Biodiversity of the snakes in northern and western mountains of Iran, with special emphasis on biodiversity in colubroids

Snakes are the second most specios group of living reptiles. Colubroidea, with more than 2500 species, is one of the most conspicuous radiations of terrestrial vertebrates. Recent studies show that globally 12% of the snake species are estimated to be threatened with extinction. This estimation increases when including the cryptic species (discrete species that are difficult, or sometimes impossible, to distinguish morphologically and thus have been incorrectly classified as a single taxon) too. It is possible that some of the snakes biodiversity may get extinct even before a proper identification. In the developing countries like Iran this situation is even more serious. The country of Iran has the greatest faunal and floral diversity of the southern and arid parts of the Palaearctic realm, including a considerable diversity in the snakes. But there is insufficient data on the biodiversity of snakes in Iran and limited data about cryptic species of snakes in the country. In this PhD study, I have aimed to investigate the taxonomy of selected species of Iranian snakes, inhabiting the northern and western mountains of Iran. Relevant taxa were detected based on a review performed on the available taxonomic data on snakes of Iran. Snake taxa with a wide distribution range that reflect complexity of adaptations to different ecosystems or have great matter of taxonomic confusion, including the Eirenis medus species complex, the Eirenis persicus species complex, the Eirenis punctatolineatus, the Montivipera raddei species complex, and Natrix tessellata, have been selected for this study. Samplings were done in the northern and western mountains of Iran between 2008 and 2011. Patterns of morphological variation and its relevance for taxonomical interpretations of the Montivipera raddei species complex, as well as the taxonomy of Natrix tessellata, Eirenis punctatolineatus and Eirenis medus species complex, were investigated using a principal component analysis (PCA) and a multivariate analysis of variance (MANOVA) on metric and meristic data of the specimens. Taxonomy of the Eirenis persicus species complex was studied using both traditional biometry and geometric morphometry on landmark data of the dorsal head scales. Two mitochondrial genes, 16S rRNA and cytochrome b, and one nuclear gene, c-mos, were sequenced and then a concatenated data set of these was analyzed to generate a Bayesian inference of phylogeny. The morphological analysis on the Montivipera raddei species complex revealed that a couple of specimens of the genus Montivipera, originating from the central Zagros mountain range, 216 is representing an unknown species. This species, named Montivipera kuhrangica Rajabizadeh, Nilson and Kami, 2011, has a higher count of head scales than other closely related species, including higher a number of intercanthal, supralabial scales and scales between the last supralabials. The field data indicate that in the Montivipera raddei species complex, there is a correlation between the dorsal color pattern variation and the environmental factors of the habitat, including vegetation and substrate color. In order to study geographic variation of Natrix tessellata in Iran, a total of 66 specimens, including 39 males and 27 females, were examined. The analysis on both sexes separately revealed that the males from the Fars province (southern Zagros) are significantly different from all other dice snakes in Iran, in the tail length, head length, head width and number of ventral scales. Further studies are needed to resolve the taxonomic problem of the southern Zagros populations of Natrix tessellata. The analysis on 23 males and 21 females of Eirenis punctatolineatus indicates that the southern Zagros populations differ significantly from the rest of the populations in tail length and number of subcaudal scales, number of preventral scales, number of scales bordering parietals and shape of the dorsal color pattern in both sexes. A subspecific subdivision is suggested for the northern and southern populations. As a new combination, Eirenis punctatolineatus condone (Boulenger, 1920), is proposed for the southern populations. Analysis on the three populations of Eirenis medus species complex from Turkmenistan and northern and western mountains of Iran, revealed a couple of specimens from Kerman province in southern Zagros that differs from known populations of Eirenis medus in their morphometric and meristic characters. Compared with Eirenis medus, this new species, named Eirenis kermanensis Rajabizadeh, Schmidtler, Orlov and Soleimani, 2012, has a higher number of subcaudals and a higher ratio of tail length over total length. Also in Eirenis kermanensis, the loreal scale is deeper than long, while in Eirenis medus the loreal is longer than deep. In studying the taxonomy of the Eirenis persicus species complex, the biometric data from 23 males and 17 females revealed that the populations of Eirenis persicus in the western mountains of Iran and Turkey are significantly different from the populations in eastern Iran, Turkmenistan and Pakistan. This significant divergence was confirmed by geometric morphometric and molecular analyses too. Both molecular and morphological analyses showed that specimens of the Eirenis persicus species complex that belong to the nigrofasciatus morph, are closely related to the eastern populations of the Eirenis persicus species complex. Within-group PCA revealed that Eirenis persicus populations of Iran and Turkey are morphologically different from each other at a subspecific level. This result was confirmed by molecular data as well. Studies on the genus Eirenis revealed the occurrence of cryptic biodiversity in these snakes. During the warming periods of the Pleistocene climatic oscillations, the suitable habitat of mountain dwelling snakes shifted to higher altitudes in the mountain. Subsequently, climatic cooling shifted the range of these habitats back to lower altitudes. These altitude shift of the habitat during the Pleistocene climatic oscillations induced the isolation and speciation in the examined snake species throughout the northern and western mountains of Iran. The present study on the selected species of the genera Eirenis, Natrix and Montivipera confirmed that the current knowledge on Iranian snake taxonomy is limited, and undescribed species remain to be discovered. This limited knowledge is to be understood due to the substantial snake biodiversity in Iran (related to its diversity of ecosystems) and lack of in-depth taxonomic studies on snake biodiversity. As such, although most of the results from this study are new related to our understanding of snake biodiversity in Iran, they still cover only a few species of this Iranian diversity, of which a lot remains to be properly assessed.

Jaar van publicatie:2013

Toegankelijkheid:Open