Duttaphrynus stomaticus ( Luetken , 1864)

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 stomaticus ( Luetken, 1864)

Figs 1 , 2 , 3 , 4 , 5

Original name and description.

Bufo stomaticus Lütken, 1864. Lütken, C. F. 1864 “1863.” Nogle ny Krybyr og Padder. Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening i Kjøbenhavn, Serie 2, 4: 292-311. Syntypes. Three adult females, ZMUC 131137 [ex 196], ZMUC 131365 [ex 198], and one unnumbered, from “Assam;” two adult males, ZMUC 131136 [ex 195] and one unnumbered, from “Assam;” and three subadults, ZMUC 131366 [ex 199] from “Hoogly,” ZMUC 131363 [ex 193] from “Calcutta,” and ZMUC 131364 [ex 194] from “Calcutta.” Type locality. “Assam,” India, based on two specimens used in the original description ( Lütken, 1864). Current status of specific name. Valid name, as Duttaphrynus stomaticus ( Lütken, 1864).

Material studied.

Syntypes: Three adult females, ZMUC 131137 [ex 196] (SVL 60.9 mm), ZMUC 131365 [ex 198] (SVL 55.2 mm), and one unnumbered (SVL 61.4 mm), from “Assam;” two adult males, ZMUC 131136 [ex 195] (SVL 55 mm) and one unnumbered (SVL 59.2 mm), from “Assam;” and three subadults, ZMUC 131366 [ex 199] (SVL 26.4 mm) from “Hoogly,” ZMUC 131363 [ex 193] (SVL 33.4 mm) from “Calcutta” (Kolkata), and ZMUC 131364 [ex 194] (SVL 30.0 mm), from “Culcutta” (Kolkata). Other referred specimens: three adult males, SDBDU 2018.4109 (SVL 57.6 mm), SDBDU 2018.4110 (SVL 69.2 mm), and SDBDU 2018.4111 (SVL 55.1 mm), from Sonitpur district , Assam State ; two adult males, SDBDU 2018.3717 (SVL 56.2 mm) and SDBDU 2018.3750 (SVL 54.2 mm), from Dehradun , Uttarakhand State ; an adult female, SDBDU 2012.2172 (SVL 67.5 mm), from Delhi ; an adult female, SDBDU 2012.2269 (SVL 68.7 mm), from Kaitha in Banka district , Bihar State ; an adult male, SDBDU 2012.2170 (SVL 51.0 mm), from Jaipur, Rajasthan State .

Taxonomic history of Bufo stomaticus Lütken, 1864.

In the original description, Lütken (1864) mentioned that the Zoological museum, Copenhagen received six specimens of a toad from "Hr. Grosserer Westerman" (= Mr. Wholesales man Westermann) from “ostindiske” (= East India). Subsequent researchers stated the type locality of this species to be 'East India’ where it was later restricted to Assam ( Boulenger 1891). Dutta (1997) stated that the type specimens are untraceable. We (SDB and SG) studied the types that are available at ZMUC, Copenhagen, and found a total of eight specimens (see 'Other material studied’). According to the museum catalogue and bottle labels, all the adult animals are from “Assam,” one juvenile from “Hoogly,” and two juveniles from “Culcutta” (Kolkata). All the specimens belong to the same species and the morphological characters were in agreement with the brief original description. Boulenger (1891) had mentioned after examining the syntypes that the exact locality from where these were procured is unknown and believed they originated from Assam or "they are perhaps from Bengal." However, while describing Bufo stomaticus Lütken (1864) provided four measurements from two specimens, without mentioning the voucher numbers-"en Han" (one male) and "en Hun" (one female) "Fra Snudespidsen til Gattet" (= from snout to cloaca) 54 mm and 61 mm, respectively. Among the eight located syntypes, two similar-sized specimens were found bearing small tags on the hind limbs stating ‘type’.

Based on the available information, it is apparent that only two specimens, ZMUC 131137 [ex 196] and ZMUC 131136 [ex 195], were used for Lütken’s (1864) description of Bufo stomaticus ; hence only these can be considered as potential syntypes. However, since the type series contains both adult and subadult specimens originating from different localities, it has led to confusion regarding the type locality and type status ( Boulenger 1891). In order to clarify the taxonomic status of B. stomaticus , we provide a detailed redescription for one potential syntype, ZMUC 131137 [ex 196], an adult female, SVL 60.9 mm, from “Assam.” The below redescription, along with live photographs, interspecific comparisons, and enumeration of diagnostic characters, may be useful for differentiating this taxon from other known Duttaphrynus species. We also provide additional information on new topotypic material, including live photographs, genetic data, inferred phylogenetic relationships, and extended geographical records, based on morphologically-characterised and genetically-confirmed records-all of which shows that D. stomaticus (as understood here) is consistent with what is known of the name-bearing types.

Description of syntype, ZMUC 131137 [ex 196]

(measurements in mm). A medium-sized, robust adult female (SVL 60.9). Head of moderate size, wider (HW 22.7) than long (HL 17.8); snout rounded in lateral, dorsal, and ventral view, projecting beyond the mouth, its length (SL 6.8) longer to horizontal diameter of eye (EL 6.0); loreal region acute with rounded canthus rostralis; distance between posterior borders of the eyes (IBE 16.2) 1.8 times the distance between the anterior borders (IFE 9.2); interorbital space concave, 1.3 times wider (IUE 6.6) than upper eyelid width (UEW 5.0); nostril oval without lateral flap of skin, closer to tip of snout (NS 1.8) than to eye (EN 3.5); tympanum distinct (TYD 3.6), rounded, 58.1% of eye diameter (EL 6.2), tympanum to eye distance (TYE 1.6); pineal ocellus absent; vomerine ridge and teeth absent; tongue small, oval, entire, median lingual projection absent; parotoid glands present, oval, elongate, without spines and warts, longer (PL 13.9) than wide (PW 6.5) and distance between them (PD 10.0) wider than their width; cephalic ridges absent.

Forelimbs short; forearm length (FAL 11.5) shorter than hand length (HAL 13.7); fingers rather thin, FLI longer to FLII, FLIII longest (7.1 mm); relative length of fingers: I<II<IV<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 21.3) shorter than shank (SHL 21.8) and foot (FOL 22.6) length; relative length of toes: I<II<V<III<IV; tips of all toes rounded without discs; webbing between toes present, small: I1-1II1-2-III1-3IV3-1V; dermal fringes present on all toes; subarticular tubercles rather well-developed, oval; inner metatarsal tubercle present, prominent, its length (IMT 3.1) shorter than outer metatarsal tubercle (OMT 3.7); numerous weakly developed supernumerary tubercles set on foot.

Skin. Dorsal surfaces of head sparsely granular; lateral surfaces of head shagreened with scattered tubercles; upper eyelids with glandular warts possessing horny spinules; anterior and posterior parts of back with glandular warts possessing horny spinules, larger warts towards posterior back; flanks glandular without warts or horny spinules; dorsal surfaces of thigh, shank, and tarsus glandular. Ventral surfaces of throat, chest, belly, and thighs with fine glandular projections without horny spinules or warts.

Secondary sexual characters. Female (ZMUC 131137): ova white, pigmented on pole (diameter 0.8-1.0 mm, N = 20); Male (SDBDU 2018.4111): light brown granular projections on the lateral surfaces of fingers I, II, and III. Colour in preservation: dorsal surfaces of head and body uniformly fawn, some spines brown; dorsal surface of fore-and hind limbs light fawn; ventral surfaces of head, body, and limbs light grey (Fig. 1 ). Colour in life (based on other material studied): dorsum yellowish-brown, straw, light brown, or olive green, with or without grey or brown patches; and a pair of faint discontinuous dorsolateral lines; ventral surfaces greyish-white (Fig. 2 ).

Variation.

Adult size range: male SVL 54-69 mm, female SVL 60-72 mm. Morphometric data from five adult males, including the described syntype, is given in Table 1 . Dorsal colouration varies from light grey or brown to olive green; the amount and degree of prominence of granulation on dorsal skin variable.

Comparisons.

Duttaphrynus stomaticus differs from the Indian species: 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 other species found outside: D. crocus (Myanmar), D. kotagamai and D. noellerti (Sri Lanka), and D. totol (Indonesia), by the absence of cephalic ridges, absence of prominent or raised parotoid glands, and absence of distinct glandular warts or horny spinules (vs. present in all species). Due to the absence of cephalic ridges D. stomaticus could be confused with three Indian species D. beddomii , D. hololius , and D. peninsularis . However, D. stomaticus differs from D. beddomii in having a tympanum larger than eye diameter (vs. smaller), finger and toe tips lacking expanded discs (vs. with weakly-expanded discs), relatively reduced foot webbing, I1-1II1-2-III1-3IV3-1V (vs. more extensive, I1-1II1-1III1-2IV2-1V), and less prominent glandular warts or horny spinules on dorsum (vs. more prominent); from D. hololius , in having a stout body (vs. flattened or dorso-ventrally compressed), absence of a prominent or broad mid-dorsal line (vs. present), snout rounded in lateral view (vs. acute), dorsum with relatively more prominent smooth or spinular warts (vs. less prominent and scattered smooth tubercles), and moderate foot webbing, I1-1II1-2-III1-3IV3-1V (vs. rudimentary). For comparisons to D. brevirostris and D. peninsularis , see the respective comparison sections of those species.

Phylogenetic relationships and genetic distances.

Duttaphrynus stomaticus is a member of the Duttaphrynus stomaticus group (Fig. 3 ), within which it is more closely related to D. ' Duttaphrynus olivaceus ' and D. peninsularis than to D. dhufarensis and D. hololius . The studied populations of D. stomaticus exhibit intraspecific distances of 0-0.4% in 16S. The sequence divergence of D. stomaticus from other members of the D. stomaticus group is as follows: 0.2-0.6% from D. ' Duttaphrynus olivaceus ', 1.3-2.6% from D. peninsularis , 1.5-3.0% from D. dhufarensis , and 3.4-5.6% from D. hololius (Suppl. materal 1: Table S4).

Relationships within Duttaphrynus stomaticus group.

The close phylogenetic relationship of Duttaphrynus stomaticus with D. dhufarensis , D. hololius , D. olivaceus , and D. peninsularis is well-supported ( Van Bocxlaer et al. 2009; Portik and Papenfuss 2015; present study). Martin (1972) also discussed the absence of conspicuous cephalic ridges as a potential morphological synapomorphy for these species. Within this group, subsequently referred to as the Duttaphrynus stomaticus group ( Inger 1972; Dubois and Ohler 1999; Silva and Mendelson 1999; Van Bocxlaer et al. 2009), the taxonomic identity of D. olivaceus has been questionable due to the lack of sufficient morphological distinctness ( Dubois 1984; Balletto et al. 1985; Minton 1966) as well as shallow genetic divergence ( Portik and Papenfuss 2015; present study). Eiselt and Schmidtler (1973) regarded D. olivaceus as the subspecies of D. stomaticus . However, subsequent workers treated D. olivaceus as a distinct species closely related to D. stomaticus with relatively weak and variable morphological diagnostic characters, such as differences in the size of parotoid glands, number of subarticular tubercles on finger III, and weakly or well-developed tibial gland and tarsal folds ( Schmidtler and Schmidtler 1969; Khan 1987; Auffenberg and Rehman 1997). The available genetic data for D. stomaticus and D. olivaceus , along with new samples reported in this study for various D. stomaticus populations from India (including topotypic sequences) show a shallow divergence of 0.2-0.6% between the two species (Fig. 3 ).

Recently, Safaei-Mahroo and Ghaffari (2020) discussed the taxonomic status of D. olivaceus ( Frost 2021). This study also proposed a new genus name Firouzophrynus Safaei-Mahroo & Ghaffari, 2020 to accommodate a single species Duttaphrynus olivaceus ( Blanford 1874), which rendered the genus Duttaphrynus paraphyletic ( Frost 2021). Subsequently, based on phylogenetic evidence from selected taxa, Dubois et al. (2021) redelimited Firouzophrynus as a genus, while also stating the possibility of considering it as a subgenus, to include members of the Duttaphrynus stomaticus group as defined by Inger (1972) and Dubois and Ohler (1999). However, as noted by Frost (2021), there continues to be lack of clarity regarding the morphological and phylogenetic affinities of some other members of the group, which may have implications on the monophyly of Firouzophrynus . The composition of Duttaphrynus stomaticus species group and its phylogenetic position have been discussed by numerous studies ( Inger 1972; Martin 1972; Maxson 1981; Van Bocxlaer et al. 2009; Portik and Papenfuss 2015). However, only five species ( D. stomaticus , D. dhufarensis , D. hololius , D. olivaceus , and D. peninsularis ) currently are included in this group based on morphological ( Inger 1972; Martin 1972; Dubois and Ohler 1999; present study) and phylogenetic analyses ( Frost et al. 2006; Van Bocxlaer et al. 2009; Portik and Papenfuss 2015; this study). At least two other species from Indonesia, D. valhallae and D. sumatranus , that are known to lack cephalic ridges, a characteristic of the group ( Inger 1972; Dubois and Ohler 1999), require further studies to establish their systematic relationships. Although we do not doubt that Firouzophrynus could be recognised as a genus or subgenus, we currently consider the taxonomic status of this taxon uncertain, pending additional studies which may provide clarity, because of its cursory description and lack of a clear definition. Because it is beyond the scope of the present work to address this question, we have provisionally referred our focal taxa to the genus Duttaphrynus , sensu lato, and make use of previously defined species-groups, which could easily be adopted to an alternate classification, as more evidence concerning the recognition of Firouzophrynus becomes available.

Distribution and natural history.

Duttaphrynus stomaticus is one of the most widely-distributed species of the genus, occurring between elevations of sea-level to 2500 m asl in India (through Indo-Gangetic Plains, upper and lower Indus Valleys) and the neighbouring Bangladesh, Nepal, Pakistan (Balochistan), Afghanistan, and Iran (Suppl. materal 1: Table S1). This species is known to occur in varying climatic conditions and habitats, ranging from dry scrub forests, arid and semi-arid regions, hot and humid mixed forests, plains, and grasslands to drier and colder regions, montane woodlands and forests ( Choudhury et al. 2001; Mehta 2005; Deuti et al. 2014; Safaei-Mahroo et al. 2015). Genetically confirmed records of this species exist from India, Afghanistan, and Pakistan (Suppl. materal 1: Table S3). In the present study, we specifically confirm the presence of D. stomaticus in the Indian States of Assam, Bihar, Delhi, Punjab, Rajasthan, and Uttarakhand (Suppl. materal 1: Table S3) and also clarify the identity of some previously published DNA sequences from Peninsular India ( Van Bocxlaer et al. 2009; Shouche and Ghate 2007, unpublished GenBank data) as belonging to D. peninsularis . Hence, records of D. stomaticus from Peninsular India (south of Maharashtra and possibly Odisha) are currently presumed to be doubtful and will require verification of all known populations (see D. peninsularis for discussion). The reports of D. stomaticus from Karnataka and Tamil Nadu States ( Hegde 2012; Ramachandra et al. 2012; Seshadri et al. 2012; Ganesh et al. 2020) likely refer to D. peninsularis . A report of D. olivaceus from Gurgaon, India ( Ray and Deuti 2008) is also questionable ( Heydari and Rastegar-Pouyani 2010) and considered to represent D. stomaticus based on our fresh collections from Delhi and surrounding North Indian regions.

Duttaphrynus stomaticus is predominantly a nocturnal species. In this study, we found individuals of this species in urban, rural, and secondary forested areas during the breeding season (usually between May-August). Calling and breeding activities were observed in agricultural fields and temporary puddles in urban and rural landscapes, whereas inside secondary forests breeding was observed in shallow parts of flowing streams.

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.