Pristimantis orestes (Lynch, 1979)

Urgiles, Veronica L., Szekely, Paul, Szekely, Diana, Christodoulides, Nicholas, Sanchez-Nivicela, Juan C. & Savage, Anna E., 2019, Genetic delimitation of Pristimantis orestes (Lynch, 1979) and P. saturninoi Brito et al., 2017 and description of two new terrestrial frogs from the Pristimantis orestes species group (Anura, Strabomantidae), ZooKeys 864, pp. 111-146 : 119-123

Pristimantis orestes (Lynch, 1979) Fig. 2

Eleutherodactylus orestes Lynch, 1979

Eleutherodactylus (Eleutherodactylus) orestes : Lynch and Duellman 1997

Pristimantis orestes : Heinicke et al. 2007

Pristimantis (Pristimantis) orestes : Hedges et al. 2008

Etymology.

Greek, Orestes, a mountaineer.

Type material. Holotype. KU141998, an adult female, obtained 11 km NE Urdaneta, Provincia Loja, Ecuador, 2970 m, 24 July 1971 by William E. Duellman and Bruce MacBryde.

Paratypes. KU141999-KU142003, collected syntopically with the holotype.

Diagnosis.

Pristimantis orestes is a small species distinguished by the following combination of traits: (1) skin on dorsum finely tuberculated (in life the skin tuberculated texture is more evident); evident dorsolateral folds absent but sometimes a continuous row of pustules is present; low middorsal fold present; skin on venter areolate; discoidal fold weak, more evident posteriorly; (2) tympanic membrane absent but tympanic annulus evident, its length about 45% of the length of eye; supratympanic fold present; (3) snout short, subacuminate in dorsal view, rounded in profile; canthus rostralis weakly concave in dorsal view, rounded in profile; (4) upper eyelid bearing several small tubercles, similar in size and shape with the ones from the dorsum, about 90% IOD in females and 60% IOD in males; cranial crests absent; (5) dentigerous processes of vomers prominent, oblique, slightly ovoid, separated medially by distance lower than width of processes; each processes bearing 3 to 6 teeth; (6) males with a subgular vocal sac and small vocal slits; nuptial pads absent; (7) Finger I shorter than Finger II; discs on fingers just slightly expanded, rounded; circumferential grooves present; (8) fingers lacking lateral fringes; subarticular tubercles prominent; supernumerary palmar tubercles present, smaller than subarticular tubercles; palmar tubercle completely divided into a larger (inner) and a smaller (outer) tubercles; thenar tubercle oval, smaller than the inner palmar tubercle; (9) small, inconspicuous, ulnar tubercles present (trait more visible in life); (10) heel with small tubercles; outer edge of tarsus with a row of small tubercles; inner tarsal tubercles coalesced into a short tarsal fold (traits more visible in life); (11) inner metatarsal tubercle broadly ovoid, about 2 × ovoid, subconical (in profile), outer metatarsal tubercle; supernumerary plantar tubercles present; (12) toes lacking lateral fringes; webbing basal; Toe V slightly longer than Toe III; discs on toes just slightly expanded, rounded, about same size as those on fingers; circumferential grooves present; (13) in life, dorsum varies from gray, copper-brown and brown; venter gray to pale brown spotted with cream and/or brown; groin, anterior and posterior surfaces of thigh, concealed shank and axillae are dark brown or black enclosing large white spots; iris whitish gray, with a reddish broad median horizontal streak, and with fine black re ticulations; (14) SVL 22.4-23.7 mm in adult females (N = 2) and 16.5-22.3 mm in adult males (20.1 ± 2.16 SD, N = 5).

Variation.

Morphometric variation is shown in Table 3. In one male (MZUA.AN.2497) the discoidal fold is more visible but the ulnar tubercles are barely distinguishable both in life and in preservative. In one female (MZUA.AN.2493) a vague dorsolateral fold (formed by a continuous row of pustules) is present in the anterior half of dorsum and the middorsal fold is not distinguishable; in this same individual the ulnar tubercles are more notorious than in the other preserved specimens. In a female (MZUA.AN.2497), the dorsum and dorsal surfaces of limbs display a brownish-green coloration; the flanks and lips are dark brown with irregular cream blotches. One male (MZUA.AN.2488) presents orange spots over a brown background in the dorsum, flanks and limbs and a continuous orange blotch in the groin and anterior surfaces of thighs ( Fig. 2 ).

Advertisement call.

Two of the analyzed recordings (FUTPL-A-130 and FUTPL-A-131) are from the same unvouchered male. Pristimantis orestes has an advertisement call characterized by a call series composed by clicking calls repeated for long periods of time ( Fig. 3 ). Because the males can call continuously for long periods of time, the call series duration is unknown. The calls are characterized by a duration of (range and mean ± SD in parenthesis): 0.008-0.013 s (0.011 ± 0.0009, N = 190), an inter-call interval of 0.705-3.824 s (1.680 ± 0.650, N = 185) and a call rate of 0.50-0.73 calls/s (0.58 ± 0.110, N = 4). The 90% bandwidth ranged from 2325.6-2756.2 Hz (2605.7 ± 88.555, N = 190) to 2756.2-3186.9 Hz (2989.2 ± 115.100, N = 190), with the dominant frequency being at 2670.1-2928.5 Hz (2773.5 ± 77.359, N = 190). The fundamental frequency is not recognizable, but 2 to 3 harmonics are sometimes visible. Three of the four recorded males increased the call rate at the end of their calls ( Fig. 3 ), intensifying the call emissions in the last 20-30 seconds. The call rate increased, and the inter-call interval decreased from 0.35-0.63 calls/s (0.47 ± 0.145, N = 3) to 0.70-1.06 calls/s (0.88 ± 0.177, N = 3), respectively, and from 1.063-3.824 s (2.111 ± 0.672, N = 64) to 0.705-2.087 s (1.253 ± 0.401, N = 88).

Distribution.

Lynch (1979) states that this species occurs on the eastern Andean Cordillera from the Cuenca hoya to the Loja hoya in southern Ecuador. However, we suggest that this distribution might be inaccurate and needs to be reviewed, as many of the records are probably erroneous belonging to very similar, but in fact different species. For example, additional localities previously reported by Lynch (1979) from the Loja Province include Saraguro, but this record is likely erroneous, and refers to observations of an undescribed, very similar species. Guayasamin and Arteaga (2013) also reported P. orestes from Susudel in the Azuay province (MZUTI 706), but this record needs to be reviewed via molecular and morphological analysis to confirm identity of this specimens. Thus, we recommend limiting the distribution of P. orestes to the confirmed localities in Urdaneta and in Sigsig, in an elevational range between 2940 to 3100 m ( Fig. 4 ).

Natural history.

We found all the specimens in a pastureland in a subpáramo habitat. Specimens were encountered at night on grassy vegetation (usually at 10-20 cm above the ground) near the road. Calling males were encountered between May and August. The only sympatric frog species registered was Gastrotheca pseustes .

Conservation status.

Pristimantis orestes is categorized as endangered based on criteria B1b(iii) ( IUCN 2018). We suggest maintaining this category because the species i) has only been found in two localities, and ii) its natural habitat ( páramo and subpáramo) has been heavily damaged and fragmented by grazing, fires and roads. Also, in its type locality, P. orestes is not locally abundant, only few individuals were registered at every visit to the population. However, additional information is needed to evaluate population trends and to assess the presence and impact of pathogenic infections in this species.

Remarks.

Lynch (1979) provides an accurate and detailed description of this species, including a brief description of the cranial osteology. Our diagnosis concurs with all the morphological features described by the author, but we also focus on characters that were not detailed in the original description but that are useful to distinguish P. orestes from other similar species (e.g., condition of discoidal fold and nuptial pads in males). The only significant difference is that the outer tarsal tubercles are not prominent, and we consider the color of the iris to be whitish gray instead of gray-bronze ( Fig. 2 ). The diagnosis provided herein is based on four specimens from the original description (KU 141998, 141999, 142000, 142002): one adult female (MZUA.AN.2488) and five adult males (MUTPL 242, 248, 249 and MZUA.AN.2493, 2497) collected from the type locality.

Figures

Figure 2. Pristimantis orestes variation in life. A MZUA. AN. 2488, profile and ventral view B MZUA. AN. 2493, profile view C MZUA. AN. 2497, profile and ventral view.

Figure 3. Advertisement call of Pristimantis orestes. A Oscillogram of a 12 - call section of the call series B Oscillogram of a single call C Spectogram of a single call D Power spectrum of a single call.

Figure 4. Map of southern Ecuador showing recording localities of Pristimantis saturninoi, P. quintanai sp. nov., P. orestes, and P. cajanuma sp. nov.