Protein polymorphisms and their genetic control in the red-backed vole, Clethrionomys rufocanus bedfordiae

Twenty enzymatic and non-enzymatic proteins in a wild population of red-backed voles, Cletrionomys rufocanus bedfordiae , were investigated by electrophoresis. Seven enzymatic and non-enzymatic protein systems were found to be polymorphic. Breeding data indicated that the mode of inheritance of the enzyme systems ME-1, ME-2, GPD and EST were consistent with a Mendelian law. Two systems, 6 PGD and SOD, were estimated to be genetically controlled from the electrophoretic patterns and mother-offspring comparison of phenotypes. In the Tf system two new additional phenotypes were observed, but their inheritance could not be elucidated. Gene frequencies at seven loci were also investigated in 88 animals. There was no significant deviation from Hardy-Weinberg equilibrium.     

Acoustic signal characters in interspecific hybrids of bank and red-backed voles

It has been found that distress signals of bank and northern red-backed voles and their hybrids do not differ in qualitative characters, but the modes of the acoustic signal parameters in many cases differ in the hybrids depending on their origin and can be correlated with the inheritance of some morphological characters that are typical for the species. It is noted that the distress-signal frequencies (quartiles) differ significantly in the first-generation hybrids of various origin and their characteristics are closer to those of the paternal parent species. It has been found that the inheritance of the frequency characteristics by the second-generation hybrids does not have a well-pronounced regularity.     

DIFFERENTIATION AMONG NINE POPULATIONS OF PHLOX. I. ELECTROPHORETIC AND QUANTITATIVE VARIATION

The organization of genetic variation in Phlox drummondii was investigated using both allozyme electrophoresis and quantitative genetics. Variation at five polymorphic enzyme loci was characterized in nine populations, and variation in 16 morphological and life-history characters was examined using an analysis of full- and half-sibs in seven populations. Significant levels of genetic variation were found at enzyme loci and for metric characters. Significant heritabilities were observed for 15 of the 16 characters examined. Genetic differences among populations were revealed both by Nei's genetic distance and by phenotypic differences, summarized by discriminant analysis. Partitioning variance in allozyme frequencies among hierarchical levels of genetic organization indicated that 94% of this variance lay within populations, 4% between populations within varieties, and 2% between varieties. Partitioning phenotypic variance for metric characters indicated that 73% lay within populations, 24% lay between populations within varieties, and 3% lay between varieties. Thus, both electrophoretic and metric characters indicated that despite extensive genetic differentiation among populations, most of the evolutionary potential of the species lies within populations.     

Enzyme heterozygosity,metabolism, and developmental stability

Developmental homeostasis, measured as either fluctuating asymmetry or variance of morphological characters, increases with enzyme heterozygosity in many, but not all, natural populations. These results have been reported forDrosophila, monarch butterflies, honeybees, blue mussels, side-blotched lizards, killifish, salmonid fishes, guppies, Sonoran topminnows, herring, rufous-collared sparrows, house sparrows, brown hares, white-tailed deer, and humans. Because heterozygosity at a few loci can not predict heterozygosity of the entiry genome, these loci must be detecting localized zones that influence the developmental environment. Studies of malate dehydrogenase in honeybees,Apis mellifera, and lactate dehydrogenase in killifish,Fundulus heteroclitus, revealed that developmental homeostasis varied with heterozygosity of individual loci. Heterozygotes differed from homozygotes in fluctuating asymmetry, morphological variance, and in correlations between morphological characters. The protein loci in these studies code for enzymes, and therefore do not directly influence morphological characters. However, some enzymatic loci substantially influence metabolism, and contribute to variation in the amount of energy available for development and growth. This argument can be made most convincingly for the LDH polymorphism in killifish. LDH genotypes differ in enzyme kinetic properties that measure differences in physiological efficiency, and these differences produce measurable and predictable differences in physiology and development. Under environmental conditions which impose a stress upon development, genotypes at these loci may have different amounts of energy available for development, and consequently exhibit different levels of developmental homeostasis.     

Genetic variability in Plantago species in relation to their ecology

Summary Genetic variation in leaf and inflorescence morphology and in generative development within the species Plantago major has been analysed by means of crosses between members of two different subspecies. The variable characters chosen are supposed to be important for determining the ecological differences between the subspecies and other ecotypes. The analyses of F₂'s indicated that a substantial number of loci controlling the above mentioned characters are situated near the Pgm-1 locus, forming a gene complex. This gene complex can exist in at least three different forms in ssp. pleiosperma, ssp. major lawn type and ssp. major roadside type, respectively. In addition, some important factors for ecotypic differentiation are situated in the neighbourhood of the Got-1 locus and in a linkage group containing three other allozyme loci. These linkages between allozyme loci and fitness-affecting loci can explain the restriction of some enzyme alleles to a particular subspecies.Grassland Species Research Group Publication No. 50     

Biochemical genetics and taxonomy in Plumatella fungosa and P. repens (Bryozoa: Phylactolaemata)

SUMMARY. Some authors have recently concluded that, using morphological criteria, the freshwater bryozoans Plumatella repens and P. fugosa cannot be separated and should be regarded as conspecific. To test this conclusion, electrophoretic techniques have been used to examine genetic differences between the two nominate species at several enzyme loci. Significant variation at a malate dehydrogenase locus and three aminopeptidase loci establish beyond doubt that P. repens and P. fugosa are separate but related species. No significant variation was found between two populations of P. repens . Morphological characters for the distinction of the two species are discussed and evaluated.     

龙牙木天然种群遗传多样性及遗传分化

采用水平切片淀粉凝胶电泳测定东北地区分布的4 个龙牙木种群的遗传结构。统计分析了10 个酶系统的11 个位点, 结果表明:龙牙木种群内存在着丰富的遗传变异, 多态位点百分率72.73%, 等位基因平均数为1.72, 期望杂合度为0.5617, 遗传一致度和遗传距离为0.9865和0.0133。这个结果与前文对其形态特征和薄层色谱特征分析所得结果基本一致, 充分说明区域龙牙木属于同一种物种的两个变种。     

龙牙楤木天然种群遗传多样性及遗传分化

采用水平切片淀粉凝胶电泳测定东北地区分布的4个龙牙楤木种群的遗传结构。统计分析了10个酶系统的11个位点,结果表明：龙牙楤木种群内存在着丰富的遗传变异,多态位点百分率72.73%,等位基因平均数为1.72,期望杂合度为0.5617,遗传一致度和遗传距离和0.9865和0.0133。这个结果与前文对其形态特片和薄层色谱特征分析所得结果基本一致,充分说明区域龙牙楤木属于同一种物种的两个变种。     

中国沿海中部珊瑚菜居群等位酶变异及其遗传多样性

利用聚丙烯酰胺凝胶电泳方法,分析了我国沿海中部（江苏、山东和浙江）海滨沙滩珊瑚菜（Glehnia littoralis Fr.Schmidt ex Miq.)7个居群8种酶系统19个位点的等位基因遗传变异特征,结果表明居群内多态位点比率平均为82．4％,每一位点平均等位基因数为2．77,有效等位基因数为2．24,固定指数F的平均值为－0．091。珊瑚菜居群基因多样性80．9％产生于居群内,19．1％产生于居群间。居群间的遗传距离平均为0．317,遗传一致性为0．728,居群内维持着较高水平的遗传多样性。据此,对珊瑚菜的渐危机理进行了讨论。     

Gene-geographical variation and genetic differentiation in red-backed voles of the genus Clethrionomys (Rodentia,Cricetidae) in the Okhotskii region

Thirteen enzyme systems and three nonenzyme proteins were electrophoretically analyzed in red-backed voles of the genus Clethrionomys. In total, 25 loci were interpreted. Gene-geographic variation was studied and indices of genetic variability and differentiation were determined. By the distribution of electrophoretic variants of hemoglobin, C. rutilus was shown to be divided into two geographical groups (northern and southern). A low level of genetic differentiation was revealed in the island isolates of C. rutilus and C. rufocanus. Separation of C. rufocanus, C. rex, and C. sicotanensis into a superspecies complex was confirmed. A study of differential G- and C-banding on C. rutilus and C. rufocanus chromosomes did not reveal intraspecific variation of autosomes. In these species, karyotypes of voles from Kamchatka Peninsula were studied for the first time. They appeared to be morphologically similar to the karyotypes continental voles by both autosomes and sex chromosomes.     

Algebraic regularities of the ratio of heterozygosity with a mean and variance of quantitative character

The relationships of heterozygosity with the mean and variance of quantitative character were considered under neutrality, additivity and overdominance of polymorphic loci. Attention was drawn to dependence of the patterns of relationships on the number of polymorphic loci (which varied from 1 to 10) and on the type of polymorphic loci, both homogeneous (polymorphic loci are of the same type) and heterogeneous (polymorphic loci are of the two types) samples of 10 polymorphic loci and their combination. It is shown that increase in the number of polymorphic loci is accompanied with extension of the limits of corresponding relations, whereas the patterns of these relations depend on the type of connection of separate polymorphic locus with the quantitative character and on the ratio of different loci in the set of polymorphic loci. It is assumed that the relationship of heterozygosity with quantitative characters, displayed in the number of experimental works, may contain a component mediated by similar statistical effects. It is inferred that the discrepancy between different authors' experimental data on existence or lack of some relationships between multiplicative heterozygosity and morphological variability of quantitative characters can be explained by different types of relations of polymorphic loci to quantitative characters encountered in their works.     

Additive Variation Maintained under Stabilizing Selection: A Two-Locus Model of Pleiotropy for Two Quantitative Characters

A model with two diallelic loci controlling two additive quantitative characters is suggested. One of the loci has a similar effect on both characters, whereas the second locus has an antagonistic effect on two characters. Both characters experience direct stabilizing selection. The model yields a stable polymorphic state, with both characters maintaining genetic variation. The genetic correlation between the characters at the equilibrium is zero, in spite of the pleiotropic effects of the loci controlling them.     

Morphological, allozymic, and karyotypic distinctions between Neritina (Dostia) violacea and N. (D.) cornucopia (Gastropoda: Neritoidea)

Two species of mangrove gastropod, Neritina (Dostia) violacea Gmelin, 1791 and N. (D.) cornucopia Benson, 1836, from Hong Kong have been compared morphologically, allozymically, and karyotypically. The two can be identified by differences in shell pigmentation patterns, ventral shell characters, and radular teeth characters. Allozymic variations at 15 presumptive gene loci were examined. Average heterozygosities were 0.058 in local populations of N. (D.) violacea and 0.138 in N. (D.) cornucopia. Six enzyme encoding loci were typically diagnostic for individuals of each species and no hybrid patterns have been recorded. Nei's standard genetic distance and genetic identity between the two species were estimated to be 0.814 and 0.443, respectively. Karyotypic investigations have revealed that both species are diplonts, with two X-chromosomes in females and one in males. Diploid numbers are 2n = 20 + XX (or XO) for N. (D.) violacea and 2n = 26 + XX (or XO) for N. (D.) cornucopia.     

Population genetic studies of leafhopper (Empoasca) species

Seven populations of the genus Empoasca Walsh 1864 (Homoptera, Typhlocybinae) collected from six different host-plants were electrophoretically analyzed for thirteen enzyme loci. By using both the allozymes and the morphological characters of the male genitalia we found that these populations consisted of only two Empoasca species; E. decedens and E. decipiens. The use of allozymes proved to be the faster and more efficient method for discrimination; nine out of thirteen enzyme loci were diagnostic. E. decedens was found to be the most abundant species in all populations studied. There are no genetic differences between E. decedens populations associated with different host-plants. The total genetic variability was mainly organized within E. decedens populations, explaining more than 95% of the total variability.     

GENETIC ANALYSIS OF A HYBRID ZONE BETWEEN THE FIRE-BELLIED TOADS,BOMBINA BOMBINA AND B. VARIEGATA,NEAR CRACOW IN SOUTHERN POLAND

The fire-bellied toads Bombina bombina and B. variegata differ extensively in biochemistry, morphology, and behavior. We use a survey of five diagnostic enzyme loci across the hybrid zone near Cracow in Southern Poland to estimate the dispersal rate, selection pressures, and numbers of loci which maintain this zone. The enzyme clines coincide closely with each other and with morphological and mitochondrial DNA clines. Although the zone lies on a broad transition between environments suitable for bombina and variegata, the close concordance of diverse characters, together with increased aberrations and mortality in hybrids, suggest that the zone is maintained largely by selection against hybrids. There are strong “linkage disequilibria” between each pair of (unlinked) enzyme loci (R? = 0.129 [2-unit support limits: 0.119–0.139]). These are probably caused by gene flow into the zone, and they give an estimate of dispersal (σ = 890 [790–940] m gen^?½). The clines are sharply stepped, with most of the change occurring within 6.15 (5.45–6.45) km, but with long tails of introgression on either side. This implies that the effective selection pressure on each enzyme marker (due largely to disequilibrium with other loci) is s* = 0.17 (0.159–0.181) at the center but that the selection acting directly on the enzyme loci is weak or zero (s_e < 0.0038). The stepped pattern implies a barrier to gene flow of 220 (48–415) km. This would substantially delay neutral introgression but would have little effect on advantageous alleles; the two taxa need not evolve independently. Strong selection is needed to maintain such a barrier: hybrid populations must have their mean fitness reduced by a factor of 0.65 (0.60–0.77). This selection must be spread over a large number of loci to account for the concordant patterns and the observed cline widths (N = 300 [80–2,000]).     

Impact of urban fragmentation on the genetic structure of the eastern red-backed salamander

Urban development is a major cause of habitat loss and fragmentation. Few studies, however, have dealt with fragmentation in an urban landscape. In this paper, we examine the genetic structure of isolated populations of the eastern red-backed salamander (Plethodon cinereus) in a metropolitan area. We sampled four populations located on a mountain in the heart of Montréal (Québec, Canada), which presents a mosaic of forested patches isolated by roads, graveyards and buildings. We assessed the genetic structure of these populations using microsatellite loci and compared it to the genetic structure of four populations located in a continuous habitat in southern Québec. Our results indicate that allelic richness and heterozygosity are lower in the urban populations. Exact differentiation tests and pairwise F _ST also show that the populations found in the fragmented habitat are genetically differentiated, whereas populations located in the continuous habitat are genetically homogeneous. These results raise conservation concerns for these populations as well as for rare or threatened species inhabiting urban landscapes.     

Pleiotropic Stabilizing Selection Limits the Number of Polymorphic Loci to at Most the Number of Characters

We demonstrate that, in a model incorporating weak Gaussian stabilizing selection on n additively determined characters, at most n loci are polymorphic at a stable equilibrium. The number of characters is defined to be the number of independent components in the Gaussian selection scheme. We also assume linkage equilibrium, and that either the number of loci is large enough that the phenotypic distribution in the population can be approximated as multivariate Gaussian or that selection is weak enough that the mean fitness of the population can be approximated using only the mean and the variance of the characters in the population. Our results appear to rule out antagonistic pleiotropy without epistasis as a major force in maintaining additive genetic variation in a uniform environment. However, they are consistent with the maintenance of variability by genotype-environment interaction if a trait in different environments corresponds to different characters and the number of different environments exceeds the number of polymorphic loci that affect the trait.     

等位酶分析的遗传学基础（续）

在等位酶分析中,对酶谱的正确解释是获取遗传学资料的基础,酶谱作为酶基因的表现型,是由该种酶蛋白质的四级结构情况（亚基的数目）、在亚细胞分室中的分布（位点的数目）以及所分析样品的倍性和基因型的情况所决定的。术语“酶型”被建议用来记录和描述各种情况下酶谱的不同。在进行分子系统学研究中,如果直接把酶谱上带的数目的多少作为遗传多样性大小的指标,或把带的多少及迁移率的大小作为数量性状进行聚类和分枝分析将会得出非常错误的结论。     

Genetic differences among host-associated populations of water mites (Acari: Unionicolidae: Unionicola): allozyme variation supports morphological differentiation

Unionicola poundsi and U. lasallei are recognized as closely related, morphologically distinct species of water mites living in symbiotic association with the mussels Villosa villosa and Uniomerus declivus, respectively. However, results of a transplant experiment suggested that the morphological characters used to separate these species are plastic and are influenced by the host species in which these mites metamorphose. These results indicate that U. poundsi and U. lasallei are variants of the same species. To test the validity of these contrasting notions, the genetic structure of mite populations from Uniomerus declivus and V. villosa was compared. An examination of allozyme variation at 9 enzyme loci revealed a high degree of genetic differentiation between these host-associated populations, with mites from U. declivus and V. villosa being fixed for different alleles at 3 loci and exhibiting significant allele heterogeneity at 71% of their polymorphic loci. Coefficients of genetic similarity and genetic distance for mites from U. declivus and V. villosa were 0.36 and 0.95, respectively. The results of this study suggest that mite populations from U. declivus and V. villosa are genetically distinct and complement morphological data recognizing them as valid species.     

Isozymatic and Morphological Diversity in the Races of Maize of Mexico

To determine the relationships and genetic diversity among the Mexican races of maize, 209 accessions representing 59 races were analyzed for 21 enzyme systems encoded by 37 loci; 154 out of the 209 accessions were grown in multiple locations and seasons in Mexico and 47 morphological characters were measured. A very high level of variation among and within the Mexican races was found. However, more than 65% of the alleles found in the accessions studied are rare, occurring at frequencies below 0.01. In addition, some populations have low levels of genetic diversity and have values of genetic differentiation similar to selflng crops. Most of the accessions with low values of genetic diversity are specialty varieties.