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Friday, 20 December 2013

Last chance of a European rodent: the fate of the Vojvodina blind mole rat

 by Gábor Csorba and Attila Németh

Rodents are usually not in the focus of conservation biology and proper evaluation of the conservation status of rodent species is complicated by the confusion that surrounds almost all levels of rodent systematics. However, the vulnerability of this order is demonstrated by the fact that rodent species contributed roughly half of mammalian extinctions in the last 500 years.

Nannospalax leucodon montanosyrmiensis
The situation is clearly mirrored in the case of the Eurasian blind mole rats. These small mammals represent a distinct group among rodents which is extremely adapted to subterranean life. They have cylindrically shaped body with no external ear and a vestigial tail, and are completely blind spending their entire life in their tunnel system built underground. Compared to other rodents, the conditions resulting from their lifestyle created a decreased morphological variability and the species are very similar both externally and osteologically. Putting aside the lineage of large mole rats (genus Spalax), taxa belonging to Nannospalax present a long-standing source of dispute and disagreement on their systematics. Within the latter genus one of the recognised species groups (regarded as superspecies) which include a large number of karyologically different taxa is the Lesser blind mole rat, Nannospalax (superspecies leucodon). Molecular genetic investigations of this superspecies are quite limited so far both in terms of geographic and taxonomic coverage and the species status of taxa differentiated on chromosomal grounds have not been widely accepted. Alongside with taxonomic uncertainty the determination of conservation status of different mole rat taxa is further hampered by their exclusively subterranean lifestyle which makes it difficult to evaluate their population size. It is worth to note that Microtus bavaricus (a rare and highly localised European rodent) is regarded as Critically Endangered. and receives much attention whereas - due to the disputed taxonomy - Lesser blind mole rats are treated as a single taxon and are categorised as Least Concern (Temple and Terry 2007) or Data Deficient ( In the meantime, populations and habitats of many different European chromosomal forms of the Lesser blind mole rats are disappearing at an alarming rate, a phenomenon which has just recently been realized...

A recently published paper presents a case study where a mammal within Europe can drift to the
Habitat fragments in the foothills of Fruska gora
rink of extinction almost unnoticed as a result of the lack of information, unclear taxonomic status and unrecognised tasks in conservation biology. On-going research of Carpathian Basin blind mole rats identified a small and fragmented population of these rodents on both sides of the Hungarian-Serbian border. Cytogenetic investigations proved that this population karyologically identical with the Vojvodina blind mole rat described earlier as Nannospalax (leucodon) montanosyrmiensis near the Fruska Gora, Serbia. Based on cytochrome b gene sequences, these blind mole rats form a discrete phylogenetic clade which, with a difference of about 10%, is well separated from other blind mole rat taxa inhabiting the Carpathian Basin.
According to the results of an other study, which is so far the most comprehensive molecular biological research on blind mole rats, montanosyrmiensis forms a well separated lineage that diverged from the closest taxon examined about 1.8 million years ago.

Habitat fragment near the Hungarian-Serbian border with a mole rat mound
The Vojvodina blind mole rat has only three extant populations that are widely separated from each other by unsuitable habitats e.g. agricultural fields and geographical barriers. The combined occupied area is estimated to be less than 10 km2, and the total estimated number of individuals is less than 400. These remaining populations are heavily fragmented and many fragments are under imminent threat by the establishment of tree plantations, small-scale and agro-industrial farms and land development. A study of the landscape history based on military maps spanning over the last 200 years has shown a drastic decrease in the extent and quality of potential habitats. Two of the three populations inhabits unprotected areas although the newly established Kőrös-ér Landscape Protection Area (declared on 18 April 2013) in the Hungarian side of the distribution area gives us the glimmer of hope to save this critically endangered endemic rodent of Europe from extinction.

Based on our present knowledge, the Vojvodina blind mole rat is one of the most seriously threatened, rarest mammal in Europe, the remaining population of which can disappear within years unless immediate conservation actions are taken.

Gábor Csorba
Hungarian Natural History Museum

Attila Németh
MTA-ELTE-MTM Research Group for Paleontology

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