Silverstoneia nubicola (Dunn)

Grant, Taran & Myers, Charles W., 2013, Review of the Frog Genus Silverstoneia, with Descriptions of Five New Species from the Colombian Chocó (Dendrobatidae: Colostethinae), American Museum Novitates 2013 (3784), pp. 1-60 : 43-44

Silverstoneia nubicola (Dunn)

Figures 2D , 21D , 22B ; map 2

Phyllobates nubicola Dunn, 1924: 7–9 , unnumbered fig. (right forefoot), pl 2, fig. 4, 4a (tadpole). Holotype UMMZ 58292 from “rain forest above Boquete on the trail to Chiriqui Grande , 4,500 feet, by F.M. Gaige, May 15, 1923.” Dunn, 1931a: 391.

[ Phyllobates nubicola nubicola Dunn ]: Dunn, 1933: 70 (new combination by inference since P. flotator was relegated to a subspecies of P. nubicola ).

Colostethus nubicola (Dunn) : Part (includes C. flotator ). Savage: 1968: 755–757, figs. 1D (larval mouthparts of flotator ), 1E ( flotator ?), 2 (part), 3 (part), 4C, fig. 9 (map, part).

Colostethus nubicola (Dunn) : Ibáñez D. and Smith, 1995: 452–454, figs. 2B, 3B, 4B, 5B, 7A. Savage, 2002: 378–380, figs. 7.119d, 7.122, map 7.119, color pl. 213

Silverstoneia nubicola (Dunn) : Grant et al. 2006: 167, figs. 28C, 30E, 30F.

As mentioned in the discussion of Silverstoneia flotator , the identity of frogs assigned to S. nubicola in the mountains along the Colombia-Panama border is equivocal. We have not noticed undisputed S. nubicola males to mature while remaining relatively pigment-free ventrally, whereas there is great variation in extent of throat coloration in the adult males of series from this area (even among specimens clearly larger and darker than S. flotator ). Similarly, there are intriguing differences in the flank coloration of some specimens, which leads us to suspect that these localities may harbor yet another unnamed species. The available sample is inadequate to provide decisive evidence, and we therefore refer these specimens to S. nubicola , the taxon they most resemble.

Clearly the entire nubicola - flotator complex needs more detailed investigation at all levels. Those wishing to identify specimens can consult Ibáñez D. and Smith (1995) and Savage (2002)—but should do so with awareness that purported diagnostic characters must be used cautiously. To differentiate adult males of the two species in Costa Rica, Savage (2002) reported adult male S nubicola as having black throats and yellow venters and S. flotator as having gray throats and white venters. Ibáñez D. and Smith (1995) wrote that male Panamanian S. flotator have gray throats but either white or yellow venters, depending on population. 10 Both sets of authors agree that male nubicola have a black throat, the black often extending posteriad over some if not all the venter, but variation in posterior ventral coloration is not explicitly described. Myers noted that of six adult black-throated males, five had the posterior venter white whereas the largest one (KU 115708) had it “light, bright yellow” (C.W.M. field notes for KU 115708– 115720; see text associated with fn. 8 herein). Degree of darkness of throat color in male Silverstoneia appears to be correlated with size and/or age; it is less certain if appearance of bright colors is similarly correlated.

Figures

FIG. 2. Species of Silverstoneia in life. A. Silverstoneia minima, n. sp. (one of the series UVC 13111–13127, 13131, 13170–13710; photograph by T.G.). B. Silverstoneia punctiventris, n. sp. (adult female MHNUC 321, 18.6 mm SVL; photograph by T.G.). C. Silverstoneia flotator (Dunn), adult male (AMNH A-69821, 15.0 mm SVL; photograph by R.G. Zweifel). D. Silverstoneia nubicola (Dunn), adult female (UVC 11654, 18.1 mm SVL; photograph by T.G.).

FIG. 21. Larval mouths of Silverstoneia spp. A. S. flotator (Dunn), AMNH A-116795 (1 of 7) from Barro Colorado Island, Panama. B. S. minima, n. sp., AMNH A-102090 (1 of 4 from back of holotype), Alto del Buey, Chocó, Colombia. C. S. dalyi, n. sp., AMNH A-155163 (1 of 6 from back of holotype, see fig. 3 bottom), Río San Juan, Chocó, Colombia. D. S. nubicola (Dunn), AMNH A-104230 from stream near El Llano–Cartí Road, central Panama. A–C show the mouths of three species of back-riding tadpoles in late stage 24 (spiracular tubes absent or indistinct), with total lengths of 10–12 mm. D shows the mouth of a larger (20 mm total length) free-living S. nubicola tadpole, stage 25; note developing keratinization of the beak. Arrows indicate weak anterolateral emargination of oral disc in S. dalyi and S. nubicola.

FIG. 22. Silverstoneia flotator and S. nubicola tadpoles: A. Back-riding S. flotator, late stage-24 larva, 13 mm total length, with clumped brown pigmentation and conspicuous, silvery reflecting iridophores (AMNH A-124209, 1 of 6 from Cerro Miramar, Bocas del Toro, western Panama). Prominent iridophores seem lacking in S. flotator larvae from the type locality (Barro Colorado Island, central Panama), but may characterize Colombian S. dalyi (see fig. 7). B. Free-living S. nubicola tadpole, stage 26, total length 28 mm; pale with thinly distributed melanophores (AMNH A-94849, largest of 3 from Fortuna Dam Site, Chiriquí, Panama).