Introduction
The genus
Pseudoceramodactylus
Haas, 1957 comprises a single species, the Gulf Sand gecko
Pseudoceramodactylus
khobarensis
, described from eastern Saudi Arabia (Haas 1957) and is known to be distributed across
parts of the Arabian Gulf, including Kuwait, Bahrain, Qatar and the United Arab Emirates
(U.A.E.) (Sindaco and Jeremčenko 2008, Valdeón et al. 2013). It has also been reported
from Qeshm Island, Iran (Dakhteh et al. 2007, Sharifi et al. 2012) and a few localities
are known from coastal eastern Oman (Fujita and Papenfuss 2011, Gardner 2013, Metallinou
et al. 2012).
Pseudoceramodactylus
khobarensis
are nocturnal geckos, found on moist, salt-impregnated to solid, salt-encrusted flats
(sabkhas) (Fig. 1
a, b, c) and are often the sole reptile dweller of such extreme environments (Arnold
1977, Gardner 2013). Their fingers are swollen with loose connective tissue and bear
numerous elongated spiny scales on the underside (Arnold 1977), considered to be an
adaptation to this particular substrate.
Pseudoceramodactylus
khobarensis
was transferred to the genus
Stenodactylus
by Kluge (1967) on the basis of external and internal similarities. Nevertheless,
authors recognized its singularity among the other
Stenodactylus
members, due to its remarkably swollen nasal area, enlarged postmental scales and
slender, elongated extremities (Arnold 1980). Using molecular data, Fujita and Papenfuss
(2011) showed that its inclusion in
Stenodactylus
rendered the latter paraphyletic, so the genus
Pseudoceramodactylus
was resurrected. Metallinou et al. (2012) confirmed this result but, performing topological
tests, they showed that the sister relationship between
Pseudoceramodactylus
and
Stenodactylus
could not be rejected. The same authors included specimens from the two extremes of
the species’ range – Kuwait and Oman – in their study, and found only small genetic
divergence in mitochondrial DNA (12S and 16S rRNA markers) between specimens from
these areas (see Additional file 2 – Figure S1 in Metallinou et al. 2012). However,
according to the known range, localities of
Pseudoceramodactylus
khobarensis
in coastal Oman are isolated and separated by more than 420 km from the eastern localities
in inland U.A.E.
Herein, we report two new records for this species from the eastern edge of the Rub
Al Khali desert (‘Uruq al Mu’taridah area), in inner Oman (Fig. 2), indicating that
this distributional gap is rather attributed to incomplete knowledge of the species’
distribution than actual absence. Morphological data and mitochondrial DNA (mtDNA)
analyses are presented and the distribution and biogeography of this monotypic genus
are briefly discussed.
Materials and methods
During intensive fieldwork in Oman, in October 2013, we surveyed the easternmost tip
of the Rub Al Khali desert (Fig. 2). Individual transects were carried out by five
observers and collecting was conducted manually. We collected two specimens of
Pseudoceramodactylus
khobarensis
in two different localities near the border between Oman and Saudi Arabia, in an area
of salt-encrusted flats and interdune sabkha (Table 1 and Fig. 1
c). The two vouchers collected are housed at Salvador Carranza’s reptile collection
at the Institute of Evolutionary Biology, Barcelona, Spain.
Data for the updated distribution map were compiled from Gallagher (1971), Osborne
(1994), Martens (1996), Meinig and Kessler (1998), Cunningham (2000), Dakhteh et al.
(2007), Fujita and Papenfuss (2011), Gardner (2013), Valdeón et al. (2013). The map
was produced by representing coordinates from literature records and by georeferencing figures
and extracting point coordinates with ArcGIS 10.0 (ESRI 2010).
A total of five individuals, the two newly collected ones and three additional specimens
from the extremes of the species’ range (Fig. 2), were analyzed for variation in the
mtDNA. Genomic DNA was extracted from ethanol-preserved tongue tissue samples from
the newly collected specimens using the SpeedTools Tissue DNA Extraction kit (Biotools,
Madrid, Spain). The mtDNA marker 12S rRNA gene was partially amplified using primers
and conditions from Metallinou et al. (2012). Amplified fragments were sequenced for
both strands and chromatograph contigs were assembled in Geneious v. R6 (Biomatters
Ltd.). The online version of MAFFT v.6 (Katoh and Toh 2008) was used for sequence
alignment, applying parameters by default. A median-joining haplotype network was
constructed using the Fluxus Phylogenetic Network Analysis software v.4.612 (Bandelt
et al. 1999; http://www.fluxus-engineering.com). Uncorrected p-distances between individuals
were calculated with MEGA 5 (Tamura et al. 2011).
A series of morphological measurements were performed on the same five individuals,
as well as three additional specimens from the locality in coastal Oman belonging
to the field series of S. Carranza (Table 2 and Fig. 2) Measurements were taken by
the first author on the right side of each specimen (unless defective), using a digital
caliper with accuracy to the nearest 0.01 mm. Specimens were sexed by observing presence
or absence of hemipenal bulges in adult specimens and measurements were performed
as follows: snout-vent length (SVL) measured from tip of snout to vent; head length
(HL), measured tip of snout to posterior ear opening border; head width (HW), measured
dorsally as the distance between the eyes excluding the eyelid; transverse eye diameter
(ED); forearm length (FL), from base of palm to elbow; arm length (AL), from elbow
to the insertion of the forelimb on the posterior side; tibia length (BL), measured
from base of foot to knee; femur length (ML), measured from knee to the insertion
of the hind limb on the posterior side; tail length (TL), from vent to tip of tail;
number of upper labial scales (ULS) and number of lower labial scales (LLS).
Taxon treatments
Pseudoceramodactylus
khobarensis
Haas, 1957
http://reptile-database.reptarium.cz/species?genus=Pseudoceramodactylus&species=khobarensis
http://eol.org/pages/461035/overview
http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=819426
Materials
Type status:
Other material. Occurrence: recordedBy: Salvador Carranza; Raquel Vasconcelos; Margarita
Metallinou; Roberto Sindaco; Jiri Smid; individualCount: 1; sex: male; Taxon: taxonID:
http://www.gbif.org/species/2447065#
; scientificNameID: urn:lsid:organismnames.com:name:2791139; Location: country: Oman;
stateProvince: Al Wusta; verbatimLocality: north of Hasirah oil field, ‘Uruq al Mu’taridah
area; verbatimElevation: 143 m; verbatimLatitude: 20 30 7.704N; verbatimLongitude:
55 41 56.2554E; Event: eventDate: 2013-10-07T00:30+0400; Record Level: collectionID:
IBE-CN7611; institutionCode: Institute of Evolutionary Biology (CSIC - Universitat
Pompeu Fabra)
Type status:
Other material. Occurrence: recordedBy: Salvador Carranza; Roberto Sindaco; Margarita
Metallinou; Raquel Vasconcelos; Jiri Smid; individualCount: 1; sex: juvenile; Taxon:
taxonID:
http://www.gbif.org/species/2447065#
; scientificNameID: urn:lsid:organismnames.com:name:2791139; Location: country: Oman;
stateProvince: Al Wusta; verbatimLocality: about 13km by air east of Sahmah oil filed, ‘Uruq
al Mu’taridah area; verbatimElevation: 96 m; verbatimLatitude: 20 39 37.0434N; verbatimLongitude:
55 32 28.716E; Event: eventDate: 2013-10-07T02:00+0400; Record Level: collectionID:
IBE-CN8073; institutionCode: Institute of Evolutionary Biology (CSIC - Universitat
Pompeu Fabra)
Analysis
Analysis of the mitochondrial 12S marker revealed that both newly collected specimens
share the same haplotype. Along a 380-bp alignment, there are 3 differences compared
to sample IBE-S7746 from Barr Al-Hickman, in coastal Oman (M196 in Metallinou et al.
2012) (0.6% p-distance) and 2 differences compared to either one from Kuwait BEV.10039
and BEV.10040 (M16 and M37 in Metallinou et al. 2012, respectively) (0.3% p-distance).
The overall genetic variability based on this marker was 0.4%.
The mean SVL of the specimens measured was 53.87 mm (50.71–61.37, N=7), and did not
differ for males (53.92, 51.71–61.37, N=5) and females (53.76, 50.72–56.80, N=2).
Tail length measured between 71.1 and 95.1% of SVL.
Discussion
The Rub Al Khali is the largest desert in Arabia, the largest sand desert in the world and
one of the driest (Garzanti et al. 2003, Vincent 2008). It extends across Saudi Arabia
with its southern and eastern edges reaching Yemen, Oman and the U.A.E. In Oman, accessibility
to this region is limited, and this is mirrored in the paucity of reptile records
available, contrasting with the more abundant records from the U.A.E. in areas of
similar ecological characteristics (Gardner 2013). We surveyed the easternmost tip
of this desert in Oman on the night of 7 October 2013 and we collected two specimens
of
Pseudoceramodactylus
khobarensis
in two different localities near the border between Oman and Saudi Arabia (Fig. 2
and Table 1): a male specimen (voucher code IBE-CN7611) (Fig. 1
a, b) north of Hasirah oil field, and a juvenile specimen (IBE-CN8073) about 13 km
by air east of Sahmah oil filed. In the first locality, the habitat was exclusively
salt-encrusted flats, and
Pseudoceramodactylus
khobarensis
was the only species encountered during a 40-minute survey carried out by 5 observers.
In the second locality, there was a succession between salt flats and sand dunes (Fig.
1
c), with
Pseudoceramodactylus
khobarensis
found on the former and
Stenodactylus
arabicus
on the latter. These records constitute the first inland records of
Pseudoceramodactylus
khobarensis
from Oman and are located almost 250 km from both the eastern records in inland U.A.E.
and those in eastern coastal Oman (Fig. 2). The finding of
Pseudoceramodactylus
khobarensis
in this area indicates that its presence in Oman is most probably underestimated,
due to the aforementioned difficulty of access to large parts of the inland deserts.
Interestingly, the low variability of the mtDNA observed with the sequenced marker
(12S) indicates that there is probably connectivity between populations across its
distribution range and corroborates the hypothesis that this species inhabits larger
inland areas. Indeed, coastal and inland sabkhas are abundant in eastern Saudi Arabia
(Barth 2002) and continental sabkhas are commonly found at the interdune corridors
of north-eastern Rub Al Khali (Edgell 2006). This low variability observed in
Pseudoceramodactylus
khobarensis
contrasts with the much higher values observed in some members of the closely related
genus
Stenodactylus
, as calculated based on specimens distributed across similar ranges in Metallinou
et al. (2012) and Metallinou and Carranza (2013). Intraspecific variability ranged
from 0.9% in
Stenodactylus
leptocosymbotes
, to 1.6% in
Stenodactylus
arabicus
and 2.9% in
Stenodactylus
doriae
.
Based on the measurements performed on voucher specimens in this study,
Pseudoceramodactylus
khobarensis
is shown to have substantially higher maximum SVL than previously documented. One
female reached 56.80 mm (BEV.10040) and one male 61.37 mm (IBE-CN7611), both exceeding
SVL of the largest specimens measured by Haas (1957) and Arnold (1980). Moreover, numbers
of labial scales presented herein (upper 10–13, lower 9–12) seem to be slightly different
from the counts given for the type series by Haas (1957) (9/10 upper, 8/9 lower labials)
but are in perfect agreement with those by Arnold (1980) who included one specimen
from the original description in his examined material. Therefore, this situation
can probably be attributed to observer-related discrepancies, rather than an actual
difference in counts of this meristic variable.
Pseudoceramodactylus
khobarensis
is a remarkable desert reptile in that it is the only lizard habitually found on sabkha
substrate (Arnold 1977), a habitat almost devoid of vegetation due to extraordinary
salinity (König 2012). The species is widespread and classified by the International
Union for Conservation of Nature (IUCN) as Least Concern, but a decreasing population
trend is observed in parts of its range due to ongoing significant habitat loss through
coastal development, especially in the U.A.E. (Sharifi et al. 2012). In this way,
it is important to document the species’ distribution and understand its ecological
requirements at national and regional scales in order to prevent imperilment in larger
parts of its range.
Supplementary Material
XML Treatment for
Pseudoceramodactylus
khobarensis