Is Evolution of Blind Mole Rats Determined by Climate Oscillations?

Abstract

The concept of climate variability facilitating adaptive radiation supported by the “Court Jester” hypothesis is disputed by the “Red Queen” one, but the prevalence of one or the other might be scale-dependent. We report on a detailed, comprehensive phylo-geographic study on the ∼4 kb mtDNA sequence in underground blind mole rats of the family Spalacidae (or subfamily Spalacinae) from the East Mediterranean steppes. Our study aimed at testing the presence of periodicities in branching patterns on a constructed phylogenetic tree and at searching for congruence between branching events, tectonic history and paleoclimates. In contrast to the strong support for the majority of the branching events on the tree, the absence of support in a few instances indicates that network-like evolution could exist in spalacids. In our tree, robust support was given, in concordance with paleontological data, for the separation of spalacids from muroid rodents during the first half of the Miocene when open, grass-dominated habitats were established. Marine barriers formed between Anatolia and the Balkans could have facilitated the separation of the lineage “Spalax” from the lineage “Nannospalax” and of the clade “leucodon” from the clade “xanthodon”. The separation of the clade “ehrenbergi” occurred during the late stages of the tectonically induced uplift of the Anatolian high plateaus and mountains, whereas the separation of the clade “vasvarii” took place when the rapidly uplifting Taurus mountain range prevented the Mediterranean rainfalls from reaching the Central Anatolian Plateau. The separation of Spalax antiquus and S. graecus occurred when the southeastern Carpathians were uplifted. Despite the role played by tectonic events, branching events that show periodicity corresponding to 400-kyr and 100-kyr eccentricity bands illuminate the important role of orbital fluctuations on adaptive radiation in spalacids. At the given scale, our results supports the “Court Jester” hypothesis over the “Red Queen” one.

Possible incipient sympatric ecological speciation in blind mole rats (Spalax)

“…This remarkable evolution followed stepwise climatic cooling and drought stresses during the transition from the Middle Eocene to the Early Oligocene (3). The evolutionary history of spalacids during the Neogene (35) and Pleistocene (3,22,23) also was channeled by climatic stresses and oscillations. Thus, ecological stresses influenced the evolution of spalacids in both adaptation and speciation.…”

Chromosomal evolution of the Genus Nannospalax (Palmer 1903) (Rodentia, Muridae) from western Turkey

“…Which factor causes these rearrangements is still not conclusively known. On the other hand, recently published molecular studies (Krystufek et al, 2011;Hadid et al, 2012;Kandemir et al, 2012) showed that differentiation of chromosomal races of blind mole rats in Anatolia was already done and each chromosomal race might be a good candidate to be a separate species. However, more detailed molecular studies using techniques such as genome analysis and mtDNA are still required.…”

“…Chromosomal races with small diploid numbers were grouped together, and leucodon was closer to xanthodon rather than to ehrenbergi. Hadid et al (2012) also used molecular tools to draw a maximum likelihood tree of blind mole rats from 3 different species. In their results, Aydın (2n = 36) and Beyşehir (2n = 40) grouped together.…”

Revised classification design of the Anatolian species of Nannospalax (Rodentia: Spalacidae) using RFLP analysis

“…More recently, Hadid et al (2012) analyzed the phylogenetic relationships among samples of Nannospalax using mitochondrial DNA genes, and they recognized 4 major clades (vasvarii, leucodon, xanthodon, and ehrenbergi).…”

“…Phylogenetic studies using data from allozymes (Nevo et al, 1995), randomly amplified polymorphic DNA (Kankılıç et al, 2013), mitochondrial sequences (Arslan et al, 2010;Hadid et al, 2012;Kandemir et al, 2012;Kryštufek et al, 2012), and cytogenetics (Ivanitskaya et al, 2008;Arslan et al 2011) have been conducted in an attempt to understand relationships within Nannospalax. These molecular studies with limited cytotype sampling supported the monophyly of the genus and recognized 4 major clades (vasvarii, leucodon, xanthodon, and ehrenbergi) (Hadid et al, 2012). The clade vasvarii represents the cytotypes (2n = 62 and 60) from the Central Anatolian Plateau.…”