. The crista parotica is visible dorsally along the lateral edge of the bony prootic. 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 acc.u.mulates 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 gra.s.sy 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 gra.s.s 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 s.p.a.ced 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 s.p.a.ce greater than distance between eye and snout but equal to internarial s.p.a.ce; 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 a.n.u.s; a.n.a.l opening not reaching edge of ventral fin; dorsal fin barely extending onto body; caudal musculature pointed distally.