The Knight and the King: two new species of giant bent-toed gecko (Cyrtodactylus, Gekkonidae, Squamata) from northern New Guinea, with comments on endemism in the North Papuan Mountains

Abstract The diverse biota of New Guinea includes many nominally widespread species that actually comprise multiple deeply divergent lineages with more localised histories of evolution. Here we investigate the systematics of the very large geckos of the Cyrtodactylus novaeguineae complex using molecular and morphological data. These data reveal two widespread and divergent lineages that can be distinguished from each other, and from type material of Cyrtodactylus novaeguineae, by aspects of size, build, coloration and male scalation. On the basis of these differences we describe two new species. Both have wide distributions that overlap extensively in the foothill forests of the North Papuan Mountains, however one is seemingly restricted to hill and lower montane forests on the ranges themselves, while the other is more widespread throughout the surrounding lowlands. The taxon endemic to the North Papuan Mountains is related to an apparently lowland form currently known only from Waigeo and Batanta Island far to the west – hinting at a history on island arcs that accreted to form the North Papuan Mountains.


Introduction
Integrated morphological and molecular investigations of the exceptionally diverse biota of New Guinea are confirming that many nominally widespread species comprise multiple deeply divergent lineages (Donnellan and Aplin 1989;Oliver et al. 2013;Georges et al. 2014). In turn, as estimates of lineage diversity and phylogenetic relationships improve, so too does our understanding of patterns of regional and elevational endemicity and turnover, and the processes that have shaped them -most notably the complex geological history and extreme topography of New Guinea (Unmack et al. 2013;Toussiant et al. 2014).
The Bent-toed geckos (Cyrtodactylus) are the most species-rich radiation of geckos in the world Uetz 2015). Cyrtodactylus diversity is concentrated in Indochina, South-east Asia and the Greater Sunda islands, however the clade extends from India and Sri Lanka in the west, the Himalayas in the north, through southeast Asia to the Philippines, Lesser Sundas, New Guinea and into northern Australia . Within the south-eastern region of this distribution New Guinea and surrounding islands are a centre of diversity, with an endemic radiation of at least 25 species, a majority of which have only been recognised in the last decade (Kraus and Allison 2006;Kraus 2007Kraus , 2008Rösler et al. 2007;Oliver et al. 2008Oliver et al. , 2009. Recent work has also indicated that the main Papuan lineage has evolved in at least one novel direction -it includes several lineages that are significantly larger than other Cyrtodactylus (SVL > 160 mm) (Zweifel 1980;Kraus 2007Kraus , 2008Oliver et al. 2008;Bauer 2013;Oliver et al. 2014).
Cyrtodactylus novaeguineae Schlegel (1837) is the largest of these giant Cyrtodactylus, with a maximum recorded snout-vent length in excess of 170 mm (Zweifel 1980;Bauer 2013). While the type locality of Cyrtodactylus novaeguineae is in the Triton Bay area (now in Papua Barat Province) on the southern edge of the 'Bird's Neck' in western New Guinea (Schlegel 1837), specimens from a wide range of localities both north and south of New Guinea's Central Cordillera are currently assigned to this species (Brongesma 1934;Zweifel 1980;Kraus 2008) -generally on the basis that they possess enlarged tubercles extending onto and often across the posterior region of the throat (Zweifel 1980;Rosler et al. 2007;Kraus 2008).
Here we present an analysis of genetic and morphological variation within geckos referred to Cyrtodactylus novaeguineae from across New Guinea (with a focus on the much better sampled eastern half of the island). These data reveal two genetically and morphologically distinct lineages in northern New Guinea that are not conspecific with this nominal taxon -and which we therefore describe as new taxa. We also review the biogeography of these geckos in the context of recent phylogenetic investigations into the role that orogeny and arc accretion has played in shaping the biota of northern New Guinea.

Genetics
Sequence data from the NADH dehydrogenase subunit 2 (ND2) for 13 nominal C. novaeguineae were aligned with a subset of Papuan Cyrtodactylus sequence data published elsewhere, and chosen to include all potential close relatives . GenBank accession numbers and associated specimen data for newly amplified material are given in Appendix 2. Laboratory protocols largely followed Sistrom et al. (2009). ND2 and partial flanking tRNAs were amplified using the primers M112F (5'-AAGCTTTCGGGGCCCATACC-3') and M1123R (5'-GCTTAATTAAAGT-GTYTGAGTTGC -3') designed in the flanking Methionine and Alanine tRNAs.
Our final alignment included up to 987 bp of data and was aligned using the MUSCLE algorithm (Edgar 2004) in Geneious version 6.0.5 (Biomatters 2012), and subsequently checked by eye. Phylogenetic trees were estimated using standard maximum Likelihood (RAxML v7.2.8;Stamakakis 2006) analyses implemented on the CIPRES web portal version 3.1 for online phylogenetic analysis (www.phylo.org/por-tal2). Data were not partitioned by codon (first, second and third base positions) and analyses were run using the default settings for RAxML on the CIPRES portal -the GTRGAMMA model of sequence evolution and ceasing bootstrapping when MREbootstrapping criteria had been reached.

Morphology
Measurements taken with digital calipers to the nearest 0.1 mm largely follow Kraus (2006): snout-vent length (SVL), tail length (from the posterior edge of the vent to the tip of the tail) (TL), total length of original portion of tail (OT), trunk length from posterior edge of axilla to anterior edge of groin with limbs held at right angles (TrK), maximum head width (HW), maximum head height (HH), head length from tip of snout to anterior margin of ear opening (HL), distance from posterior edge of naris to eye (EN) (used as a proxy for snout-length), transverse diameter of eye (EYE), internarial distance (IN), transverse diameter of ear (EAR), forearm length from base of palm to outer edge of elbow (FA), and crus length from base of heel to outer edge of knee (CS).
We counted left and right enlarged supralabials to both the midpoint of the eye and to the rictus, left and right infralabials to rictus, dorsal tubercle rows between the lateral folds (not including the lateral fold) at the midpoint of body, ventrals at midpoint of the body in transverse series between ventral folds, the number of narrow lamallae distal to the inflection of the digit (not including the claw sheath), the number of wide subdigital lamellae proximal to the inflection of the joint under the first and fourth digits of the left manus and pes, precloacal and femoral pores where present, and postcloacal tubercles. Finally, we also recorded the extent of large tubercles on the lower jaw: absent, extending to the infra-angular region only, or extending across the throat.

Genetics
We identify three major mitochondrial lineages of 'C. novaeguineae': 'south' -from three sites to the south of the Central Cordillera in Western and Gulf Provinces of Papua New Guinea; 'north 1' -North Papuan Mountains (Foja, Bewani and Torricelli Mountains); and 'north 2' -northern lowlands and foothills of Papua New Guinea from close to the Indonesian border in Sandaun Province east as far as Morobe Province. A clade comprising 'north 1', 'south', and Cyrtodactylus zugi from Batanta Island off the western coast of New Guinea is strongly supported. Within this clade there is strong support for the close relationship of C. zugi and 'north 1' (Figure 1). The 'north 2' lineage is more divergent, but a clade comprising all members of the novaeguineae group and its inferred closest relative Cyrtodactylus mimikanus (see  is supported. Mean levels of ND2 sequence divergence between these four clades calculated using the Jukes Cantor Model ranges from (13.6-15.7%). There is evidence of additional mitochondrial structure in 'north 1' (mean 4.9%, max 7.5%) and 'north 2' (mean 4.7%, max 8.1%), but low diversity between samples of 'south' (mean 0.01%, max 0.01%).

Morphology
Each of the three genetic lineages shows consistent differences in colour pattern, body size and aspects of scalation (see further details in Table 1, Figures 2-5, and comparisons below). The 'south' lineage is characterised by smaller size, narrow head ( Figure  2), low number of ventral scales in transverse series, higher number of and darker and  unbroken dorsal bands (Figure 3), plain venter and unbroken pore series in males. The 'north 1' lineage is of intermediate size, has a broad head (Figure 2), higher number of ventral scales, a dorsal colour pattern consisting of three relatively indistinct light brown transverse bands or patches on a light greyish brown background (Figure 4), a relatively plain venter with at most scattered small dark brown maculations, and a widely broken pore series in males. Finally, 'north 2' is distinctly larger, has a broad head (Figure 2), high number of ventral scales, a 'messier' three toned dorsal colour pattern comprising alternating but indistinctly defined regions of dark brown, medium grey and light grey to dirty off white ( Figure 5), extensive amounts of dark-brown barring underneath the throat ( Figure 2) and often also on the ventral surfaces of the body, and a generally continuous pore series in the males.

Systematics
Concordant patterns of genetic and morphological variation indicate that at least three evolutionarily distinct lineages (species) have been confounded within Cyrtodactylus novaeguineae. No genetic samples are available from the vicinity of the type locality so determining which, if any, of these populations represents true C. novaeguineae relies on comparisons of morphology. The two male syntypes of C. novaeguineae (RENA (formerly RMNH) 2708A-B) are of relatively small size (SVL 115 and 129 mm) with narrow heads (HW/SVL 0.18 and 0.19), and continuous to near-continuous pore series (divided only by one or two medial scales).This combination of morphological characters clearly distinguishes the types from both of the 'north' lineages, but does not distinguish them from the lineage we refer to here as 'south'. A colour plate accompanying the description of C. novaeguineae (Schlegel, 1834)presumably of one of the syntypes although this is not clear -shows three continuous and clearly defined brown dorsal bands ( Figure 6). Recently collected specimens of 'south' also have strong dorsal bands, but usually have four instead of three. Unfortunately the colour patterns illustrated by Schlegel are no longer evident on the types and Schlegel does not report whether the non-illustrated material had a different number of dorsal bands. Nearly one thousand kilometres separates the type locality of C. novaeguineae from the nearest locality for genetically typed 'south' lineage. Brongersma (1934) lists additional samples from southern New Guinea, especially from around the Lorentz River, however there are again few recent collections from this area and none with matching tissue samples. Given the limited morphological divergence between material from 'south' populations and the types of C. novaeguineae, and the lack of genetic and colour pattern data for the population from the type locality, we conservatively consider the 'south' population to represent easternmost populations of C. novaeguineae at this stage.
The populations from southern New Guinea that we here refer to C. novaeguineae can be distinguished from other Papuan Cyrtodactylus by the following unique combination of characters -moderately large size (SVL to 129 mm), narrow head (HW/SVL 0.18-0.19), enlarged tubercles on the infra-angular region and often extending across the posterior region of the throat, mid dorsal tubercles in 21 to 22 rows at midpoint of body, subcaudal scales not transversely widened, moderate number of mid-body ventral scales (31-44) and a continuous or near-continuous, relatively straight, row of femoral and precloacal pores in adult males (up to at least 43 pores in total).
The two northern forms ('north 1' and 'north 2') differ from C. novaeguineae from southern New Guinea (including the types) in having broader heads and in being of slightly to much larger size ( Figure 2). The 'north 1' lineage also has a discontinuous series of femoral and preclocal pores divided by one or two regions of poreless scales. We consider that these characters, coupled with substantial genetic divergence be-  tween the northern lineages and southern C. novaeguineae, and between 'north 1' and 'north 2' are sufficient to differentiate these two lineages and we present their formal descriptions below. Diagnosis. A large Cyrtodactylus (SVL to 139 mm), with a moderately broad head (HW/SVL 0.19-0.22), enlarged tubercles on the infra-angular region and often extending across the posterior throat, mid-dorsal tubercles in 19 to 25 rows at midpoint of body, subcaudal scales not transversely widened, high number of mid-body ventral scale rows (42-59), femoral pores in two separated rows of 9-19, usually with a further medial precloacal row of 6-13 pores (up to 39 pores in total), venter relatively plain brown with at most scattered darker brown maculations, and dorsum with three distinct to indistinct medium-brown transverse bands on relatively plain light brownishgrey background.

Cyrtodactylus equestris
Description of holotype. A moderately large (113 mm SVL) and slender gecko. Head large (HL/SVL 0.28), moderately wide (HW/SVL 0.21) and clearly distinct from neck. Snout rounded in dorsal profile, broadly truncate in lateral profile, eye to naris distance longer than eye diameter (EN/EYE 1.4), loreal region slightly inflated, interorbital region and top of snout concave, canthus rostralis rounded, weakly defined. Eyes large (EYE/HL 0.26), pupil vertical, supraciliaries extending from anter- oventral to posterodorsal edge of orbit, longest at the anterodorsal corner. Ear opening rounded, bordered by distinct dorsal skin fold.
Rostral rectangular, wider than high, with medial suture extending approximately halfway from dorsal edge towards ventral edge, bordered dorsally by two flattened nasals and single tiny internasal. Nares bordered by first supralabial (point contact), rostral, nasal, 2-3 enlarged postnasals and 2-3 tiny granular postnasals. Supralabials generally wider than high, 10 on right, 11 on left, 8 to midpoint of eye. Head, temporal and nuchal scales small and granular, interspersed with numerous enlarged weakly conical tubercles, approximately 3-4 times width of surrounding scales, on temporal and posterior nuchal regions. Enlarged infralabials slightly to much wider than high, 11 on right and 10 on left, bordered by rows of slightly enlarged scales that grade into small granular gular scales. Mental slightly wider than long, broadly triangular, but with distinctly concave edges at contact with postmentals, in contact with first infralabials. Scattered small conical tubercles (approximately twice size of surrounding scales) in the infra-angular regions of the lower jaw only.
Body moderately robust (TrK/SVL 0.44) with distinct ventrolateral folds. Moderately tuberculate, tubercles along lateral fold heterogeneous, up to 3 times larger than surrounding scales. Dorsum with approximately 23 rows (not including lateral fold) of often keeled tubercles up to 4 times width of surrounding granular scales. Ventral scales much larger than dorsal scales, increasing in size medially, arranged in approximately 39 rows at midpoint of body. Several continuous rows of enlarged femoral scales, posterior row extending almost to knee, distinctly larger and contrasting against granular posterior femorals. Precloacal pores in a series of 8, femoral pores in individual series of 15-16, respective series separated by 7 poreless scales.
Tail almost completely regrown, scalation heterogeneous and irregular. Cloacal sacs swollen and prominent, each with 3 rounded cloacal spurs at anterior edge. Color in ethanol. Dorsal pattern consisting of alternating light brown and medium brown regions. Nuchal band medium brown, posterior edge triangular with thin continuous dark brown margin and extending along dorsum to level of forelimb insertion, anterior edge deeply notched and less clearly margined. Nuchal dark band bordered posteriorly by a deeply notched light brown band with distinct thin dark brown edging on medial anterior and posterior edges, and extending anteriorly onto lower jaw. Subsequent dark bands not deeply notched and less distinctly margined, but generally with at least some dark brown edging at their midpoint. Dorsal surface of head medium brown, darker anteriorly, without pattern, with the exception of a pair of small curved dark brown lines on the nape. Lower lateral region of head whitish brown, strongly demarcated against upper lateral and dorsal brown colouration. Ventral colouration dirty brown with scattered darker brown maculations on the throat and and across the venter. Limbs medium brown dorsally, slightly lighter ventrally, largely unpatterned except for scattered dark maculations and very small blotches on the hindlimbs. Stub of original tail medium brown dorsally with a pair of smeared very dark brown markings. Regrown tail plain light brown on all surfaces.
Dorsum generally with alternating transverse regions of light and medium brown, however the width and distinctiveness of these region varies. Some variation in the intensity of colouration may be ontogenetic. On the largest specimens the medium brown regions are relatively narrow, and not or only weakly defined by dark brown edging, giving the overall impression of a somewhat faded pattern. On smaller specimens the transverse bands are more distinct and strongly defined. An indistinct trace of medium brown mottling or barring is also sometimes apparent on the dorsal and lateral surfaces of the hindlimbs. Venter medium to light brown, sometimes with very scattered darker brown maculations. Original tails with alternating medium-brown dorsal blotches and light-brown to creamish regions, border between colours often sharply defined by dark-brown edging. Regrown tails creamish or light brown with at most a few very indistinct light brownish streaks and patches. Iris in life deep chestnut brown with dark brown vermiculations (Figure 4).
Comparisons. Cyrtodactylus equestris sp. n. can be distinguished from most other Cyrtodactylus by its large size (males to 129 mm, females to 139 mm), including all species from west of Lydekker's Line (maximum size <130 mm). It can be differentiated from the other large Papuan taxa as follows. Cyrtodactylus equestris sp. n. differs from Cyrtodactylus loriae and Cyrtodactylus serratus in having enlarged tubercles on the infraangular region and often extending across the throat (vs. absent), a lower number of pores (up to 39 vs. up to 81) in a discontinuous series (vs. continuous), and in lacking enlarged tubercles extending the length of the tail (vs. C. serratus only). Cyrtodactylus equestris sp. n. differs from members of the C. lousiadensis group (C. epiroticus, C. klugei, C. lousiadensis, C. murua, C. robustus, C. salomonensis and C. tripartitus) in its smaller subcaudal scales, in having tubercles on the infra-angular region and throat, and in its more poorly defined light-brown bands or blotches on the dorsum (vs. strongly defined and unbroken transverse brown banding). Cyrtodactylus equestris sp. n. differs from C. zugi in its smaller size (139 vs. 159 mm SVL), more extensive tuberculation that usually extends across the throat (vs. on infra-angular region only), and dorsal colour pattern on torso consisting of light-brown transverse bands on a plain greyishbrown background (vs. alternating dark brown blotches on a mottled dark-grey and off-white background). Cyrtodactylus equestris sp. n. differs from C. irianjayaensis by its smaller size (139 vs. 163 mm SVL), the presence of enlarged tubercules usually extending across the throat (vs. infra-angular region only) and its higher number of femoral and precloacal pores (24-39 vs. 7-16). Cyrtodactylus equestris sp. n. differs from other populations of Cyrtodactylus here referred to C. novaeguineae (both syntypes and genotyped material) in its wider head (HW/SVL 0.19-0.23 vs. 0.18-0.19), larger size (SVL 139.0 vs. 129.0) and tripartite femoral and precloacal pore arrangement (vs. continuous or at most one poreless intervening scales).
Distribution and natural history. Known from scattered localities in the Foja, Torricelli and possibly the Adelbert Ranges (see below) of northern New Guinea (Figure 7). Specimens for which detailed information is available were collected in relatively undisturbed hill or lower montane forest between 500-1200 m a.s.l.
Etymology. Equestris latin for knight, in reference to the relative size of this species -large for the genus, but still subordinate to some of its near relatives.
Comments. The referred material include two specimens in the American Museum of Natural History (AMNH 82360, AMNH 103193) from separate localities in the Adelbert Ranges, Morobe Province. These specimens have plain venters and twotoned brown and light brown dorsal colouration. On this basis they do not conform with 'north 2' (the only other member of the C. novaeguineae complex from northern New Guinea) and are tentatively assigned to Cyrtodactylus equestris sp. n. However these localities are separated from the other localities in the North Papuan Mountains by the low swampy country around the Sepik River, and the single male from this region has a bipartite pore arrangement (vs. clearly tripartite). Fresh material and genetic samples are required to confirm the taxonomic status of these easternmost populations.   Description of holotype. A very large (169 mm SVL) and robust gecko. Head very large (HL/SVL 0.27), very wide (HW/SVL 0.23) and clearly distinct from neck. Snout longer than eye diameter, eye to naris distance longer the eye (EN/EYE 1.4), curved in dorsal profile, broadly truncate in lateral profile, mid-loreal region slightly inflated, interorbital region and top of snout slightly concave, canthus rostralis weakly defined. Oval patch of skin missing from top of snout. Eyes large (EYE/HL 0.24), pupil vertical, supraciliaries extending from anteroventral to posterodorsal edge of orbit, longest at the anterodorsal edge. Ear opening roughly circular, bordered by distinct dorsal skin fold.

Cyrtodactylus rex
Rostral broadly rectangular, approximately 1.5 times wider than high with medial suture extending approximately 60% from dorsal edge towards ventral edge, bordered dorsally by two nasals and three smaller internasals. Nares bordered by first supralabial (point contact), rostral, nasal, and series of five to eight granular postnasals. Supralabials generally slightly wider than high, 13 right, 14 left, 10 to midpoint of eye. Head, temporal and nuchal scales small and granular with conical tubercles approximately 2-3 times width of surrounding scales densely distributed across the temporal and nuchal regions. Enlarged infralabials to rictus 14 right, 13 left, anterior infralabials higher than wide, posterior infralabials wider than high, infralabials bordered by rows of enlarged scales that grade into small granular gular scales. Mental triangular, approximately as wide as long, bordered by first infralabials and two pentagonal postmentals. Numerous wide flat tubercles present across posterior region of throat.
Body robust (TrK/SVL 0.43) with distinct ventrolateral folds. Skin heavily tuberculate dorsally and laterally, 33-34 prominent enlarged tubercles along lateral folds, dorsum with up to 23 rows (not including lateral fold) of enlarged conical tubercles up to four times width of surrounding small and granular scales. Ventral scales larger than dorsal scales, increasing in size medially, arranged in approximately 54 rows at midpoint of body, one or two poorly defined rows of enlarged ventral tubercles present just inferior to the lateral fold. Enlarged precloacal and femoral scales in three rows, posterior row longest (47 scales) and extending laterally approximately two thirds length of femur, medial scales distinctly larger.
Tail original, partially fractured approximately halfway from base, long and moderately robust, numerous low conical tubercles on dorsal and lateral surfaces close to base, but not extending beyond anterior third of tail, subcaudal scales enlarged, not wider than long, arranged in series 2-4 scales wide, 4 rounded cloacal spurs. Color in ethanol. Dorsum consists of alternating regions of dark greyish-brown, medium grey, and light-grey to dirty off-white. Four dark-brown regions most clearly defined, and consisting of three paired sets of oval, pentagonal and triangular blotches between fore-and hindlimbs, and an additional distinct dark-brown triangular nuchal patch anterior to insertion of forelimbs, and extending anterio-laterally as a stripe through eye and along dorsal edge of supralabials. Ventro-lateral regions of head with wide off-white stripe extending to lower edge of supralabials. Supraciliaries and dorsal tip of snout dark brown. Limbs and toes dirty grey with broad indistinct dark-brown bands on upper and lateral surfaces. Ventral ground colouration off-white with brownish tinge and extensive dark-brown flecks, often covering just a single scale, but also coalescing to form four distinct sets of jagged transverse bars on throat, and less prominent bars and ocelli on torso. Dorsal and lateral surfaces of tail dirty grey with four indistinctly edged dark-brown blotches or bands, and extensive smaller dark brown maculations, stripes or blotches. Subcaudal surfaces dark-brown with scattered lighter grey spots.
Dorsal pattern always consists of indistinctly defined alternating regions of dark grey brown, medium brown and dirty off-white. Dark grey-brown markings usually most clearly defined, but showing extensive variation in shape and size -usually less than half width of torso, but occasionally wider and varying in shape from small diamonds, transverse bands to paired blotches or triangles. Dark brown ventral barring always present, but on some specimens restricted to throat only, while in others forming a network across throat and venter. All specimens with at least some indistinct dark brown barring on toes and four or five dark brown longitudinal blotches or bands on original tails. Iris in life brick red with extensive fine brown vermiculations ( Figure 5).
All specimens heavily tuberculate with usually several indistinct rows of large tubercles extending as much as 10 mm inferior to lateral fold at midpoint of torso. Throat tuberculation varies in extent from a broad band spanning the posterior throat to concentrated in infra-angular regions and largely absent from the throat.
Comparisons. Cyrtodactylus rex sp. n. is readily distinguished from most other Cyrtodactylus by its very large size (SVL up to 172 mm vs generally < 130mm). It further differs from the relatively small number of other large Papuan species as follows. Cyrtodactylus rex sp. n. differs from C. loriae and C. serratus in having enlarged tubercles on the infra-angular region and often extending onto and across the throat (vs absent from both regions), a lower number of pores (up to 38 vs. up to 81), and in lacking  Figure  7). Photographs of a specimen from the vicinity of Senggi Village to the south of Jayapura in West Papua Province (kindly provided by Burhan Tjaturadi), indicate that this species also occurs in adjacent parts of Indonesian New Guinea.
The holotype was collected on a low ridge in Sago-dominated swamp forest. Other specimens were collected in lowland and foothill forest at altitudes ranging from near sea level up to 690 m a.s.l.
Etymology. From the latin for king as it is the largest of the over 200 species of Cyrtodactylus, and amongst the largest of all known geckos (Bauer 2013).

Discussion
The complex geological history of New Guinea has played a major role in shaping Papuan biodiversity (Toussaint et al. 2014). The high Central Cordillera is the dominant mountain complex in New Guinea, however the lower and smaller upland regions of the North Papuan Mountains also have an endemic biota that remains poorly understood (Helgen 2007;Richards et al. 2009;Kraus and Myers 2012). The North Papuan Mountains are derived from the (ongoing) accretion of formerly isolated island arcs onto the northern edge of New Guinea (Polhemus 2007). One key question is the extent to which endemism in these ranges is attributable to dispersal from other (relatively distant) montane habitats, persistance of a previously insular biota of terranes, or localised in situ transitions from surrounding lowland habitats (Toussaint et al. 2014).
The two new geckos described here have overlapping, yet somewhat complementary distributions: Cyrtodactylus equestris sp. n. is seemingly restricted to hill and lower montane forests on the North Papuan Mountains themselves, while C. rex sp. n. is more widespread throughout the surrounding lowlands (Figure 7). Cyrtodactylus equestris sp. n. is the second Cyrtodactylus that has only been recorded from hill and low montane forest on the North Papuan Mountains -the other being Cyrtodactylus boreoclivus from the Foja, Torricelli and Bewani Mountains (Oliver et al. 2011). Sampled populations of both of these apparent North Papuan Mountain endemics show levels of mitochondrial genetic diversity (< 10%) consistent with the hypothesis that they represent single (ableit structured) species and suggest some degree of historical connectivity between the ranges that comprise the North Papuan Mountains (Oliver et al. 2012, this study).
The as yet ungenotyped populations referred to Cyrtodactylus equestris sp. n. from the Adelbert Mountains in the east may prove to be an exception to this.
In contrast to their broadly overlapping intraspecific distribution, the distribution of sister lineages to these two North Papuan Mountain Cyrtodactylus differs. On the one hand C. boreoclivus is closely allied to C. medioclivus, an allopatric lower montane form currently known only from a small area of the Central Cordillera ). On the other hand, records of the inferred relatives of the newly described Cyrtodactylus equestris sp. n. (C. novaeguineae, C. rex sp. n. and C. zugi) are concentrated in lowland habitats spanning New Guinea, and suggest that the upland habitat association of this taxon is derived. The putative sister taxon C. zugi is currently known only from other still discrete northern terranes -the islands of Batanta and probably Waigeo (Oliver et al. 2008). Batanta and especially Waigeo have moved significantly westward through the Miocene and Pliocene (Polhemus 2007) -highlighting the possibilty that the evolutionary history of the clade comprising C. equestris sp. n. and C. zugi may be linked to the northern arc islands.
The contrasting distribution of sister lineages in the North Papuan Ranges suggests endemism is accumulating through multiple processes -colonisation by taxa already associated with hill and lower montane habitats from the older Central Cordillera (eccentric endemism), accretion of pre-existing island arc biotas, and potentially even de novo shifts up elevational gradients within otherwise lowland lineages (centric endemism) (Merckx et al. 2015) and complements recent work addressing the same question in water beetle (Toussaint et al. 2014).
Cyrtodactylus is also an exceptionally species rich genus of lizards with over 200 recognised species (Uetz 2015), however, how potentially key factors such as competition, ecological diversification, isolation and dispersal, have shaped the evolution of this diversity remain largely untested. Within New Guinea a number of lineages have larger body sizes than elsewhere, with the giant Cyrtodactylus rex sp. n. sitting at the apex of this trend. It has been suggested that this is indicative of a unique trajectory of ecological evolution in the Papuan region -potentially linked to either competitive and/or predatory release (Oliver et al. 2014). The ongoing elucidation of a suite of apparently lower montane and hill forest species suggests that altitudinal segregation has also played some role in mediating the accumulation of regional diversity in this lineage (Oliver et al. 2013;this paper), at least within the exceptionally complex orogeny of New Guinea, and potentially also other topographically variable tropical regions (Grismer et al. 2012).