Liophryne similis, ZWEIFEL, 2000

ZWEIFEL, RICHARD G., 2000, Partition Of The Australopapuan Microhylid Frog Genus Sphenophryne With Descriptions Of New Species, Bulletin of the American Museum of Natural History 2000 (253), pp. 1-130 : 71-74

Liophryne similis , new species Figure 31G

HOLOTYPE: AMNH A130570 (field no. RZ 13518 ), collected by Richard G. Zweifel and Laurence T. Penny on August 10, 1987, at Myola Guest House, 2080 m, 7 km south, 6 km west of Mt. Bellamy , Northern Province, Papua New Guinea. 11

PARATYPES: AMNH A130561–130565 , A130567–130569 , A130571–130578 , A130580 , A130581 , UPNG 8274 , collected at the type locality by Fred Parker, R. Zweifel, and L. Penny on Aug. 8–10, 1987 ; UPNG 7080–7082 , collected by James I. Menzies at the type locality in March 1986 .

ETYMOLOGY: The Latin adjective similis refers to the morphological resemblance of this species to Liophryne rhododactyla .

DIAGNOSIS: Morphologically identical to Liophryne rhododactyla except for the lack of vocal slits and sac in the adult male. The call is a series of rapidly repeated notes rath- er than the single note of rhododactyla .

DESCRIPTION OF HOLOTYPE: Adult male (calling when captured) with the following measurements and proportions: SVL 49.7, HW 19.3, TL 22.9, EY 5.1, EN 3.5, IN 5.2, TY 3.5, HD 12.0, FT 24.3, disc of third finger 1.55 (penultimate phalanx 1.1), disc of fourth toe 1.95 (1.25); HW/SVL 0.388, TL/ SVL 0.461, EY/SVL 0.103, EN/SVL 0.070, IN/SVL 0.105, EN/IN 0.673, HD/SVL 0.241, FT/SVL 0.489, FD/SVL 0.031, TD/ SVL 0.039.

Head slightly narrower than the somewhat flat-sided body. Snout bluntly pointed seen from above, rounded and slightly projecting in profile; nostrils lateral, scarcely visible from above, slightly closer to tip of snout than to eye; canthus rostralis relatively sharp, straight; loreal region nearly vertical, concave. Eyes moderately large, corneal outline visible from beneath, eyelid almost as wide as interorbital space. Tympanum distinct, relatively large, 69% of orbit, its diameter greater than distance from eye. Relative lengths of fingers 3> 4> 2> 1, first finger long, nearly equal to second, all fingers with rounded discs bearing terminal grooves, disc of first finger not enlarged, those of other fingers wider than penultimate phalanges; subarticular and metacarpal elevations moderately prominent, rounded. Toes unwebbed, relative lengths 4> 3> 5> 2> 1, all with terminally grooved discs broader than those on fingers, that of first toe smallest but broad- er than penultimate phalanx; subarticular and

11 See footnote 4 for location of Myola Guest House.

inner metatarsal elevations moderately prominent, rounded. Skin fairly smooth except for indistinct, convergent scapular folds and narrow postocular fold passing across upper edge of tympanum, broadening into an elevated triangular area, narrowing again above front leg, and becoming obscure on midflank.

There are neither vocal slits nor (of course) a vocal sac.

In preservative, the dorsal surfaces of head and body are medium brown with faint, indefinite smaller spots. The front legs and hind legs are a deeper plumbeous shade, with pale spots prominent on the front legs and hands. The posterior thigh surface is colored like the dorsum of the body but is unmarked. A pale vertical line on the tip of the snout bifurcates, passing along the canthus rostralis and edge of eyelid and following the postorbital-dorsolateral fold. The line is obscure in places. The area below the pale line (loreal region, flanks) is darker brown, but the tympanum bears the paler dorsal shade. The lips are light spotted. The ventral surfaces of body and legs are brown with pale irregular spots, smallest on the chin.

VARIATION IN TYPE SERIES: The largest male in the series is 49.7 mm SVL. Because of the lack of vocal slits in this species, I cannot infer the size at male sexual maturity. The largest females are gravid at 51.9 and 49.0 mm, whereas one of 39.6 mm appears to be immature. Body proportions are summarized in table 6, and regression statistics are presented in table 7.

Inasmuch as the species is known only from a single locality, nothing can be said of geographic variation. Occasionally the scapular folds are more evident than in the holotype, and there are traces of short folds and tubercles on the back. The dorsolateral fold may extend almost to the groin.

Most specimens closely resemble the holotype in color and pattern. Exceptions include two specimens with more pale pigment on the snout and eyelids instead of its restriction to the canthal-dorsolateral line, one specimen that is much paler all over (above and below), one specimen with an asymmetrical dark area in the anterior dorsal region, and one specimen with a dark-edged dorsal region and a pale band above the dorsolateral fold. A midvertebral pale hairline is more evident in living specimens. The colors in life are not greatly different from those of the preserved specimens except for their relatively greater brightness.

HABITAT AND HABITS: The habitat of Liophryne similis at Myola Guest House is heavily mossed forest (mapped by Paijmans, 1975, as Lower Montane Forest) bordering a grassy meadow (see Zweifel and Parker, 1989: fig. 7). We found most of our specimens by day beneath surface cover. One discovered at night was active on the surface of the leaf litter (see also under Call, below).

A male L. similis of 29 mm SVL (AMNH A130565, fig. 11) was associated with a group of 24 eggs (AMNH 130565) with capsular diameters of 6–7 mm and connected by peduncles of about the same length. Judged from the size at maturity of L. rhododactyla , a similis of this size would not be mature, so the association probably was fortuitous. However, the large clutch size and relatively large size of the eggs favors the identification of the eggs as those of L. similis , unless there is a large terrestrial microhylid present that we did not find.

ILLUSTRATIONS: Hand and foot, fig. 54C.

CALL: I recorded the call at the type locality in August 1987 (AMNH Herpetology tape reels 252 and 253). It is a series of 7– 10 clear, moderately loud piping notes, each about 0.06 sec long delivered over the space of 0.75– 1.24 sec (fig. 77B). Notes are unpulsed and frequency is modulated, with an initial rapid rise of the dominant frequency from about 540–600 Hz to a peak of 680– 720 Hz and then a lesser, slower descent. Four calls of the holotype recorded in the field at an air temperature of 12.8°C averaged 1.20 sec long (1.09–1.24) with a rate of 7.65 (7.6–7.7) notes per sec. Intervals of almost exactly 1 min separated the four calls. Another recording involved several frogs in a collecting bag, at least two of which called at 15.5°C. The anticipated correlations with higher temperature are confirmed in the data for these eight calls: shorter call length (mean 0.98, range 0.75–1.17 sec) and faster note repetition rate (mean 8.5, range 8.2–8.8 notes per sec). Only L. similis were in the bag, so there is no question of the association of species and call.

The holotype was calling from among the prop roots of a pandanus at about 2300 hours following an afternoon rain. It was on the surface, not hidden in the litter.

COMPARISONS WITH OTHER SPECIES: In all but the call and morphological features associated with vocalization, this species appears to be identical to L. rhododactyla . This is emphasized by the extreme closeness (identical means in two instances) of the various morphological ratios of adults (table 6), and by the similarity of ontogenetic trends revealed by the regressions (table 7). In addition to the clearcut character of the presence or absence of vocal sac and slits, there may be a specific difference in the size of the tympanum of adults. Regression lines for tympanum diameter relative to snout–vent length diverge notably, with similis having the larger tympanum. There is broad overlap in tympanum size, however, and the sample is not adequate for determining a possible influence of sexual dimorphism.

Juvenile L. similis may be confused with the much smaller, sympatric Austrochaperina brevipes , as is discussed in the account of that species.

DISTRIBUTION: Known only from the type locality (fig. 34). See Holotype and Paratypes for details.

REMARKS: Evidence provided by the calls strongly indicates that L. rhododactyla and L. similis are different species, their close morphological similarity notwithstanding. Differences between the calls may be explained by (1) functionally different calls (e.g., territorial and mate-attracting) that were recorded for the same species, or (2) the samples represent sibling species. With respect to the first possibility, I heard the sort of call recorded at Myola on several nights and did not hear the other call there. Allen Allison has had much field experience with L. rhododactyla , and reported to me (personal commun.), ‘‘I have never heard anything else from this species and have heard this species calling practically every time that I visited Bulldog Road.’’ He listened to a playback of the similis call and assured me that he had not heard that call before. This information, coupled with the single morphological difference (vocal slits and sac present in rhododactyla , absent in similis ) leads me to conclude that two species should be recognized.

The type locality of Liophryne rhododactyla, Mt. Victoria, is much closer to Myola Guest House (38 km) than to the region southeast of Wau (about 190 km) where recordings of rhododactyla were made. Presumably at least three disjunct populations are involved (fig. 34)—two of rhododactyla and one of similis . On the basis of proximity, one might expect the frogs at Mt. Victoria and Myola to represent the same species, with the disjunct northern population near Wau requiring a new name. Countering this interpretation is the morphological evidence of the vocal sac apparatus, intimately associated with the difference in calls. Verification of the call of rhododactyla at the type locality is much desired.

A striking, parallel geographic situation exists in the microhylid genus Aphantophryne (Zweifel and Parker, 1989) . This genus has the same basic distribution as L. rhododactyla and L. similis —high elevations near Wau and in the Owen Stanley Mountains. Aphantophryne pansa occurs with L. rhododactyla near Wau and both inhabit high elevations in the central Owen Stanley Range. At Myola Guest House , Aphantophryne sabini , a sibling of A. pansa distinguished mainly by its call, occurs with L. similis .

Figures

Fig. 31. Examples of Austrochaperina, Liophryne, and Sphenophryne. A. S. cornuta, AMNH A130544, adult. B. A. brevipes, AMNH A130534, SVL 21.9 mm. C. A. guttata, QM J67256, SVL 43.2 mm. D. A. macrorhyncha, MZB 3564, SVL 36.8 mm. E. A. rivularis, holotype, AMNH A130551, SVL 49.0 mm. F. A. palmipes, AMNH A130550, adult. G. L. similis, AMNH A130564, SVL 40.0 mm. H. A. derongo, MZB 3563, SVL 36.7 mm. Photos C, D, and H by S. Richards.