Protease inhibitor subtypes in some population groups from Israel

Results of protease inhibitor (PI) subtyping on polyacrylamide gel isoelectrofocusing of 599 Israeli non-Jews and 1,393 Israeli Jews are recorded. A discriminant analysis (DS) was performed on frequency data of the 5 PI alleles (M1, M2, M3, S and Z) with data of Europeans, Israeli non-Jews and Israeli Jews. A higher percentage of correct classification was obtained when Jews were treated as a separate population group rather than when distributed in their areas of origin. This suggests a greater resemblance, in the PI system, of the studied Jewish groups to each other than of the European Jews to Europeans and of the studied mediterranean Jews to Middle Eastern non-Jews. A cluster analysis disclosed distance relationships in a similar direction. PI allele distribution, in the studied Jewish samples, has the following characteristics: Jews share with Middle Eastern non-Jews an absence of PIZ, which is present in Europeans. Mediterranean Jews have higher frequencies than Ashkenazi Jews, of PIS alleles, which are absent in Middle Eastern non-Jews. European Jews are closer to the Europeans than Middle Eastern Jews in their PIM allele frequencies. An original common gene pool of Jews with Middle Eastern non-Jews is postulated, of which the Sephardic (Spanish) and Middle Eastern Jews differ, now, in having PIS, and European Jews differ in having slightly lower PIM3 and PIM2 and higher PIM1 frequencies. A possibility of admixture and selection, affecting different alleles in different Jewish communities at different times, is suggested to have contributed to the present-day deviations from the supposed original gene pool.     

Foraging strategy in a subterranean rodent,Spalax ehrenbergi: a test case for optimal foraging theory

Summary The foraging behavior of the subterranean mole rat Spalax ehrenbergi (Rodentia, Spalacidae) was tested according to the framework of optimal foraging theory. We compared the frequencies of food species hoarded in storage chambers of mole rats with the frequencies of these species occurring in the vicinity of the mole rats' nest mounds during the winter and spring seasons. In addition, we examined the food composition of several summer nest mounds. Laboratory observations were conducted in order to test the foraging behavior of mole rats under simulated subterranean conditions. The mole rat is a generalist and collects a variety of food species. Out of 33 plant species that were hoarded by mole rats in the 21 studied nest mounds, 61% (n=20) were geophytes, 21% (n=7) perennial herbs, 15% (n=5) annual herbs and 3% (n=1) dwarf shrubs. The frequency of each collected species in the 16 winter and spring nest mounds is in general accordance with its frequency in the mole rat's territory. This implies that the mole rat randomly samples the food reserve of its territory without special preference or directed search for a particular species. The collection or avoidance of any food item is not dependent on the presence or absence of any other food item. We suggest that the foragin generalism of the mole rat is a product of the constraints of a subterranean niche — the necessity to hoard food as much as possible in a limited time period and the high energetic investment of tunneling to the food items.     

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.     

Evidence for improved myocardial oxygen delivery and function during hypoxia in the mole rat

Summary The high capillary density of the hypoxic adapted mole rat may provide an efficient oxygen extraction system that permits the maintenance of a normal metabolic rate during hypoxia. We compared myocardial function and energetics in the isolated working heart of the mole rat with that of the white rat during oxygenation (567 torr O₂) and 3 hypoxic periods of 319, 232 and 155 torr O₂, each followed by a reoxygenation period. Control hearts were perfused for a similar time but with oxygenated buffer. The control oxygenated mole rat heart had higher coronary flow (CF), systolic pressure and myocardial O₂ consumption and lower coronary resistance compared with the heart of the white rat. The hypoxic heart of the mole rat had higher CF, aortic flow, stroke volume, , mechanical power and efficiency, and lower coronary resistance compared with the hypoxic heart of the white rat. The better performance of the hypoxic mole rat heart was not due to a more efficient O₂ extraction but was associated with a lower coronary resistance. The findings correlate with the known cardiac physiology of the intact mole rat.     

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.     

Natural selection of allozyme polymorphisms: a microgeographic climatic differentiation in wild emmer wheat (Triticum dicoccoides)

Summary Allozymic variation in proteins encoded by 48 loci was analyzed electrophoretically in 1984 and 1985 in 137 individual plants of wild emmer wheat, Triticum dicoccoides, from a microsite in Yehudiyya, northeast of the Lake of Galilee, Israel. The test involved two climatic microniches in the open Tabor oak forest (1) sunny between trees and (2) shady under trees' canopies. Significant genetic differentiation at single-, two- and multilocus structures was found between neighboring climatic niches, which were only separated by a few meters. Our results suggest that allozyme polymorphisms in wild emmer wheat are partly adaptive, and differentiate primarily at the multilocus level by climatic factors presumably related to aridity stress.