Chapter 4

Distribution.—This species is known only from elevations between 1500 and 1700 meters on the Atlantic slopes of the Chiapan Highlands; it is to be expected in cloud forests on the northern slopes of the Sierra de Cuchumatanes in Guatemala.Specimens examined.—Mexico:Chiapas: 15 km. N of Pueblo Nuevo Solistahuacán, UMMZ 123325 (4);16.5 km. N of Pueblo Nuevo Solistahuacán, UMMZ 123322 (10);18 km. N of Pueblo Nuevo Solistahuacán, UMMZ 121395-9, 123324 (8), 123326 (5);18.6 km. N of Pueblo Nuevo Solistahuacán, UMMZ 123323 (4);5.6 km. S of Rayón Mescalapa, KU 58062, 58200 (tadpoles);6.2 km. S of Rayón Mescalapa, KU 58063-74, 58199 (tadpole), 58234-8, 59936 (skeleton).

Specimens examined.—Mexico:Chiapas: 15 km. N of Pueblo Nuevo Solistahuacán, UMMZ 123325 (4);16.5 km. N of Pueblo Nuevo Solistahuacán, UMMZ 123322 (10);18 km. N of Pueblo Nuevo Solistahuacán, UMMZ 121395-9, 123324 (8), 123326 (5);18.6 km. N of Pueblo Nuevo Solistahuacán, UMMZ 123323 (4);5.6 km. S of Rayón Mescalapa, KU 58062, 58200 (tadpoles);6.2 km. S of Rayón Mescalapa, KU 58063-74, 58199 (tadpole), 58234-8, 59936 (skeleton).

Ptychohyla ignicolorDuellman

Ptychohyla ignicolorDuellman, Uni. Kansas Publ. Mus. Nat. Hist., 13:352-353, pl. 25, fig. 1, April 27, 1961 [Holotype.—UMMZ 119603 from 6 kilometers south of Vista Hermosa, Oaxaca, México; Thomas E. Moore collector].

Diagnosis.—Diameter of tympanum less than one-half diameter of eye; internarial region flat; 3-7 vomerine teeth; toes one-half webbed; no white spot below eye; no lateral white stripe; in life dorsum green; groin and thighs having bright red flash-colors.Description.—The following description is based on UMMZ 119603 from 6 kilometers south of Vista Hermosa, Oaxaca, México (Pl. 18). Adult male having a snout-vent length of 30.0 mm.; tibia length, 14.6 mm.; tibia length/snout-vent length, 48.7 per cent; foot length, 12.3 mm.; head length, 9.2 mm.; head length/snout-vent length, 30.7 per cent; head width, 9.3 mm.; head width/snout-vent length, 31.0 per cent; diameter of eye, 3.2 mm.; diameter of tympanum, 1.3 mm.; tympanum/eye, 40.6 per cent. Snout in lateral profile square, and in dorsal profile rounded; canthus pronounced; loreal region slightly concave; lips moderately flaring; top of head flat; nostrils protuberant; internarial distance, 2.8 mm.; internarial region flat; interorbital distance, 3.3 mm., much broader than width of eyelid, 2.8 mm. A heavy dermal fold from posterior corner of eye above tympanum to insertion of forelimb, covering upper edge of tympanum; tympanum elliptical, its greatest diameter equal to its distance from eye. Forearm moderately robust having distinct dermal fold on wrist; pollex moderately enlarged without nuptial spines; second and fourth fingers equal in length; subarticular tubercles round, none is bifid;discs on fingers moderate in size, that on third finger slightly larger than tympanum; no web between first and second fingers; vestige of web between other fingers. Heels overlap when hind limbs adpressed; tibiotarsal articulation extends to anterior corner of eye; no tarsal fold; inner metatarsal tubercle large, flat, and elliptical; outer metatarsal tubercle near inner one and triangular in shape; subarticular tubercles round; length of digits from shortest to longest 1-2-5-3-4; third toe webbed to proximal end of penultimate phalanx; fourth toe webbed to distal part of antepenultimate phalanx; fifth toe webbed to middle of penultimate phalanx; discs on toes smaller than on fingers. Anal opening directed posteriorly at upper edge of thighs; no anal flap; pair of large tubercles below anal opening; small tubercles ventral and lateral to these. Skin of dorsum and ventral surfaces of limbs smooth; that of throat and belly granular. Ventrolateral glands noticeably thickened, extending from axilla nearly to groin and only narrowly separated midventrally on chest; skin of anterior part of chin thickened and glandular. Tongue cordiform, shallowly notched behind and only slightly free posteriorly; vomerine teeth 0-3, situated on rounded elevations between somewhat larger, round inner nares; openings to vocal sac large, one situated along posterior margin of each mandibular ramus.Dorsal ground-color of head, body, and limbs dull brown with dark brown reticulations on head and body and dark brown transverse bands or spots on limbs; first and second fingers cream color; third and fourth fingers dull tan; anterior surfaces of thighs pale brown; posterior surfaces of thighs cream color with heavy suffusion of brown; dorsal surfaces of tarsi and third, fourth, and fifth toes dull brown with dark brown spots; first and second toes creamy white; webbing on foot brown; axilla and groin cream color; flanks brown; no white stripes on edge of upper lip or on flank; faint, barely discernible tan streak above anal opening; faint creamy tan line on ventrolateral edges of tarsi; throat, belly, ventral surfaces of limbs, inner edges of tarsi, and first toes cream color; outer ventral surfaces of tarsi and other toes brown; chest and throat spotted with brown; ventrolateral and chin glands orange-brown.In life the dorsum was uniform green (Cosse Green) becoming paler green (Bright Green-Yellow) on flanks, later changing to paler green (Javel Green) on dorsum with irregular darker green (Lettuce Green) markings and greenish yellow (Green-Yellow) on flanks; anterior and posterior surfaces of thighs, ventral surfaces of shanks, anterior surfaces of tarsi, and upper proximal surfaces of first, second, and third toes red (Coral Red); venter pale creamy yellow (Sulfur Yellow); iris pale golden color (Aniline Yellow).Variation.—Of 13 specimens, six have a cordiform tongue; the others have an emarginate tongue. Five specimens have round subarticular tubercles beneath the fourth fingers; six specimens have a bifid tubercle on one hand, and two specimens have bifid tubercles on both hands. A round gland is present on the chin of all specimens; in some the gland is barely visible, but in others it is large and distinct. In two specimens the ventrolateral glands are weakly developed; in the others the glands are well developed and orange-tan. The white anal stripe varies from a thin line to a series of white flecks. Dark brown or black flecks are present on the throat, chest, and flanks of all specimens. In some the flecks are small and widely scattered; in others the flecks are larger and more numerous. All specimens were pale green abovewhen calling at night; later they changed to dull green with darker green reticulations. The flash-colors on the thighs and in the groin vary from red to orange-red or brownish red.Description of tadpole.—The following description is based on KU 71716 from Vista Hermosa, Oaxaca, México (Figs.5Cand6G). Hind limbs small; total length, 39.6 mm.; body length, 11.8 mm.; body length/total length, 29.8 per cent. Body moderately depressed, only slightly wider than deep, in dorsal profile ovoid, widest just posterior to eyes; in lateral profile snout rounded; mouth directed ventrally; eyes small, directed dorsolaterally; nostrils barely protuberant, directed anteriorly, somewhat closer to eye than snout; spiracle sinistral and posteroventrad to eye; anal tube dextral. Tail long and slender; caudal fin low and rounded posteriorly; depth of caudal musculature about one-half greatest depth of caudal fin; musculature not extending to tip of tail.Mouth large; thin fleshy lips greatly expanded and forming large funnel-shaped disc; width of mouth about two-thirds greatest width of body; outer edge of lips having one row of small papillae; inner surface of mouth smooth; scattered large papillae forming one nearly complete row around teeth; other papillae laterally; one large papilla just above each end of first lower tooth-row; beaks moderately developed bearing long, pointed denticulations; no lateral projections on upper beak; tooth-rows3⁄3, all short; second and third upper rows subequal in length; first upper row shorter; first lower row equal in length to second and third upper rows; second lower row slightly shorter; third lower row shortest.Body creamy gray with dark brown flecks above and below; mouth colored like body; caudal musculature creamy tan; caudal fin transparent; dark brown streak on anterior third of caudal musculature; rest of tail and all of caudal fin, except anterior two-thirds of ventral fin, heavily flecked with brown; iris silvery bronze color in life.Variation.—The only other known tadpole, which was collected with the individual described above, differs in having only two upper tooth-rows. The first upper tooth-row seems not to have developed.Comparisons.—FromP. schmidtorum chamulaeandP. s. schmidtorum,P. ignicolordiffers as follows: Tympanum smaller; snout more nearly square; less webbing on toes; internarial region flat instead of depressed; white lateral stripes lacking.Ptychohyla ignicolorand several small and moderate sized hylids are sympatric. FromP. ignicolorthese hylids can be distinguished as follows:Hyla dendroscartahas a round snout and yellow dorsum;Hyla erythrommahas a round snout, green dorsum, white flanks, and a red eye;Hyla hazelaehas a tarsal fold, green dorsum, and a black line on the canthus; andPtychohyla leonhardschultzeihas a tarsal fold, brown dorsum, black and white flanks, and horny nuptial spines in breeding males.

Description.—The following description is based on UMMZ 119603 from 6 kilometers south of Vista Hermosa, Oaxaca, México (Pl. 18). Adult male having a snout-vent length of 30.0 mm.; tibia length, 14.6 mm.; tibia length/snout-vent length, 48.7 per cent; foot length, 12.3 mm.; head length, 9.2 mm.; head length/snout-vent length, 30.7 per cent; head width, 9.3 mm.; head width/snout-vent length, 31.0 per cent; diameter of eye, 3.2 mm.; diameter of tympanum, 1.3 mm.; tympanum/eye, 40.6 per cent. Snout in lateral profile square, and in dorsal profile rounded; canthus pronounced; loreal region slightly concave; lips moderately flaring; top of head flat; nostrils protuberant; internarial distance, 2.8 mm.; internarial region flat; interorbital distance, 3.3 mm., much broader than width of eyelid, 2.8 mm. A heavy dermal fold from posterior corner of eye above tympanum to insertion of forelimb, covering upper edge of tympanum; tympanum elliptical, its greatest diameter equal to its distance from eye. Forearm moderately robust having distinct dermal fold on wrist; pollex moderately enlarged without nuptial spines; second and fourth fingers equal in length; subarticular tubercles round, none is bifid;discs on fingers moderate in size, that on third finger slightly larger than tympanum; no web between first and second fingers; vestige of web between other fingers. Heels overlap when hind limbs adpressed; tibiotarsal articulation extends to anterior corner of eye; no tarsal fold; inner metatarsal tubercle large, flat, and elliptical; outer metatarsal tubercle near inner one and triangular in shape; subarticular tubercles round; length of digits from shortest to longest 1-2-5-3-4; third toe webbed to proximal end of penultimate phalanx; fourth toe webbed to distal part of antepenultimate phalanx; fifth toe webbed to middle of penultimate phalanx; discs on toes smaller than on fingers. Anal opening directed posteriorly at upper edge of thighs; no anal flap; pair of large tubercles below anal opening; small tubercles ventral and lateral to these. Skin of dorsum and ventral surfaces of limbs smooth; that of throat and belly granular. Ventrolateral glands noticeably thickened, extending from axilla nearly to groin and only narrowly separated midventrally on chest; skin of anterior part of chin thickened and glandular. Tongue cordiform, shallowly notched behind and only slightly free posteriorly; vomerine teeth 0-3, situated on rounded elevations between somewhat larger, round inner nares; openings to vocal sac large, one situated along posterior margin of each mandibular ramus.

Dorsal ground-color of head, body, and limbs dull brown with dark brown reticulations on head and body and dark brown transverse bands or spots on limbs; first and second fingers cream color; third and fourth fingers dull tan; anterior surfaces of thighs pale brown; posterior surfaces of thighs cream color with heavy suffusion of brown; dorsal surfaces of tarsi and third, fourth, and fifth toes dull brown with dark brown spots; first and second toes creamy white; webbing on foot brown; axilla and groin cream color; flanks brown; no white stripes on edge of upper lip or on flank; faint, barely discernible tan streak above anal opening; faint creamy tan line on ventrolateral edges of tarsi; throat, belly, ventral surfaces of limbs, inner edges of tarsi, and first toes cream color; outer ventral surfaces of tarsi and other toes brown; chest and throat spotted with brown; ventrolateral and chin glands orange-brown.

In life the dorsum was uniform green (Cosse Green) becoming paler green (Bright Green-Yellow) on flanks, later changing to paler green (Javel Green) on dorsum with irregular darker green (Lettuce Green) markings and greenish yellow (Green-Yellow) on flanks; anterior and posterior surfaces of thighs, ventral surfaces of shanks, anterior surfaces of tarsi, and upper proximal surfaces of first, second, and third toes red (Coral Red); venter pale creamy yellow (Sulfur Yellow); iris pale golden color (Aniline Yellow).

Variation.—Of 13 specimens, six have a cordiform tongue; the others have an emarginate tongue. Five specimens have round subarticular tubercles beneath the fourth fingers; six specimens have a bifid tubercle on one hand, and two specimens have bifid tubercles on both hands. A round gland is present on the chin of all specimens; in some the gland is barely visible, but in others it is large and distinct. In two specimens the ventrolateral glands are weakly developed; in the others the glands are well developed and orange-tan. The white anal stripe varies from a thin line to a series of white flecks. Dark brown or black flecks are present on the throat, chest, and flanks of all specimens. In some the flecks are small and widely scattered; in others the flecks are larger and more numerous. All specimens were pale green abovewhen calling at night; later they changed to dull green with darker green reticulations. The flash-colors on the thighs and in the groin vary from red to orange-red or brownish red.

Description of tadpole.—The following description is based on KU 71716 from Vista Hermosa, Oaxaca, México (Figs.5Cand6G). Hind limbs small; total length, 39.6 mm.; body length, 11.8 mm.; body length/total length, 29.8 per cent. Body moderately depressed, only slightly wider than deep, in dorsal profile ovoid, widest just posterior to eyes; in lateral profile snout rounded; mouth directed ventrally; eyes small, directed dorsolaterally; nostrils barely protuberant, directed anteriorly, somewhat closer to eye than snout; spiracle sinistral and posteroventrad to eye; anal tube dextral. Tail long and slender; caudal fin low and rounded posteriorly; depth of caudal musculature about one-half greatest depth of caudal fin; musculature not extending to tip of tail.

Mouth large; thin fleshy lips greatly expanded and forming large funnel-shaped disc; width of mouth about two-thirds greatest width of body; outer edge of lips having one row of small papillae; inner surface of mouth smooth; scattered large papillae forming one nearly complete row around teeth; other papillae laterally; one large papilla just above each end of first lower tooth-row; beaks moderately developed bearing long, pointed denticulations; no lateral projections on upper beak; tooth-rows3⁄3, all short; second and third upper rows subequal in length; first upper row shorter; first lower row equal in length to second and third upper rows; second lower row slightly shorter; third lower row shortest.

Body creamy gray with dark brown flecks above and below; mouth colored like body; caudal musculature creamy tan; caudal fin transparent; dark brown streak on anterior third of caudal musculature; rest of tail and all of caudal fin, except anterior two-thirds of ventral fin, heavily flecked with brown; iris silvery bronze color in life.

Variation.—The only other known tadpole, which was collected with the individual described above, differs in having only two upper tooth-rows. The first upper tooth-row seems not to have developed.

Comparisons.—FromP. schmidtorum chamulaeandP. s. schmidtorum,P. ignicolordiffers as follows: Tympanum smaller; snout more nearly square; less webbing on toes; internarial region flat instead of depressed; white lateral stripes lacking.

Ptychohyla ignicolorand several small and moderate sized hylids are sympatric. FromP. ignicolorthese hylids can be distinguished as follows:Hyla dendroscartahas a round snout and yellow dorsum;Hyla erythrommahas a round snout, green dorsum, white flanks, and a red eye;Hyla hazelaehas a tarsal fold, green dorsum, and a black line on the canthus; andPtychohyla leonhardschultzeihas a tarsal fold, brown dorsum, black and white flanks, and horny nuptial spines in breeding males.

Life History.—At Vista Hermosa, Oaxaca, males were calling on vegetation above small streams on March 30, 1959, and on June 28, 1962; males were found on vegetation overhanging a stream 6 kilometers south of Vista Hermosa on June 27 and July 3, 1962. The call consists of a series of short notes, three to thirteen notes perseries, sounding like "raa-raa-raa." The duration of each note is about .08 of a second and has a rate of 123 to 129 pulses per second. The dominant frequency of notes in short series is about 2100 cycles per second, whereas the dominant frequency of notes in long series is about 3150 cycles per second (Pl. 11E).

On June 28, 1962, two tadpoles of this species were found in a quiet pool in a spring-fed rivulet at Vista Hermosa, Oaxaca. Females are unknown.

Remarks.—The absence of a tarsal fold and of nuptial spines in breeding males, the nature of the breeding call, and the form of tadpole are characters that placePtychohyla ignicolorin theP. schmidtorum-group.

Distribution.—This species is known from only two localities at elevations of 1500 and 1850 meters in the cloud forest on the northern (Atlantic) slopes of the Sierra Madre Oriental in northern Oaxaca.Specimens examined.—Mexico:Oaxaca: Vista Hermosa, KU 71334, 71716 (tadpoles), UMMZ 119602; 6 km. S of Vista Hermosa, KU 71335-42, 71343 (skeleton), UMMZ 119603, 123327 (2).

Specimens examined.—Mexico:Oaxaca: Vista Hermosa, KU 71334, 71716 (tadpoles), UMMZ 119602; 6 km. S of Vista Hermosa, KU 71335-42, 71343 (skeleton), UMMZ 119603, 123327 (2).

DISTRIBUTION AND ECOLOGY

Geographic Distribution of the Species

The distribution of species ofPtychohylareflects the distribution of cloud forest in southern México and northern Central America. The frogs are restricted to mountainous areas, usually at elevations higher than 1000 meters above sea level.Ptychohyladoes not range to great heights in the mountains, where west of the Isthmus of Tehuantepec the mountain streams are inhabited by frogs of theHyla bistinctagroup, and in Chiapas and Guatemala by species ofPlectrohyla.

Frogs of thePtychohyla euthysanotagroup have a greater combined geographic range than the species comprising thePtychohyla schmidtorumgroup (Fig. 7). No two species in the same group are sympatric, but members of different groups are sympatric in at least parts of their ranges. ApparentlyP. leonhardschultzeiranges around the southern edge of the Mexican Highlands, where the species occurs on both Atlantic and Pacific slopes; as can be seen from the distribution map, there are many gaps in the known range of this species. The range ofP. euthysanota euthysanotais along the Pacific slopes of the Sierra Madre in Chiapas, Guatemala, and El Salvador, whereas that ofP. euthysanota macrotympanumis along the southern interior slopes of the Central Highlands of Chiapas and the Sierra de Cuchumatanes in Guatemala.Ptychohylaspinipollexoccurs on the wet Atlantic slopes of the Guatemalan and Honduranean Highlands; the range of the species in Honduras is poorly known.

Map showing record localities.Fig. 7.Map showing locality records for the species and subspecies ofPtychohyla.

Fig. 7.Map showing locality records for the species and subspecies ofPtychohyla.

The frogs of thePtychohyla schmidtorumgroup have more restricted geographic ranges than members of the former group.Ptychohyla schmidtorum schmidtorumoccurs on the Pacific slopes of the Sierra Madre in Chiapas and Guatemala, where it occurs withP. euthysanota euthysanota;P. schmidtorum chamulaeis known from only two localities on the Atlantic slopes of the Central Highlands of Chiapas, where it occurs close to, but as now known not with,P. euthysanota macrotympanum. On the Atlantic slopes of the Sierra Madre Oriental in northern OaxacaP. ignicoloroccurs withP. leonhardschultzei.

In the Sierra de los Tuxtlas in southern Veracruz and in the cloud forests along the eastern slopes of the Sierra Madre Oriental northward to Nuevo León,Hyla miotympanumseems to be the ecological replacement ofPtychohyla. On the Pacific slopes north of Guerrero, México, humid forests in which there are cascading mountain streams are absent; consequently, noPtychohylaare known from that region. In the mountains of El SalvadorPtychohyla euthysanota euthysanotaoccurs sympatrically with another small stream-breeding hylid,Hyla salvadorensis. To the south of Honduras the highlands diminish into the lowlands of Nicaragua, where habitat suitable forPtychohylaapparently does not exist. In the mountains of Costa Rica and Panamá, the habitats occupied byPtychohylain northern Central America are filled by a variety ofstream-breedingHyla, such asHyla legleri,H. rivularis,H. rufioculis,H. alleei, andH. uranochroa.

Although members of the genusPtychohylaoccur in the southern part of the Mexican Highlands to the west of the Isthmus of Tehuantepec, the greater distribution and differentiation in the genus is in the Chiapan-Guatemalan Highlands. In this respectPtychohylais a counterpart ofPlectrohyla.

Habitat Preference

Frogs of the genusPtychohylaare ecologically associated with mountain streams at elevations between 650 and 2200 meters; in the geographic region where these frogs occur the vegetation between those elevations consists of cloud forest or pine-oak forest. In some places the frogs have been found in a mixture of oak and semi-deciduous scrub forest. At Vista Hermosa, Oaxaca,P. leonhardschultzeiandP. ignicolorwere found in cloud forest, whereas at Agua del Obispo, Guerrero, the former species was found in pine-oak forest.Ptychohyla schmidtorumis known only from cloud forest;P. euthysanota euthysanotaandP. spinipollexgenerally are found in cloud forest, but in some places they live in pine-oak forest.Ptychohyla euthysanota macrotympanumhas been found in pine-oak forest and in a mixture of oak and semi-deciduous scrub forest. With the possible exception of the members of thePtychohyla schmidtorumgroup, which has been found only in cloud forest, it seems as though the type of vegetation is not the controlling factor in the ecological distribution of these frogs.

Ptychohylahas been found only where there are clear, cascading streams overhung by vegetation, on which adults and young perch at night, or even by day. The presence of these streams, in which the tadpoles live, seems to be an important factor in the distribution ofPtychohyla. As has been shown previously, the tadpoles ofPtychohylaare adapted for existence in torrential streams, where the water is cool, and the amount of oxygen is high. Clearly these tadpoles are unsuited for life in ponds or sluggish streams in the lowlands, where the temperature of the water is high, a layer of silt on the bottom is deep, and the amount of oxygen is low. The tadpoles cling to rocks on the bottom of the streams; there they move slowly across the rocks, apparently feeding on the thin covering of algae. Tadpoles were not observed on rocks having a thick covering of algae or moss. The tadpoles were observed to swim against the current in torrential streams, in which no fishes werefound. Therefore, it seems as though the presence of the stream-habitat for the tadpoles is a significant factor in the ecological distribution of the species ofPtychohyla.

Interspecific Competition

At localities where two species ofPtychohylaoccur sympatrically (P. ignicolorandP. leonhardschultzeiat Vista Hermosa, Oaxaca, andP. euthysanota euthysanotaandP. schmidtorum schmidtorumat Finca La Paz, Depto. San Marcos, Guatemala) effort was made to determine what, if any, ecological interspecific relationships existed. Although adults of the sympatric species were found on adjacent leaves or branches of bushes overhanging the streams at both localities, segregation at the time of breeding seems to be maintained by the notably different breeding calls in sympatric species (see discussion of breeding calls). Thus, as has been shown by Blair (1956), Fouquette (1960), and others working on a variety of pond-breeding frogs and toads, the breeding call inPtychohylaacts as an important reproductive isolating mechanism.

At no locality werePtychohylaand associated species of hylids found so abundantly as were species of pond-breeding hylids in the lowlands. Apparently reproductive activity is not concentrated in a short breeding season, and it is highly doubtful if the populations of these frogs are as large as those of the lowland pond-breeders. The continual humid conditions and abundance of insect food throughout the year in the cloud forest are perhaps indicative of little interspecific competition among adults ofPtychohylaand other sympatric hylids.

At Finca La Paz, Guatemala, tadpoles of two species ofPtychohylawere ecologically segregated. The tadpoles ofP. euthysanota euthysanotawere found in riffles in the streams, whereas those ofP. schmidtorum schmidtorumwere found in slower water, chiefly in small pools in the streams. At Vista Hermosa, Oaxaca, tadpoles ofP. leonhardschultzeiwere found in riffles, and tadpoles of the sympatricP. ignicolorwere found in a small pool in a stream. Similar ecological relationships were observed for several species of Costa Rican hylids. Throughout the range ofPtychohylaeast of the Isthmus of Tehuantepec, members of the genus occur with species ofPlectrohyla, all of which are larger thanPtychohyla, and all of which have tadpoles that live in torrential streams. Tadpoles ofPtychohyla spinipollexhave been found in streams inhabited by the tadpoles ofPlectrohyla guatemalensisandP. quecchi; tadpoles ofPtychohyla euthysanota euthysanotaandP. schmidtorum schmidtorumwere found in streams inhabited by tadpoles ofPlectrohyla guatemalensis,P. matudai, andP. sagorum. In some streams great numbers of tadpoles occur. The habitat is rather restricted, and the food supply is limited. Consequently, interspecific competition among the various species of hylids whose tadpoles live in the torrential streams probably is highest during the larval stage. Unfortunately, this aspect of salientian population ecology has received no intensive study.

Reproduction and Development

Since the cloud forests inhabited byPtychohylaare daily bathed in clouds and have a fairly evenly distributed rainfall throughout the year, the frogs living in these forests are active throughout the year. At least some of the species evidently have a long breeding season, for I found calling males ofP. leonhardschultzeiin February, March, and August, and found tadpoles in February, March, June, and August. Tadpoles of the various species have been obtained throughout much of the year, as follows:P. euthysanota euthysanota, February, March, May, and July;P. euthysanota macrotympanum, March, June, and August;P. spinipollex, February, March, April, June, July, and August;P. schmidtorum schmidtorum, March, May, June, July, and August;P. schmidtorum chamulae, June and August;P. ignicolor, June. I suspect that this temporal distribution more accurately reflects the seasonal activities of collectors than of the frogs.

Calling frogs usually are on vegetation adjacent to or overhanging streams; some calling males ofP. spinipollexwere on rocks in or by streams. Clasping pairs ofP. euthysanotaandP. schmidtorumwere observed on vegetation by streams. Despite intensive search, no eggs were found. It is doubtful ifPtychohyladeposit eggs on vegetation overhanging streams, as do centrolenids andPhyllomedusa, for egg-clutches of these frogs are easily found. Possibly the eggs are laid separately on vegetation above the stream, in which case they could be overlooked easily. In streams wherePtychohylaand other hylid tadpoles occur, empty egg capsules have been found on the lee sides of rocks, but there is no way to determine which species laid the eggs.

Numbers of eggs were counted in gravid females; the largest eggs have diameters ranging from 2.5 to 3.0 mm. The smaller species, comprising thePtychohyla schmidtorumgroup, have fewer eggs than do the larger species. Numbers of eggs found in females of the various species are:P. euthysanota euthysanota, 108;P. euthysanotamacrotympanum, 136, 160;P. leonhardschultzei, 141;P. spinipollex, 119, 134, 143;P. schmidtorum schmidtorum, 59, 61, 90;P. schmidtorum chamulae, 60, 71, 89.

Duration of the larval stage is unknown. Metamorphosing young have been found from May through August. From two to six completely metamorphosed young are available for each of the species, except forP. ignicolorof which none is available. The smallest young frog is aP. euthysanotahaving a snout-vent length of 14.2 mm.; the largest young frog is aP. schmidtorum schmidtorumhaving a snout-vent length of 17.0 mm.

PHYLOGENY OF PTYCHOHYLA

The preceding data on morphology, life histories, and behavior form the basis for the following interpretation of the phylogeny ofPtychohyla. Additional data are needed to support some of the ideas discussed below; many of the data that are available forPtychohylaare lacking for other, possibly related, hylids. The family Hylidae is composed of several hundred species, and most of the species are poorly known. Consequently, any attempt to placePtychohylain the over-all scheme of hylid phylogeny would be premature at this time. But, as between the five species of two species-groups here recognized as constituting the genusPtychohyla, some estimate of relationships can be made. First, it is necessary to determine the validity of the genus itself.

Ptychohylaas a Natural Assemblage

As stated in the diagnosis of the genus, the only character that sets this group of species apart from other hylids is the presence of ventrolateral glands in the breeding males. To many systematists the thought of being able to identify to genus only breeding males is sufficiently disturbing to cause them to view with disfavor the recognition of the genus. Nonetheless, the question is raised: Do the five species herein placed in the genusPtychohylaconstitute a natural assemblage? If the genus is considered to be more than a category of convenience, that is to say, a group of related species having a common origin, the primary problem is to determine whether or not the five species form a phylogenetic unit.

The species ofPtychohylaare divided into two groups on the basis of external morphology, breeding calls, and tadpoles. ThePtychohyla euthysanotagroup seems to be a natural group composed of three species, all of which are more closely related to one another than to any other hylid. Likewise, the species comprisingthePtychohyla schmidtorumgroup seem to represent a natural unit. If the presence of ventrolateral glands in breeding males is ignored, a student of salientian systematics might derive thePtychohyla euthysanotagroup from a hylid stock containingHyla miotympanumandHyla mixomaculata. Likewise,Ptychohyla schmidtorumcould be placed withHyla uranochroaand related species in Costa Rica. Nonetheless, the fact remains that all of the species assigned to the genusPtychohylahave ventrolateral glands in the breeding males; furthermore, ventrolateral glands are unknown in other hylids. If theP. schmidtorumgroup and theP. euthysanotagroup each evolved from separate hylid stocks, then the ventrolateral glands must have developed independently in both groups. That ventrolateral glands developed independently in five species of frogs in southern México and northern Central America and not in any of the other approximately 500 species of hylids in the world is untenable. It is more logical to assume that the development of the glands took place only once in a stock of hylids that gave rise to the five species herein recognized as members of the genusPtychohyla.

Generic Relationships

The affinities ofPtychohylaapparently are not with any of the other groups that have been generically separated fromHyla. Of the daughter genera in Middle America onlyPlectrohylahas stream-adapted tadpoles, but these large frogs are not closely related toPtychohyla. Stuart (1954:169) suggested that certain montane species ofHylain lower Central America andHyla salvadorensisin El Salvador may be related toPtychohylaor even congeneric. I have had experience with most of these species in the field and believe that Stuart was correct in his suggestion of relationships. The species concerned are four red-eyed stream-breedingHylain Costa Rica—H. alleei,H. legleri,H. rufioculis, andH. uranochroa, plusHyla salvadorensisin the mountains of El Salvador. Morphologically all of the species are similar;Hyla uranochroa,H. legleri, andH. rufioculishave a lateral white stripe that is expanded to form a spot beneath the eye, as inPtychohyla schmidtorum. The tadpoles ofHyla rufioculisandH. uranochroahave large funnel-shaped mouths and long slender tails like those ofPtychohyla schmidtorum. Lips of the tadpoles ofH. legleriandH. salvadorensisare folded laterally, in this respect resembling those of thePtychohyla euthysanotagroup. I do not know the tadpoles and the breeding call ofHyla alleei. The breeding calls ofHyla rufioculisandH. uranochroaconsist of high melodious notes; the calls ofH. legleriandH. salvadorensisconsist of series of short notes that have the general characteristics of the call ofPtychohyla schmidtorum. Affinities of the genusPtychohylaseem to me to be with the red-eyed species forming theHyla uranochroagroup in Costa Rica. All of the species in theHyla uranochroagroup have large frontoparietal fontanelles, rather small ethmoids, and small nasals that are not in contact with one another or with the ethmoid. Some species have a complete quadratojugal-maxillary arch; others do not. Assuming that the parental stock that gave rise both to theHyla uranochroagroup and toPtychohylawas widespread in Central America at a time of cooler, more humid conditions, it is possible that with subsequent warming temperatures and seasonal rainfall in the lowlands the parental stock was restricted to the Costa Rican highlands, where theHyla uranochroagroup developed, and to the Chiapas-Guatemala highlands, wherePtychohylaevolved.

Interspecific Relationships

Ptychohyla schmidtorumis thought to resemble more closely the parental stock of the genus than does any other species ofPtychohylanow extant. This parental stock is discussed above in the account of the generic relationships.Ptychohyla schmidtorumhas a red eye, white lateral stripe, frontoparietal fontanelle, funnel-shaped mouth in tadpoles, and lacks nuptial spines; in all of these characters it resembles members of theHyla uranochroagroup. Probably during times of glaciation during the Pleistocene, when climates in México and Central America were depressed, thePtychohylastock was more widespread than it is now. Subsequent elevation of climatic zones during interglacial periods would have isolated populations as they are today in regions of cloud forests. Thus, through geographic isolation populations could have differentiated and evolved into the present species. Climatic fluctuation in the Pleistocene must have been of sufficient magnitude to permit the spread of cool, moist forests containingPtychohylaacross the Isthmus of Tehuantepec into the mountains of Oaxaca.

Because of its small nuptial spines, small triangular vomers, coloration, and absence of a rostral keel,Ptychohyla euthysanota, more than any of the other species in theP. euthysanotagroup, resemblesP. schmidtorum. At the present timeP. euthysanotaandP. schmidtorumare sympatric.

As I have mentioned previously, ecological segregation andinterspecific competition probably is highly developed in the tadpoles ofPtychohyla. If this ecological segregation resulted from intraspecific competition in a stock ofPtychohyla, possiblyP. euthysanotaandP. schmidtorumdifferentiated sympatrically in this way. Specific identity is maintained, at least in part, by different breeding calls in males.

Ptychohyla spinipollexandP. leonhardschultzeiseem to be more closely related to one another than either is toP. euthysanota. Probably a stock ofP. euthysanotawas isolated on the Atlantic slopes of northern Central America fromP. euthysanotaon the southern slopes. The frogs on the Atlantic slopes differentiated and spread into the mountains of Oaxaca, where through isolation by the barrier of the Isthmus of Tehuantepec they developed intoP. leonhardschultzei, while the stock on the northern slopes of Central America evolved intoP. spinipollex. Subsequent to the differentiation ofP. leonhardschultzeiandP. spinipollexfromP. euthysanotaand during a time of cooler more equable climate than exists now,P. euthysanotaandP. schmidtoruminvaded the Central Highlands of Chiapas. Subsequent climatic changes isolated populations of each in the Central Highlands, whereP. euthysanota macrotympanumandP. schmidtorum chamulaeevolved.Ptychohyla ignicolorprobably represents stock ofP. schmidtorumthat crossed the Isthmus of Tehuantepec and became isolated in Oaxaca on the western side of the isthmus.

PLATE 12Ptychohyla euthysanota euthysanotaPtychohyla euthysanota euthysanota(KU 58008). × 2.

PLATE 12

PLATE 13Ptychohyla euthysanota macrotympanumPtychohyla euthysanota macrotympanum(KU 58049). × 2.

PLATE 13

PLATE 14Ptychohyla leonhardschultzeiPtychohyla leonhardschultzei(KU 64117). × 2.

PLATE 14

PLATE 15Ptychohyla spinipollexPtychohyla spinipollex(KU 58054). × 2.

PLATE 15

PLATE 16Ptychohyla schmidtorum schmidtorumPtychohyla schmidtorum schmidtorum(KU 58043). × 2.

PLATE 16

PLATE 17Ptychohyla schmidtorum chamulaePtychohyla schmidtorum chamulae(KU 58069). × 2.

PLATE 17

PLATE 18Ptychohyla ignicolorPtychohyla ignicolor(UMMZ 119603). × 2.

PLATE 18

LITERATURE CITED

Ahl, E.

1934. Über eine sammlung von Reptilien und Amphibien aus Mexiko,Zool. Anz., 106:184-186, April 15.

Blair, W. F.

1956. Call difference as an isolation mechanism in southwestern toads(genusBufo). Texas Jour. Sci., 8:87-106, March.

Duellman, W. E.

1956. The frogs of the hylid genusPhrynohyasFitzinger, 1843. Misc.Publ. Mus. Zool. Univ. Michigan, 96:1-47, pls. 1-6, February 21.

1960. Synonymy, variation, and distribution ofPtychohyla leonhard-schultzeiAhl. Studies of American Hylid Frogs, IV. Herpetologica,16:191-197, September 23.

1961. Descriptions of two species of frogs, genus Ptychohyla. Studies ofAmerican Hylid Frogs, V. Univ. Kansas Publ. Mus. Nat. Hist.,13:349-357, pl. 25, April 27.

Fouquette, M. J.

1960. Isolating mechanisms in three sympatric treefrogs in the CanalZone. Evolution, 14:484-497, December.

Kellogg, R.

1928. An apparently newHylafrom El Salvador. Proc. Biol. Soc. Washington,41:123-124, June 29.

Mertens, R.

1952. Die Amphibien und Reptilien von El Salvador. SenckenbergischenNaturf. Gesell., 487:1-120, pls. 1-16, December 1.

Ridgway, R.

1912. Color standards and color nomenclature. Washington, D. C., 44pp., 53 pls.

Shannon, F. A.

1951. Notes on a herpetological collection from Oaxaca and other localitiesin Mexico. Proc. U. S. Nat. Mus., 101:465-484, May 17.

Stuart, L. C.

1954. Descriptions of some new amphibians and reptiles from Guatemala.Proc. Biol. Soc. Washington, 67:159-178, August 5.

Tanner, W. W.

1957. Notes on a collection of amphibians and reptiles from southernMexico, with a description of a newHyla. Great Basin Nat.,17:52-56, July 31.

Taylor, E. H.

1937. New species of hylid frogs from Mexico with comments on the rareHyla bistinctaCope. Proc. Biol. Soc. Washington, 50:43-54, pls.2-3, April 21.

1942. New tailless amphibia from Mexico. Univ. Kansas Sci. Bull., 28:67-89, May 15.

1944. A new genus and species of Mexican frogs. Univ. Kansas Sci.Bull., 30:41-45, June 12.

1949. New or unusual Mexican amphibians. Amer. Mus. Novitates,1437:1-21, December 7.

Transmitted December 27, 1962.

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