Description
Gastrotheca trachyceps is a marsupial frog with snout-vent lengths (SVL) up to 50.0mm in males and 67.9 mm in females. Their heads are characterized as slightly wider than long with a bluntly round snout from the dorsal view and truncate snout from the profile. This species has an interorbital distance that is twice the width of the eyelid, and an eye diameter that is approximately equal to the distance between the eye and the nostril. Gastrotheca trachyceps have long tibias that measure approximately half the SVL and long feet that are just slightly shorter than the tibias. The skin of G. trachyceps is smooth on the dorsum but co-ossified with the head. Relative finger lengths are 1 = 2 < 4 <3, with all fingers displaying large discs. Relative toe lengths are 1 < 2 < 3 < 5 < 4, with webbing that extends from the fourth toe’s penultimate subarticular tubercle to the fifth toe’s distal tubercle and sometimes the fifth toe’s disc. Like adults, tadpoles of G. trachyceps have bluntly round snouts in the dorsal view and abruptly inclined profiles. Also from the profile, tadpole throats are concave and they have small eyes that point dorsolaterally and are positioned greater than a third of the width of the head apart from each other. Gastrotheca trachyceps tadpoles have gradually rising dorsal fins that starts at the posterior edge of the body. Their cloaca is located medially, and their mouthparts consist of alternating ventral and ventrolateral rows with a single anterolateral row (Duellman 1987).

Gastrotheca trachyceps is one of only two known Gastrotheca species to have co-ossifed skin on the head. The other species, G. nicefori can be differentiated from G. trachyceps by having a bony transverse occipital crest, dark uniform flanks, hidden limb surfaces, and a longer first than second finger (Duellman 1987).

In life, the dorsum of G. trachyceps is green or brown with dark brown strips and/or dark spots paravertebrally while the ventral surface is a pale creamy grey with a darker vocal sac and dark flecks along the belly. The species has pale strips along the lip, dorsoventrally, and on the supra-cloacal. Like the dorsum, G. trachyceps flanks are green or brown, while the groin and thighs, both anterior and posterior, are speckled with black dots on a blue background. The tympanum is brown in life. When preserved, the dorsum of the head, forelimbs, shanks, and loreal region become a uniform bluish grey. There is a large cream spot located on the upper base of the forearm. The postorbital region becomes brown and the flanks and dorsal surfaces of the thigh a lighter brown. The full-length narrow dorsolateral stripe becomes creamy white and is connected to the labial stripe by a pale rostral stripe that is located above the insertion of the forelimbs and continues for two-thirds the length of the flank. The supra-cloacal and heel strip, which runs along the outer side of the food to the disc, are cream colored. The axilla is blue as are the groin, thighs, ventral surface of the shanks, and inner surfaces of the feet; the latter surfaces also have dark grayish brown or black spots or mottling. The belly, throat, and ventral surfaces of the thighs become creamy grey with black speckles (Duellman 1987).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia

View distribution map in BerkeleyMapper.

Gastrotheca trachyceps occurs within the Northwestern Andean montane forests ecoregion. This species is currently known solely from the region of the type locality, Cerro Munchique on the western slopes of the Cordillera Occidental, in Cauca Department, Colombia. The estimated elevation range of the species lies between 2170 - 2540 m. All known occurrences are within the Parque Nacional Natural Munchique (Acosta-Galvis 2000; Castro and Lynch 2004).

It is possible that this species range extends beyond the type locality, however detailed surveys for this species have not been performed. Additionally, based upon altitude preferences and the limited extent of preferential habitat, it is unlikely that the G. trachyceps’ total area extent exceeds 5000 km² (Castro and Lynch 2004).

This frog is frequently found upon shrub or tree vegetation, most often in subtropical or tropical moist montane forests as well as sub-tropical or tropical high-altitude paramo (Duellman 1987). Gastrotheca trachyceps most commonly occurs in forest interiors or forest edges, in forest understory or middle-tier vertical location under the canopy. The species has both terrestrial and arboreal traits. Densities are greatest near forest streams; moreover, G. trachyceps may also be found on shrubs in paramo type habitat as long as bromeliads are present, especially in proximity to surface water sources. The species is commonly found hiding in bromeliads that are in turn situated on shrubs or trees (Castro and Lynch 2004).

Life History, Abundance, Activity, and Special Behaviors
Genus Gastrotheca contain most of the marsupial frogs, which are characterized by the presence of a dorsal brood pouch in females. Eggs may be fertilized upon the lower back of the female, and then inserted into the brood pouch. After fertilization, eggs stay in contact with the female vascular tissue, which tissue provides the eggs with an oxygen supply. As with other marsupial frogs, the essential element of reproduction is direct development, with each egg retained in the female pouch female until the offspring is hatched. After developing to the tadpole stage in the female pouch, the tadpoles are deposited in ponds or stream pools (del Pino et al 1975).

Trends and Threats
Although there is no detailed long-term population study data for G. trachyceps, the species population is thought to be in decline due to deforestation and subsequent habitat loss and fragmentation for timber and agricultural development. While much of G. trachyceps habitat is under protection as a national park, there are limited resources for enforcement of protections. There are currently no specific conservation measures for this species (Castro and Lynch 2004).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Prolonged drought
Habitat fragmentation
Intentional mortality (over-harvesting, pet trade or collecting)
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species epithat trachyceps roughly translates to “rough head” in Greek and is in reference to G. trachyceps’ co-ossified head that binds the skin to the skull (Duellman 1987).

Phylogeny and Evolution: In 2005, the entire genus was moved from the family Hylidae to Amphignathodontidae (Falvovich et al. 2005). In 2007, Wiens et al. examined alternative hypotheses for the evolution of genus Gastrotheca. In that analysis a phylogeny for marsupial frogs (Hemiphractidae) was reconstructed using nuclear and mitochondrial DNA sequences, with resultant estimation of patterns of life-history evolution across the ensuing tree. Wiens et al. then reasoned that all genus Gastrotheca species with complex life cycles (egg, tadpole and adult stages) are phylogenetically nested among species and genera with direct development (only egg and adult stages). As a consequence Wiens et al. further argued that the most likely explanation for tadpole evolution in this genus is that the tadpole stage evolved from direct development within Gastrotheca, “the only known case of such a reversal in frogs.”

Generally all the ancestral development of genus Gastrotheca occurred approximately sixty million years before present in the lowlands of northwestern South America. As Andean uplift occurred, corresponding speciation resulted for the higher altitude niche species members including G. trachyceps; this higher altitude adaptation likely reflected the floral palette and microclimate more than the air pressure of the altitude itself, but in any case such altitude speciation occurred around twenty million years before present (Hertwig and Sinsch 1995).

Associates: Biodiversity within the range of G. trachyceps is very high, with an exceptional level of endemism as well. Notable mammals present here are the Spectacled Bear (Tremarctos ornatus), jaguar (Panthera onca) and Andean Tapir (Tapirus pinchaque). Example avian species occurring in this eco-region are the endemic Booted Racket-tail (Ocreatus underwoodii), Empress Brilliant (Heliodoxa imperatrix), the Fulvus Treerunner (Margaromis stellatus), the Black Solitaire (Entomodestes corocinus) and the Borgeted Sunangel (Heliangelus strophianus).

There are an extraordinary number of amphibian taxa within the same eco-region inhabited by G. trachyceps. Example associate endemic amphibians are the Burrowes Robber Frog (Pristimantis laticlavius), Duellman's Robber Frog (Pristimantis duellmani) and the Pirri Range Stubfoot Toad (Atelopus glyphus). Example reptilian endemics that overlap (or nearly overlap) the range of G. trachyceps are Antioquia Anole (Anolis Antioquia) and the Saphenophis Snake (Saphenophis sneiderni).

References

Acosta-Galvis, A. R. (2000). ''Ranas, salamandras y caecilias (Tetrapoda: Amphibia) de Colombia.'' Biota Colombiana (available online as .pdf), 1, 289-319.

Castro, F., Lynch, J. (2004). ''Gastrotheca trachyceps.'' IUCN Red List of Threatened Species. Version 2012.1

Duellman, W.E. (1987). ''The taxonomic status of populations of hylid marsupial frogs referred to Gastrotheca argenteovirens (Boettger). .'' Journal of Herpetology, 21(1), 38-47.

Hertwig, I., and Sinsch, U. (1995). ''Comparative toe pad morphology in marsupial frogs (genus Gastrotheca): arboreal vs. ground-dwelling species.'' Copeia, 1995, 38-47.

Wiens, J.J., Kuczynkski, C.A., Duellman, W.E. & Reeder,T.W. (2007). ''Loss and re-evolution of complex life cycles in marsupial frogs: does ancestral trait reconstruction mislead.'' Evolution, 61(8), 1886-1899.

del Pino, E. M., Galarza, M. L., de Albuja, C. M., and Humphries, A. A. Jr. (1975). ''The maternal pouch and development in the marsupial frog Gastrotheca riobambae (Fowler).'' The Biological Bulletin, 149, 480-491.

Species Account Citation: AmphibiaWeb 2013 Gastrotheca trachyceps: Cerro Munchique Marsupial Frog <https://amphibiaweb.org/species/1403> University of California, Berkeley, CA, USA. Accessed Nov 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2024.

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