Brain size diversity in adaptation and speciation of subterranean mole rats

We have tested brain size diversity and encephalization in the actively speciating subterranean mole rats of the Spalax ehrenbergi superspecies in Israel. Our sample involved 171 individuals comprising 12 populations and 4 chromosomal species (2n = 52, 54, 58 and 60) distributed parapatrically from the northern Mediterranean region southward (2n = 52, 54→+58→60) into increasingly more arid and unpredictable climatic regimes, approaching the Negev Desert. Our results indicate that relative brain size and encephalization are highest in 2n = 60 as compared with 2n = 52, 54 and 58. We hypothesize that this pattern is adaptive and molded by natural selection. Brain evolution and higher encephalization in the S. ehrenbergi complex appears to be associated with increasing ecological stresses of aridity and climatic unpredictability.     

Ribosomal DNA non-transcribed spacer polymorphism in subterranean mole rats: genetic differentiation,environmental correlates and phylogenetic relationships

Summary An analysis is presented of genetic differentiation in the non-transcribed spacers of ribosomal DNA (NTS rDNA). Diversity, environmental correlates and the phylogenetic relationships are examined within and between species of the actively speciating subterranean mole rat, superspeciesSpalax ehrenbergi (2n=52, 54, 58, 60) in Israel. This analysis is based on a previous study of the geographic distribution of restriction fragment length polymorphisms of NTS rDNA. Here we present results indicating that NTS rDNA diversity exists mostly (66%) within populations, while 20% is between populations within species, and 14% between species. Multivariate discriminant analysis succeeded in separating 10 of the 13 populations (77%) into their correct chromosomal species, on the basis of the combination of three NTS rDNA repetypes. The phylogenetic relationships suggest that the complex involves two pairs of closely related species (2n=52–54 and 2n=58–60). NTS rDNA diversity, as well as the decrease southward in frequency of repetype C, are correlated with climatic factors of humidity and temperature. These data are discussed in terms of the evolutionary forces of migration and selection which may cause NTS rDNA differentiation. Climatic selection appears to be the major differentiating factor of NTS rDNA.     

Developmental stability and adaptive radiation in the Spalax ehrenbergi superspecies in the Near-East

Chromosomal species of the mole rat, Spalax ehrenbergi, in Israel have been shown to display distinct adaptive strategies to increasing aridity. This adaptive radiation appeared to be associated with an increase in allozymic heterozygosity. In the present study, the developmental stability (DS) estimated by fluctuating asymmetry (FA) of dental traits was used to assess the suitability of habitat and the efficiency of adaptation to local environmental conditions among populations and chromosomal species. Although FA levels were highly heterogeneous among populations, they were not found to differ between species. DS of populations appeared, however, to be impaired at higher altitudes and in indurate soils. Since these environmental features were largely covariant, the effect of each one could not be precisely determined. Interestingly, while aridity is considered as the major selective force acting on populations southwards, DS was not altered under arid conditions, suggesting that mole rat populations were adapted to their local conditions of aridity. However, the cline of aridity is matched to several environmental and genetic clines among which are the increasing heterozygosity and recombination rate among species southwards. In studies of natural populations, the potential complementary effects of environmental and genetics on DS have to be considered and hamper the interpretation of habitat suitability expressed by DS in terms of adaptive strategies.     

Adaptive physiological variation in nonshivering thermogenesis and its significance in speciation

Summary Nonshivering thermogenesis (NST) magnitude was studied in the four chromosomal species of subterranean mole rats of theSpalax ehrenbergi superspecies in Israel. The four species show a distribution pattern which correlates with increasing aridity. The 2n=52 species inhabits the cold and humid regions, 2n=54 cold and dry, 2n-58 warm and humid, and 2n=60 the more arid regions in which temperatures fluctuate daily and annually. NST was measured as the ratio between maximal oxygen due to noradrenaline injection and minimal measured in anaesthetized animals.The chromosomal species 2n=60 from semiarid and arid habitats has the highest NST value. This fact emerges from the low Basal Metabolic Rate (BMR) of this species relative to all the other three species. A linear correlation was found between NST magnitude and the average daily range of temperature during June and September.We conclude that speciation of theS. ehrenbergi complex in Israel has thermoregulatory correlates such as heat production by NST, among others. The level of NST appears to be an adaptive physiological characteristic in the ecological speciation of subterranean mole rats.     

Morphometrics of speciating mole rats: Adaptive differentiation in ecological speciation

The morphometrics of subterranean mole rats, Spalax ehrenbergi superspecies in Israel, were studied. A total of 42 skull and body variables of 327 adults from 44 populations across the ranges of the 4 chromosomal species (2n = 52, 54, 58 and 60) were measured. The results showed: a. in general, significantly higher morphological values in males than in females; b. significant interspecific quantitative diffferences in 15 skull variables of males, and in 3 of females; but no qualitative diagnosis of any of the species; c. an intercorrelation between most skull variables at different orgamsmal levels, and a uniform and complete correlation with weight; d. a statistical discrimination in both metric and nonmetric multivariate analyses between most species pairs; e. an indication of high morphological similarity based on the relatively small multivariate Mahalanobis distances of dissimilarity between species; f. a possible explanation for a significant part of the variance in most skull and body variables resulting from a combination of temperature variables and water availability; g. a declination in size in skull and body variables between northern and southern species; h. the order of speciation events to be 2n = (54, 52)→58→60. Based on these results we conclude: 1. no morphological breaks are associated with the speciation of the S. ehrenbergi complex, and morphological differentiation is quantitative rather than qualitative between the species: 2. morphological diversity is significantly explained by climatic selection, and is therefore adaptive and explicable on even very low selective pressures over evolutionary time: 3. the morphospecies seem unable to reliably reflect the biological species in the S. ehrenbergi complex, and morphological differentiation, at least in this superspecies, evolves in a gradual rather than a punctual way: this would conform with Neo-Darwinian evolutionary theory.     

Nidicolous arthropods associated with different chromosomal types of Spalax ehrenbergi Nehring*

The mole rat, Spalax ehrenbergi Nehring, is a complex group involving four chromosomal types of In = 52, 54, 58 and 60. These are clinally distributed from Mount Hermon in the north to the Negev in the south, covering humid, semihumid, semiarid and arid climates. Forty-seven breeding nests of Sehrenbergi were collected from 23 localities throughout the range and processed for nidicolous arthropods. A total of five species of fleas and 53 species of gamasid mites were collected. Their distribution in the investigated area has been analysed in relation to that of the chromosomal types of S.ehrenbergi. The following conclusions have been reached:(a) Only three of the species (two haematophagous gamasids and one fungivorous acarid) range across the whole investigated area, showing strong host specificity, (b) A correlation is apparent between the distribution of several nidicolous arthropods (fleas and gamasids) and the ‘54’ geographic region. This probably reflects geographical distribution rather than host specificity, (c) Palaearctic species reach their southern limit of distribution on Mount Hermon and the Golan Heights; possibly Ethiopian ones reach their northern limit in the Negev. (d) No direct correlation has been found between nidicolous arthropods and the chromosomal types of S. ehrenbergi. (e) Subjects for future investigation are outlined.     

Adaptive variation in structure and function of kidneys of speciating subterranean mole rats

Summary We report on kidney structure and function in subterranean mammals of four chromosomal species (2n=52, 54, 58 and 60) belonging to the Spalax ehrenbergi superspecies, in relation to their speciation and adaptive radiation from mesic (2n=52) to xeric (2n=60) environments in Israel. Structural variables measured involved: (1) Relative Medullary Thickness, (RMT); (2) Relative Kidney Weight. (RKW); and (3) Percentage of Kidney out of Body Weight (PKW). Functional variables involved: (i) Urine Solid Concentration, (USC); and (ii) Urine Osmotic Concentration (UOC). The results for chromosomal species 2n=52, 54, 58 and 60 indicated nonsignificant increase southward for RMT, but displayed significant increase along the same transect for RKW, PKW, and USC. The UOC was significantly lower in mesic 2n=52 as compared to the other three species when experimental animals were fed in the laboratory on regular carrot food. However, protein stress food (soybean) and salt stress of 0.45 mol NaCl, caused significant, three and a half fold increase of UOC in 2n=52, 54 and 58; but four and a half fold increase in 2n=60, significantly higher than in the other three species. We conclude that both structurally and functionally, the kidneys differentiated adaptively during the Pleistocene evolution of S. ehrenbergi in Israel, in accordance with aridity stress and halophyte food resources towards the desert. Nevertheless, Spalax generally shows clear upper limits in kidney structural and functional capacities, preventing it from colonizing the true desert, south of the 100 mm isohyete.     

Molecular Evolution of Cytochrome b of Subterranean Mole Rats, Spalax ehrenbergi Superspecies, in Israel

We describe the molecular evolution of cytochrome b of blind subterranean mole rats. We examined 12 individuals for nucleotide differences in the region of 402 base pairs of mitochondrial cytochrome b. Each individual represents a different population from the entire ecological and speciational range of the four chromosomal species in Israel (2n= 52, 54, 58, and 60) belonging to the Spalax ehrenbergi superspecies. Our results indicate the following. (i) There are seven first-position transitional differences, compared to 34 variable third positions, with no observed second-position substitutions. (ii) A maximum of four amino acids differences occurs across the range. (iii) Within-species diversity increases southward. Only 1 autoapomorphic substitution characterizes either 2n= 52 or 2n= 54, but 6–11 substitutions characterize 2n= 58, and 9–13 substitutions characterize 2n= 60. (iv) Both parsimony and maximum-likelihood trees suggest two monophyletic groups: (a) 2n= 52 and 54, and (b) 2n= 58 and 60, as identified earlier by other protein and DNA markers. (v) Mitochondrial cytochrome b heterogeneity is significantly correlated with climatic factors (rainfall) and biotic factors (body size and allozymes). We hypothesize that two selective regimes direct cytochrome b evolution in the S. ehrenbergi superspecies: (i) purifying selection in the flooded, mesic, hypoxic northern range of 2n= 52 and 54 and (ii) diversifying selection in the climatically spatiotemporal, xeric, and variable southern range of 2n= 58 and 60. Thus, the molecular evolution of mitochondrial cytochrome b in S. ehrenbergi is explicable by opposite selective stresses across the range of S. ehrenbergi in Israel, associated with the ecological adaptive radiation of the complex. Received: 23 October 1998 / Accepted: 2 May 1999     

Individual Odours in Two Chromosomal Species of Blind,Subterranean Mole Rat (Spalax ehrenbergi): Conspecific and Cross-species Discrimination

Mole rats from two chromosomal species (2n = 58 and 2n = 60) of the Spalax ehrenbergi superspecies of Israel were tested to determine whether they were able to discriminate differences in the odour of urine from same-sex individuals of their own and of the other chromosomal species. An habituation-discrimination apparatus was designed for use with these solitary and blind subterranean rodents. Animals habituated to the odour of urine from one individual presented for 10 min at a centre sniffing area in the roof of a 50 cm long Perspex tunnel. The odour of urine from the original donor and from a second individual were presented at two other sniffing areas in the tunnel roof during a 5 min discrimination phase. Significant differences in the time spent investigating the two odours demonstrated successful discrimination between them. The results indicate that male and female mole rats of both species can discriminate between the individual-specific odour cues in urine from pairs of conspecifics and pairs of heterospecific mole rats.     

Sexual selection and natural selection in body size differentiation of subterranean mole rats

We exlored indirectly, the operation of sexual selection in subterranean mole rats of the Spalax ebrenbergi superspecies in Israel comprising four chromosomal species, 2n = 52, 54, 58 and 60. We reanalzed two previously available data sets of 1. body size differentiation (Nevo et al. 1986a) and 2. the intensity of “Total Aggression” in mole rats (Nevo et al. 1986b). We correlated the mean size difference between the two sexes, in each of the 12 populations of the chromosomal species, with the mean level of agression, and with climatic factors, both displaying significant correlations. The results indicated that for 2n = 52, 54, 58 and 60, the population averae difference in body weight between the sexes decreases southward as follows: 37.7g (30.8 % of females body weight), 39.3g(29.0%) 26.3g(22.8%) and 20.3g (19.3%), respectively. We interpret the higher body size diherential ketween the sexes in the north as due to sexual selection.     

Chromosomal polymorphisms in subterranean mole rats: origins and evolutionary significance

Two distinct chromosomal polymorphisms, among others, characterize the short (p) and long (qh) arms of chromosome number 1 of the Spalax ehrenbergi complex in Israel. We have studied the geographic distributions of these two polymorphisms in 60 animals belonging to four chromosomal species (2 n = 52, 54, 58 and 60). These comprised 15 populations: 12 from continuously distributed populations, two from semi-isolates, and one isolate in the northern Negev Desert.
Our results indicate that: (i) the two polymorphisms are widespread not only within populations and species but most strikingly between different bone marrow cells within an individual; this may reflect a diversity generating mechanism; (ii) the two polymorphisms of p and qh, primarily of p, are correlated with climatic factors of water availability and temperature, as well as geographical distances; these correlations are significantly above those expected by chance, (iii) The semi-isolates and the isolate display high levels of polymorphism in both p and qh, but particularly in qh, despite the small size population effects.
We suggest that at least the polymorphism in p is involved in the adaptive radiation of mole rats into diverse climatic regimes. Furthermore, we speculate that the forces generating chromosomal polymorphisms relevant to speciation (i.e. Robertsonian mutations), coupled with the evolutionary forces operating in small peripherally isolated populations, may be appropriate for the origin of new chromosomal species through peripatric speciation.     

Ribosomal DNA (rDNA) spacer polymorphism in mole rats

Genetic differentiation of ribosomal DNA (rDNA) nontranscribed-spacer (NTS) polymorphism was analyzed in 50 individuals from 13 populations among the four chromosomal species (2n = 52, 2n = 54, 2n = 58, and 2n = 60) of subterranean mole rats of the Spalax ehrenbergi complex in Israel. Southern blot analysis with a mouse rDNA probe and two restriction enzymes, EcoRI and BamHI, revealed various sizes of major restriction fragments. The assumption that this variation is due to length polymorphism of NTS DNA was supported by the construction of restriction-site maps. On the basis of the EcoRI and BamHi fragment lengths, we could characterize the major types of NTS rDNA repeating units in each individual. Each member of the central population in the four chromosomal groups of mole rats has a characteristic combination of the NTS types, suggesting that the karyotype groups were genetically diverged. Some near-hybrid-zone populations reflect similarities with the rDNA spectra of a neighbor chromosomal group. This might have resulted from gene flow across the hybrid zones.      

Aggression patterns in adaptation and speciation of subterranean mole rats

The patterns and correlates of aggressionwithin andbetween actively speciating subterranean mole rats of theSpalax ehrenbergi superspecies in Israel were tested in an attempt to approach an evolutionary theory of aggression related to both adaptation and speciation. Laboratory experiments were conducted on 314 adult mole rats (188 males and 126 females) caught in nature, representing 12 populations and comprising four chromosomal species (2n = 52, 54, 58, 60). The present analysis concentrates on “total aggression” comprising four aggressive variables: attacks, bitings, head-ons and sniffing with open mouth, out of 23 recorded variables. The results indicate that (a) aggression is distributed as a multipeak, discontinuous phenotypic parameter, displaying polymorphism within all 12 populations and 4 species tested; (b) the level of aggression was higher in males than in females, in the breeding than in the nonbreeding season, and displayed clinal geographic variation in both sexes across the superspecies range, where “militancy” increased northwards; (c) aggression was significantly correlated with ecological, physiological, genetical and ethological factors. These results support an evolutionary theory of aggression related to the intertwined processes of adaptation and speciation.     

Total body water and adaptive water turnover rate in four chromosomal species of subterranean mole rats of the Spalax ehrenbergi superspecies in Israel

Total body water (TBW) and water turnover rate (WTR) were measured in 24 subterranean mole rats comprising four populations, each belonging to a different chromosomal species of the Spalax ehrenbergi superspecies in Israel. The four species range in different climates: humid-cool (2n = 52); semiarid-cool (2n = 54); humid-warm (2n = 58) and arid-warm (2n = 60). TBW, as a percentage of body weight, measured by tritiated water (HTO), was 72.4%±4–7 in 2n = 52, significantly ( P < 005) higher than the similar estimates 61.7%± 7.2, and 59.4%± 5–3, for 2n = 60 and 58, respectively. A comparison of HTO space, as a percentage of TBW, closely approximated TBW, ranging from 97% to 108%. WTR was high, 218.1 and 230.9 ml/kg^0-75/day in the mesic populations of 2n = 58 and 52, respectively. By contrast, WTR estimates were significantly lower , ( P < 0.001), 150.2 and 148.9 ml/kg^0-75/day in the xeric populations of 2n = 54 and 60, respectively. The biological half-life time, T_1/2, was similar and faster, 32.7 and 27.9 hours in the mesic populations of 2n = 52 and 58, as compared with slower, 47.9 and 40.8 hours in the xeric populations of 2n = 54 and 60, respectively. Urine osmolarity in the most xeric northern Negev steppic population of 2n = 60 (737 ± 45 mmol/kg) was significantly ( P < 0.001) higher than in the other species.
We conclude that adaptive radiation in the Spalax ehrenbergi superspecies involves speciation in semiarid (2n = 54) and arid (2n = 60) climates by physiological adaptations of kidney water conservation, along with multiple morphological, physiological and behavioural syndromes of climatic adaptations to increasing aridity (Nevo, 1986).     

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Summary Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.     

Genetic polymorphism of urine deoxyribonuclease I isomerases of subterranean mole rats,Spalax ehrenbergi superspecies,in Israel: Ecogeographical patterns and correlates

Genetic polymorphism of urine deoxyribonuclease I (DNase I) of mole rats was analyzed by isoelectric focusing in a thin-layer polyacrylamide gel (IEF-PAGE). One hundred and three subterranean mole rats, comprising 13 populations belonging to the four chromosomal species (2n = 52, 54, 58, 60) of the actively speciating Spalax ehrenbergi superspecies in Israel, were tested. The following results were indicated. (i) Spalax DNase I consisted of 6-12 major isozymes. (ii) Four phenotypes (numbers in parentheses) were 1 (92), 1-2 (5), 1-3 (4), and 2 (1). The decreasing order of genetic diversity, He, in the four species was 0.37, 0.13, 0.10, and 0.0 for 2n = 58, 52, 54, and 60, respectively. (iii) Spearman rank correlations and multiple regression analyses indicated associations of allele frequencies and genetic diversity with climatic and vegetation factors. We concluded that (a) climatic selection, either directly or indirectly through plant (i.e., food resources) diversity, plays an important role in DNase genetic differentiation and (b) no gene flow and introgression occur between the recent derivative of speciation (2n = 60) and its ancestor (2n = 58), suggesting the operation of reproductive isolation between both species despite natural hybridization.     

Germination behaviour of annual plants under changing climatic conditions: separating local and regional environmental effects

The role of local adaptation and factors other than climate in determining extinction probabilities of species under climate change has not been yet explicitly studied. Here we performed a field experiment with annual plants growing along a steep climatic gradient in Israel to isolate climatic effects for local trait expression. The focus trait was seed dormancy, for which many theoretical predictions exist regarding climate-driven optimal germination behaviour. We evaluated how germination is consistent with theory, indicating local adaptation to current and changing climatic conditions, and how it varies among species and between natural and standardised soil conditions. We reciprocally sowed seeds from three or four origins for each of three annual species, Biscutella didyma, Bromus fasciculatus and Hymenocarpos circinnatus, in their home and neighbouring sowing locations along an aridity gradient. Our predictions were: lower germination fraction for seeds from more arid origins, and higher germination at wetter sowing locations for all seed origins. By sowing seeds in both local and standard soil, we separated climatic effects from local conditions. At the arid sowing location, two species supported the prediction of low germination of drier seed origins, but differences between seed origins at the other sites were not substantial. There were no clear rainfall effects on germination. Germination fractions were consistently lower on local soil than on standard soil, indicating the important role of soil type and neighbour conditions for trait expression. Local environmental conditions may override effects of climate and so should be carefully addressed in future studies testing for the potential of species to adapt or plastically respond to climate change.     

Adaptive energy metabolism in four chromosomal species of subterranean mole rats

Summary Gross energy intake and apparent dry matter digestibility of animals fed carrots ad lib in the laboratory, were measured in the four chromosomal species of the Spalax ehrenbergi superspecies in Israel. Gross energy intake of 132.8 and 155.9 kJ/day was measured for the 2n=52 and 2n=58 chromosomal mesic species, while in the 2n=54 and 2n=60 chromosomal xeric species it measured only 80.3 and 75.0 kJ/day, respectively. Dry matter digestibility ranged between 92.3 and 95.6% in thefour chromosomal species. The differences in gross energy intake between the mesic and xeric species, appeared to reflect adaptive energy metabolism variation associated with geographic variation in climate, habitat productivity, and food availability.     

Adaptive differentiation of body size in speciating mole rats

Summary We report the body weight of 1,653 subterranean mole rats comprising 12 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. The sample was collected from 1970 to 1985 and includes all captured animals with a minimal age of 10 months. The results indicated the following. (a) Body weight of males was significantly higher than that of females. (b) There is a southward latitudinal gradient in body size. Northern animals living in cooler and more productive mesic environments are larger than southern animals living in warmer and less productive xeric environments. (c) The interspecific differences for each sex are statistically significant. (d) Body size is negatively correlated with temperature variables, and positively correlated with plant cover (reflecting productivity or food resources) and rainy days. (e) The best predictors of body size, explaining up to 87% of the variation in size included various combinations of temperature variables and plant cover.We conclude that in both adaptation and speciation natural selection is a major agent of differentiation of body size in accordance with multiple factors, primarily temperature and food resources operating on the energetics balance.     

Adaptation of Pelage Color and Pigment Variations in Israeli Subterranean Blind Mole Rats,Spalax Ehrenbergi

Background

Concealing 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.

Methods

We 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.

Results

Due 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/Significance

Darker 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.