Shimon Simson

Karyotype and genetic evolution in speciation of subterranean mole rats of the genus Spalax in Turkey

Karyotype (2n) and allozyme diversity at 37 gene loci were determined in 69 subterranean mole rats in Turkey belonging to the two superspecies: the ancestor Spalax leucodon (n = 55; 20 populations) and the descendant S. ehrenbergi (n = 14: four populations. We identified remarkable variation of diploid chromosome numbers in the S. leucodon superspecies: 2n = 38, 40, 50, 54, 60 and 62; and in the S. ehrenbergi superspecies: 2n = 52, 56 and 58. Genetic diversity indices were low on average in both S. leucodon and S. ehrenbergi superspecies: Allele diversity, A = 1.081 and 1.074; polymorphism, P-50 0 = 0.077 and 0.068; heterozygosity, H = 0.038 and 0.027; and gene diversity, H = 0.038 and 0.034, respectively. H ranged from 0 in mesic or semimesic regions to 0.088 in arid Anatolia. We consider the populations with different diploid chromosome numbers, 2n, as good biological species. Karyotypic diversity may mark extensive ecological speciation. Nees genetic distances, D average 0.174, range 0.002 0.422) and ecogeographical criteria suggest that almost each population may represent a different biological species, but critical future testing is necessary to support this claim. Karyotypes and allozymes are nonrandomly distributed across Turkey, displaying remarkable correlations with climatic and biotic factors. Both 2n and H are significantly correlated with aridity stress (2n/rainfall. r = −0.74; P < 0.001), and in our region also with climatic unpredictability. These results support the niche-width genetic variation hypothesis in space and time. Climatic selection in Turkey appears to be a major architect of karyotype and genetic (allozyme) diversity and divergence in mole rat evolution, in both speciation and adaptation.

Evolutionary biology of the genus Apodemus Kaup, 1829 in Israel. Allozymic and biometric analyses with description of a new species: Apodemus hermonensis (Rodentia, muridae)

Abstract Allozymic and biometric analyses were conducted on 195 speci mens belonging to the genus Apodemus from Israel. Genetic varia tion and differentiation were investigated by means of electro‐phoretic analysis of 36 gene loci. The electrophoretic results, com bined with biometric analysis, indicated the existence of a new Apodemus species, A. hermonensis, for which a formal description is given. The most common species in Israel, after A. mystacinus, is A. flavicollis and not A. sylvaticus, as commonly believed. So far we have found no A. sylvaticus in Israel. A. hermonensis was found on Mount Hermon, at about 2000 m. The body and skull sizes are intermediate between those of A. microps and A. sylvaticus. Geneti cally, it is very close to A. flavicollis, from which it can be distin guished by one locus (Np) fixed for an allele never found in Israeli populations of A. flavicollis, and another locus which is partially discriminant (Ada). In both A. mystacinus and A. flavicollis, the Israeli populations...

Size and Shape Variation in the Mandible of the Fossorial Rodent Spalax ehrenbergi

Three-dimensional Procrustes analysis was used to study the variation of mandible size and shape in the fossorial rodent superspecies Spalax ehrenbergi across the four chromosomal species in Israel (2n = 52, 54, 58 and 60) and the Egyptian species (2n = 60). Because the animals use their incisors to dig their underground tunnel systems, we selected the mandible as a potentially rich source of information on phylogenetic and adaptive processes that characterized the evolution of the superspecies during Pleistocene and Holocene times. Eleven landmarks were recorded from the mandible in three dimensions as x, y and z coordinates. Differences in landmark position among populations and species, based on a 3D graphic visualization of the landmarks, were studied after Procrustes Generalized Least Square (GLS) fitting through uni- and multivariate statistical analysis. Sexual dimorphism was found only for size. Size also changes in a consistent pattern for species, geography, soil type and other ecological descriptors. A principal component analysis of the “shape” GLS residuals and the Mahalanobis distances between populations shows a pattern consistent with species differences in chromosomes. This favors a phylogenetic interpretation for the observed pattern of variation. However, Partial Least Squares indicate that the change is also related to geography and current ecology and is associated with the increase in diploid number, suggesting that ecological factors affected speciation.

Adaptive differentiation of body size in speciating mole rats

SummaryWe 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.

Adaptive Pacifistic Behaviour in Subterranean Mole Rats in the Sahara Desert, Contrasting To and Originating From Polymorphic Aggression in Israeli Species

Aggression is a polymorphic trait that occurs in subterranean blind mole rats of the Spalax ehrenbergi superspecies in Israel (NEVO et al., 1975, 1986; NEVO, 1991). We found Egyptian mole rats in the isolates to be pacifistic. This supports our evolutionary theory of aggression in Spalax which predicts that aggression should decrease in the desert habitat (NEVO et al., 1986), presumably to minimize overheating, water and energy expenditure. The described behaviour is a pre-requisite for social evolution. We hypothesize that pacifistic behaviour in Spalax isolates in North Africa has been adaptively selected for survival in the harsh Sahara desert ecology.

Adaptive energy metabolism in four chromosomal species of subterranean mole rats

SummaryGross 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.

The chromosomes of the Israeli garden dormouse, Eliomys melanurus Wagner, 1849 (Rodentia, Gliridae)

Abstract Preliminary results of karyological analysis of the Israeli garden dormouse are reported. The chromosomes of Eliomys melanurus from the northern Negev Desert are described. The karyotype shows a diploid number of 2n = 48 (aFN= 86). These results reinforce the discordance between morphotypes and karyotypes observed in the genus Eliomys, showing the occurrence of different chromosome numbers also in the melanurus‐group of subspecies.

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

SummaryWe 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.

ALLOZYME VARIATION AND DIVERGENCE IN ERINACEIDAE (MAMMALIA, INSECTIVORA)

ABSTRACT Data are given on the genetic variation and divergence among 14 hedgehog populations of the species Erinaceus europaeus, E. concolor, and Hemiechinus auritus from Spain, Italy, Germany, Croatia, Greece, Turkey, Israel, and Egypt. The electrophoretic analysis was carried out on 30 gene loci. The overall mean heterozygosity for all the populations sampled was H = 0.032. The mean value of genetic distance between the two genera Hemiechinus and Erinaceus was D = 0.572, ranging from 0.494 to 0.687. The mean value of genetic distance between E. europaeus and E. concolor was D = 0.201. Populations of E. concolor from Israel and Asia Minor were highly differentiated from those from Europe. The mean genetic distance between these populations and European ones was D = 0.154, ranging from 0.122 to 0.207. The present results indicate that European E. concolor populations are genetically distinct from the Anatolian and Israeli ones, supporting the validity of the taxon roumanicus as a separate species. Among ...