Leptodactylus rugosus Noble, 1923

Myers, C. W. & Donnelly, M. A., 2008, The Summit Herpetofauna Of Auyantepui, Venezuela: Report From The Robert G. Goelet American Museum-Terramar Expedition, Bulletin of the American Museum of Natural History 2008 (308), pp. 1-147 : 82-88

Leptodactylus rugosus Noble Figures 49–52

Leptodactylus rugosus Noble, 1923: 297–299 . Holotype AMNH A-1169, an ‘‘adult male’’ [actually an immature male fide Donnelly and Myers, 1991: 23], from near Kaieteur Falls , British Guiana [ Guyana], collected August 13, 1911 by F. E. Lutz. Heyer, 1995 (latest revision, including mention of a tadpole from Auyantepui). Heyer and Thompson, 2000 (synopsis).

Leptodactylus rugosus, Part : Heatwole et al., 1965: 360 (includes a specimen of L. lithonaetes ); Heyer, 1979: 32 (includes the later recognized sibling species L. lithonaetes and L. myersi ); Gorzula and Señaris, 1999: 65 (includes L. lithonaetes from Cerro Guanay).

MATERIAL: Camp 1, 1700 m: AMNH A- 164957–164963, EBRG 2653–2659. Camp 3, 1850 m: AMNH A-164964–164985, EBRG 2660–2680. 4 km NE Camp 3, 1430 m: EBRG 2681. Camp 4, 1600 m: AMNH A-164986– 164989, A-164854–164857 (4 larvae), EBRG 2652 (larva), 2682–2685. All from the 1994 AMNH –TERRAMAR Expedition to Auyantepui. Color and pattern are somewhat variable (figs. 49–50), as is size. Combining all adult males and all adult females gives the following measurements:

Adult8(21), x¯ 5 54.75, SD 3.752, 48.5–63.2 mm SVL Adult ♀ (10), x¯ 5 58.16, SD 2.952, 54.6–63.7 mm SVL Size overlap between the sexes is considerable, but females are significantly larger than males (t 5 22.7482, P 5 0.0117). Sexual maturity in males on Auyantepui seems to be attained between about 48 and 54 mm SVL21 ;

21 Donnelly and Myers (1991: 23) found that maturity in males ‘‘seems to be approached starting at about 41 mm’’ on Cerro Guaiquinima, about 80 km west of Auyantepui. They also reported a smaller maximum of 55 mm SVL for the Guaiquinima sample of 11 adult males ; the one adult female was 56 mm SVL .

four subadults in the range 49–54 mm SVL had unopened vocal slits, unpigmented or pale gray vocal sacs, and small and/or noncornified thumb spines ; two males, coded as adult at 52 mm SVL, each had only one open vocal slit ; the vocal sacs were dark and the thumb spine weakly cornified in one of these specimens, but the other had pale vocal sacs and a noncornified thumb spine.

Most adult males have a single, externally evident thumb spine (fig. 51) in various stages of cornification, but a specimen each from camps 1 and 3 have two thumb spines. Less than half the adult males have 1–2 small spines on each side of the chest. Some have several minute spinules clustered around the spines, and one specimen ( AMNH A-164979) from Camp 3 has a band of small spinules or tubercles extending across the chest (fig. 51). Adult male rugosus are characterized by paired chest spines but not by such a ‘‘distinctive band of black tubercles across the chest in larger males’’, which is a property of Leptodactylus lithonaetes ( Heyer, 1995: 699, 701, 708). A patch of black skin tubercles on the anterior throat is diagnostic of L. lithonaetes (Heyer, 1955: 708) but absent in L. rugosus , including all specimens from Auyantepui.

COLOR IN LIFE: See figures 49–50 and table 6, which summarizes color and pattern by locality.

TADPOLES

Three tadpoles were netted in isolated pools on sandstone near the river at Camp 4; larvae of Hypsiboas siblezsi were found in the same pools. The Leptodactylus larvae are in stages 39/40 and 40. These are long, slender tadpoles about 41–50 mm total length, tail 71 % –74 % of total, with protuberant eyes, dorsoventrally compressed bodies, median vent tube, and very low, inconspicuous tail fins; the posterior sides of the body are wrinkled or ridged in a longitudinal pattern (fig. 52).

The vent tube has a large opening and is strictly medial in all three larvae; the proximal end is attached dorsally to the anterior end of the low tail fin.22 One larva in stage 39/ 40 ( EBRG 2652 ) has a rather large, pointed flap extending ventrad from between the legs and the proximal end of the vent tube. It is a double-walled flap of the same translucent tissue that comprises the vent tube. Although it conceivably corresponds with the ‘‘vent flaps’’ found in several genera with suctorial larvae (Altig and McDiarmid, 1999: 34), the flap is present only in one of the three larvae .

22 Heatwole et al. (1965: 361) also reported the larva of Leptodactylus rugosus as having a median vent tube, whereas Duellman (1997: 25) described one as having the vent tube ‘‘attached dextrally for its entire length to ventral fin, with diagonal opening’’. Heyer (1995: 711) described a tadpole of the very similar L. lithonaetes as having a median vent.

TABLE 6 Leptodactylus rugosus Noble. Color and Pattern Variation (in Life) in Three Populations on the Summit of Auyantepui

Descriptions or partial descriptions of tadpoles of this species were given by Heatwole et al. (1965: 361), Heyer (1995: 701), and Duellman (1997: 25–26, fig. 21). Heyer noted the ‘‘series of glandular ridges on the body above the abdominal cavity’’, which appear to be characteristic for L. rugosus and also for the very similar L. lithonaetes . The tadpole of L. rugosus corresponds closely with that of L. lithonaetes (compare fig. 52 with the virtually identical illustration in Heyer, 1995: 711, fig. 5); however, another published illustration for larval L. rugosus does not show the posterior ridging on the body and the mouthparts are configured somewhat differently (see Heyer and Thompson, 2000: fig. 2).

Gorzula and Señaris (1999: 66, color photos 53–56) observed that rugosus tadpoles can wriggle out of the water completely ‘‘to graze on damp rock surfaces several centimeters away from any water in which they could have taken refuge’’.

NATURAL HISTORY

Leptodactylus rugosus is not confined to areas of granitic bedrock as formerly believed ( Heyer, 1979: 34); it is now known to also occur abundantly on some sandstone outcrops and tepuis. The species was collected in an elevational range of 1430–1850 m, near three of our five camps on Auyantepui. It was common in the vicinity of Camp 1 (14 specimens collected), where it was found by night along the river below camp, sitting in and out of shallow flowing water ; it also was found at night sitting on bare sandstone flats in and around camp, well above the river (fig. 3). The species was even more abundant at Camp 3 (44 specimens taken), where some were found at night on bare sandstone in and along the river (fig. 5 bottom). However, the majority of Camp- 3 specimens were found by day, hiding under rocks in open areas of sandstone, sometimes under the same rocks with hylid frogs ( Tepuihyla edelcae ) or lizards ( Tropidurus bogerti ). Only eight specimens were taken at Camp 4, but these were found in the open by night and day in a diversity of habitats—on sandstone near the river and on the ground in both forest and marshy places .

The call was not heard and there was no other evidence of current breeding activity; females coded as sexually mature in our February sample had enlarging ova of about 1.5–2 mm in diameter. Heyer (1979: 34–35), Duellman (1997: 26), and Heyer and Thompson (2000) described and illustrated calls from Venezuelan localities.

REMARKS

Sibling species in the Leptodactylus rugosus group have been difficult to demonstrate, but, as shown by Heyer (1995), L. rugosus as now recognized occurs in eastern Venezuela and Guayana, replaced to the south and east by L. myersi and to the west by L. lithonaetes .23 Subtle differences perceived in

23 The questioned westernmost locality in Heyer and Thompson’s (2000) range map of Leptodactylus rugosus was based on juvenile specimens from Cerro Guanay in the northwestern tepuis. Adult males from Cerro Guanay are assignable to Leptodactylus lithonaetes (unpublished data).

the field had us wondering whether frogs collected at Camp 1 on Auyantepui really represented the same species as the frogs at camps 3 and 4. After comparing the specimens, we tentatively assign all to L. rugosus , which, however, shows more interpopulational variation on Auyantepui than might be expected.

As suggested by table 6, there are subtle differences between Camp-1 frogs and those from camps 3 and 4, at least in dorsal pattern, ventral pattern, and iris coloration. At Camp 1, longitudinal and transverse whitish lines (partly separating irregular dark blotches) tended to be conspicuous (fig. 49 top). Both juveniles and adults from Camp 1 tend to have paler ventral surfaces than those at camps 3 and 4. Specimens from Camp 1 have the throat and chest less heavily mottled with brown or gray, and the bellies are paler on average (fig. 50). Iris coloration at Camp 1 differed from that at camps 3 and 4—the last two agreeing with Donnelly and Myers’ (1991: 22) description for L. rugosus on Cerro Guaiquinima, about 80 km to the west (table 6).

Of 66 specimens collected, 30 (218, 10♀) were sexually mature. Males from Camp 3 average smaller than those from the other camps:

Camp 3 (N 5 15), x¯ 5 53.75, SD 3.246, 48.5– 60.3 mm SVL

Camp 1 (N 5 4), x¯ 5 57.05, SD 2.517, 55.4– 60.8 mm SVL

Camp 4 (N 5 2), x¯ 5 57.60, SD 7.920, 52.0– 63.2 mm SVL

Assuming that the more than 3 to 1 difference between the largest and smallest standard deviations is due merely to sampling inadequacy at Camp 4 (where N 5 2), analysis of variance shows no statistically significant difference among mean snout-vent lengths at the 95 % confidence level (F 5 2.05, P 5 0.1573). None of the four adult males from Camp 1 has chest spines, compared with their presence in 6 of 10 adult males (excluding 5 skinned carcasses) from Camp 3; we do not know whether these small spines are permanently present or correlated with breeding condition (collections at Camp 3 started nine days after the last rugosus was taken at Camp 1).

Considering that Leptodactylus rugosus occurred both along open flowing rivers and also on bare rock well away from streams, we were puzzled in the field as to why we failed to find this conspicuous frog in apparently suitable habitats around Camp 2 (1750 m elev.; figs. 5 top, 7). Neither was it found at the higher elevation of Camp 5 (2100 m, fig. 10). Our only conclusion is that L. rugosus has a spotty distribution on the summit of Auyantepui. Perhaps isolation or colonization from different source areas has led to the interpopulational variation mentioned above. The possibility that two sibling species of ‘‘ rugosus ’’ exist on Auyantepui seems unlikely but cannot be dismissed out of hand. These frogs, conspicuous and often abundant where they occur, would be suitable subjects for finer-grain comparisons of possible genetic differences on Auyantepui.

LIZARDS

FAMILY GYMNOPHTHALMIDAE

The three species of teiioid lizards occurring on the summit of Auyantepui are all ‘‘microteiids’’, family Gymnophthalmidae . We previously argued against recognition of family status for microteiids as premature and misleading, since there was no convincing evidence for monophyly. Macroteiids and microteiids seemed monophyletic ( Harris, 1985), but acceptance of Gymnophthalmidae was based on undocumented characters, incomplete data, and, especially, on authoritarianism (Myers and Donnelly, 2001: 48– 49). That is no longer true.

In a major re-classification of microteiids based on mitochondrial and nuclear DNA from 50 species in 26 genera, Pellegrino et al. (2001) provided reasonably strong support for microteiid monophyly. Castoe et al. (2004) added taxa and re-evaluated the classification, making changes and corrections, but they did not disturb the support for monophyly.