Mapping the terrestrial reptile distributions in Oman and the United Arab Emirates

Th e terrestrial reptile fauna of Oman and the United Arab Emirates is rich, with at least 79 species of lizards and snakes and a single species of worm lizard. However, to date there have been no accurate maps published of their distribution ranges, and distribution data relies on scattered museum specimen localities and published accounts. Considerable numbers of locality data points do exist, collected by visting and resident herpetologists, and more recently, from ecologists working on surveys for environmental impact assessments and biodiversity action plans. Th ese data are invaluable, as amongst other uses, they can assist conservation planning and management, and will eventually document changes in distributions over time. Th is is especially true where there has been extensive habitat loss and degradation due to urbanisation and development activities. Data have been collected from museum records, published accounts and unpublished data from a variety of sources, including many records made by the author over the last 20 years, with the aim of producing an atlas of species distributions. Th e number of records is now approaching 5.000, giving suffi cient coverage to produce maps that are useful for a variety of applications. Examples are discussed, including endangered and endemic species, snakes of medical importance and species of potential interest in ecological and evolutionary studies.


Introduction
Oman and the United Arab Emirates support a diverse terrestrial reptile fauna, including a number of species which are endemic at the regional and national levels (Gardner 1999(Gardner , 2005b(Gardner , 2008Hornby 1996). Th is refl ects the countries' position at the crossroads of the Ethiopian, Palaearctic and Oriental biogeographic regions, a wide range of habitats, and the abilities of reptiles to thrive in hot and arid regions. At present, eighty species of terrestrial reptiles have been recorded from Oman and the UAE: these being 58 lizards, 1 amphisbaenian and 21 snakes (Table 1, Appendix 1). Th e numbers of species on the country lists in both Oman and the UAE has increased dramatically over the last 20 years, as entirely new species have been described, existing species have been split, and further species have been recorded within the national boundaries. For example, since the year 2000, the following fi ve species and subspecies have been added to the known reptile list in the UAE: Leptien's spiny-tailed lizard Uromastyx aegyptia leptieni (Wilms andBöhme 2000, 2007;Wilms et al. 2009), Blanford's fringe-toed lizard Acanthodactylus blanfordii (Gardner 2005a), Persian leaf-toed gecko Hemidactylus persicus, Carter's semaphore gecko, Pristurus carteri (Gardner in press) and the Arabian cat snake Telescopus dhara (Gardner et al. in press). Due to the relatively poor knowledge of the herpetofaunas in south eastern Arabia, this process will undoubtedly continue, and indeed is likely to accelerate when molecular methodologies are brought to bear on some of the widespread and highly variable "species".
While an up to date and accurate listing of the species is a fi rst requirement for species conservation and management, knowledge of the distributions of the species is critical to guide conservation planning, mitigation for environmental degradation and to follow changes in species status that may occur as habitats become fragmented and lost, climate change alters species ranges or other variables aff ect individual species. To this end, I have been collating reptile distribution data from published and museum sources, from the fi eld, and from other herpetologists and natural historians who have been generous with their observations. While an atlas project is never ending, suffi cient data are now available as a useful tool for a variety of scientifi c and conservation management applications. A few examples, to illustrate the value of preparing a distribution atlas, are presented.

Th e data
Data have been collected by numerous herpetologists, ecologists and natural historians, mainly over the last 40 years. A total of 4.683 data points are used here, and this number is continuously increasing. Each data point is a species record at a single locality and time. Th e number of data points per species ranges from 2 to 361, with a mean of 58. As the data improves, it will be possible to map changes in distributions including range reductions. Older data are mapped to within one kilometre, though most recent data are collected using GPS and are accurate to within about 20 m. Figure 1 illustrates the coverage for all species as of October 2008. It can be seen that the coverage remains patchy, especially in Oman, even at a coarse scale. For example the Muscat area and the Jebel Akhdar mountains in northern Oman are relatively well covered, whilst in the central desert there are many "blanks on the map". Indeed the main Muscat to Salalah road can be traced by the dot records, with under-recorded areas to either side. On a fi ner scale the patchiness is much more apparent. Over the last 4 years, much data has been recorded in the UAE during baseline ecology surveys undertaken as part of environmental impact assessments. However these tend to be concentrated in the main areas of urban and industrial development, such as around Dubai, Abu Dhabi, Al Ain and Ruwais.
Th e data are only as good as the identifi cations they are based on. Hence only data from recognised authorities, or that are backed up by specimens or clearly identifi able photographs have been included. Even so, there remains some inevitable confusion. For example, before the description of Uromastyx aegyptia leptieni in 2000, all spinytailed lizards in the UAE and northern Oman were assumed to be Uromastyx aegyptia microlepis and were recorded as such. Following the separation of U. a. leptieni, it must be assumed that some of these records are misidentifi ed. As the two forms are so similar and cannot be reliably identifi ed without scale counts, fi eld observations still remain problematic. Records are therefore assigned to subspecies depending on the location of the assumed contact zone, with an assumption that the subspecies have non-overlapping distributions. However, until the exact location and nature of the contact zone is mapped, the identity of some records remains impossible to determine.
Another potential source of confusion arises where records were made on the basis of tracks and traces. While some tracks are unambiguous, such as those of adult Persian wonder geckos Teratoscincus keyserlingii (being far larger than any other sand gecko tracks), or the distinctive track of the Diplometopon zarudnyi, the only amphisbaenian in the area, other track identifi cations are problematic. For example a sinuous snake track in the sands of western Abu Dhabi could be a sand boa (Eryx jayakari) or a leaf-nosed snake (Lytorhynchus diadema). Diff erent herpetologists appear to have made diff erent assumptions in identifying species from their tracks.

Endangered species: Th e Persian Wonder Gecko Teratoscincus keyserlingii
Th is beautiful gecko species (Fig. 2) is restricted in Arabia to the lowlands of northern Abu Dhabi, Dubai, Sharjah and Umm al Quwayn (Fig. 3), especially those areas with sand sheet or low dune habitats with a relative abundance of grass clumps (Pennestum divisum and Panicum turgidum). Although now classifi ed as the Iranian species T. keyserlingii, the degree of diff erentiation between the Arabian form and the Iranian  has not yet been assessed. It is possible that the Arabian form is endemic to the UAE at the sub-specifi c level. Unfortunately the area of its range is undergoing extremely rapid development, and it remains to be seen whether the species will survive the extensive habitat loss and fragmentation. Already many of the sites at which it was recorded in the 1990s and early 2000s have been cleared, levelled and converted into industrial estates, green golf courses and residential suburbs. A more detailed and current survey of its range is now urgently required to estimate its present status and identify any areas which could be protected as conservation areas.

Endemism
Endemic species are a special responsibility for a country as they are aspects of biodiversity found nowhere else. A knowledge of their distributions is therefore important to ensure that there range can be protected within a system of protected areas. Examples of two regionally endemic species are the two sympatric lacertids in the endemic genus Omanosaura, which are restricted to the Hajar mountains (Fig. 4). Th eir distributions are almost totally overlapping, suggesting they are able to avoid competition. Omanosaura jayakari is considerably larger than O. cyanura and presumably takes diff erent prey.

Species of medical importance
Th ere are nine species of land snakes of signifi cant medical importance in SE Arabia. Th ese are seven species of vipers, of which four are saw-scaled vipers in the genus Echis, and one species of cobra and one burrowing asp (Egan 2007;Gardner 2005b). Th ese species are responsible for signifi cant, but often underestimated, morbidity and mortality (Scrimgeour et al. 2001). Indeed, many people living in the cities are unaware that there may be potentially lethal snakes in their vicinity. Of these dangerous species, the saw-scaled vipers are of the greatest health concern. In northern Oman and the UAE, two species occur: the Oman saw-scaled viper Echis omanensis is restricted to the Hajar mountains, while the Sind saw-scaled viper Echis carinatus sochureki is generally found in sandy habitats in the lowlands. Figure 5 clearly shows the nonoverlapping nature of their distributions, based largely on their habitat choice. Th e other two species, Echis coloratus and E. khosatzkii are both restricted within this region to south and central Oman.
It is widely recognised that there is interspecifi c and intraspecifi c variation in the venom components of snakes, and that this may have major consequences on the neutralisation capacity of antivenoms (Fry et al. 2003). A knowledge of the snake species found in particular areas allows a more informed selection of antivenom and an under-

Echis omanensis Echis carinatus
standing of its potential effi cacy. In the future, it may be possible to develop more specifi c and eff ective antivenoms towards particular species, subspecies or venom components. An understanding of the snake distributions will be important in this endeavour.

Studies in ecology and evolution
A study of species distributions may allow questions to be formulated to test scientifi c theories. For example, two species with contiguous but non-overlapping distributions, that are able to utilise similar habitats, may have distributions resulting from ecological competition, species movements, or evolution and speciation. Figure 6 illustrates the ranges of two species of sand geckos that have contiguous distributions: Stenodactylus leptocosymbotes and S.slevini which both live on fi rmer desert surfaces such as sandy gravel inter-dune plains and mountain outwash plains. Th ese distributions suggest that they cannot coexist in sympatry, though the reasons for this have not been investigated.

Future developments
A handbook and atlas of the reptiles and amphibians of Oman and the United Arab Emirates is currently being prepared and will detail the current state of knowledge of this herpetofauna, as well as facilitate identifi cations for professional