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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.

SUBMITTER: Hadid Y

PROVIDER: S-EPMC3253805 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Is evolution of blind mole rats determined by climate oscillations?

Hadid Yarin Y Németh Attila A Snir Sagi S Pavlíček Tomáš T Csorba Gábor G Kázmér Miklós M Major Agnes A Mezhzherin Sergey S Rusin Mikhail M Coşkun Yüksel Y Nevo Eviatar E

PloS one 20120109 1

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 o ...[more]

PMID: 22253871

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Project description:Changes in gene regulation have long been though to underlie most phenotypic differences between species. Subterranean rodents, and in particular the naked mole-rat (NMR), have attracted substantial attention due to their proposed phenotypic adaptations, which include hypoxia tolerance, metabolic changes and cancer resistance. However, it is largely unknown what regulatory changes may associate with these phenotypic traits, and whether these are unique to the NMR, the mole-rat clade or also present in other mammals. Here, we undertook a comparative genomics approach to identify genome-wide promoter and enhancer regions harbouring epigenomic hallmarks of regulatory activity, in heart and liver from two mole-rat species (NMR and DMR) and two rodent outgroups. To identify promoters and enhancers displaying robust shifts in regulatory activity in the mole-rat clade, we adapted and applied a phylogenetic modeling approach to quantitatively compare epigenomic signals at orthologous locations, while accounting for phylogenetic distance and inter-species variation. This method identified thousands of orthologous promoter and enhancer regions with increased activity in ancestral or single-species mole-rat branches, as well as hundreds of promoters and enhancers with reduced activity in mole-rats versus other rodents. These elements underlie both shared tissue-specific changes in gene regulation associated with mole-rat evolution, which include metabolic and functional adaptations in heart and liver. Moreover, by comparing mole-rat specific changes in promoters and enhancers between ancestral and single-species branches, our data revealed a number of candidate pathways with stepwise regulatory changes during mole-rat evolution. Lastly, we analysed the genomic properties of non-alignable promoters and enhancers in mole-rats, and report (i) their overlap with specific repetitive elements and transcription factor binding sites; and (ii) their association with metabolic gene functions. On the whole, these comparative analyses reveal mole-rat specific epigenomic changes across orthologous and non-mappable promoters and enhancers - which inform previously reported mole-rat adaptations from a gene regulation perspective.

Project description:BackgroundConcealing coloration in rodents is well established. However, only a few studies examined how soil color, pelage color, hair-melanin content, and genetics (i.e., the causal chain) synergize to configure it. This study investigates the causal chain of dorsal coloration in Israeli subterranean blind mole rats, Spalax ehrenbergi.MethodsWe examined pelage coloration of 128 adult animals from 11 populations belonging to four species of Spalax ehrenbergi superspecies (Spalax galili, Spalax golani, Spalax carmeli, and Spalax judaei) and the corresponding coloration of soil samples from the collection sites using a digital colorimeter. Additionally, we quantified hair-melanin contents of 67 animals using HPLC and sequenced the MC1R gene in 68 individuals from all four mole rat species.ResultsDue to high variability of soil colors, the correlation between soil and pelage color coordinates was weak and significant only between soil hue and pelage lightness. Multiple stepwise forward regression revealed that soil lightness was significantly associated with all pelage color variables. Pelage color lightness among the four species increased with the higher southward aridity in accordance to Gloger's rule (darker in humid habitats and lighter in arid habitats). Darker and lighter pelage colors are associated with darker basalt and terra rossa, and lighter rendzina soils, respectively. Despite soil lightness varying significantly, pelage lightness and eumelanin converged among populations living in similar soil types. Partial sequencing of the MC1R gene identified three allelic variants, two of which were predominant in northern species (S. galili and S. golani), and the third was exclusive to southern species (S. carmeli and S. judaei), which might have caused the differences found in pheomelanin/eumelanin ratio.Conclusion/significanceDarker dorsal pelage in darker basalt and terra rossa soils in the north and lighter pelage in rendzina and loess soils in the south reflect the combined results of crypsis and thermoregulatory function following Gloger's rule.

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Is evolution of blind mole rats determined by climate oscillations?

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Is evolution of blind mole rats determined by climate oscillations?

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