Allobates sieggreenae, Gagliardi-Urrutia & Castroviejo-Fisher & Rojas-Runjaic & Jaramillo & Solís & Simões, 2021

Gagliardi-Urrutia, Giussepe, Castroviejo-Fisher, Santiago, Rojas-Runjaic, Fernando J. M., Jaramillo, Andrés F., Solís, Samantha & Simões, Pedro Ivo, 2021, A new species of nurse-frog (Aromobatidae, Allobates) from the Amazonian forest of Loreto, Peru, Zootaxa 5026 (3), pp. 375-404 : 379-393

Allobates sieggreenae sp. nov.

Figs. 2–6

Colostethus trilineatus Grant & Rodríguez 2001: 5–8 (partim), Jenaro-Herrera specimens.

Allobates conspicuus Guerrero et al. 2011: 1 .

Allobates sp. 1 and sp. 2 Gagliardi-Urrutia et al. 2015: 119–120, 299–301, 436.

Allobates sp. 1 and sp. 2 Gagliardi-Urrutia et al. 2016: 1.

Holotype. CRBIIAP 1754 (field code GGU 6144 ). An adult male collected by Giussepe Gagliardi-Urrutia and Pedro Ivo Simões on March 24, 2018, in an area of low-canopy white-sand forest (chamizal) within the boundaries of Centro de Investigaciones Jenaro-Herrera , municipality of Jenaro-Herrera , province of Requena, Loreto, Peru (4.902309° S, 73.625303° W). Advertisement calls of the holotype were recorded at 17:51 h and 26.1 °C.

Paratypes (n = 34). Eight adult males: CRBIIAP 1829, 1867, 1877, 1896, MCP 14524, 14525 , 14526 , 14527 (field codes GGU 5066 , 5125 , 5142 , 5181 , 5124 , 5126 , 5144 , 5172 , respectively) and five adult females: CRBIIAP 1824, 1842, 1858, MCP 14559, 14528 (field codes GGU 5057 , 5088 , 5109 , 5061 , 5185 , respectively) collected by Giussepe Gagliardi-Urrutia, Ehiko Rios-Alva , and Samantha Solís-Ruiz , between March 26 and April 05, 2017, in Río Blanco , Frontera village , municipality of Soplín, province of Requena, Loreto, Peru (5.88903° S, 73.76537° W) . Four adult males: CRBIIAP 1537, 1708, MCP 14529, 14531 (field codes GGU 5254 , 5572 , 5328 , 5538 , respectively) and five adult females: CRBIIAP 1622, 1635, 1668, MCP 14530, 14532 (field codes GGU 5408 , 5428 , 5492 , 5477 , 5582 , respectively) collected by Giussepe Gagliardi-Urrutia, José Manuel Padial, Ehiko Rios-Alva, and Samantha Solís-Ruiz, on April 18–27, 2017, same locality as the holotype. Six adult males: CRBIIAP 1740, 1774, 1779, MCP 14533, 14535 , 14536 (field codes GGU 6122 , 6181 , 6190 , 6143 , 6180 , 6182 , respectively) and four adult females: CRBIIAP 1750, 1757, MCP 14534, 14538 (field codes GGU 6137 , 6150 , 6145 , 6272 , respectively) collected by Giussepe Gagliardi-Urrutia, Pedro Ivo Simões , and Ramón Aguilar-Manihuari , between March 22 and April 10, 2018, same locality as the holotype. Two adult females: CRBIIAP 1903 and MCP 14539 (field codes GGU 6302 and 6296, respectively) collected by Giussepe Gagliardi-Urrutia and Layné Guerra-Vargas , on April 23–25, 2018, in Río Blanco , Frontera village , municipality of Soplín, province of Requena, Loreto, Peru .

Etymology. The specific epithet “ sieggreenae ” honors the late Marcy Sieggreen, biologist and curator of amphibians at Detroit Zoological Society from 2008 until her untimely passing in 2016. Marcy developed very important initiatives on biological conservation and environmental education in the region of Loreto, Peru. We take great pleasure in honoring her passion, love, dedication, and legacy to Amazonia and its people.

Generic placement. In addition to molecular evidence (see Phylogenetic reconstruction and relationships, below), we assigned the new species to Allobates based on overall morphological similarity with other species of the genus and by the presence of the following diagnostic characters ( Grant et al. 2006): (1) Finger IV reaching distal half of distal subarticular tubercle of Finger III, (2) webbing absent on postaxial side of Toe I, (3) webbing absent on preaxial side of Toe II, (4) webbing absent on postaxial side of Toe II, (5) webbing absent on preaxial side of Toe III, (6) pale paracloacal mark present, (7) pale oblique lateral line absent or diffuse, (8) abdomen of males pale, free of or with few scattered melanophores.

Characterization. Allobates sieggreenae is characterized by the unique combination of the following character states: (1) skin texture of dorsum granular, flat granules scattered from snout to the urostyle region, more prominent on posterior dorsum; (2) paired dorsal scutes on digits; (3) distal subarticular tubercle absent on Finger IV; (4) discs on fingers I–IV moderately expanded; (5) dermal lateral fringes and basal webbing absent on fingers; (6) metacarpal ridge absent; (7) fingers II and III swollen preaxially in adult males; not swollen in adult females; (8) carpal pad absent; (9) male excrescences on thumbs absent; (10) thenar tubercle conspicuous; (11) black gland absent on arm; (12) tarsal keel present, tubercle-like, strongly curved; (13) disc of Toe I weakly expanded; discs of toes II, III, IV and V moderately expanded; (14) basal webbing present between toes III and IV, absent between other toes; (15) metartarsal fold absent; (16) external coloration cryptic; background color of dorsum brown, with small dark brown dots in tips of skin granules; background color of dorsal surface of arms dark yellow in life, cream in preserved specimens; pale dorsolateral stripe present, wide and well defined; dark brown lateral band surrounds the whole body, reaching leg-body insertion; pale oblique lateral stripe short and diffuse; pale ventrolateral stripe present, irregular, with a diffuse lower margin from behind the eyes to groin, iridescent white to cream in life; pale ventrolateral stripe inconspicuous in preserved specimens; (17) dorsal surface of thigh light brown in live and preserved specimens; transverse dark bars on dorsal surface of thigh usually absent; (18) pale paracloacal mark present; (19) throat lightly pigmented in male specimens, with light grayish-brown melanophores scattered on chin, chest, and belly on a light cream background; throat without melanophores in female specimens, yellow to translucent in life, uniformly light cream in preserved specimens; ventral surfaces light gray on throat, light cream to translucent on abdomen, and yellow to translucent on thighs in live male specimens; ventral surfaces yellow to translucent in female specimens, lighter yellow on abdomen; throat and vocal sac white to translucent in live male specimens, peppered with light brown or light gray melanophores; (20) iris with metallic dark gold flecks and a dark golden pupil ring; (21) large intestine unpigmented; (22) testis unpigmented; (23) mature oocytes with brown pigments; (24) median lingual process absent; (25) tympanum inconspicuous to the naked eye, visible under magnification; (26) vocal sac single; (27) maxillary teeth present, generally inconspicuous; (28) habit diurnal, males vocalizing in daytime; (29) advertisement calls characterized by the emission of tonal notes in trills, irregularly spaced, and by the sporadic emission of single tonal notes, with a peak frequency of 4.97–5.74 kHz; (30) snout-vent length (SVL) of adult males 15.7 mm on average (range 15.2–16.4 mm), adult females 16.2 mm on average (range 15.4–17.2 mm).

Description of the holotype. Adult male, SVL = 15.9 mm, in good state of preservation and with a piece of muscle ventrally cut from its right leg and preserved as tissue sample ( Figs. 2–5 ). Measurements of the holotype are provided in Table 1.

Body robust, head wider than long (HL/HW = 0.9), head length 30% of SVL. Distance from anterior corner of the eye to nostril shorter than eye diameter (EN/ED = 0.7). Nares located posterolaterally to tip of snout, directed ventrolaterally, visible in lateral, ventral, and anterior views ( Figs. 2–3 ). Distance between nostrils 44% of HW. Canthus rostralis convex from tip of snout to nostril, straight from nostril to anterior corner of the eye. Loreal region vertical. Tympanum round, small, 36% of the maximum diameter of the eye. Tympanum indistinct to the naked eye, barely visible under 10x magnification ( Fig. 3 ). Maxillary teeth inconspicuous under magnification. Tongue longer than wide, with anterior third attached to the mouth floor. Median lingual process absent. Lateral vocal slits conspicuous. Choanae round, small, positioned anteriorly to eye bulge. Vocal sac single, extending from middle level of throat to chest.

Palmar tubercle round to elliptical ( Fig. 3 ). Thenar tubercle present, elliptical, evident in ventral view, less conspicuous in profile. Maximum diameter of thenar tubercle 83% of maximum diameter of palmar tubercle. Subarticular tubercle of Finger IV round, small, not exceeding the width of phalanx. Distal subarticular tubercle absent on Finger IV. Finger III with a round, protuberant proximal subarticular tubercle and a small, round distal subarticular tubercle. Subarticular tubercles on fingers I and II very protuberant, elliptical. Subarticular tubercles on all fingers smaller than thenar tubercle in maximum diameter. Supernumerary tubercles absent. Metacarpal ridge absent. Fringes and webbings absent on fingers. Length of Finger II 81% of Finger I length. Tip of Finger IV reaching the distal end of distal subarticular tubercle of Finger III when fingers are juxtaposed. Relative lengths of fingers: IV <II <I <III ( Fig. 3 ). Fingers II and III preaxially swollen. Finger III swelling expanding from the base of finger disc to proximal subarticular tubercle, about half of its length. Discs of fingers I–IV moderately expanded, width of discs corresponding to 1.4, 1.2, 1.4 and 1.5 times the width of their adjacent phalanges.

Tibia length approximately half the SVL (TL/SVL = 0.47). Tarsal keel present, tubercle-like, strongly curved at its proximal end, flattening and straightening in direction of metatarsal tubercle, without reaching it ( Fig. 3 ). Fringes absent on preaxial edge of tarsus. Metatarsal fold absent. Basal webbing present between toes III and IV, absent between other toes. Relative lengths of toes: I <II <V <III <IV ( Fig. 3 ). Disc of Toe I weakly expanded, width 1.2 times the width of adjacent phalanx. Discs of toes II, III, IV and V moderately expanded, width of discs 1.9, 1.8, 1.9 and 1.7 times the width of adjacent phalanges, respectively.

Skin on dorsum moderately granular, with low granules scattered from snout to the urostyle region. Skin granules relatively larger from mid-body to the urostyle region. Skin smooth ventrally. Dermal flap above cloaca absent.

Color in alcohol of holotype. Background color of dorsal surface of body tan brown, lighter on tip of snout, on canthus rostralis, and at the tip of the urostyle region. Darker above the eyes ( Fig. 2 ). Dark brown dots scattered on dorsum, at the tip of skin granules. A pale, cream dorsolateral stripe is present from posterior region of the eyelid, extending posteriorly to the urostyle region. Pale dorsolateral stripe broad, 0.6 mm in width at mid-dorsum level. A few dark brown dots appear irregularly on pale dorsolateral stripe, at the tip of larger granules. Inner and outer edges of pale dorsolateral stripe well marked, not diffuse. Lateral surface of body with a solid dark brown band, extending from tip of snout to groin, surrounding the body ( Fig. 3 ). A short, faded pale narrow oblique lateral stripe is preset within the solid dark brown lateral band, at the level of the groin. Pale ventrolateral stripe inconspicuous. Upper lip pale cream laterally, with dark brown pigments present ventrally towards the occlusion surface. Background color of ventrolateral region of body white, peppered with irregular light brown blotches. Ventral surfaces light cream, with brown melanophores scattered from chin to belly, more densely distributed marginally on chin and throat regions and medially on chest ( Fig. 2 ). Abdomen solid light cream with few and scattered melanophores. Tongue light cream.

Background color of arms cream in dorsal view, with scattered light brown blotches and marbling on upper, forearm, wrist and hand. Tips of fingers II, III and IV dark brown. Tip of Finger I less pigmented, predominantly light cream. Paired scutes on discs of fingers I, II and III white, black on Finger IV ( Fig. 3 ). Upper arm light cream to translucent in ventral view, same color as abdomen. Outer surface of forearm, carpal and metarcarpal regions solid brown, densely pigmented in ventral view ( Fig. 2 ).

Area immediately around vent light brown. Pale paracloacal mark present, comma-shaped, broader at its proximal end. Dorsal surface of thigh pale brown, dark brown only marginally on outer and inner lateral surfaces, and proximally at the thigh-body insertion. Small dark brown dots present on dorsal surface of thigh, at the tip of larger skin granules. Dorsal surface of shank and tarsal region darker than thigh, with dark brown dots and small blotches densely distributed on cream background ( Fig. 2 ). Toes dark brown. Paired scutes on toes present, white on toes I, II, III and IV, black on Toe V. Ventral surfaces of thigh and shank cream to translucent, with brown irregular blotches distributed marginally along inner and outer edges. Ventral surfaces of tarsal and metatarsal regions uniformly dark brown. Toes dark brown, densely pigmented in ventral view ( Fig. 3 ).

Morphological variation in the type series. Variation in morphometric measurements of male and female types are presented in Table 1. Body size generally larger among female specimens, but all morphometric measurements overlap in range between male and female paratypes. Fingers II and III not swollen in females. Finger II not swollen in eight of the 18 male paratypes. Finger III only weakly swollen in five of 18 male paratypes (CRBIIAP 1537, 1829, MCP 14527, 14524 , 14529 ). Holotype and all paratopotypes with inconspicuous maxillary teeth. Maxillary teeth concealed by inner surface of upper lip, but visible under 30x magnification in paratypes from Río Blanco. Background brown color of dorsum variable in lightness among paratypes ( Fig. 4 ). Throat and upper lip of preserved females solid light cream, varying from absence (in 63% of females) to presence of a few scattered light gray or brown melanophores (in 37% of females) on chin and throat ( Fig. 5 ). Distribution of pigmentation on throat of males variable, denser on marginal surfaces of chin and gular region in some specimens or evenly distributed from tip of chin to chest, melanophores on belly few and scattered ( Fig. 5 ). Pale dorsolateral stripe variable in width, ranging between 0.5–0.9 mm (average 0.6 mm) ( Fig. 4 ). A solid transverse brown stripe is present medially on dorsal surface of shank of three paratypes (strongly marked in CRBIIAP 1858, a female; faintly marked in CRBIIAP 1774 and MCP 14536, two males). Pale paracloacal mark with a diffuse distal edge merging with light brown dorsal color of thigh in 13 paratypes, absent in the other specimens. Scutes of fingers I and II are always white or partially pigmented (e.g., MCP 14530 and 14525, respectively). Scutes white, partially pigmented or black on Finger III (e.g., MCP 14538, 14531 , and 14535, respectively). Scutes on tip of Finger IV partially pigmented or black ( MCP 14534 and 14529).

Color in life. Dorsum centrally dark brown, light brown only anteriorly around snout, and posteriorly, on the tip of the urostyle region. Iris dark gold with dark brown reticulation. Pale dorsolateral stripe evident, broad, pale brown to cream. Lateral surface of body surrounded by a dark brown band from tip of snout to groin. Lateral dark brown stripe darker than dorsum.A very short, faint oblique lateral stripe may be present posterolaterally on the dark brown band on the inguinal region, formed by a series of small cream-colored dots, more or less diffuse among specimens. Irregular, wave-edged iridescent ventrolateral stripe present along the lower border of loreal dark brown stripe from the level of the eye to groin. Lower border of ventrolateral stripe is diffuse from behind arm-body insertion to groin, merging with the light cream ventral color laterally, towards the abdomen ( Fig. 6A, C ). Upper lip same color as pale ventrolateral stripe, iridescent, darker only ventrally, on the occlusion surface. Throat translucent yellow in female specimens. Throat and vocal sac white or cream to translucent in live male specimens, with light gray or light brown melanophores scattered on chin, throat and chest. Remaining ventral surfaces of body uniformly yellow in females, paler medially on the abdomen, where underlain by peritoneum. Abdomen light cream to translucent in males, yellowish towards groin and on the underside of thigh ( Fig. 6B, D, E ).

Dorsal surface of upper and forearm with irregular brown spots scattered on dark yellow to dark orange background. Brown irregular spots present dorsally and laterally on upper and forearm. Upper arm translucent yellow in ventral view. Inner lateral surface of forearm translucent yellow. Outer lateral surface of forearm dark brown. Carpal and metacarpal regions dark brown in ventral view. Fingers brown in ventral and dorsal views, darker in ventral view. Paired dorsal scutes on finger discs iridescent white, sometimes black or dark gray ( Fig. 6 ).

Surfaces immediately adjacent to vent light brown. Paracloacal mark short, comma-shaped, iridescent cream. Dorsal surface of thigh uniformly brown, with sparse, irregular dark brown blotches appearing at the tips of larger skin granules. Dorsal surface of shank generally darker than thigh, with dark brown spots and blotches densely scattered. Ventral surface of thigh translucent yellow, with dark brown spots and blotches present marginally towards lateral inner and outer surfaces. Dorsal surface of shank and tarsal region brown, with large dark brown blotches irregularly distributed. Ventral surfaces of shank and tarsal region with large dark brown blotches on translucent yellow background. Tarsal and plantar regions dark brown in ventral view. Toes with gray and dark brown patterning. Paired dorsal scutes on toe discs iridescent white, sometimes black or dark gray.

Color pattern of juveniles generally similar to that of adults, but with a solid dark brown dorsal color, rendering a more emphasized pale dorsolateral stripe ( Fig. 6F ). Ventral surfaces of juveniles uniformly light gray to translucent, with no yellow shades or pigmentation ( Fig. 6G ).

Call description. Advertisement calls of Allobates sieggreenae are characterized by the emission of tonal notes arranged in irregular trills ( Fig. 7A ). Descriptive statistics of temporal and spectral call parameters of the holotype and of pooled calls of males from Jenaro-Herrera and Río Blanco are presented in Table 2.

Silent intervals between consecutive notes and between consecutive note trills are extremely variable, as well as the number of notes emitted in each trill. Single notes are sporadically emitted between consecutive note trills. Thus, the advertisement call of Allobates sieggreenae can also sound as a continuous, yet irregular emission of notes to the human ear.

Trills are formed by 5 to 16 notes (mode = 10 notes) and consecutive trills are split by very unpredictable silent intervals, ranging between 1.20– 22.20 s (7.00 ± 5.60 s). Length of trills is variable, trill duration ranging from 2.03 to 8.02 s (4.27 ± 1.27 s). Rate of note emission within trills vary between 0.92–3.30 notes/s (2.46 ± 0.49 notes/s).

Notes are tonal, with ascending frequency modulation ( Fig. 7B ). Note duration ranges from 0.02 to 0.04 s (0.03 ± 0.005 s). Silent interval between consecutive notes ranges from 0.20– 0.80 s (0.36 ± 0.09 s). Peak frequency of notes varies from 4.97 to 5.74 kHz (5.35 ± 0.19 kHz). The lower and upper frequency of notes range between 4.66–5.19 kHz (4.94 ± 0.11 kHz) and 5.13–5.99 kHz (5.66 ± 0.20 kHz), respectively. When visible on spectrograms, the fundamental frequency is located between 2.63–3.33 kHz.

Phylogenetic reconstruction and relationships. Our 16S dataset consisted of 140 terminals and 605 aligned characters. The optimal nucleotide substitution model was GTR+I+G. Our optimal ML topology ( Fig. 8 ; lnL = -8,552.38) was relatively well resolved (i.e., few polytomies), but with most of the deeper nodes with bootstrap support (BS) <50% ( Fig. 8 ). Specimens of Allobates sieggreenae form a highly supported clade (BS = 100%), which is the sister group of the A. trilineatus sensu lato (s.l.) clade (BS = 81%) as defined by Jaramillo et al. (2021). Uncorrected-pairwise genetic distances based on the same 16S rRNA fragment among specimens from Jenaro- Herrera and Río Blanco and samples of A. trilineatus s.l. ranged between 4.9–5.9% ( Table 3). Pairwise genetic distances among A. sieggreenae and remaining Allobates samples included in our analyses were always larger than 5%.

Morphometric comparisons with Allobates trilineatus s.s. Principal component analysis resulted in a first principal component (PC1) accounting for 86.0% of the morphometric variation among specimens of Allobates sieggreenae and topotypical A. trilineatus (Appendix 4). Snout-vent-length was heavily represented in this component, reflecting the generally larger size of A. sieggreenae relative to A. trilineatus s.s. The second principal component explained 2.7% of the remaining morphometric variation among specimens and was mostly associated with variation in head length (Appendix 4). The distribution of specimens along the morpho-space PCA ( Fig. 9 ) indicates a clear distinction between A. sieggreenae and A. trilineatus s.s. along the head size-related axis (PC2).

Diagnosis. Allobates sieggreenae is found in northeastern Peruvian Amazonia, relatively close to the borders with Brazil, Colombia, and Ecuador. These countries harbor a great diversity of Allobates species. Hence, we focus our comparisons on Amazonian species. To facilitate readership, we organized the diagnosis into morphological and bioacoustic characters.

Morphological diagnosis. Character states of the new species are in parentheses throughout the diagnosis. The most closely related and similar species is Allobates trilineatus . Considering the uncertainty regarding the taxonomic identity of the clade identified as A. aff. trilineatus by Jaramillo et al. (2021), we frame our comparison between the new species and A. trilineatus s.s.: overall darker coloration, dark brown dorsum, blackish brown lateral dark stripe, generally paler from mid-body to groin ( Fig. 7 ) (dorsum brown, solid dark brown lateral dark stripe, not fading towards groin). Adult males with dark melanophores on throat, chest, and belly very abundant and dense, producing a dark solid background with few and small white or cream patches corresponding to areas free of melanophores (few and scattered melanophores on a white or cream background from chin to belly). Dark transverse bar generally present on dorsal surface of thighs (dark transverse bar usually absent on thighs). Longer head, HL = 5.8–6.2 mm, n = 4 females and 8 males, (HL = 4.3–5.5 mm, n = 14 females and 19 males).

Live specimens of Allobates femoralis (Boulenger, 1884) , A. zaparo ( Silverstone, 1976) , A. myersi ( Pyburn, 1981) , and A. hodli Simões, Lima & Farias, 2010 have bright yellow, orange, or red flash marks on dorsal surface of thighs, and black and white marbling on the surface of abdomen in live or preserved specimens (bright colored marks absent on dorsal surface of thighs, black and white marbling absent on abdomen). Minimum SVL reported for individuals of these species is 22.2 mm, a male A. hodli (largest male of A. sieggreenae 16.4 mm).

Allobates brunneus ( Cope, 1887) , A. carajas Simões, Rojas & Lima 2019 , A. crombiei ( Morales, 2002) , A. flaviventris Melo-Sampaio, Souza & Peloso, 2013 , A. gasconi ( Morales, 2002) , A. goianus ( Bokermann, 1975) , A. humilis ( Rivero, 1980) , A. juanii ( Morales, 1994) , A. magnussoni Lima, Simões & Kaefer, 2014, A. ornatus ( Morales, 2002) , A. pacaas Melo-Sampaio, Prates, Peloso, Recoder, Dal Vechio, Marques-Souza & Rodrigues, 2020 , and A. undulatus ( Myers & Donnelly, 2001) have a rhomboid, hourglass-shaped or wave-edged dark brown mark on dorsum (dorsum brown, with lateral edges flanked by a straight pale dorsolateral stripe). Pale dorsolateral stripe absent in live specimens of A. crombiei ( Lima et al. 2012) (pale dorsolateral stripe wide and conspicuous). Throat and chest gray with dark spots in male specimens of A. gasconi , throat marginally pigmented in female and densely pigmented in male A. pacaas , and throat darkly pigmented in male specimens of A. ornatus (throat and chest with faint gray or brown pigmentation, with no dark spots). Dorsal surface of thighs of A. carajas , A. gasconi and A. pacaas with one or more dark transverse bars, of A. juanii with two dark transverse bars flanking a single pale transverse bar (dark brown transverse bar on thighs absent dorsally). Distal subarticular tubercle present on Finger IV of A. pacaas (distal subarticular tubercle absent on Finger IV). Male A. undulatus with a swollen supracarpal pad on wrist, minimum SVL of males 19.6 mm (maximum male SVL 16.4 mm, supracarpal pad on wrist absent).

Dorsal color pattern of Allobates algorei Barrio-Amorós & Santos, 2009 characterized by the presence of a wide dark brown vertebral band flanked by paired dark brown paravertebral rows (dorsum uniformly brown, with dark brown spots, flanked by a pale cream dorsolateral stripe, not by dark paravertebral rows). Dorsum generally with intercrossed X-shaped dark brown marks, pale ventrolateral stripe conspicuous, solid iridescent white, straight from groin to upper lip in A. olfersioides ( Lutz, 1925) (X-shaped marks absent on dorsum, pale ventrolateral stripe indistinct in preserved specimens, irregular to diffuse in live specimens, with overlaying brown pigmentation at the level of upper lip).

Throat of male specimens of Allobates fuscellus ( Morales, 2002) , A. granti Kok, MacCulloch, Gaucher, Poelman, Bourne, Lathrop & Lenglet, 2006 , A. insperatus ( Morales, 2002) , A. marchesianus ( Melin, 1941) , A. masniger ( Morales, 2002) , A. nidicola ( Caldwell & Lima, 2003), A. nunciatus Moraes, Pavan & Lima 2019 , A. paleovarzensis Lima, Caldwell, Biavati & Montanarin, 2010 and A. pittieri ( La Marca, Manzanilla & Mijares-Urrutia, 2004) with dark pigmentation, formed by dark black or brown melanophores, rendering a uniformly black, dark gray, dark brown color pattern, or marbled or stippled color patterns (throat predominantly light cream, peppered with brown or gray melanophores, but not forming dark surfaces or patterning). Ventral surfaces of body and limbs dark gray in preserved males of A. fuscellus ( Morales, 2002) (ventral surfaces of body light cream to peppered with light gray or brown melanophores in preserved males, ventral surfaces of upper arm and thigh light cream to translucent). Pale dorsolateral stripe in A. granti , A. masniger , and A. nidicola absent (pale dorsolateral stripe present and conspicuous). Dorsal surface of thigh with a dark transverse bar in A. insperatus and A. marchesianus (dark transverse bar absent on thigh). Minimum SVL reported for individuals of A. masniger (17.9 mm), A. nidicola (18.5 mm), A. nunciatus (20.8 mm) and A. paleovarzensis (19.7 mm) (largest male of A. sieggreenae 16.4 mm). Pale ventrolateral stripe evident, iridescent and unbroken from tip of snout to groin in preserved specimens of A. tinae Melo-Sampaio, De Oliveira & Prates, 2018 (ventrolateral stripe inconspicuous in preserved specimens). Vocal sac bright yellow in live male specimens, ventral surfaces uniformly white in live female specimens of A. tinae (vocal sac translucent white to light cream in males, ventral surfaces yellow in females).

Allobates bacurau Simões, 2016 and A. grillisimilis Simões, Sturaro, Peloso & Lima, 2013 , have predominantly white to translucent ventral surfaces, with no shades of yellow in life (ventral surfaces predominantly yellow in live females, and posteriorly yellow in live males). Throat light gray to gray, with scattered melanophores in female A. bacurau (female throat immaculate). Ventral surfaces uniformly white to translucent in preserved male specimens of A. grillisimilis (throat and chest darker than mid and posterior abdomen in males).

Allobates amissibilis Kok, Hölting & Ernst, 2013 , A. caeruleodactylus ( Lima & Caldwell, 2001) and A. subfolionidificans ( Lima, Sanchez & Souza, 2007) lack a defined pale dorsolateral stripe (pale dorsolateral stripe present and conspicuous). Allobates amissibilis with a variable number of dark transverse bars on dorsal surface of thigh (transverse bars usually absent). Fingers sky-blue in live males of A. caeruleodactylus (fingers brown in males). Ventral surfaces of male A. subfolionidificans immaculate, with no pigmentation (throat and chest of males with scattered light brown or light gray melanophores).

Throat and chest of males immaculate, with no melanophores in Allobates conspicuus ( Morales, 2002) , A. sumtuosus ( Morales, 2002) and A. tapajos Lima, Simões & Kaefer, 2015 (throat and chest of males peppered with light brown or light gray melanophores). Dark transverse bar present on dorsal surface of thighs in A. conspicuus (transverse bars on thigh usually absent). Dorsal surfaces of thighs and shanks bluish gray in live A. sumtuosus (dorsal surfaces of thighs and shanks brown). Vocal sac bright yellow when inflated in live A. tapajos (vocal sac white or cream to translucent, with scattered light melanophores).

Dorsum olive-colored in life, lateral dark brown stripe on flank fading posteriorly from mid-body to groin in Allobates bromelicola ( Test, 1956) (dorsum brown in live specimens, lateral dark brown stripe solid and continuous).

Throat solid black in Allobates melanolaemus males ( Grant & Rodríguez, 2001), dark gray in A. vanzolinius ( Morales, 2002) , reticulated or black spotted in A. kingsburyi ( Boulenger, 1918) (throat with light pigmentation in males). Basal or rudimentary webbing present between all toes except IV–V in A. mcdiarmidi ( Reynolds & Foster, 1992) (basal webbing between toes III–IV). Pooled minimum SVL of adult A. kingsburyi , A. mcdiarmidi , A. melanolaemus , and A. vanzolinius is 19.6 mm for the latter species (adults SVL ≤ 16.4 mm).

Bioacoustic diagnosis. Character states of the new species are in parentheses. Advertisement calls of Allobates trilineatus s.s. ( Jaramillo et al. 2021; Fig. 7 ) are formed by trills of note-pairs (single notes) and trills are 0.96– 1.61 s long (2.03– 8.02 s). Furthermore, Grant & Rodríguez (2001: Fig. 7 ) provided a cursory description of the advertisement call of specimens that most likely are part of A. aff. trilineatus revealing that they share a call structure of paired notes with A. trilineatus s.s., reinforcing the results of the molecular data that A. sieggreenae is an independently evolving lineage from A. trilineatus s.l. Other species with advertisement calls formed by trills of pairs of notes are A. flaviventris , A. granti , A. hodli , A. kingsburyi and A. tapajos ( Grant & Rodríguez 2001; Kok et al. 2006; Kok & Ernst 2007; Castillo-Trenn & Coloma 2008; Simões et al. 2010; Melo-Sampaio et al. 2013; Lima et al. 2015).

Advertisement calls of Allobates femoralis , A. myersi and A. nunciatus ( Amézquita et al. 2006; Simões & Lima 2011; Moraes et al. 2019) are emitted as trills of three, four, six or eight notes (single note trills).

Advertisement calls of Allobates goianus , A. magnussoni , A. nidicola and A. masniger ( Caldwell & Lima 2003; Lima et al. 2014; Bastos et al. 2011; Kaefer et al. 2012) are characterized by the continuous emission of a single note, spaced by regular inter-note silent intervals, not arranged in note trills (notes arranged in trills, irregular internote silent intervals). Advertisement calls of A. algorei , A. caeruleodactylus and A. subfolionidificans ( Lima & Caldwell 2001; Lima et al. 2007; Barrio-Amorós & Santos 2009) are formed by a single note, emitted continuously between irregular silent intervals, but never arranged in note trills (notes arranged in trills).

Advertisement calls of Allobates amissibilis , A. bacurau , A. crombiei , A. grillisimilis , A. humilis , A. insperatus , A. juami , A. melanolaemus , A. paleovarzensis and A. tinae are emitted as trills of short, regularly spaced notes (irregularly spaced notes). In these species, consecutive trills are separated by distinctively long silent intervals, with no sporadic emission of single notes between them (silent intervals variable and interrupted by sporadic and isolated single notes). The advertisement calls A. bacurau , A. crombiei , A. insperatus , and A. juami ( Lima et al. 2012; Simões 2016; Simões et al. 2018) have a larger number of notes, pooled number 25–81, more closely spaced, pooled interval duration between notes 0.010 – 0.085 s (5–16 notes, 0.20– 0.80 s). In A. grillisimilis ( Simões et al. 2013b) , note peak frequency is 5.87–6.65 kHz (4.97–5.74 kHz) and silent interval between notes 0.01– 0.04 s (0.20– 0.80 s). Pooled note peak frequency of A. humilis and A. paleovarzensis is 3.90–4.93 kHz (4.97–5.74 kHz) ( La Marca et al. 2002; Lima et al. 2010). Pooled note duration of A. melanolaemus and A. tinae ( Grant & Rodríguez 2001; Melo-Sampaio et al. 2018) is 0.044 – 0.844 s (0.02 to 0.04 s).

The advertisement call of Allobates sumtuosus ( Simões et al. 2013a) alternates between continuous emission of notes and emission of note trills (continuous emission of notes absent). When emitting notes arranged in trills, silent interval between notes are 0.07– 0.12 s (0.20– 0.80 s).

Advertisement calls of Allobates sieggreenae cannot be distinguished from those of A. amissibilis , A. brunneus , A. marchesianus and A. olfersioides by means of the quantitative spectral or temporal parameters measured here (Caldwell et al. 2002; Lima et al. 2009; Kok et al. 2013; Forti et al. 2017). However, these species are easily distinguished from A. sieggreenae by their external morphology.

Natural history remarks. Allobates sieggreenae is locally common, occupying a variety of forest habitats, such as dense canopy rainforests in clay soils, white-sand low canopy forests subject to seasonal flooding (chamizales), white-sand forests (varillales) and disturbed environments at the forest edge. Specimens were active during the day, males calling more actively early in the morning or near sunset. All specimens were found while calling, or when moving on the leaf litter on the forest floor. Eggs, tadpoles and detailed information on the reproductive behavior of Allobates sieggreenae remain unknown.

Geographic distribution. The type series of Allobates sieggreenae comes from two localities in the interfluve between the Amazonian rivers Ucayali, Tapiche, and Yavarí ( Fig. 1 ) in Loreto, Peru. Although the Ucayali-Amazon rivers probably constitute a very hard geographic barrier to the east and north, the upper courses of the Blanco and Yavarí rivers are probably not. Thus, Allobates sieggreenae may be present in the Brazilian headwaters of the Yavarí, to the east, and on the Peruvian headwaters of the Tapiche River, to the south.

Figures

FIGURE 1. (A) Map of western Amazonia and neighboring areas (inset map indicates its location within South America) showing rivers (blue lines), country borders (black contours), and known localities of Allobates sieggreenae sp. nov. and A. trilineatus sensu lato. (B) Satellite image of the Ucayali-Tapiche-Yavarí interfluve and neighboring regions with main rivers, cities, and conservation areas labeled (the area of the latter shaded with light green). Centro de Investigaciones Jenaro-Herrera (CIJH) and Río Blanco (RB).

FIGURE 2. Dorsal and ventral views of preserved specimens of Allobates sieggreenae sp. nov. Left: holotype adult male (CRBIIAP 1754). Right: paratype adult female (MCP 14534).

FIGURE 3. (A) Lateral view of the holotype (CRBIIAP 1754) of Allobates sieggreenae sp. nov. (B, C) Ventral view of the left hand of the preserved holotype and paratype (MCP 14534, adult female), respectively. (D, E) Ventral view of the left foot of the same aforementioned preserved specimens. Scale bar = 5 mm (A) and 1 mm (B–E).

FIGURE 4. Variation in dorsal color pattern of preserved specimens of Allobates sieggreenae sp. nov. Top row: three male paratypes (CRBIIAP 1779, 1740, MCP 14526). Bottom row: three female paratypes (CRBIIAP 1757, 1750, 1842).

FIGURE 5. Variation in ventral color pattern of preserved specimens of Allobates sieggreenae sp. nov. Top row: three male paratypes (CRBIIAP 1779, 1740, MCP 14526). Bottom row: three female paratypes (CRBIIAP 1757, 1750, 1842).

FIGURE 6. Color in life of type specimens, information of specific vouchers not recorded, of Allobates sieggreenae sp. nov. (A) Dorsolateral and (B) ventral views of an adult male. (C) Dorsolateral and (D) ventral views of an adult female. (E) An adult male vocalizing with its vocal sac inflated. (F) Dorsolateral and (G) ventral views of a juvenile specimen.

FIGURE 7. Comparative oscillograms and power spectra (top and bottom graphs of each figure, respectively) of the advertisement call of the holotype of Allobates sieggreenae sp. nov. (A, B) and a topotypic A. trilineatus (C). (A) Call trill formed by irregularly spaced single notes. (B) Detailed view of three notes of the same call. (D, E) dorsolateral and ventral views of the recorded specimen (MCP 14309).

FIGURE 8. Phylogenetic hypothesis of Allobates and outgroup taxa inferred from a maximum likelihood analysis (ln = - 8,552.38) of 605 bp of the 16S rRNA mitochondrial gene. Numbers on branches are bootstrap frequencies (percentage)> 50% from 1,000 pseudoreplicates. The taxonomy of A. trilineatus follows Jaramillo et al. (2021) and is highlighted by different branch colors.

FIGURE 9. Morphometric comparisons among adult specimens of Allobates sieggreenae sp. nov. and A. trilineatus sensu stricto. (A) Scatter plot of the first two principal components explaining 88.6% of the variance. (B) Violin plots of the four most important morphometric variables explaining the variance of the first two principal components. SVL: snout vent length, ED: eye diameter, FL: foot length, HL: head length.