Martinique Volcano Frog
© 2013 Mael Dewynter (1 of 1)
At the type locality, Allobates chalcopis can be potentially confused with Eleutherodactylus johnstonei and Eleutherodactylus martinicesis. The juveniles of these species are very similar in coloration to the juvenilles of Allobates chalcopis, which have not yet developed their ventral coloration. The presence of digital scutes quickly allows for differentiation. Also, the snout of Eleutherodactylus is more elongate. Other diagnostic characteristics of Allobates chalcopis include: disc of Finger 3 is expanded, Finger 1 same length or barely shorter than Finger 2, vestigial toe webbing that is barely visible, absence of dorsolateral, oblique lateral, and ventrolateral stripes, absence of outer tarsal fold, disc on toe 3 is expanded, some individuals have markings on the chest and throat, light orange belly, males have dark pigmentation on throat that cover the entire hyoid region, endotrophic, nidicolous larvae, and the finger III is not swollen (Kaiser et al. 1994).
In life, the dorsum is a pale brown with some darker brown markings. There is a triangle mark in between the eyes, but this character is not well defined in many of the paratopotypes. There is also a “u”-shaped marking on the snout, which was also indistinctive in some of the paratopotypes. Males have a dark, black, throat coloration, which fades into a dark gray anteriorly, and a black collar which covers the hyoid region. Females do not have such coloration of throats or hyoid regions and instead, have a homogenous pale orange throat and venter. Males also have a light orange venter. The eye is a brown with the upper portion of the iris being a copper hue. When preserved, the brown and dark brown markings on the dorsal side become gray and dark gray, respectively. The “u”-shaped marking between the nostrils is dark, the bottom on this marking being on the upper lip. The triangle in between the eyes has its apex region pointing posteriorly. The head has a strong strip along the canthus rostralis from eyes to nostril. There is an additional line, not as defined, which goes along the upper lip, parallel to the canthus rostralis. There is a dark supratympanic stipe that extends from the eye just past the tympanum that connects to a dark wedge. At the scapular level, there are two small, dark bilateral marks with pale centers. There are two more bilateral black spots at the posterior lateral sacral regions. On the anterior sacral region, there is an expansive dark mark. A diffuse pale band that stretches transversally across the thighs surrounds the dark brown anal region. The gray flanks have two dark brown bands; one of these bands is posterior to the forelimbs while the other band is anterior, obscuring the upper portion of the tympanic region. The forelimbs are light brown on the dorsal surface; the upper arm has some gray shading, diffused dark longitudinal stripes both anteriorly and posteriorly. There are also two dark stripes across the lower arm and lighter ones across the fingers. The digital discs of Fingers 1 and 2 are white while those of Fingers 3 and 4 are a little darker. The hind limbs are light brown on the dorsal side with dark bars across the entire length. Each limb has four narrow bars: one on the thighs, one on the shanks, one of the tarsus, and on across the base of toes. The toe pads and scutes have color to them while the throat is a homogenous gray with a black collar decorating the hyoid region. The chest and the abdomen have lost their pale orange coloration and are instead a pale gray with a light reticulated pattern on the abdomen. The limbs are grayish white ventrally (Kaiser et al. 1994).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Martinique
Life History, Abundance, Activity, and Special Behaviors
Allobates chalcopis is the only known dendrobatid frog that is endemic to an oceanic island. It was first formally described in 1990 by Kaiser et al. Twenty years after this last observation, Fouquet et al. found an isolated population on the same island but at higher altitudes. The rediscovery of this species allowed for a confirmation of its molecular-based phylogenetic position: it is nested within a clade of lowland Amazonian Allobates (trilineatus clade) but only distantly related to any species within this group. All of the species within this clade occur in lowland Amazonia and are morphologically distinct from Allobates chalcopis. Molecular dating shows that it actually diverged from the rest of these species 11.3 Ma, which is in line with the emergence of the island of Martinique (9 Ma) and the establishment of the South Pole ice caps and consequently, a low eustatic sea level. This is also the period in which the Andean chains closed, the Pebas system of South America ended, and the Amazon and Orinoco modern drainages were established. This changing topography and low sea level could have been the cause of a large fresh water discharge into the sea of the Guiana Shield which faces the Caribbean. According to Measey et al. (2007), these fresh water connections between the Amazon and the Caribbean would have facilitated migration on rafts, such as those documented in the “congo plume” (as cited in Fouquet et al. 2013). This scenario seems like a likely explanation for the arrival of Leptodactylus fallax in the Lesser Antilles, which is similar in age to Allobates chalcopis. While salt-water dispersal is possible, there are some groups that are more prone to it; dendrobatids, given their small size and forestrial life history, are not among them, making the distribution of Allobates chalcopis unique. It's presence on an oceanic island might be the result of direct raft dispersal from South America to Martinique or a result of stepping stone dispersal by the island of the Grenadines, St Vincent, and Ste Lucia (Fouquet et al. 2013).
Trends and Threats
Possible reasons for amphibian decline
Subtle changes to necessary specialized habitat
Fouquet, A., Pineau, K., Rodrigues, M.T., Mailles, J., Schneider, J.B., Ernst, R., and Dewynter, M. (2013). ''Endemic or exotic: the phylogenetic position of the Martinique Volcano Frog Allobates chalcopis (Anura: Dendrobatidae) sheds light on its origin and challenges current conservation strategies.'' Systematics and Biodiversity, 11(1), 87-101.
Kaiser, H., Coloma, L.A., and Gray, H.M. (1994). ''A new species of Colostethus (Anura: Dendrobatidae) from Martinique, French Antilles.'' Herpetologica, 50(1), 23-32.
Measey, G.J., Vences, M., Drewes, R.C., Chiari, Y., Melo, M., and Bourles, B. (2007). ''Freshwater paths across the ocean: molecular phylogeny of the frog Ptychadena newtoni gives insights into amphibian colonization of oceanic islands.'' Journal of Biogeography , 34, 7-20.
Written by Adolfo Ivan Gomez (adolfoivangomez AT gmail.com), Museum of Vertebrate Zoology, UC Berkeley
First submitted 2013-04-12
Edited by Ann T. Chang (2013-06-12)
Species Account Citation: AmphibiaWeb 2013 Allobates chalcopis: Martinique Volcano Frog <http://amphibiaweb.org/species/1551> University of California, Berkeley, CA, USA. Accessed Jun 3, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Jun 2020.
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