Appearances are deceptive : molecular phylogeny recovers the Scaly Gecko Hemidactylus scabriceps ( Reptilia : Squamata : Gekkonidae ) as a member of a scansorial and rupicolous clade

We reassess the systematics of Hemidactylus scabriceps, a recently rediscovered and poorly known gecko, and elucidate its phylogenetic position using molecular data for the first time. Contrary to previous speculations prompted by its morphological resemblance to other terrestrial Hemidactylus, our phylogenetic analyses recovered H. scabriceps to be a part of a clade consisting of the large-bodied, rock-dwelling Hemidactylus – the H. prashadi group. Hemidactylus scabriceps also shows high levels of intraspecific genetic divergence, indicative of cryptic diversity. We also confirm the synonymy of the monotypic genus Lophopholis (erected for H. scabriceps) with Hemidactylus. We elaborate on the morphology of the type specimen and other recent voucher specimens, and compare it with sister species and other ground-dwelling Hemidactylus in peninsular India. Species distribution of this ‘outlier’ clade member has been modeled using MaxEnt. These exercises confirm that it is primarily a smooth-scaled, plain-dwelling, terrestrial species unlike other members in its clade. This unexpected pattern of genetic alliance and contrasting body form plus habitat associations further underscores the unstudied complexity of peninsular India’s geological history. Historical denudation of rock formations could have driven evolution of some of these otherwise rupicolous, scansorial gekkonids into smaller terrestrial lizards.


INTRODUCTION
Hemidactylus Oken, 1817 is one of the most speciose gekkonid genera in the world, with about 150 congeners currently recognized, of which around 34 are found in India (Carranza & Arnold 2006;Giri & Bauer 2008;Bauer et al. 2010;Uetz & Hošek 2018;Chaitanya et al. 2018).The Indian Hemidactylus are part of a tropical Asian radiation, and consist of five major clades -H.prashadi, H. flaviviridis, H. brookii, H. frenatus and H. platyurus groups (Bansal & Karanth 2010).Of these, the H. brookii group encompasses all the thus-far sampled ground-dwelling Hemidactylus that are found in central and peninsular India (Bansal & Karanth 2010;2013).Previous studies show that the ground dwelling clade of geckos are sister to H. brookii, the clade that consists of five currently recognized terrestrial species namely H. reticulatus Beddome, 1870, H. albofasciatus Grandison & Soman, 1963, H. satarensis Giri & Bauer, 2008, H. imbricatus Bauer, Giri, Greenbaum, Jackman, Dharne & Shouche, 2008, H. gracilis Blanford, 1870 (Bansal & Karanth 2010).Hemidactylus scabriceps was considered to be closely related to the ground-dwelling Hemidactylus due to its superficial morphological similarities such as a reduced subdigital scansorial apparatus, imbricate tail scales, reduced subcaudal scales and a terrestrial lifestyle (Bauer et al. 2010).Similar assumptions were made for Dravidogecko anamallensis (Günther, 1875) which was later resolved and found to be sister to the Indian Hemidactylus radiation (Bansal & Karanth 2013).In the past, H. scabriceps has been misidentified on many occasions with other marginally co-occurring terrestrial congeners such as H. reticulatus, despite its distinctive scalation (Ganesh et al. 2017).Annandale (1906) originally described this species as Teratolepis scabriceps based on its imbricate scalation, as the second congener next to T. fasciatus (currently H. imbricatus, after Bauer et al. 2008).Later, a new monotypic genus Lophopholis was erected by Smith & Deraniyagala, 1934 to accommodate this species as it was considered quite unique (Smith 1935).Parker & Taylor (1942) reassigned the species back to Teratolepis along with various other African geckos such as H. isolepis and H. ophiolepis, attributing this generic transfer to the imbricate scalation.Due to the similarity of H. scabriceps with other oriental Teratolepis and Hemidactylus geckos, it was called the 'Oriental imbricate-scaled Hemidactylus'.Subsequently, the generic allocation of this species was debated and later the genus Lophopholis was synonymized with Hemidactylus by Loveridge (1947).Furthermore, Bauer et al. (2008) synonymized the genus Teratolepis with Hemidactylus based on a multilocus molecular phylogeny and mentioned the possible close relationship of H. scabriceps with H. imbricatus (Image 5), along with other small-bodied, ground-dwelling endemic geckos such as H. albofasciatus, H. gracillis and H. reticulatus, which themselves are genetically-tested clade members (Bansal & Karanth 2010).
Since its description, H. scabriceps was not re-sighted for 104 years till an uncollected specimen was reported from Mayiladuthurai in the Coromandel Coastal Plains (Ganesh & Chandramouli 2010).
More recently, Ganesh et al. (2017) dug up some obscure publications reporting this species under a wrong name, described a series of preserved specimens including its hemipenal morphology, provided natural history notes and mapped its locality based on newer fieldwork.Hemidactylus scabriceps, however, still remains an intriguing gecko for both Indian and Sri Lankan herpetologists due to its assumed rarity and unknown phylogenetic relationships, since it is underrepresented and poorly sampled (Bauer et al. 2010).In this paper, we provide for the first time data on its phylogenetic position, elaborate on its morphology, habitat associations and distribution.

MATERIALS AND METHODS
Specimens of H. scabriceps were opportunistically collected from three ecoregions: Coimbatore plateau, Thanjavur delta and Kalakad foothills, abutting Western Ghats in peninsular India.The specimens were deposited in the collections of BNHS (Bombay Natural History Society, Mumbai), IISc -CES (Indian Institute of Science, Bengaluru -Center for Ecological studies), and IISER (Indian Institute of Science, Education and Research, Thiruvananthapuram). Tissue samples were collected from the tail tips and liver of the specimens and sent for molecular analysis and sequencing at the Indian Institute of Science (IISc), Bengaluru and Osmania University, Hyderabad.The geographic coordinates of the localities were obtained from Garmin 62 GPS.Other comparative materials, including the type specimens, were examined at the Natural History Museum, London (BMNH).

Morphological analysis
Morphological and meristic data were collected following methods described by Giri & Bauer (2008) and Mahony (2009) with Mitutoyo™ digital calipers (to the nearest 0.1mm).The following measurements were taken from collected specimens and the museum types: snout vent length (SVL; from tip of snout to vent), trunk 12149 length (TRL; distance from axilla to groin measured from posterior edge of forelimb insertion to anterior edge of hind limb insertion), body width (BW; maximum width of body), crus length (CL; from base of heel to knee); tail length (TL; from below vent to tip of tail), tail width (TW; measured at widest point of tail near the tail base); head length (HL; distance between retroarticular process of jaw and snout-tip), head width (HW; maximum width of head), head height (HH; maximum height of head, from occiput to underside of jaws), forearm length (FL; from base of palm to elbow); ear length (EL; longest dimension of ear); orbital diameter (OD; greatest diameter of orbit), nares to eye distance (NE; shortest distance between anterior most point of eye and nostril), snout to eye distance (SE; distance between anterior most point of eye and tip of snout), eye to ear distance (EE; distance from anterior edge of ear opening to posterior corner of eye), internarial distance (IN; distance between nares), interorbital distance (IO; shortest distance between left and right supraciliary scale rows).Scale counts and external observations of morphology, meristic characters were made using a Wild M5 dissecting microscope.

Species distribution modeling
Species distribution modeling was carried out using MaxEnt v.3.3 (Phillips et al. 2006), which is based on maximum entropy modeling.MaxEnt, a machine learning program that estimates the probable species distribution based on constraints of the environment.It uses presence-only data for prediction and studies show that it has good success rate for small sample sizes compared to other SDMs (Elith et al. 2006;Wisz et al. 2008).We have considered 21 environmental variables -the 19 bioclimatic layers, one topographic layer representing elevation (Hijmans et al. 2005) and one vegetation layer-NDVI (NRSC, ISRO).The 13 location points used in the model were obtained from the recent collections, literature which includes historical points Adayar (13.0012 0 N & 80.2565 0 E), and Maricukatte (8.588 0 N & 79.933 0 E).The environmental layers were derived from globally interpolated datasets observed from climate stations around the world.All the layers are of approximately 1,000m resolution, clipped for the Indian subcontinent including Sri Lanka and projected on WGS84 Lat-Long map datum.The layers were subjected to a multicollinearity test and 10 bioclimatic variables that were least correlated (Pearson's correlation coefficient r<0.85) were selected for the distribution modeling.
MaxEnt program with following changes was used in the model: auto feature for environmental variables was selected.The random test percentage was set to 20%, making the training percentage 75%.The regularization multiplier and maximum number of background points for sampling was kept at 1 and 10,000 respectively.With subsampling as replicating model, 15 replicates were used.Maximum iterations were set to 5,000, with 10 -5 as convergence threshold with threshold rule of 10 percentile training presence as it relatively better at predicting suitable habitat for endemic species (Escalante et al. 2013).The logistic output of the model shows the suitability of the habitat, graded over a range of 0 to 1.

Molecular analysis
Genomic DNA was isolated from 95-100 % ethanol preserved liver tissue sample using phenol: chloroform: isoamyl alcohol reagent (25:24:1 v/v) as described by Sambrook & Russell (2001).Two partial mitochondrial markers, cytochrome b (cyt b) and NADH dehydrogenase 2 (ND2) along with two nuclear markers, Recombination Activation Gene 1 (RAG-1), Phosducin (PDC) were used to infer the phylogeny of H. scabriceps (see Agarwal et al. 2011).These molecular markers were useful for resolving the phylogenetic relationships at deeper nodes.Primers and PCR conditions used were as described in Bauer et al. (2008).PCR products were purified and sequences were obtained commercially from Bioserve Biotechnologies, Hyderabad, India.All PCR amplifications were carried out in 25µL reaction volumes, with 12.5µL of the 2X PCR master mix (Thermo Scientific), 0.5µL forward primer, 0.5µL reverse primer (10 pm/ µL concentration each) and 2µL template DNA added and the final volume was adjusted with nucleasefree water.Reactions were carried out with Thermo Scientific Mastercycler gradient thermocycler.The sequence integrity was analyzed by BLAST tool (Altschul et al. 1997), processed and submitted to NCBI GenBank under the accession numbers given in Table 3 (Appendix 1).

Phylogenetic analysis
The mitochondrial genes cyt b (379 bp), ND2 (981 bp) and the nuclear genes PDC (400 bp) and RAG-1 (1000 bp) sequences of representative members of major, well supported Hemidactylus groups -H.flaviviridis, H. brookii, H. prashadi and H. frenatus (Bansal & Karanth 2010, 2013;Murthy et al. 2015;Giri et al. 2017;Chaitanya et al. 2018) were downloaded from GenBank (accession numbers listed in Table 3 in the appendix).Sequences were aligned with default gap penalties using ClustalW (Thompson et al. 1994) in MEGA 7.0. (Tamura et al. 12150 2011).Protein-coding genes were translated to amino acids to check for the reading frame and premature stop codons.Uncorrected pairwise distances were calculated using the inbuilt program in MEGA.
Sequences of the members of the H. brookii sensu lato group that were published prior to the revisions of the group (Mahony 2011;Lajmi et al. 2016) were labeled as H. brookii due to the inability to trace and identify the specimens from which the sequences were derived.The same revision, however, shows that the group including the ground-dwelling Hemidactylus is monophyletic and is sister to the H. frenatus group.Hence, the H. brookii epithet is used here indicating individuals that may represent H. murrayi, H. gleadowi, H. treutleri, H. kushmorensis or H. parvimaculatus (Lanfear et al. 2012).
We used Partition Finder 2.1.1 to pick the partitions and best substitution model for the analysis.The concatenated gene dataset (cyt b, ND2, PDC and RAG1) comprise a total of 2760 bp.We built a maximum likelihood (ML) tree in RAxML HPC 7.4.2through RAxMLGUI v1.3.1 (Silvestro & Michalak 2012) by running ML + thorough bootstrap for 10 runs and 1000 repetitions.

Molecular phylogeny and relationships
Our tree (Image 1) recovered From a broader perspective, the ML analyses on the concatenated dataset with sequence lengths of 2760 bp yielded a tree (Image 1) of similar topology to previous studies (Chaitanya et al. 2018).Comparing tree topologies from prior works corroborated the integrity of our trees.Dravidogecko anamallensis is sister to all Indian Hemidactylus that consists of four well-supported groups, H. flaviviridis, H. brookii, H. prashadi and H. frenatus (Bansal & Karanth 2010;2013).As previously known, H. brookii sensu lato is sister to the H. frenatus group; while H. scabriceps falls within the H. prashadi group (support seen in tree).The relationship of H. scabriceps with other rock-dwelling Indian and Sri Lankan Hemidactylus is strongly supported in our tree.
From a species-specific viewpoint, the pairwise distance matrix revealed 6% divergence in the cyt b gene between the two individuals of H. scabriceps sampled from different localities (Thanjavur and Coimbatore).The genetic distance between H. scabriceps and other species of the H. prashadi and H. brooki clades are given in Table 1.The high genetic divergence between the populations sampled may indicate that H. scabriceps could be a potential species complex that requires further study.

Morphology and body configurations (n=7, in mm) (Images 2 & 3)
A small-sized Hemidactylus (30.1-41.3);head short (9.6-13.8);distinct from neck; head broader (4.3-7.4)than high (3.9-6.9);forehead flat; snout (3.5-4.6)longer than orbital diameter (1.0-2.7);snout concave; covered with heterogeneous granular scales; scales on head keeled; small warty scales on parietal region intermixed with granular scales; scales largest on canthal region, size similar to tubercles on parietal region; pupil vertically elliptical with sharp crenellated edges, supraciliaries large when compared to scales on canthal region; pointed posteriorly; becoming smaller and less pointed towards posterior; spinose posteriorly; nostrils close to snout-tip (2.8-3.0),moderately wide (1.3-2.7),fairly close to eye (2.3-3.5);ear opening small (0.2-1.5); orbital diameter slightly smaller than orbit to ear distance; eyes distant from each other (1.4-3.8);rostral large; subrectangular to pentagonal in shape; in contact with nostril and the 1 st supralabial, medial groove dorsally, extending more than half the length of the rostral depth; supralabials 7/7 (left/right); infralabials 6/6 (left/right); mental triangular; two pairs of post mentals, inner pair in contact with mental and each other, outer pair not in contact with each other; a pair of smaller chin shields in contact with the outer postmentals followed by elongated shields in two rows in contact with the infralabials; no chin shields posterior to the postmentals; a row of smaller, slightly elongated scales with slightly pentagonal scales wedged in the intersection of the postmental scales; gular covered with small granular scales; trunk of moderate size (13.1-20.7);body slightly depressed, oval in crosssection, dorsolateral fold weak to indistinct; dorsum covered with mildly keeled, imbricate scales with no tubercles; granular scales from head gradually changing into sub-imbricate scales on nape and imbricate scales towards torso; mild keels on dorsal scales distinct, gradually disappearing towards ventral scales, scales at paravertebral line comparatively smaller than other   stripes across the body found; smaller white and black spots intermixed with the light brown parts of the body; head covered with dark and light-colored spots, labials characterized with a black patch forming a stripe pattern throughout the labials, sometimes extending into stripes in the gular region; venter dirty white, rarely with small black dots; mental shields with small black blotches; manus and pes darker beneath.indicating that the resultant model is reliable.

Distribution and niche modeling
The relative contribution (approx.) of the environmental variables to the MaxEnt model is as shown in Table 4.It is observed that the following variables are the major contributors to the model -bio2 (mean diurnal temperature range), bio12 (Annual Precipitation) and alt12 (altitude) signifying that the habitat most suitable for H. scabriceps is low altitudes, less rainfall and relatively less change in maximum and minimum temperature with annual mean temperature of approximately around 28.5 0 C.
As per the output of MaxEnt modeling (Image 4), H. scabriceps is predicted to be distributed from the far south of Tamil Nadu (including Tirunelveli and Tuticorin) northwest till about Coimbatore, northeastwards till about Madras (currently Chennai), with high possibilities of being present in dry parts of northern Sri Lanka.This species is possibly confined to this range within the dry parts of Tamil Nadu, Kerala and Sri Lanka, bound by the Western and Eastern Ghats; and the highlands in central Sri Lanka.

DISCUSSION
Hemidactylus scabriceps is a member of a clade comprising large-bodied, rock-dwelling, scansorial geckos, although it has a small terrestrial body-build and is found in low-elevation plains that are not dominated by rock formations.Our new molecular phylogenetic analyses provide a radically different and contrasting relationship for Hemidactylus scabriceps, as shown in Image 1.To untangle this complex interplay between morphology, habitat associations / distribution and genetic relationships, we herein elaborate on these three seemingly disparate features and discuss their dynamics in light of potential evolutionary trajectories that might have acted upon this species shaping it into what it is now.
The morphological characterization and ecological data of our new individuals are for the most part in conformity with literature reports (Annandale 1906;Smith 1935;Ganesh & Chandramouli 2010;Ganesh et al. 2017).Another important facet of morphology of H. scabriceps is the persistence of transverse series of white spots / dotted lines across the trunk, typical of all the known members of H. prashadi group and absent in H. albofasciatus, H. imbricatus, H. reticulatus and H. sataraensis (Smith 1935;Bauer et al. 2008;Giri & Bauer 2008).We postulate that the white spots and barred pattern on the back are a synapomorphy of the H. prashadi clade, present either bold or diffuse in all of its members.Based on our phylogeny we postulate that the under-developed or rudimentary claws and digits in general, along with the partial fusion of digital lamellae of H. scabriceps, are ecologically derived traits consequent upon a strictly terrestrial lifestyle.Similar to the phenotypically biased taxonomic allocations that taxa from the H. brookii clade have had, the current study confirms that the genus Lophopholis, originally erected for H. scabriceps, is actually a synonym of Hemidactylus (also see Bauer et al. 2008).
We observed this species in grassland/ dry thorn scrub jungle dominated by palmyra trees, in coconut grove and paddy fields.The species is strictly nocturnal, found resting under rocks during the day, preferably on mounds of gravel under moderately large rocks.It was repeatedly observed to be in a 's' shaped position under rocks and trying to stay still and not trying to get away while the rock was disturbed.This behavior was also observed in H. reticulatus (Ganesh et al. 2017;this work) and H. sataraensis (see Bauer & Giri 2008).It is also common for H. scabriceps to be found in sympatry with H. triedrus (Image 8).Some specimens were also found inside termite-eaten and weathered palm and coconut logs, leaves and fruits.This species was observed to be highly territorial.Two individual male specimens in the same vicinity showed territorial behavior, circling each other making chirping calls to each other (the only time the species was heard vocalizing) with a raised waving tail, stretched legs and arched body, and trying to bite at the neck of opponent male.Individuals were found to occur at quite a distance from one another (15-20 m).Thus our observations on the microhabitat associations of H. scabriceps along with previously published notes (Ganesh & Chandramouli 2010;Ganesh et al. 2017) do attest its strictly terrestrial lifestyle.
We found some of our adult male individuals to have either 2 or 4 pores on a single side, whereas it usually numbers 3 (Ganesh et al. 2017).Such variations in characters of diagnostic importance in gecko taxonomy, coupled with high levels (6% in cyt b) of inter-individual genetic divergence point out to the possibility of cryptic speciation within this complex.It is also noteworthy to highlight that though the original description (Annandale 1906) and subsequent expanded characterizations, both historical (Smith 1935) and recent (Ganesh & Chandramouli 2010;Ganesh et al. 2017) of this species still stems from Coromandel Coastal Plains population, except for the sole record of a specimen from near Madurai (see Ganesh et al. 2017).
Thus the current study describes previously

© M. Rameshwaran
unsampled populations from Coimbatore near the foothills of the Western Ghats, a different ecoregion altogether.Even here, we observed fine-scale landscape partitioning between H. scabriceps and the ecologically similar H. reticulatus (see Ganesh et al. 2017).This makes H. scabriceps the only member of H. prashadi clade to be distributed exclusively in a primarily sandy alluvial plains terrain not dominated by rock outcrops.The loose occurrence of individuals of H. scabriceps at some distance between each other was observed to be similar to other Hemidactylus species such as H. mabouia (see Regalado 2003).Our niche distribution model shows an indication that rivers Cauvery and Amaravathi (a tributary of Cauvery) could be geographic barriers between the Coimbatore plateau population and the Cauvery delta and Palk Strait populations, which might explain the high genetic divergence between the individuals sampled from these distinct populations.Other ground-dwelling Hemidactylus occur both in the H. prashadi and the H. brookii clades.In the H. prashadi clade, in as far as is known, only H. triedrus is terrestrial and is currently known to be distributed in most of the dry zones of peninsular India including the transitional zones of the Western Ghats.From the H. brookii clade, H. reticulatus is a similarly distributed terrestrial species, closely associated with rocky habitats.Hemidactylus gracillis has its close affinities with black soil throughout its distribution in central India and northern peninsular India, while H. albofasciatus and H. satarensis are distributed in parts of the northern Western Ghats occupying rocky plateaus.Hemidactylus scabriceps occupies the dry zone of Tamil Nadu and northern Sri Lanka (rainfall <1,000mm/year), restricting itself to the grasslands of the alluvial plains and sandy regions in Northern Sri Lanka and towards the east of Tamil Nadu and red soils towards its west in the Tamil Nadu uplands till the foothills of the Western Ghats.The rocky outcrops in Tamil Nadu (both Eastern and Western Ghats), though interrupted by H. scabriceps habitat, are occupied by H. reticulatus.Both the Western and Eastern Ghats in the west and north respectively restrict H. scabriceps within Tamil Nadu.Informed by our MaxEnt analysis, we hypothesize that the farthest inland locality of H. scabriceps disclosed herein (Coimbatore) is inhabited by this species largely because of the deep erosion of the plateau created by the Cauvery River system, engraving a low, alluvial, plains ecosystem into the table-land, much far west than in other nearby parts of the peninsula.This scenario is comparable to the Moyar Gorge being an important biogeographic barrier for terrestrial lizards such as Sitana sp. that are predominantly plateau dwelling (Deepak & Karanth 2018).Hemidactylus scabriceps also shows the contrast of shared fauna between the dry zones of Tamil Nadu and Sri Lanka (Guptha et al. 2015;Deepak et al. 2016;Deepak & Karanth 2018).
Our findings have a direct bearing on the evolutionary history of this species.The inferred trees from the current work showed strong support for the previously known groups-H.prashadi, H. flaviviridis, H. brookii, H. frenatus and H. platyurus.From our study, it is also revealed that H. scabriceps belongs to the H. prashadi group (recognized by Bansal & Karanth 2010).The reduced subdigital scansoral apparatus, imbricate tail scales, imbricate dorsal scales, reduced subcaudal scales and a terrestrial lifestyle are traits that seem to be visually convergent within sub-groups of Hemidactylus geckos both from Africa (H.isolepis, H. ophiolepis) and India (H.imbricatus) (Bauer et al. 2008).The ground dwelling clade of geckos that share similar traits was previously known to be sister to the H. brookii group of geckos and H. scabriceps was assumed to be related to this group (Bauer et al. 2008).Our phylogenetic analysis reveals that H. scabriceps is related to the large rock dwelling clade of geckos contrary to what was previously assumed prompted by morphological similarity.
The unexpected and contrasting genetic relationship of the morphologically and ecologically discordant H. scabriceps and H. prashadi group underscores the complexity of peninsular India's geological history.Previous studies on peninsular India's terrestrial lizard species have all revealed such discordant patterns of genetic alliance and eco-morphology.Agarwal & Karanth's (2015) molecular phylogenetic analyses revealed that the fat-bodied, forest-floor dwelling taxa 'Geckoella' is actually a part of primarily scansorial and rupicolous Cyrtodactylus radiation.Deepak et al.'s (2015) study on 'Brachysaura' minor also points out a similar structure, i.e. the short body form and completely terrestrial habits of that taxon, contrary to its arboreal congeners in the genus Calotes, is nothing but a result of reduction in tree cover and other associated landscape changes (Stromberg 2011;Ponton et al. 2012).Similarly, the Miocene landscape changes such as aridification of the Indian sub-continent has shown large influence on lizard groups such as Cyrtodactylus, Ophisops, Sitana and Sarada in the Indian subcontinent (Agarwal & Karanth 2015;Agarwal & Ramakrishnan 2017;Deepak & Karanth 2018).Similar to the phenotypically biased taxonomic allocations the above taxa have had, the current study confirms that the genus Lophopholis, originally erected for H. scabriceps, is actually a synonym of Hemidactylus (also see Bauer et al. 2008).
Although previous studies on other peninsular Indian lizard taxa have revealed such unexpected yet consistent patterns of genetic and eco-morphological discordance, such an instance within the better-studied Indian Hemidactylus radiation (Bansal & Karanth 2010;2013;Bauer et al. 2008Bauer et al. , 2010) ) exhibiting this sharp a contrast is without precedent.This is particularly intriguing, especially when another member of the H. prashadi clade, H. triedrus, occurring in areas inhabited by H. scabriceps (see Smith 1935) can afford to survive in sandy low-elevation alluvial tracts without changing its body form too much.But it must be borne in mind that though H. triedrus occurs in plains habitat it could still scale vertical rock surfaces when such formations are present within its range, whereas H. scabriceps cannot (Ganesh et al. 2017;this work).Additionally, in most of the range of H. scabriceps, there are no other strictly-terrestrial geckoes, neither Hemidactylus nor other genera (Smith 1935;Somaweera & Somaweera 2009;Ganesh et al. 2017;this work), thereby throwing open prospects of an empty niche for a potential species to exploit.Thus the current work brings to light a case of so far hidden historical competition between a eurytopic (H.triedrus, H. lankae) versus a stenotopic (H.scabriceps) clade member.These species are geographically sympatric (Image 6), in India and Sri Lanka respectively, genetically related but morphologically very different (see Image 1).This sharp discordance amply illustrates the complex interplay of historical landscape changes, eco-morphological reactions and resource-use competition.

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Image 1. ML tree constructed using cyt b, ND2 mitochondrial sequences and RAG1, PDC nuclear sequences representing the Indian groups of Hemidactylus.Bootstrap support values are mentioned in the nodes.Specimens of Hemidactylus scabriceps are suffixed with the location collected from (Cbe-Coimbatore and Tan-Thanjavur).The taxa highlighted in grey denote the plains dwelling taxa.A visual comparison of Dorsal scale images of representative clades are as follows: (1) H.
Hemidactylus scabriceps has so far been recorded from the dry, low-elevation plains of Tamil Nadu ranging from 10 to 380 m (Image 4).In the Coromandel Coastal Plains this species is known from Adayar (in Madras) near Palar Bay, southwards to Mannampandal near Cauvery Delta, further down in Ramanathapuram and Thoothukudi north and south of the Palk Strait, respectively.Apart from the earlier records we sighted this species from Thitai (11.083 0 N & 77.031 0 E; 44m) in Thanjavur Delta region, Kalapatti (11.083 0 N & 77.0317 0 E, 385m) further westwards in the Coimbatore Plateau, south in Pottal (8.644 0 N & 77.484 0 E, 77m) just east of Tirunelveli foothills and Mariccukatte (Marichchukkaddi) in Sri Lanka (8.580 0 N & 79.946 0 E).The input for species distribution modeling are nine least correlated bioclim variables, altitude and NDVI layers with 13 sample locations of the species.The logistic output of the model shows the suitability of the habitat, graded over a range of 0-1.A binary map is created indicating suitable and unsuitable habitat for occurrence of H. scabriceps.A threshold of 0.3491 was selected to classify the suitability which is the average value of the threshold rule used for the MaxEnt model.The AUC for the run/model is above 0.9 showing high goodness of fit.The AUC value of the model is 0.987 Image 4. Habitat Suitability Map projected based on MaxEnt modeling of H. scabriceps occurrences (both previously published and new) in India and Sri Lanka, revealing dry-zone plains (green shade) abutting Coromandel Coast, Cauvery flood-plains and dry peneplain of Sri Lanka as its realised range.Image 5. Habitat spectrum of H. scabriceps in India (left) rocky habitat from the most inland locality Kalapatti, Coimbatore; (right) sandy habitat of H. scabriceps from the most coastal locality Mandapam, Rameshwaram.
H. scabriceps as member of a clade containing H. triedrus of peninsular Indian plains, H. lankae of Sri Lankan plains, H. maculatus of the northern Western Ghats, H. prashadi of central Western Ghats, H. acanthopholis and H. vanam of southern Western Ghats, H. hunae of Sri Lankan hill tracts, H. graniticolus of southern Eastern Ghats, H. sushilduttai and H. kangenerensis of northern Eastern Ghats and Chota Nagpur plateau, and more closely with H. depressus of Sri Lanka.

Table 1 . Percentage values of uncorrected pairwise divergence (p-distance) for the cyt b, RAG-1, PDC and ND2 genes between the closely related congeners of H. scabriceps and morphologically similar members of H. prashadi and H. brookii clades. The percentage divergence of cyt b gene between the two specimens of H. scabriceps used in this study is 6.3 %.
# -syntopic clade-member in Sri Lanka.

Table 3 . List of specimens used for the molecular analysis and genetic comparison with the museum numbers, localities and GenBank accession numbers. Highlighted species are the samples used in this study.
of Threatened Taxa | www.threatenedtaxa.org| 26 August 2018 | 10(9): 12147-12162