The skinks (Squamata: Scincidae) of Ecuador, with description of a new Amazonian species

Omar Torres-Carvajal; Camila Sandoval; Diego A. Paucar

doi:10.3897/vz.74.e130147

Abstract

The taxonomic status of the skinks from Ecuador has never been carefully addressed. In this paper we examine populations of Mabuya lizards across Amazonian Ecuador in an attempt to establish their taxonomic identity and phylogenetic affinities. We confirm the presence of both M. altamazonica and M. nigropunctata and describe a new species from Yasuní National Park, one of the most biodiverse places on Earth. The new species differs from its congeners in lepidosis and color patterns. For the first time, we include samples from Ecuador in a molecular phylogenetic analysis of Mabuya, which confirms the monophyly of the new species and the taxonomic identity of both M. altamazonica and M. nigropunctata from Ecuador. The new species is closely related to M. bistriata. Finally, we present an identification key for species of Ecuadorian Mabuya.

Resumen

El status taxonómico de los esquincos de Ecuador nunca ha sido abordado cuidadosamente. En este artículo examinamos las poblaciones de las lagartijas Mabuya a lo largo de la Amazonía ecuatoriana en un intento por establecer su identidad taxonómica y afinidades filogenéticas. Confirmamos la presencia de M. altamazonica y M. nigropunctata, y describimos una especie nueva del Parque Nacional Yasuní, una de los lugares más biodiversos de la Tierra. La especie nueva difiere de sus congéneros en lepidosis y patrones de coloración. Por primera vez incluimos muestras de Ecuador en un análisis filogenético molecular de Mabuya, el cual confirma la monofilia de la especie nueva, así como la identidad taxonómica de M. altamazonica y M. nigropunctata de Ecuador. La especie nueva está relacionada cercanamente con M. bistriata. Finalmente, presentamos una clave para la identificación de especies de Mabuya de Ecuador.

Keywords

Hemipenial morphology, lizards, Mabuya, systematics, western Amazonia, Yasuní National Park

Palabras clave

Amazonía occidental, lagartijas, Mabuya, morfología hemipeneal, Parque Nacional Yasuní, sistemática

Introduction

Neotropical lizards in the clade Mabuya Fitzinger, 1826, traditionally ranked as a genus, are widely distributed in Central America, South America, and several Caribbean islands (Dunn 1935; Mausfeld et al. 2002). Once considered a circumtropical taxon with >100 species (Greer and Nussbaum 2000), Mausfeld et al. (2002) restricted the name Mabuya to Neotropical taxa, recognizing that the species from Fernando de Noronha islands off the Brazilian Atlantic coast, currently recognized as Trachylepis atlantica Schmidt, 1945, belonged to an Afro-Malagasy radiation. There are currently 67 recognized species of Mabuya, of which ~60% have been described from Central America and the Caribbean islands since 2012 (Hedges and Conn 2012; McCranie et al. 2020).

The taxonomy of Mabuya has been controversial mostly due to remarkable morphological similarity among species and incomplete sampling in taxonomic and phylogenetic studies. In spite of the taxonomic stability of the taxonomic proposal by Mausfeld (2002), a decade later Hedges and Conn (2012) split Mabuya into 16 genera and proposed the family level name Mabuyidae to allocate them as part of a family-level rearrangement of Scincidae Oppel, 1811. However, both the generic and supra-generic proposals by Hedges and Conn (2012) were not broadly accepted because of (1) non-monophyly (as revealed in subsequent studies) of many of the proposed taxa (e.g., Alinea, Marisora, Dasiinae) and (2) unnecessary disruption of available taxonomy (Pyron et al. 2013; Lambert et al. 2015; Pinto-Sánchez et al. 2015; Karin et al. 2016; Sánchez-Martínez et al. 2020; Shea 2021). Of the 16 genera proposed by Hedges and Conn (2012), 25% are monotypic and 50% contain only 2–3 species each. Taxon sampling in systematic studies of Mabuya is still far from complete, which following Hedges and Conn’s taxonomy can lead to species being moved from one genus to another as more species are sampled. For example, two of the four species of Alinea, one of the genera erected by Hedges and Conn (2012), were recently placed within Marisora (McCranie et al. 2020). The splitting of Mabuya into so many genera is an example of unnecessary taxonomic inflation and we reject it because it creates confusion to both taxonomists and other end-users (e.g., funding agencies, conservationists, museum curators, educators, lay public) who benefit from stable taxonomic systems (Mahony et al. 2024).

Although large molecular phylogenetic studies of Mabuya have been published since Mausfeld et al. (2012), none of them (Miralles et al. 2009; Miralles and Carranza 2010; Hedges and Conn 2012; Pinto-Sánchez et al. 2015) has included samples from Ecuador, where two species—M. altamazonica Miralles, Barrio-Amorós, Rivas & Chaparro-Auza, 2006, M. nigropunctata Spix, 1825—have been reported (Torres-Carvajal et al. 2019). Moreover, specimens of Mabuya from Ecuador have been rarely included in morphological comparative studies, such as species descriptions. In an attempt to clarify the taxonomic status of populations of Mabuya from Ecuador, we examined their morphology and included for the first time Ecuadorian samples in a molecular phylogenetic analysis of Mabuya. As a result of this taxonomic revision, we identified an undescribed lineage, which we describe herein as a new species.

Materials and Methods

Specimen sampling and morphology

We examined 32 specimens of Mabuya from eastern Ecuador (Appendix 1) deposited at Museo de Zoología QCAZ, Pontificia Universidad Católica del Ecuador, Quito. Morphological terminology for lepidosis, measurements and color patterns follows Ávila-Pires (1995), Greer and Nussbaum (2000), Miralles et al. (2006), and Hedges and Conn (2012). Measurements including snout-vent length (SVL) and tail length (TL) were recorded to the nearest 0.01 mm with digital calipers. For those specimens without everted hemipenes, we determined sex by gonad inspection through dissection. We prepared and described the hemipenes of two preserved specimens of the new species described here (QCAZ 4839, 11832) following Sánchez-Martínez et al. (2020). We used QGIS v3.28 (QGIS Development Team 2024) to generate a distribution map based exclusively on locality data of examined specimens.

Phylogenetic analyses

We obtained new DNA sequences from eight specimens of Mabuya—M. altamazonica (n = 4), M. nigropunctata (n = 1), M. sp. nov. (n = 3)—corresponding to two mitochondrial genes, ribosomal small subunit gene (12S) and cytochrome b (cyt b). Muscle or liver tissue samples were mixed with Proteinase K and lysis buffer and digested overnight. Total genomic DNA was extracted using a guanidinium isothiocyanate extraction protocol. DNA samples were quantified using a Nanodrop ND-1000 (NanoDrop Technologies, Inc.), re-suspended and diluted to 25 ng/ul in ddH₂O prior to amplification. Primers and amplification protocols follow Pinto-Sánchez et al. (2015), who published a dataset including the aforementioned genes, as well as three nuclear genes (RAG2, NGFB, R35), to which we added the new sequences to produce a matrix of 256 taxa and 3,211 aligned nucleotides (File S1). GenBank accession numbers of sequences produced in this study are presented in Table 1.

Table 1.

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Vouchers, locality data, and GenBank accession numbers of taxa and gene regions sequenced in this study.

Taxon	Voucher and locality	Coordinates		GenBank accession number
Taxon	Voucher and locality	Lat.	Long.	12S	cyt b
Mabuya altamazonica	QCAZ 8374. ECUADOR: Pastaza: K10 Camp, Villano Camp, Bloque 10-Agip Oil.	-1.473	-77.531	PP799538	PP806564
Mabuya altamazonica	QCAZ 12520. ECUADOR: Zamora Chinchipe: Mayo River, 4.5 km ESE Zumba, east bank.	-4.881	-79.091	PP799533	PP806559
Mabuya altamazonica	QCAZ 13087. ECUADOR: Pastaza: Oglán Scientific Station, entrance trail.	-1.321	-77.706	PP799534	PP806560
Mabuya altamazonica	QCAZ 16657. ECUADOR: Morona Santiago: Amaru Shuar community.	-2.903	-77.872	PP799535	PP806561
Mabuya nigropunctata	QCAZ 8107. ECUADOR: Pastaza: Villano B, Villano Camp, Bloque 10-Agip Oil.	-1.457	-77.443	PP799537	PP806563
Mabuya yasuniensis sp. nov.	QCAZ 4839 (paratype). ECUADOR. Pastaza: Jatun Yaku community, 5 km SE Montalvo.	-2.084	-76.921	PP799536	PP806562
Mabuya yasuniensis sp. nov.	QCAZ 10229 (paratype). ECUADOR: Orellana: Yasuní National Park, near PUCE scientific station, north trail of 50 ha dynamic forest plot.	-0.681	-76.403	PP799531	PP806557
Mabuya yasuniensis sp. nov.	QCAZ 10740 (paratype). ECUADOR: Orellana: Oasis community, 500 m from Napo River.	-0.460	-76.135	PP799532	PP806558

We assembled and aligned DNA sequences in GENEIOUS PRIME 2022.1.1 (https://www.geneious.com) under default settings for MAFFT (Katoh and Toh 2010). We translated cyt b sequences into amino acids for confirmation of alignment. In addition, we realigned 12S regions with multiple gaps in an attempt to minimize indels and optimize nucleotide identities across different individuals. Phylogenetic relationships were inferred under the maximum likelihood optimality criterion in IQ-TREE (Nguyen et al. 2015; Trifinopoulos et al. 2016) under default settings. We used MODELFINDER (Kalyaanamoorthy et al. 2017) to infer models of evolution for each gene. Branch support was also assessed in IQTREE with 1000 replicates under ultrafast bootstrapping (Hoang et al. 2018). Finally, we used DIVEIN (Deng et al. 2010) to calculate 12S and cyt b uncorrected pairwise genetic distances among species of Mabuya; for this, the taxonomy of the dataset of Pinto-Sánchez et al. (2015) was updated following McCranie et al. (2020).

Species delimitation

Following the unified species concept (de Queiroz 1998, 2007), we support the recognition of the species mentioned below based on morphological and phylogenetic criteria, which we interpret as evidence of lineage separation.

Results

Based on morphological and coloration characters, as well as phylogenetic relationships, we confirm the presence of both Mabuya altamazonica and M. nigropunctata in Ecuador (Figs 1–3). Our data match the descriptions presented by Miralles et al. (2006) and Avila-Pires (1995), respectively (Table 2). Our analyses also support recognition of a new species, which we describe below. The new species is sister to an unnamed sample from Colombia (see Discussion below), and they both are sister to M. bistriata, which includes samples from French Guiana and Brazil. The clade containing M. bistriata and the new species is sister to M. altamazonica (Fig. 1).

Figure 1.

Phylogeny of Mabuya, with a close-up of clades containing M. nigropunctata (blue) and both M. altamazonica and M. yasuniensis sp. nov. (red). All samples of M. yasuniensis correspond to paratypes. This maximum likelihood tree was obtained from an analysis of five genes (two mitochondrial, three nuclear) and 256 terminals. Numbers above branches are ultrafast bootstrap support values, not shown in short branches for clarity. Specimens sampled in this study are shown in bold. Taxon name (M.: Mabuya) followed by voucher number and country of origin are provided. BR: Brazil, CO: Colombia, EC: Ecuador, FG: French Guiana, LA: Lesser Antilles, PE: Peru, TT: Trinidad and Tobago, VE: Venezuela.

Figure 2.

Four species of skinks Mabuya in life, from top to bottom: M. yasuniensis sp. nov. (QCAZ 14814, holotype, SVL = 72.98 mm), M. altamazonica (QCAZ 13087, SVL = 92.11 mm), M. nigropunctata (QCAZ 8107, SVL = 104.58 mm), and M. bistriata. Photographs from Bioweb.bio, except M. bistriata (Laurie J. Vitt).

Figure 3.

Known distribution of Mabuya in Ecuador: M. altamazonica (squares), M. nigropunctata (circles), M. yasuniensis sp. nov. (triangles). Red-filled symbols correspond to localities of sequenced specimens. Red star indicates type locality of M. yasuniensis sp. nov.

Table 2.

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Summary of lepidosis and measurements of Mabuya altamazonica, M. bistriata, M. nigropunctata, and M. yasuniensis sp. nov. Range followed by mean ± standard deviation is presented. Sample size is given in parentheses if different from heading.

Character	Mabuya yasuniensis sp. nov.	*Mabuya altamazonica*	*Mabuya altamazonica*	*Mabuya bistriata*	*Mabuya nigropunctata*	*Mabuya nigropunctata*
	n = 14	n = 14	n = 26	n = 61	n = 4	n > 200
	This study	This study	(Miralles et al. 2006)	(Avila-Pires 1995)	This study	(Avila-Pires 1995; Miralles et al. 2006)
Longitudinal scale rows around midbody	26–30 28.36 ± 1.28	25–32 28.71 ± 2.30	26–31 29.19 ± 1.35	28–33 (38) 30.4 ± 1.1	30–31 30.50 ± 0.58	27–34 30.5 ± 1.3 (67)
Transverse rows of dorsal scales	47–52 50.29 ± 1.68	49–54 51.07 ± 1.33	48–55 52.44 ± 1.98	53–59 (38) 56.3 ± 1.5	46–53 49.75 ± 2.99	48–57 52.40 ± 1.9 (65)
Transverse rows of ventral scales	32–40 36.07 ± 1.94	35–40 36.54 ± 1.45	28–36 32.12 ± 1.91 (24)	36–43 (39) 38.6 ± 1.8	34–40 36.25 ± 2.63	33–40 36.7 ± 1.7 (64)
Number of supraciliaries	3 (1) 4 (13)	5	4–6 usually 5	4	5 (1) 6 (1)	4–6 usually 5
Size of supraciliaries	2^nd largest	all subequal	all subequal	2^nd largest	all subequal	all subequal
Supralabials, enlarged scale under eye	7, 5^th (12) 8, 6^th (1)	6, 5^th (1) 7, 5^th (13)	7, 5^th	mostly 7, 5^th 8, 6^th	8, 6^th (3)	7, 5^th (18.7%) 8, 6^th (78.4%)
Infralabials	6 (4) 7 (8) 8 (1)	6 (8) 7 (5)	7	6–8 mostly 7	6 (1) 7 (2)	7–8 rarely 6 or 9
Lamellae under Finger IV	12–16 13.46 ± 1.13	11–13 12.36 ± 0.74	11–15 12.19 ± 1.04 (24)	11–15	13–14 13.33 ± 0.58	10–16 12.85 ± 0.98 (206)
Lamellae under Toe IV	16–19 17.23 ± 1.09	14–17 15.29 ± 0.99	13–19 15.67 ± 1.49 (23)	15–19	16–18 17.00 ± 1.00	14–20 16.30 ± 1.26 (202)
Parietals in contact	yes (79%) no (21%)	yes	yes (96%)	yes	no	no (90.7%) yes (9.3%)
Maximum SVL in mm	78.56	92.11	97.2	75	108.61	113
Tail length/SVL	1.37–1.74 1.52 ± 0.18 (4)	1.15–1.50 1.28 ± 0.11 (8)	—	1.4–1.8 (16) 1.68 ± 0.12	0.98 (1)	1.2–1.6 1.38 ± 0.12 (20)
Head length/SVL	0.19–0.25 0.21 ± 0.02	0.17–0.25 0.21 ± 0.03	0.18 (1)	0.16–0.20 (38)	0.18–0.23 0.21 ± 0.02	0.17–0.24 (43)
Head length/head width	1.35–1.63 1.51 ± 0.08	1.29–1.86 1.51 ± 0.14	—	1.3–1.6 (38) 1.43 ± 0.07	1.23–1.59 1.48 ± 0.17	1.2–1.6 1.42 ± 0.08 (43)
Head width/head height	1.10–1.59 1.41 ± 0.16	1.14–1.61 1.32 ± 0.14	—	1.2–1.6 (38) 1.33 ± 0.10	1.19–1.50 1.33 ± 0.13	1.1–1.6 1.32 ± 0.10 (44)
Forelimb/SVL	0.24–0.30 0.27 ± 0.02 (13)	0.25–0.31 0.27 ± 0.02	—	0.22–0.28 (38) 0.25 ± 0.02	0.27–0.30 0.29 ± 0.02	0.24–0.32 0.28 ± 0.02 (44)
Hindlimb/SVL	0.33–0.42 0.36 ± 0.02	0.32–0.38 0.36 ± 0.02	—	0.29–0.38 (36) 0.34 ± 0.02	0.35–0.39 0.37 ± 0.02	0.32–0.43 0.37 ± 0.03 (43)
Pair of thin, pale dorsolateral stripes from neck to midbody	absent	absent	absent	present	absent	absent
Palms and soles	dark, darker than venter	dark, darker than venter	dark, darker than venter	light or tan, similar in color to venter	dark, darker than venter	dark, darker than venter

12S mean genetic distances among species of Mabuya vary from <0.003 (e.g., M. monitae Hedges & Conn, 2012 vs. M. sloanii Daudin, 1803, M. culebrae Hedges & Conn, 2012, and M. macleani Mayer & Lazell, 2000) to 0.133 (M. meridensis Miralles, Rivas & Schargel, 2005 vs. M. agilis Raddi, 1823 and M. heathi Schmidt & Inger, 1951). The 12S mean genetic distances between the new species described here and other species of Mabuya range from 0.023 (M. cf. yasuniensis) to 0.111 (M. caissara Rebouças-Spieker, 1974); the distance with M. bistriata is and 0.032. The mean genetic distances for cyt b among species of Mabuya vary from <0.025 (e.g., M. monitae vs. M. sloanii, M. culebrae, and M. macleani) to 0.200 (M. culebrae vs. M. carvalhoi Rebouças-Spieker & Vanzolini, 1990). The cyt b mean genetic distances between the new species and other species of Mabuya range from 0.055 (M. cf. yasuniensis) to 0.171 (M. carvalhoi); the distance with M. bistriata is 0.094. 12S and cyt b genetic distances among species of Mabuya are presented in Tables S1 and S2, respectively.

Mabuya yasuniensis sp. nov.

https://zoobank.org/41A31B4B-EC6F-42DC-9D40-8DDE5D22B00E

Holotype

An adult male, QCAZ 14814 (Figs 2, 4, 5), field number SC55292, collected on 29 July 2016 at 1630 h by Rubén Jarrín at Yasuní National Park in a lagoon close to Yasuní River, 6 km S Rumiyacu River mouth (0.967°S, 75.875°W, 190 m), Orellana Province, Ecuador.

Figure 4.

Male holotype (QCAZ 14814; SVL = 72.98 mm) of Mabuya yasuniensis sp. nov. in dorsal (top), lateral (middle) and ventral (bottom) views. Photographs by D. A. Paucar. Scale bar: 10 mm.

Paratypes (13)

ECUADOR: Orellana: Oasis community, 500 m from Napo River, 0.460°S, 76.135°W, 220 m, QCAZ 10740; Puerto Yuturi, 0.557°S, 76.008°W, 230 m, QCAZ 3609; Yasuní National Park, near PUCE (Pontificia Universidad Católica del Ecuador) scientific station, 0.677°S, 76.401°W, 273 m, QCAZ 5901; Yasuní National Park, near PUCE scientific station, 0.674°S, 76.398°W, 264 m, QCAZ 17519; Yasuní National Park, near PUCE scientific station, north trail of 50 ha dynamic forest plot, 0.681°S, 76.403°W, 285 m, QCAZ 10229; Puerto Francisco de Orellana (El Coca), 0.467°S, 76.983°W, QCAZ 185; Río Bigal Biological Reserve, 0.537°S, 77.425°W, 955 m, QCAZ 17646; Taracoa, 0.490°S, 76.773°W, 251 m, QCAZ 1118. Pastaza: Jatun Yaku community, 5 km SE Montalvo, 2.084°S, 76.921°W, 286 m, QCAZ 4839; K10 camp, Villano camp, Bloque 10-Agip Oil, 1.475°S, 77.534°W, 468 m, QCAZ 11832. Sucumbíos: La Selva Amazon Ecolodge, 0.498°S, 76.374°W, 229 m, QCAZ 2926; Cuyabeno Wildlife Reserve, PUCE scientific station, 0.002°S, 76.176°W, QCAZ 2623; Cuyabeno Wildlife Reserve, bridge on Cuyabeno River, 0.031°S, 76.321°W, QCAZ 7138.

Figure 5.

Head of the holotype (QCAZ 14814) of Mabuya yasuniensis sp. nov. in dorsal (top), ventral (middle), and lateral (bottom) views. Photographs by D. A. Paucar. Scale bar: 5 mm.

Diagnosis

Mabuya yasuniensis sp. nov. can be distinguished from other congeners by the combination of the following character states: (1) prefrontals paired; (2) frontoparietals paired; (3) supraciliaries four, second longest; (4) supraoculars four, second largest; (5) supralabials seven, fifth longest and below eye; (6) nuchals in one pair; (7) dorsals smooth; (8) scales around midbody 26–30; (9) dorsals 47–52; (10) ventrals 32–40; (11) caudals smaller and similar in shape to dorsals; (12) lamellae under fourth finger 12–16; (13) lamellae under fourth toe 16–19; (14) palms and soles dark; (15) dark dorsolateral stripes absent; (16) pale dorsolateral stripes absent.

Among species of Mabuya known to occur in Ecuador—M. altamazonica and M nigropunctata—, M. yasuniensis is most similar to M. altamazonica in having (1) seven supralabials, with the fifth being the largest and located under the eye (eight supralabials, with the sixth being the largest and located under the eye in M. nigropunctata), and (2) parietals in contact posterior to interparietal (no contact in M. nigropunctata). However, M. yasuniensis can be readily distinguished by having four supraciliaries, of which the second is longer than the others (usually five subequal supraciliaries in both M. altamazonica and M. nigropunctata). The new species is closely related to M. bistriata Spix, 1825 (Fig. 1), which also has four supraciliaries, the second the longest. It differs from M. bistriata in (1) lacking a pair of thin, pale dorsolateral stripes from neck to midbody (Fig. 2), and having (2) dark palms and soles (Fig. 4), darker than venter (palms and soles cream or tan, similar in color to venter in M. bistriata), and (3) 47–52 transverse rows of dorsal scales (53–59 in M. bistriata; Table 2).

Description of the holotype

Adult male (QCAZ 14814) (Figs 2, 4, 5); SVL 72.98 mm; TL 126.72 mm; head length 14.39 mm, head width 11.29 mm, head depth 8.45 mm; rostral wider than high (2.86 × 1.31 mm), in contact with first supralabials, nasals and supranasals; paired, posterolaterally oriented supranasals in median contact, with posterolateral end contacting anteriormost loreal; frontonasal with rounded anterior border and pointed posterior border, wider than long (3.76 × 2.50 mm), in contact with anterior loreal laterally; paired prefrontals roughly rectangular, anterolaterally oriented, in contact medially, and contacting frontonasal anteriorly, both anterior and posterior loreals laterally, first supraciliaries and first and second supraoculars posterolaterally, and frontal posteromedially; frontal rhomboid, longer than wide (3.93 × 2.59 mm), wider anteriorly, in contact with prefrontals anteriorly, second supraoculars laterally, and frontoparietals posteriorly; supraoculars four, the first the smallest, the second the largest; first supraocular in contact with prefrontal anteriorly, first and second supraciliaries laterally, and second supraocular medially; second supraocular in contact with prefrontal anteromedially, frontal medially, frontoparietal and third supraocular posteriorly, and second supraciliary laterally; third supraocular in contact with frontoparietal laterally, fourth supraocular posteriorly, second and third supraciliaries laterally and second supraocular anteriorly; fourth supraocular in contact with frontoparietal medially, parietal and one pretemporal posteriorly, and third and fourth supraciliaries laterally; supraciliaries four, the second more than twice the length of others, which are similar in length; frontoparietals paired, longer than wide, in broad contact at midline, in contact with frontal anteriorly, all supraoculars except the first laterally, parietal and interparietal posteriorly; interparietal rhomboid, longer than wide (3.03 × 2.54 mm); parietal eye distinct on posterior end of interparietal; parietals more than twice as long as interparietal, wider than long, in contact with each other posterior to interparietal and overlapping the upper anterior temporal scales; each parietal in contact with frontoparietal and fourth supraocular anteriorly, two pretemporals anterolaterally, two temporals (overlapped by parietal) posterolaterally, nuchal posteromedially, and interparietal medially; nasal subrectangular; nostril approximately half the size of nasal, located posteriorly; postnasal small, in contact with supranasal dorsally, anterior loreal and first and second supralabials ventrally, and nasal anteriorly; two subrectangular loreals posterior to nasal, subequal in size, the posteriormost slightly higher; anterior loreal in contact with second supralabial, posterior loreal in contact with second and third supralabials; presubocular single, in contact with fourth and fifth supralabials; preocular single, between presubocular and posterior loreal, in contact with third and fourth supralabials; lower eyelid with large transparent disk, one elongated scale across its dorsal edge (an additional small, anterior scale on right side); supralabials seven, the fifth ventral to eye and more than twice as long as the others; infralabials seven on right side and six on left side; temporals imbricate, smooth, cycloid, not distinctly delimited from scales on the nape or sides of the neck; pretemporals two; primary temporal single, two secondary temporals in contact with three tertiary temporals; ear opening relatively small (maximum diameter = 1.04 mm), round, with two scales overlapping anterior margin; auricular lobules absent; mental about three times as wide as long (3.21 × 1.05 mm), with straight posterior margin; postmental wider than long, in contact with first and second infralabials laterally and one pair of chin shields posteriorly; three pairs of chin shields, anterior one in contact medially, posterior ones separated by three longitudinally arranged gular scales; anterior pair of chin shields in contact with second infralabial and first sublabial laterally, posterior pairs separated from infralabials by sublabials; gulars similar in size and shape to ventrals, separated from supralabials by sublabials; palms and soles covered with small tubercles, subequal in size, both regions delimited by a row of larger and flatter scales; subdigital lamellae smooth, single, 14 under fourth finger and 18 under fourth toe on both sides; finger and toes clawed; relative length of the toes in the following order: I < II < V < III < IV; conspicuous posthumeral mite pocket with slit-like opening; all scales, except head shields and scales on sole and digits, cycloid, smooth and imbricate; longitudinal scale rows around midbody 26, transverse rows of dorsal scales 49, transverse rows of ventral scales 36; preanals four, larger than adjacent ventral scales; median subcaudal series of scales twice as wide as long on posterior half of tail.

Coloration of the holotype (Figs 2, 4, 5)

Dorsal background olive-bronze; ventral side of head, body, and limbs immaculate bluish-grey; ventral aspect of tail with dense brown pigmentation; dorsum with series of small (~1/3 of a dorsal scale) dark brown spots more or less longitudinally arranged from scapular region onto tail; lateral and dorsal sides of limbs spotted with small, fused dark dots; palms and soles dark brown; preanals pale cream; dark lateral and ventrolateral stripes present; dark lateral stripe wider, about three scales wide at midbody, extending from nostrils through loreals, upper half of supralabials, around eyes, temporals, upper half of ear openings, neck, above arms, and along flanks up to insertion of hindlimbs; dark ventrolateral stripe diffuse, extending from corner of mouth, along ventral aspect of ear opening, above forelimbs, up to insertion of hindlimbs; dark lateral and ventrolateral stripes separated from each other by ill-defined pale lateral stripe, same color as venter, about one scale wide at midbody, with brown pigmentation (denser on posterior half).

Hemipenis

The following description is based on two partially everted hemipenes of two male paratypes of Mabuya yasuniensis (Fig. 6); character numbers in parentheses correspond to those listed by Sánchez-Martínez et al. (2020). Organ tubular, bilobed, not capitate, with both external and internal membranous layers; sulcus spermaticus diagonally oriented, bifurcating at base of lobes, with crotch before branches deep and exposed; proximal half of sulcus spermaticus overlapped by large thick fold (1); two small horizontal ridges below the base of each lobe (2) on sulcate side; obtuse projection (lower fold, 3) proximal to each pair of small horizontal ridges; broad, medial bell-shaped fold (4) below lobes on asulcate side, its upper tip (5) extending on surface between lobes; two large protuberances (6) proximal to bell-shaped fold; lateral fold (7) connecting lower fold (3) of sulcate side with large protuberance (6) of asulcate side.

Figure 6.

Hemipenes of two male paratypes of Mabuya yasuniensis sp. nov. (top: QCAZ 4839, SVL = 77.46 mm; bottom: QCAZ 11832, SVL = 76.64 mm) in asulcate, sulcate and lateral views from left to right. Number labels correspond to characters described in the text based on Sánchez-Martínez et al. (2020). Photographs by D. A. Paucar. Scale bar: 2 mm.

Variation

Intraspecific morphological variation in M. yasuniensis is presented in Table 2. One of the most distinctive characters of M. yasuniensis is having four supraciliaries, of which the second is elongated; however, of 14 examined specimens, one had only three supraciliaries, possibly as a result of scale fusion. Contact of parietals behind interparietal, a diagnostic character for M. altamazonica, was observed in 79% of the specimens. The dorsal color pattern of M. yasuniensis varies from having a few longitudinally aligned dark brown spots (usually restricted to scale tips) to a densely spotted back, whereas the dark ventrolateral stripe can be ill-defined as a few longitudinally arranged dark spots on flank scales (Fig. 7).

Figure 7.

Paratypes (top: QCAZ 4839, SVL = 77.46 mm; bottom QCAZ 17646, SVL = 54.81 mm) of Mabuya yasuniensis sp. nov. in dorsal and lateral views. Photographs by D. A. Paucar. Scale bar: 10 mm.

Etymology

The specific epithet yasuniensis derives from the words “Yasuní” (Spanish) and “-ensis” (Latin adjectival suffix denoting place or locality). It refers to Yasuní National Park, where M. yasuniensis was discovered. With 9,820 km², Yasuní is the largest protected area in continental Ecuador and one of the most biodiverse places on Earth (Bass et al. 2010). In 1989 Yasuní was declared a UNESCO Biosphere Reserve.

Distribution and natural history

Mabuya yasuniensis is known from the Amazonian lowlands of Ecuador—Orellana, Pastaza and Sucumbíos provinces, at elevations between 200–955 m (Fig. 3). Some localities lie within protected areas, including Yasuní National Park, Cuyabeno Wildlife Reserve and Río Bigal Biological Reserve, suggesting that some populations of M. yasuniensis are well protected. Specimens were found active mostly on the ground between 1030 h and 1630 h in primary and secondary forests. The holotype was found within moss 1 m above water on a tree standing within a lagoon. Mabuya yasuniensis occurs in sympatry with both M. altamazonica and M. nigropunctata.

Identification key to species of Mabuya from Ecuador

1	Supraciliaries usually five, subequal in size	2
	Supraciliaries four, second longest	M. yasuniensis sp. nov.
2	Parietals in contact behind interparietal; supralabials seven, fifth longest and placed below eye	*M. altamazonica*
	Parietals separated by interparietal; supralabials eight, sixth longest and placed below eye	*M. nigropunctata*

Discussion

Our phylogenetic tree shows that samples of M. yasuniensis form a clade sister to sample MHUA 11475 from Leticia (4.17ºS, 69.95ºW), Amazonas department in southeastern Colombia (Fig. 1). This sample was included in the phylogenetic analysis of Pinto-Sánchez et al. (2015), who assigned it tentatively to M. bistriata based on their tree topology. However, Pinto-Sánchez et al. (2015) could not verify the identity of this sample because the corresponding voucher specimen was poorly preserved and they acknowledged that it could “correspond to a new species closely related to M. bistriata” given the high genetic divergence with other specimens of M. bistriata (12S: 1.6%, cyt b: 8.5–8.9%). Our results corroborate this hypothesis, but we cannot confirm if sample MHUA 11475 belongs to either M. yasuniensis or an undescribed species.

The type locality of the species described in this paper lies within Yasuní National Park (YNP), the largest national park (nearly one million hectares) in Ecuador. YNP is also a UNESCO Biosphere Reserve and one of the most biodiverse places on Earth (Bass et al. 2010). With Mabuya yasuniensis sp. nov., 124 species of reptiles have been registered in YNP to date (Torres-Carvajal et al. 2024), which makes YNP one of the most reptile-rich places worldwide. Other areas in South America with high reptile richness are Manu National Park (132 spp.), Tambopata (112 spp.), and Iquitos (140 spp.) (Dixon and Soini 1986; Doan and Arriaga 2002; Catenazzi et al. 2013). Despite its conservation significance, Yasuní National Park faces major threats including oil extraction and road construction. In 2007, Ecuador launched the Yasuní-ITT Initiative in an attempt to receive compensation from developed nations to leave nearly a billion oil barrels underground in the Isphpingo-Tambococha-Tiputini area of YNP (Finer et al. 2010). The initiative failed and oil platforms and wells were constructed in ITT in subsequent years. However, in an unprecedented referendum in 2023, most Ecuadorians voted in favor of closing the oil block and halt any future drilling at ITT. We hope that Ecuador’s government sets up a clear and transparent plan to suspend oil extraction in Yasuní-ITT as an example of respect to Amazonian indigenous communities and nature. The description of a new species of skink from YNP underscores the need for scientific research and conservation action in one of Earth’s most biodiverse places.

Acknowledgments

We thank Claudia Terán for laboratory work, as well as S. Aldás, J. Brito, M. Díaz, T. García, R. Jarrín, P. Menéndez, J. Molineros, A. Narváez, G. Onore, M. Read, A. Rodríguez, F. Velásquez, L. J. Vitt, T. Walla, and others for their hard work in the field. Special thanks to L. Ceríaco and A. Miralles for their helpful comments that improved this manuscript. Specimens included in this study were obtained under collection permits 001-10 IC-FAU-DNB/MA, 001-11 IC-FAU-DNB/MA, 002-16 IC-FAU-DNB/MA, 008-09 IC-FAU-DNB/MA, 008-IC-FAU-DPPZ/MA, 009-2018-IC-PNY-DPAO/AVS, MAE-DNB-CM-2015-0025 issued by the Ecuadorian Ministry of Environment, Water, and Ecological Transition. This research was funded by the Secretaría de Educación Superior, Ciencia, Tecnología e Innovación (SENESCYT) under the ‘Arca de Noé’ Initiative (PIs: SR Ron and OTC); and Pontificia Universidad Católica del Ecuador.

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Appendix 1

Specimens examined.

Mabuya nigropunctata (n = 4). — ECUADOR: Orellana: QCAZ 4041: Yasuní National Park, km 37 Pompeya Sur-Iro road (0.646°S, 76.457°W, 238 m), QCAZ 6187: Yasuní National Park, km 38 Pompeya Sur-Iro road (0.653°S, 76.451°W); Pastaza: QCAZ 8107: Villano B, Villano Camp, Bloque 10-Agip Oil (1.457°S, 77.443°W, 353 m), QCAZ 8369: K10 Camp, Villano Camp, Bloque 10-Agip Oil (1.474°S, 77.535°W, 442 m).

Mabuya altamazonica (n = 14). — ECUADOR: Pastaza: QCAZ 8232: Comunidad Paparawua, Villano Camp, Bloque 10-Agip Oil (1.483°S, 77.439°W, 385 m), QCAZ 8283: Comunidad Kurintza, Villano Camp, Bloque 10-Agip Oil (1.506°S, 77.509°W, 357 m), QCAZ 8359: K10 Camp, Villano Camp, Bloque 10-Agip Oil (1.476°S, 77.534°W, 475 m), QCAZ 8374: K10 Camp, Villano Camp, Bloque 10-Agip Oil (1.473°S, 77.531°W, 501 m), QCAZ 13087, 13090, 13114–13118: Oglán Scientific Station, entrance trail (1.321°S, 77.706°W, 826 m); Morona Santiago: QCAZ 16657: Amaru Shuar community (2.903°S, 77.872°W, 247 m); Zamora Chinchipe: QCAZ 12520: Mayo River, 4.5 km ESE Zumba, east bank (4.881°S, 79.091°W, 763 m).

Supplementary materials

Supplementary material 1

File S1

Torres-Carvajal O, Sandoval C, Paucar DA (2024)

Data type: .nex

Explanation notes: Nexus data matrix of 256 taxa and 3,211 aligned base pairs. Genes: 12S = 1–388; cyt b = 389–1528; R35 = 1529–2179; Rag2 = 2180-2608; NGFB = 2609–3211.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.

Download file (811.42 kb)

Supplementary material 2

Table S1

Torres-Carvajal O, Sandoval C, Paucar DA (2024)

Data type: .xlsx

Explanation notes: 12S uncorrected pairwise distances among species of Mabuya calculated in DIVEIN.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.

Download file (64.18 kb)

Supplementary material 3

Table S2

Torres-Carvajal O, Sandoval C, Paucar DA (2024)

Data type: .xlsx

Explanation notes: Cyt b uncorrected pairwise distances among species of Mabuya calculated in DIVEIN.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.

Download file (78.36 kb)