Description
Hyperolius molleri is a rather small treefrog with males having a snout-vent-length range of 24 - 31 mm and females having a range of 31 - 33 mm (Schiøtz 1999). The species was re-described in 2016 with the male neotype having a snout-vent length of 26.9 mm. The body is moderately slender. The head is wider than long and the snout is short, obtusely pointed in dorsal view and round in profile. The laterally positioned nostrils are closer to the tip of snout than eye and are visible in dorsal view. The canthus rostralis is distinct and slightly constricted behind nostril. The lores are concave and oblique. The eye diameter is less than snout length (Bell 2016). The pupil is horizontal (Schiøtz 1999). The interorbital distance is greater than width of upper eyelid. The pineal body not visible. The tympanum is indistinct, round, and half of the eye diameter. The tympanic annulus is raised relative to tympanum, visible on anterior and ventral margin. The vocal sac is positioned medial. There is a small, rounded gular gland that occupies less than half of gular area. The ulnar tubercle, metacarpal, palmar and thenar tubercles are absent. The relative finger lengths are I < II < IV < III. The subarticular tubercles on Fingers I – IV are round while the distal tubercle on Finger IV is bifid. The finger webbing formula is I 2 – 2 II 2 – 3 II 2 – 1 IV. The tips of all four fingers are expanded with circummarginal grooves. The width of the disc on Finger III is ~1.9 times the width of phalanx. The nuptial pad absent. The outer metatarsal tubercle ill-defined, inner metatarsal tubercle distinct, ovoid. The plantar surfaces smooth. The relative toe lengths are I < II < III < V < IV. Well- developed, round subarticular tubercles are found on the toes. The toe webbing formula is I 1 – 1 II ½ – 1 III 0 – 1 IV 1 – 0 V. The tips of all five toes are expanded with the width of Toe IV disc being ~1.7 times width of phalanx. The skin on dorsum is finely granular. The skin on limbs is smooth. The skin on ventral surface is also smooth but increasingly granular towards posterior end. Dorsolateral folds are absent. There are fine dorsal asperities (Bell 2016).

Multilocus molecular data indicate that H. molleri is in the genus Hyperolius and is part of the H. cinnamomeoventris species complex, which includes six described species: H. cinnamomeoventris, H. olivaceus, and H. veithi from continental Africa, H. molleri and H. thomensis endemic to São Tomé Island, and H. drewesi endemic to Príncipe Island in the Gulf of Guinea archipelago (Schick et al. 2010; Bell et al. 2015 J Biogeography, Bell 2016, Bell et al. 2017). Hyperolius molleri is sexually monochromatic (both sexes are green) and differs in color from H. cinnamomeoventris and H. olivaceus, which are sexually dichromatic (females are green and males are tan with bright yellow dorsolateral lines), and from H. veithi, which is sexually monochromatic (both sexes are tan with bright yellow dorsolateral lines). Hyperolius molleri differs from H. thomensis in male body size (H. molleri snout-vent length is 23 – 32 mm, H. thomensis snout-vent length is 36 – 41 mm), in the distal portion of the terminal phalanx (H. molleri disc shaped, H. thomensis oval/wider in horizontal plane), and in ventral coloration (H. molleri is red/orange/white, H. thomensis is marbled black/orange; Bell 2016). Hyperolius molleri differs from H. drewesi by having a black contour along the edges of the green/yellow band of coloration that extends down the dorsal side of the thigh (always absent in H. drewesi), by having red/orange coloration on the dorsal and ventral sides of the thigh (always absent in H. drewesi; Bell 2016).

Juvenile coloration resembles the juvenile coloration in H. cinnamomeoventris but they can be differentiated based on geography (tan with bright yellow dorsolateral lines; Bell 2016).

In life, the dorsum, side of head, and dorsal surfaces of forelimb and hindlimb are green. The dorsal surface of thigh is red and patterned by a thin yellow medial band with black contour extending from dorsum to lower limb. The dorsal surface of the fingers and toes are translucent and with green, red, or yellow wash. Dorsal asperities are black. The ventral surfaces are translucent, except for the chest, which is white with red or orange blotches, and the feet and thighs, which have a red wash. The iris gold (Bell 2016).

In preservative, the dorsum, the side of head, and dorsal surfaces of forelimb and hindlimb are brown. The dorsal surface of thigh is cream colored with black speckling and a thin brown medial band with black contour extending from dorsum to lower limb. Dorsal asperities are dark. The ventral surfaces are cream (Bell 2016).

Juveniles are tan with bright yellow dorsolateral lines (Schiøtz 1999, Bell 2016).

Males with round gular gland that occupies less than half of gular area, vocal sac, and dorsal asperities. The snout-vent length of males is smaller (23 – 32 mm) than females (33 – 38 mm; Bell 2016).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Sao Tome and Principe

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (10 records).

Hyperolius molleri is endemic to São Tomé Island. The species spans much of the elevational range (0 – 1400 m) and ecological variation across São Tomé Island, including disturbed habitats. Sites at higher elevations or at the boundary of primary and second forest contain a high proportion of hybrid H. molleri – H. thomensis frogs (Bell et al. 2015 Evolution).

Life History, Abundance, Activity, and Special Behaviors
Hyperolius molleri are commonly found during visual surveys at night approximately 1 – 2 m above the ground on leaves and thin branches overhanging streams or small pools of standing water (Gilbert and Bell 2018).

Hyperolius molleri breed near slow-moving streams and temporary ponds in primary forest and in marginal habitats with high levels of human disturbance (Gilbert and Bell 2018). As in many Hyperolius, females deposit eggs on the surface of leaves overhanging water.

The average dominant frequency of the calls ranges from 2898 – 3236 (average 3036) Hz (Gilbert and Bell. 2018).

Trends and Threats
Hyperolius molleri is a listed as an IUCN Red List species of “Least Concern” because it appears to be adaptable and common. The population trend also appears to be stable (IUCN 2013).

Comments
The species authority is: Bedriaga, J. v. (1892). “Notes sur les amphibiens et reptiles recueillis par M. Adolphe F. Moller aus Iles de la Guinée.” O Instituto. Coimbra. Series 2, 39: 642–648.

Analysis of 16S and cytb mtDNA indicate that H. molleri sister to H. drewesi with H. thomensis being the next most closely related species. Hyperolius olivaceus is the most closely related species to these island endemic species (Bell et al. 2017).

At high elevations, H. molleri interbreeds with H. thomensis to produce viable offspring (Bell et al. 2015 Evolution).

References

Bell R.C., Drewes, R.C., Zamudio K.R. (2015). ''Reed frog diversification in the Gulf of Guinea: overseas dispersal, the progression rule, and in situ speciation.'' Evolution , 69(4), 904–915. [link]

Bell RC, Drewes, RC, Channing A, Gvozdik V, Kielgast J, Lötters S, Stuart BL, Zamudio KR (2015). ''Overseas dispersal of Hyperolius reed frogs from Central Africa to the oceanic islands of Sao Tome and Principe.'' Journal of Biogeography, 42(1), 65-75. [link]

Bell RC, Parra JL, Badjedjea G, Barej MF, Blackburn DC, Burger M, Channing A, Dehling JM, Greenbaum E, Gvozdík V, Kielgast J, Kusamba C, Lötters S, McLaughlin PJ, Nagy ZT, Rödel M-O, Portik DM, Stuart BL, VanDerWal J, Zassi-Boulu, A-G, Zamudio KR (2017). ''Idiosyncratic responses to climate-driven forest fragmentation and marine incursions in reed frogs from Central Africa and the Gulf of Guinea Islands.'' Molecular Ecology, 26(19), 5223-5244. [link]

Bell, R.C. (2016). ''A new species of Hyperolius (Amphibia: Hyperoliidae) from Príncipe Island, Democratic Republic of São Tomé and Príncipe.'' Herpetologica , 72(4), 343-351. [link]

Gilbert C.M., Bell R.C. (2018). ''Evolution of advertisement calls in an island radiation of African reed frogs.'' Biological Journal of the Linnean Society, 123(1), 1–11. [link]

IUCN SSC Amphibian Specialist Group (2013). “Hyperolius molleri.” The IUCN Red List of Threatened Species 2013: e.T56288A18390243. https://dx.doi.org/10.2305/IUCN.UK.2013-2.RLTS.T56288A18390243.en. Downloaded on 21 August 2020.

Schick S, Kielgast J, Rödder D, Muchai V, Burger M, Lötters S. (2010). ''New species of reed frog from the Congo basin with discussion of paraphyly in Cinnamon-belly reed frogs.'' Zootaxa, 2501(1), 23-36. [link]

Schiøtz, A. (1999). Treefrogs of Africa. Edition Chimaira, Frankfurt am Main.

Species Account Citation: AmphibiaWeb 2020 Hyperolius molleri <https://amphibiaweb.org/species/553> University of California, Berkeley, CA, USA. Accessed Jan 3, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Jan 2025.

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