Duttaphrynus peninsularis (Rao, 1920) Bisht & Garg & Sarmah & Sengupta & Biju, 2021

Bisht, Karan, Garg, Sonali, Sarmah, A. N. D. Akalabya, Sengupta, Saibal & Biju, S. D., 2021, Lost, forgotten, and overlooked: systematic reassessment of two lesser-known toad species (Anura, Bufonidae) from Peninsular India and another wide-ranging northern species, Zoosystematics and Evolution 97 (2), pp. 451-470 : 451

Duttaphrynus peninsularis (Rao, 1920) comb. nov.

Figs 1 , 2 , 3 , 4 , 5

Original name and description.

Bufo stomaticus peninsularis Rao, 1920. Rao, C. R. N. 1920. Some South Indian batrachians. "Journal of the Bombay Natural History Society" 27: 119-127. Holotype. ZSIC 19176, SVL 45.1 mm (designated by Chanda et al. 2001 “2000”), from "Mavkote and Watekolle, Coorg," Karnataka State, India. Current status of specific name. Valid name, as Duttaphrynus peninsularis (Rao, 1920), comb. nov.

Material studied.

Topotype. An adult male, SDBDU 6370 (SVL 50.8 mm), collected by S. D. Biju, from Wattakolli, Karnataka State. Other referred specimens. Four adult males, SDBDU 4018 (SVL 51.8 mm), SDBDU 4019 (SVL 45.5 mm), SDBDU 4020 (SVL 49.5 mm), and SDBDU 4021 (SVL 46.5 mm), from Coimbatore, Tamil Nadu State.

Reassessment and validation of taxonomic status.

Rao (1920) described a new variety of Bufo stomaticus from "Mavkote and Watekolle, Coorg" as " Bufo stomaticus peninsularis var. nov." The original description mentioned two specimens ("Type and syntype in the Indian Museum") and subsequently Chanda et al. (2001 “2000”) proposed ZSIC 19176 to be the holotype. Currently a single specimen is available in the ZSIC (Kolkata) collection (S. D. B., personal observation). It is noteworthy that, prior to describing this taxon, Rao (1920) took an opinion from Boulenger (then Curator, British Museum Natural History, London), who was not in favour of separating this collection from D. stomaticus . However, Rao being unconvinced mentioned "no doubt about their being racially distinct" in the original description and went on to formally describe Bufo stomaticus peninsularis as a new variety of D. stomaticus . This nomen was considered to be a synonym of Bufo stomaticus (= Duttaphrynus stomaticus ) by Daniel (1963), without any justification or comparison, other than considering the characters mentioned by Rao (1920) as variation, based on examination of D. stomaticus specimens from Bombay. This action was followed by Dubois (1974) and Dutta (1997). In later years, regional anuran lists reported Duttaphrynus stomaticus from Peninsular India based on earlier reports and photographs, without citing any voucher specimens ( Hegde 2012; Ramachandra et al. 2012; Seshadri et al. 2012). Srinivasulu et al. (2013) identified the “captioned-photographs” of Seshadri et al. (2013) and Hegde (2012) as belonging to D. scaber , a species that is widely distributed in Peninsular India ( Dutta 1997; Chanda 2002; Daniels 2005; Dinesh et al. 2009; Padhye et al. 2013). Srinivasulu et al.'s (2013) notes concerning the misidentifications of D. scaber as D. stomaticus (and not D. peninsularis ) was by implication considered as a synonymisation action of Bufo stomaticus peninsularis with D. scaber by Frost (2021).

In order to verify the above, we compared the type specimen and the original description of Bufo stomaticus peninsularis Rao, 1920. Although the holotype ( ZSIC 19176) was found to be in a severely damaged and dehydrated condition (Fig. 1 ), the head portion was relatively better preserved. Diagnostic morphological characters, such as absence of prominent cephalic ridges, weakly developed parotoid glands, distinct tympanum (about 63% of the eye), and the relatively smooth skin texture of the head and dorsum, match with the original description of Bufo stomaticus peninsularis Rao, 1920. Additionally, Rao (1920) clearly stated six differences between his new variety and the typical form of Bufo stomaticus from "Indian Museum nos., 16067, 16068, 17254 and 17274" (see the detailed comparison section), which we further re-examined to confirm distinctness of the two taxa.

We examined specimens from two populations of Duttaphrynus " Duttaphrynus stomaticus ," sampled from different localities (including Wattakolli) in Peninsular India, which were found to be comparable to the original description and type specimen of Bufo stomaticus peninsularis Rao, 1920 with respect to snout-vent length, absence of cephalic ridges, weakly developed parotoid glands, and relatively smooth skin. Based on re-examination of the holotype and assessment of newly-collected material, and molecular data, we conclude that Bufo stomaticus peninsularis Rao, 1920 and Bufo stomaticus Lütken, 1864 represent two distinct species, both individually diagnosable from other Indian congeners and each other. Hence, we formally resurrect Bufo stomaticus peninsularis Rao, 1920, as a distinct species: Duttaphrynus peninsularis (Rao, 1920), comb. nov. Furthermore, since the holotype is poorly preserved, we also provide a detailed redescription of this species, based on new topotypic material from Wattakolli, which matches the original description and the type.

Description of topotype, SDBDU 6370

(measurements in mm). A medium-sized, robust adult male (SVL 50.9); head of moderate size, wider (HW 18.0) than long (HL 14.0); snout truncate in dorsal and ventral view, rounded in lateral view, projecting beyond the mouth, its length (SL 5.8) nearly equal to horizontal diameter of eye (EL 5.7); loreal region acute with rounded canthus rostralis; distance between posterior borders of the eyes (IBE 13.9) 1.6 times the distance between the anterior borders (IFE 8.2); interorbital space about 1.4 times wider (IUE 6.2) than upper eyelid width (UEW 4.5); nostril oval without lateral flap of skin, closer to tip of snout (NS 1.7) than eye (EN 3.2); tympanum distinct (TYD 3.1), vertically oval, about 56.4% of eye diameter (EL 5.5), tympanum to eye distance (TYE 1.0); pineal ocellus absent; vomerine ridge and teeth absent; tongue small, oval, entire, median lingual projection absent; parotoid glands present, oval, flat, without spines and warts, slightly longer (PL 10.4) than wide (PW 5.5), distance between them (PD 6.2) more than the width.

Forelimbs short; forearm length (FAL 11.5) longer than hand length (HAL 10.9); fingers rather thin, FLI longer than FLII, FLIII longest (5.6); relative length of fingers: II<IV<I<III; tips of fingers rounded; subarticular tubercles prominent, single, all present; prepollex oval, distinct; single rounded prominent palmar tubercle; numerous supernumerary tubercles irregularly set on palm.

Hind limbs relatively long and thin, thigh length (TL 19.7) longer than shank (SHL 17.8) and foot (FOL 18.4) length; relative length of toes: I<II<V<III<IV; tips of all toes rounded, without discs; webbing between toes present, small: I1+-2II1+-3-III 1½-3IV3-1½ V; dermal fringes present on all toes; subarticular tubercles rather weakly developed, oval; inner metatarsal tubercle present, prominent, its length (IMT 1.6) shorter than outer metatarsal tubercle (OMT 1.8); numerous weakly developed supernumerary tubercles set on foot.

Skin. Dorsal and lateral surfaces of head and snout, and skin between eyes relatively smooth to sparsely granular; anterior and posterior parts of back with flat and smooth glandular projections; flanks glandular without horny spinules or warts; dorsal surfaces of thigh, shank, and tarsus with smooth glandular warts. Ventral surfaces of throat, chest, belly, and thighs glandular.

Male secondary sexual character. Light brown granular projections on the lateral surfaces of fingers I, II, and III.

Colour in preservation. Dorsum and limbs greyish-brown without any prominent markings; lateral surfaces of head, flank, and groin slightly lighter than dorsum; ventral surfaces (including limbs) greyish-white, throat with a faint light blue calling patch (Fig. 1 ). Colour in life: dorsum yellowish-brown with reddish patches; limbs yellowish brown; ventral surfaces white with a prominent bluish-yellow calling patch on throat (Fig. 2 ).

Variation.

Adult size range: male SVL 45-52 mm. Morphometric data from five adult males, including the described topotype, is given in Table 1. The dorsal colour is highly variable in life: SDBDU 4018: light brown with light grey patches, SDBDU 4019: light brown with reddish blotches, and SDBDU 4020: uniformly olive green.

Comparisons.

Duttaphrynus peninsularis differs from the Indian congeners: D. chandai , D. himalayanus , D. kiphirensis , D. mamitensis , D. manipurensis , D. melanostictus , D. microtympanum , D. mizoramensis , D. nagalandensis , D. parietalis , D. silentvalleyensis , D. scaber , D. stuarti , and D. wokhaensis , and species from other regions: D. crocus (Myanmar), D. kotagamai and D. noellerti (Sri Lanka), and D. totol (Indonesia), by the absence of conspicuous cephalic ridges (vs. present), absence of prominent or raised parotoid glands (vs. present), and dorsal skin without distinct glandular warts or horny spinules (vs. present in all species). Due to the lack of conspicuous cephalic ridges D. peninsularis could be confused with four Indian species D. beddomii , D. brevirostris , D. hololius , and D. stomaticus . However, it differs from D. beddomii in having a relatively larger tympanum (vs. smaller), finger and toe tips without discs (vs. with weakly developed discs), relatively reduced foot webbing, I1+-2II1+-3-III 1½-3IV3-1½ V (vs. extensive, I1-1II1-1III1-2IV2-1V), and absence of prominent glandular warts or horny spinules on dorsum (vs. present). Duttaphrynus peninsularis differs from D. hololius by its robust body (vs. dorso-ventrally flattened), absence of mid-dorsal line (vs. present), snout rounded in lateral view (vs. acute), tympanum smaller than eye diameter (vs. nearly equal), and more extensive webbing between toes, I1+-2II1+-3-III 1½-3IV3-1½ V (vs. rudimentary). Duttaphrynus peninsularis differs from D. stomaticus by its relatively shorter snout-vent length, male SVL 45-52 mm (vs. longer, male SVL 54-69 mm), its snout truncate in dorsal and ventral view (vs. rounded), snout longer than eye diameter (vs. nearly equal), dorsal skin granulation relatively smooth (vs. with prominent glandular warts), and relatively reduced foot webbing, I1+-2II1+-3-III 1½-3IV3-1½ V (vs. more, I1-1II1-2-III1-3IV3-1V). For comparisons to D. brevirostris , see the respective comparison section.

We quantitatively assessed the degree of morphometric differentiation of Duttaphrynus peninsularis from the other two Indian members of the Duttaphrynus stomaticus group ( D. hololius and D. stomaticus ). An ordination of the first two principal components resulted in formation of three distinct clusters, what we consider to be three species (Fig. 5 ). The first two principal components (PC) accounted for 50.73% of the total variance, of which PC1 was able to explain 32.08%, and PC2 explained 18.65% of the variation in the dataset. Variables with the highest factor loadings for PC1 were HW, TYD, EL, IUE, and IN, while PC2 was highly loaded for UEW. The third and fourth principal components (PC3 and PC4) accounted for 9.37% and 9.07% of the total variance, respectively, taking the cumulative variance for the first four components to 69.17% (Suppl. materal 1: Table S5). The Box and whiskers plots of the five most significant characters recovered from PCA showed diagnostic differences between the three species (Fig. 5 ). Of the three species, D. hololius was more distinct for all the studied characters, whereas D. peninsularis and D. stomaticus could be clearly delineated based on SVL, EL/SVL, TYD/SVL, and IN/SVL.

Phylogenetic relationships and genetic distances.

Duttaphrynus peninsularis is a member of the Duttaphrynus stomaticus group (Fig. 3 ), within which it is more closely related to D. stomaticus and D. ' Duttaphrynus olivaceus ' than to D. dhufarensis and D. hololius . The studied populations of D. peninsularis exhibit intraspecific distances of 0-0.4% in 16S. The sequence divergence of D. peninsularis from other members of the Duttaphrynus stomaticus group was as follows: 2.3-3.8% from D. dhufarensis , 5.2-5.4% from D. hololius , 1.3-2.6% from D. stomaticus , and 1.0-1.5% from D. ' Duttaphrynus olivaceus ' (Suppl. materal 1: Table S4).

Distribution and natural history.

Duttaphrynus peninsularis is currently known only from the Peninsular Indian States of Karnataka, Tamil Nadu, and Maharashtra. Genetically confirmed records are from Karnataka: Kodagu district (Wattakolli); Tamil Nadu: Coimbatore district (Coimbatore); and Maharashtra: Solapur district (Barshi and Solapur). We have also observed this species at Namakkal district (Kolli Malai) of Tamil Nadu. DNA sequences of this species were previously reported as D. stomaticus (FJ882787, Van Bocxlaer et al. 2009). Another genetically identical sample from an unknown locality in India is currently available (EU071742, Shouche and Ghate, unpublished GenBank data). Given that this species currently has a disjunct distribution based on available genetically confirmed records, it is likely to be more widely distributed in the intervening regions of Peninsular India (Kerala, Tamil Nadu, and Karnataka, up to southern Maharashtra). Furthermore, its most closely related congener D. stomaticus is frequently and widely reported in Peninsular India, which could be misidentifications of D. peninsularis ; hence the identity of all ' D. stomaticus ' records from this region require further verification. Based on the present study, the geographical boundary between D. peninsularis (southern species) and D. stomaticus (northern species) could lie in the northern Western Ghats regions of Maharashtra state, where we have observed and genetically confirmed the presence of both these species (see Distribution and Natural History section of D. stomaticus ). Further extensive sampling will be necessary to understand the patterns of population structure and delineate the ranges of these two species, using integrative approaches focusing on quantified ranges of phenotypic variation, traditional morphology, bioacoustics, ecological information, and phylogeny.

Most individuals reported here were located during night searches (between 17:00-21:00 hours) largely in vegetated urban areas. The species were also found in secondary forest patches adjacent to human settlements. Ganesh et al. (2020) reported this species as D. stomaticus from Tuticorin, Tamil Nadu.

Figures

Figure 1. Morphological characters for topotype of Duttaphrynus brevirostris (Rao, 1937), topotype of D. peninsularis (Rao, 1920), and syntype of D. stomaticus (Luetken, 1864) in preservation. A-G. Duttaphrynus brevirostris, BNHS 6126: A. Dorsal view; B. Ventral view; C. Lateral view of head; D. Dorsal view of hand showing brown nuptial pad on fingers I, II, and III; E. Ventral view of hand; F. Ventral view of foot; G. Schematic illustration of webbing on foot. H-N. Duttaphrynus peninsularis: H. Holotype, ZSIC 19176; I-N. Topotype, SDBDU 6370: I. Dorsal view; J. Ventral view; K. Lateral view of head; L. Ventral view of hand; M. Ventral view of foot; N. Schematic illustration of webbing on foot. O-T. Duttaphrynus stomaticus, ZMUC 131137 (ex 196): O. Dorsal view; P. Ventral view; Q. Lateral view of head; R. Ventral view of hand; S. Ventral view of foot; T. Schematic illustration of webbing on foot.

Figure 2. Topotype of Duttaphrynus brevirostris (Rao, 1937), topotype of D. peninsularis (Rao, 1920), and referred specimens of D. stomaticus (Luetken, 1864) in life. A. Duttaphrynus brevirostris (BNHS 6126) from Kempholey Ghat region in Sakleshpur taluk. B. Duttaphrynus peninsularis (SDBDU 6370) from Wattakolli. C-F. Duttaphrynus stomaticus: C. SDBDU 2015.2909 from Assam; D. SDBDU 2012.2170 from Rajasthan; E. SDBDU 2012.2172 from Delhi; and F. SDBDU 2012.2268 from Bihar.

Figure 3. Phylogenetic relationships and genetic differentiation in the genus Duttaphrynus. A. Maximum Likelihood phylogenetic tree based on 5,737 bp DNA comprising nine mitochondrial gene regions and two nuclear genes, showing phylogenetic relationships between the major species-level lineages. Values above and below the branches indicate Bayesian Posterior Probabilities (BPP) and RAxML Bootstrap Support (BS), respectively; B. Maximum Likelihood barcoding tree based on 524 bp of the mitochondrial 16 S rRNA sequences. BPP and BS support values are indicated above and below the branches, respectively. Coloured vertical bars outside the terminal node labels indicate putative species delimited in the bPTP analysis; C. Median-Joining haplotype network based on 42 haplotypes recovered from 133 sequences of the 16 S gene (420 bp). Size of the coloured circles is proportional to the number of haplotypes; black circles indicate median vectors; each branch represents a single mutation step; additional mutational steps are indicated by values in parentheses; photo credits: D. crocus (Guinevere O. U. Wogan), D. olivaceus (Parham Beyhaghi), and D. dhufarensis (Todd W. Pierson).

Figure 4. Geographical distribution of Duttaphrynus brevirostris (dark grey), D. peninsularis (blue), and D. stomaticus (orange).

Figure 5. Morphometric analyses for Indian members of the Duttaphrynus stomaticus group. A. Principal component analysis showing distinct clusters for three species in a scatter plot of the first two principal components; B-G. Box and whiskers plots depicting the most significant diagnostic characters for the three species.