Diversity, distribution and conservation of the terrestrial reptiles of Oman (Sauropsida, Squamata)

Abstract

In the present work, we use an exceptional database including 5,359 records of 101 species of Oman's terrestrial reptiles together with spatial tools to infer the spatial patterns of species richness and endemicity, to infer the habitat preference of each species and to better define conservation priorities, with especial focus on the effectiveness of the protected areas in preserving this unique arid fauna. Our results indicate that the sampling effort is not only remarkable from a taxonomic point of view, with multiple observations for most species, but also for the spatial coverage achieved. The observations are distributed almost continuously across the two-dimensional climatic space of Oman defined by the mean annual temperature and the total annual precipitation and across the Principal Component Analysis (PCA) of the multivariate climatic space and are well represented within 17 out of the 20 climatic clusters grouping 10% of the explained climatic variance defined by PC1 and PC2. Species richness is highest in the Hajar and Dhofar Mountains, two of the most biodiverse areas of the Arabian Peninsula, and endemic species richness is greatest in the Jebel Akhdar, the highest part of the Hajar Mountains. Oman's 22 protected areas cover only 3.91% of the country, including within their limits 63.37% of terrestrial reptiles and 50% of all endemics. Our analyses show that large areas of the climatic space of Oman lie outside protected areas and that seven of the 20 climatic clusters are not protected at all. The results of the gap analysis indicate that most of the species are below the conservation target of 17% or even the less restrictive 12% of their total area within a protected area in order to be considered adequately protected. Therefore, an evaluation of the coverage of the current network of protected areas and the identification of priority protected areas for reptiles using reserve design algorithms are urgently needed. Our study also shows that more than half of the species are still pending of a definitive evaluation by the International Union for Conservation of Nature (IUCN).

Fig 1. Number of species displayed in a cumulative way.

Dots represent the years with species descriptions. Dashed lines divide the graph into intervals of 20 years. The last dot includes the species in the process of being described.

Fig 2. Physical map of Oman.

Map of Oman showing topographical relief and names of the most relevant toponyms mentioned in this study.

Fig 3. Map of protected areas of Oman.

Topographical map of Oman showing the distribution, limits and names of the 22 protected areas. Information provided by the Ministry of Environment and Climate Affairs of Oman.

Fig 4. Map of Oman indicating the sampling effort.

Grids of 10 arc-minutes (~18km) with observations (red dot). Empty grid cells are either due to no observation or no sampling.

Fig 5. Two-dimensional climatic space of Oman (grey dots) defined by total annual precipitation (BIO12) and mean annual temperature (BIO1).

Red dots represent the distribution of the 5,359 observations in this climatic space.

Fig 6. Principal Component Analysis (PCA) of the climatic space of Oman (grey dots) using 12 BIOCLIM variables.

Dashed lines delimit the climatic clusters that group 10% of the explained variance by PC1 and PC2. Red dots represent the distribution of the 5,359 observations in the PCA of the climatic space.

Fig 7. Climate variability of Oman.

(A) Map showing the distribution and extension of the 20 climatic clusters of Oman identified in this study that group 10% of the explained variance by PC1 and PC2; (B) Principal Component Analysis (PCA) of the climatic space of Oman using 12 BIOCLIM variables and with the 20 climatic clusters that group 10% of the explained variance by PC1 and PC2 with the same colors as in the map. Clusters have been numbered from 1 to 20 with the following order: from left to right and from bottom to top.

Fig 8. Maps of species richness.

(A) Species richness by governorate; (B) species richness by grids of 10 arc-minutes of latitude and longitude.

Fig 9. Maps of endemicity.

(A) Endemic species richness by governorate; (B) Endemic species richness by grids of 10 arc-minutes of latitude and longitude.

Fig 10. Principal Component Analysis (PCA) of the climatic space of Oman (grey dots) using 12 BIOCLIM variables.

Dashed lines delimit the climatic clusters that group 10% of the explained variance by PC1 and PC2. Green dots represent the climatic space of protected areas.

Fig 11. Percentage of the species’ distribution area included within a protected area.

Dashed lines indicate the conservation target of 17% and 12% of the total species’ distribution area within a protected area. (A) The extent of species occurrence was defined using the presence-absence in every pixel of 1 km x 1 km. (B) The extent of species occurrence was defined using a minimum convex polygon (MCP) of the observations filtered by the species’ average altitude.