Thursday, 3 July 2014

Four new species of Rock Lizard from Iran.

Rock Lizards of the genus Darevskia are found across western Asia and southeastern Europe. There are 27 recognised species, but this is thought likely to be an underestimate, as species tend to be both very similar morphologically and very variable within species, so that members of different species living in similar conditions will tend to resemble one-another more than members of the same species living under different conditions. Species groups where this is the case are often found to contain large numbers of cryptic species, which resemble one-another closely (or may even be morphologically identical) but which are distinct genetically and cannot interbreed. This has serious implications for conservation, as apparently large and healthy populations can be made up of several smaller and more vulnerable populations, leading to rapid decline or even extinction when the ‘species’ encounters adverse conditions.

Rock Lizards of along the south coast of the Caspian Sea have been for a long while been split into two species; Darevskia chlorogaster, which the subtropical mixed deciduous Hyrcanian Forest from sea level to about 1500 m, and Darevskia defilippii, which lives in grassy Alpine meadows and scree slopes at altitudes of up to 3355 m on the northern slopes of the Alborz Mountain, which separate the humid Caspian Sea coastal plain from the more arid regions of Central Iran. There is also an isolated population of Darevskia defilippii in the Kopet Dagh Mountains of Iran and Turkmenistan, considerably to the east of the Caspian Sea. Recently a third species of Darevskia has been identified from Iran, Darevskia steineri, which resembles Darevskia chlorogaster closely, and inhabits the same environment, but which appears to be more closely related to Darevskia defilippii.

In a paper published in the journal PLoS One on 4 December 2013, a team of scientists led by Faraham Ahmadzadeh of the Department of Biodiversity and Ecosystem Management at the Environmental Sciences Research Institute at Shahid Beheshti University and the Zoologisches Forschungsmuseum Alexander Koenig describe four new species of Rock Lizards from Iran, discovered using an approach that combined morphological, ecological and genetic data.

The first new species described is named Darevskia caspica, in reference to the Caspian Sea, along the southern coasts of which it dwells. This resembles and is related to Darevskia chlorogaster, but is genetically distinct. It is found in the central part of the Hyrcanian Forest in Mazandaran Province, Iran, where it dwells on tree trunks and the forest floor.

Darevskia caspica in life. Naeim Moradi in Ahmadzadeh et al. (2013).

The second new species described is named Darevskia kami, in honour of Haji Goli Kami of the Golestan University of Gorgan, a distinguished Iranian Herpetologist. This again resembles Darevskia chlorogaster closely and is related to it, but has now been shown to be a separate species. Darevskia kami is found in the western part of the Hyrcanian Forest in Golestan Province, Iran, where it dwells on tree trunks and the forest floor.

Darevskia kami in life. Omid Mozaffari in Ahmadzadeh et al. (2013).

The third new species described is named Darevskia kopetdaghica, after the Kopet Dagh Mountains of Iran and Turkmenistan. This species comprises all members of the Kopet Dagh population formerly attributed to Darevskia defilippii, which have now been shown to be genetically distinct. 

Darevskia kopetdaghica in life. Omid Mozaffari in Ahmadzadeh et al. (2013).

The final new species described is named Darevskia schaekeli, after Uwe Schäkel of the Alexander Koenig Society, for his long standing support of the Zoologisches Forschungsmuseum Alexander Koenig. This resembles and is related to Darevskia defilippii, but has now been shown to be genetically distinct, and occupies the eastern part of the Alborz Mountains in northern Iran.

Darevskia schaekeli in life. Barbod Safaei Mahroo in Ahmadzadeh et al. (2013).

The genetic differences between the different species of Darevskia in northern Iran appear to be quite deep, and Ahmadzadeh et al. suggest that these all predate the Pleistocene, when deteriorating climatic conditions split many vertebrate species into smaller groups in Eurasia, leading to the formation of many modern species. Instead they suggest that Darevskia chlorogaster and Darevskia defilippii may have spilt from a common ancestral population around the time of the Messinian Salinity Crisis, when a period of extremely arid climate linked to the drying of the Mediterranean Sea would have isolated smaller parts of a more widespread Darevskia population. This was followed at about 5 million years ago by the onset of mountain orogeny in the Lesser Caucasus, Alborz, Kopet Dagh and Balkhan Mountains, linked to the collision of the Arabian Plate with the southern Eurasian Plate, which caused folding and uplift what is now northern Iran, leading to the separation of all modern species into separate populations by the Late Pliocene.

The seven candidate species models for the Darevskia chlorogaster-complex (A) and the Darevskia defilippii-complex (B) inferred with *BEAST using combined mitochondrial and nuclear DNA. Values above branches are posterior probabilities, below branches are ML bootstrap values (support values below 0.95 and 50, respectively, are not shown). Bayesian species delimitation infers a speciation event at nodes marked by a solid circle and none at nodes with empty circles, numbers in parentheses refer to table 1 where detailed information on delimitation results is given. The geographic distribution of each candidate is shown in the maps, large points represent genetic sampling localities and small points are additional localities used for niche modeling. Supported species are encompassed by dashed lines. Ahmadzadeh et al. (2013).

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