Differential divergence in autosomes and sex chromosomes is associated with intra‐island diversification at a very small spatial scale in a songbird lineage

Recently diverged taxa showing marked phenotypic and ecological diversity provide optimal systems to understand the genetic processes underlying speciation. We used genome‐wide markers to investigate the diversification of the Reunion grey white‐eye (Zosterops borbonicus) on the small volcanic island of Reunion (Mascarene archipelago), where this species complex exhibits four geographical forms that are parapatrically distributed across the island and differ strikingly in plumage colour. One form restricted to the highlands is separated by a steep ecological gradient from three distinct lowland forms which meet at narrow hybrid zones that are not associated with environmental variables. Analyses of genomic variation based on single nucleotide polymorphism data from genotyping‐by‐sequencing and pooled RAD‐seq approaches show that signatures of selection associated with elevation can be found at multiple regions across the genome, whereas most loci associated with the lowland forms are located on the Z sex chromosome. We identified TYRP1, a Z‐linked colour gene, as a likely candidate locus underlying colour variation among lowland forms. Tests of demographic models revealed that highland and lowland forms diverged in the presence of gene flow, and divergence has progressed as gene flow was restricted by selection at loci across the genome. This system holds promise for investigating how adaptation and reproductive isolation shape the genomic landscape of divergence at multiple stages of the speciation process.     

Comparison of multivariate methods for the analysis of genetic resources and adaptation in Phytolacca dodecandra using RAPD

The extent of genetic differentiation among 17 Ethiopian populations (249 individuals) of Phytolacca dodecandra (Endod) sampled along altitudinal gradients that varied from 1600 to 3000 m was investigated using random amplified polymorphic DNA (RAPD). The populations were classified into three altitude groups: lowland (1600–2100 m), central-highland (2101–2500 m) and highland (2500–3000 m). Seventy polymorphic loci scored from 12 RAPD primers, singly or in combination with ecogeographical variables (altitude, longitude, latitude, temperature and rainfall), were used for principal component, discriminant, correlation, and stepwise multiple regression analyses. Principal component analysis (PCA) clearly differentiated lowland and the central-highland populations from those of the highlands independent of their geographical regions. Canonical discriminant analysis separated the lowland plants from those of the highlands with the central-highland plants being intermediate. Classificatory discriminant analysis corrected classification of 92.8% of the 249 plants into their respective three altitude groups. Multiple regression analysis identified a strong association between some RAPDs and altitude, temperature and rainfall, while the variation in most RAPDs was explained by combinations of the different ecogeographical variables. It is hypothesised that the different altitude groups may be (1) chemical and/or physiological ecotypes produced as a result of complex interactions of altitude with climatic and/or edaphic factors, or (2) different in ploidy levels. The significant correlations obtained between population means from some RAPDs and altitude and temperature as well as the strong association of some RAPDs with the ecogeographical variables in the multiple regression analysis suggest that part of the RAPD polymorphism could be adaptive, and responsive to environmental selection. Received: 15 December 1999 / Accepted: 12 February 2000     

Segregation distortion and differential fitness at the albumin locus in rhesus monkeys (Macaca mulatta)

The observed patterns of segregation of two co-dominant alleles at the macaque albumin locus in 400 rhesus monkey offspring were compared with those expected for five segregating mating phenotypes. Rates of reproductive loss and conception were also compared among females of each albumin phenotype. The common albumin allele in macaques, Al^A_mac, segregated more frequently than expected when the mother was heterozygous but less frequently than expected when she was homozygous for Al^B_mac. In both cases, the phenotype identical to that of the mother appeared to be favored. Mothers who were either homozygous for Al^A_mac or heterozygous were also found to experience higher conception rates than mothers homozygous for Al^B_mac. It is hypothesized that phenotypic differences in bilirubin binding, and in competitive binding by dietary constituents, by albumin influences both these results and the nonrandom distribution of Al^B_mac in Asian macaques.     

Distribution of hereditary blood groups among Indians in South America. IV. In Chile with inferences concerning genetic connections between Polynesia and America

This is the fourth paper in a series on the distribution of blood groups among Indians of South America. It reports the findings on the Indians of Chile and the Polynesians of Chile's Easter Island. Blood specimens were procured from the following putatively pure Indians and unmixed Polynesians: 44 Alacaluf of Puerto Eden, Isla Wellington, 141 Mapuche (Araucanian) of Lonquimay, Malleco Province, 80 Atacameños of Antofagasta Province, and 45 Polynesians of Easter Island. These 310 samples were tested for blood factors in the A-B-O, M-N-S-s, P, Rh-Hr, Lutheran, K-k, Lewis, Duffy, Kidd and Diego systems, and for the Wright (Wr^a) agglutinogen. Serum samples were tested for haptoglobins and transferrins. Hemolysates prepared from the blood clots were tested for hemoglobin types. The results are presented as phenotype incidences and calculated gene frequencies in appropriate tables. Locations of the populations from which blood samples were procured are shown on two maps. The high frequencies for the O gene usually reported for South American Indians obtain in putatively pure Chilean Indians but A¹ is high in Easter Island Polynesians. In both Indians and Polynesians M, s, R¹ (CDe), R² (cDE), Lu^b, k, Le^H, and Fy^a gene frequencies are high and B, N, S, Mi^a, Vw, Rº (cDe), r (cde), Lu^a, K, Le¹, Fy^b, and Wr^a (Ca) are low or absent. The Diego (Di) gene is present in the Mapuche and Atacameños but absent in the Alacaluf and Polynesians. Hp¹ gene frequencies were determined only in the Alacaluf and Atacameños, in which they are 0.48 and 0.67 respectively. Transferrins were determined for the Alacaluf and Atacameños Indians and all were classified as Tf C. All Chilean Indian and Polynesian specimens were tested electrophoretically for hemoglobin types and all contained only hemoglobin (A) as a major component.     

Distribution of hereditary blood groups among Indians in South America. 3. In Bolivia

Blood samples were procured from the following populations of putatively pure Indians in Bolivia: 503 Aymará from the Altiplano and Yungas, 30 Chama, 11 Tacana, 14 Chácobo, 109 Itonama, 67 Moré, and 27 Sirionó from the Beni and lowland rainforest. Erythrocytes from these 761 specimens were tested for antigens in the A-B-O, M-N-S-s, P, Rh-Hr, Lutheran, Kell-Cellano, Lewis, Duffy, Kidd, and Diego systems, and for the Wright agglutinogen. The serum samples were tested for haptoglobins and transferrins; and hemolysates were prepared and examined for hemoglobin types. Results of these tests are presented as phenotypes and calculated gene frequencies on appropriate tables. A map is included to show the locations of the populations from which blood samples were obtained. Frequencies are generally high for the O gene, it being the only gene of the ABO system which appears in the Chama, Chácobo and Sirionó. The presence of A₁, A₂ or B genes in the Bolivian Indians is interpreted as being most probably of caucasoid introduction. Excepting the Sirionó the frequencies are high for M and low for N genes as is usual for Amerinds, the M gene being the only one detected in the Chama. The s gene frequency in high and the S low except in the small isolated Chácobo population in which S gene frequency is extremely high for Amerinds. Inbreeding and perhaps genetic drift in this small isolate may account for this aberrancy from normal. The Bolivian specimens presented the high frequencies for genes R¹ (CDe) and R² (cDE) and the low frequencies for genes r (cde) and R⁰ (cDe) usually observed in American Indians. The Lu^a factor was observed in only one of 120 Aymará at Santa Fe in the Yungas. The Lu^a factor, when observed in Amerinds, suggests foreign introduction of the responsible gene. Fy^a gene frequencies are consistently high and excepting the Aymará and Chama so also are Jk^a frequencies. Frequencies for the Diego (Di^a) factor vary from 3.70% in 27 Sirionó to 73.33% in 30 Chama. No K, Mi^a, Vw or Wr^a antigens were demonstrable in the Indian blood samples from Bolivia. Phenotypes and calculated gene frequencies for haptoglobins and transferrins are presented. All Bolivian Indian bloods tested electrophoretically contained only hemoglobin (A) as a major component.     

Distribution of albumin variants in Indians and non-Indians of Mexico

The distribution of albumin variants amongst several Mexican Indian and non-Indian (Mestizo) groups was studied. Of the former, a total of 1606 individuals belonging to 11 different tribes were examined with an overall frequency of 1.5% of Albumin Mexico fairly uniformly distributed in all four main linguistic groups. The 2548 Mestizos studied belong in six groups, two from Mexico City and four from elsewhere in the country. The first of the Mexico City groups consisted of 1313 individuals randomly chosen from the outpatient clinic of the Instituto Nacional de la Nutrición, while the rest included healthy individuals. The overall frequency was 1.9%, also fairly evenly distributed, with no difference between the hospital population and the others. No anomalous albumin, other than Albumin Mexico was encountered in the whole study. It is concluded that the similarity between Indians and Mestizos is due to the high Indian component of the latter and that the presence of albumin Mexico is a good anthropological marker for this region of the world.     

Gc types in one Indian group and one Mestizo Mexican group

Summary The distribution of Gc types was investigated in an Indian group residing in Cuetzalan, Puebla, and in a Mestizo group from Mexico City. Gc¹ and Gc² gene frequencies were 0.862 and 0.138 in Cuetzalan, and 0.858 and 0.142 in Mexico City. These figures are similar to those obtained by other authors in one Northeastern Mexican City. A literature review showed that there appears to be a pattern of high Gc²-frequency in most Brazilian Indians (above 0.3) in contrast to a low frequency (below 0.2) in most other Amerindian groups studied.     

Distribution of albumin variants Naskapi amd Mexico among Aleuts, Frobisher Bay Eskimos, and Micmac, Naskapi, Mohawk, Omaha, and Apache Indians

In order to help define the boundaries of the distribution of the albumin variants Naskapi and Mexico which are polymorphic among several American Indian groups, we examined sera from Micmac, Mohawk, Northwest River Naskapi, Omaha and Apache Indians, and from Aleuts and Eskimos. Sera from a total of 1,524 individuals were examined. Using a cellulose acetate membrane electrophoretic system with Tris-Citric acid at pH 5.4 we were able to distinguish normal albumin and both variants in the same run. Naskapi and Mexico variants were absent from Aleut, Eskimo, Micmac, Mohawk and Omaha samples. The albumin Naskapi variant was present in an allele frequency of 0.03 in the Naskapi Indian sample. Albumin variants Naskapi and Mexico were found in the Apache sample at frequencies of 0.016 and 0.037, respectively. This report supersedes that previously published by Schell and Agarwal ('76). Generally, within an area there is a correspondence between changes in the frequency of albumin variants and changes in the ethnic background and history of the area's populations. At the same time, when viewing widely separated areas, relationships between distant groups based on linguistic and cultural similarities are paralleled on a biologic level by the distribution of normal albumin and variant albumins.     

Phylogeography of the Trans‐Volcanic bunchgrass lizard (Sceloporus bicanthalis) across the highlands of south‐eastern Mexico

We quantify the population divergence processes that shaped population genetic structure in the Trans‐Volcanic bunchgrass lizard (Sceloporus bicanthalis) across the highlands of south‐eastern Mexico. Multilocus genetic data from nine nuclear loci and mitochondrial (mt)DNA were used to estimate the population divergence history for 47 samples of S. bicanthalis. Bayesian clustering methods partitioned S. bicanthalis into three populations: (1) a southern population in Oaxaca and southern Puebla; (2) a population in western Puebla; and (3) a northern population with a broad distribution across Hidalgo, Puebla, and Veracruz. The multilocus nuclear data and mtDNA both supported a Late Pleistocene increase in effective population size, and the nuclear data revealed low levels of unidirectional gene flow from the widespread northern population into the southern and western populations. Populations of S. bicanthalis experienced different demographic histories during the Pleistocene, and phylogeographical patterns were similar to those observed in many co‐distributed highland taxa. Although we recommend continuing to recognize S. bicanthalis as a single species, future research on the evolution of viviparity could gain novel insights by contrasting physiological and genomic patterns among the different populations located across the highlands of south‐eastern Mexico. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 852–865.     

Distribution of hereditary blood groups among indians in South America. VII. In Argentina

This seventh and last paper in a series on the distribution of blood groups among Indians in South America reports the findings among Amerinds in Argentina. Blood specimens were procured from putative full-bloods of the following tribes: 38 Diaguita (Calchaqui), 230 Mataco, 90 Chiriguano, 142 Choroti, 51 Toba, 120 Chané, 96 Chulupi (Ashluslay), and 178 Araucano (Mapuche). These 945 samples were tested for blood factors in the A-B-O, M-N-S-s, P, Rh-Hr, K-k, Lewis, Duffy, Kidd, and Diego systems. Serum samples were tested for haptoglobins and transferrins. Hemolysates prepared from whole blood were tested for hemoglobin types. The results are presented in tables as phenotype distribution and calculated allele frequencies. Locations of the populations from which blood samples were procured are shown on a map of North and Central Argentina. High frequencies are reported for the O allele. Allele frequencies are high also for M, s, R¹ (CDe), R² (cDE), k, Le^H and Fy. They are usually low or absent for alleles B, N, S, Mi^a, Vw, R^o (cDe), r (cde), K, Le¹, and fy. The Di allele ranged from 0.013 in the Araucano (Mapuche) to 0.192 in the Toba. Allele frequencies aberrant for Indians were observed more often in the Araucano (Mapuche) and Diaguita tribes, due probably to greater inflow of non-Indian genes into their gene pool and perhaps also to genetic drift in small inbred populations. Hp¹ allele frequencies varied from 0.43 in the Choroti to 0.80 in the Diaguita. All samples tested for transferrins except six contained the variant Tf C; the six were B₁ C present in samples from one Mataco and six Araucano persons. All the specimens tested electrophoretically for hemoglobin types contained only (A) as a major component.     

Conostegia xalapensis (Melastomataceae): an aluminum accumulator plant

In acidic soils, an excess of Al³⁺ is toxic to most plants. The Melastomataceae family includes Al‐accumulator genera that tolerate high Al³⁺ by accumulating it in their tissues. Conostegia xalapensis is a common shrub in Mexico and Central America colonizing mainly disturbed areas. Here, we determined whether C. xalapensis is an Al accumulator, and whether it has internal tolerance mechanisms to Al. Soil samples collected from two pastures in the state of Veracruz, Mexico, had low pH and high Al³⁺ concentrations along with low Ca²⁺ levels. Leaves of C. xalapensis from pastures showed up to 19 000 mg Al kg^?1 DW (dry weight). In laboratory experiments, 8‐month‐old seedlings treated with 0.5 and 1.0 mM AlCl₃ for 24 days showed higher number of lateral roots and biomass. Pyrocatechol violet and hematoxylin staining evidenced that Al localized in epidermis and mesophyll cells in leaves and in epidermis and vascular pith in roots. Scanning electron microscope‐energy dispersive X‐ray microanalysis of Al‐treated leaves corroborated that Al is in abaxial and adaxial epidermis and in mesophyll cells (31.2%) in 1.0 mM Al‐treatment. Roots of Al‐treated plants had glutathione reductase (EC 1.6.4.2) and superoxide dismutase (EC 1.15.1.1) activity higher, and low levels of O and H ₂O₂. C. xalapensis is an Al‐accumulator plant that can grow in acidic soils with higher Al³⁺ concentrations, and can be considered as an indicator species for soils with potential Al toxicity.     

Distribution of blood groups among indians in South America. VI. In Paraguay

This paper on the distribution of hereditary factors in the blood of Indians in South America, reports the results of tests made on samples procured from Paraguayan Indians. Specimens from putatively full-blood persons were obtained from the following tribes: 88 Chamacoco, 36 Moro, 85 Chulupi, 207 Lengua, 100 Toba, 20 Yam Lengua, and 51 Guayaki, These 587 Samples were tested for factors in the A-B-O, M-N-S-s, P. Rh-Hr, Lutheran, Kell-Cellano, Lewis, Duffy, Kidd, and Diego systems. Serum samples were tested for haptoglobins and transferrins. He molysates, prepared from whole blood, were tested for hemoglobin types. The results are presented on appropriate tables as number and per cent of phenotypes for the various blood group antigens and their calculated allele frequencies. Locations of the populations from which blood samples were procured are listed on the tables and shown on a map (fig. 1). Of the 587 samples all except two Chamacoco belonged to group O. High frequencies are reported generally for M, s, P, R¹ (CDe), R² (cDE), k (100%) and Fy alleles in Paraguayn Indians. Low frequencies were generally reported for N, S, r (cde) and R° (cDe) alleles. There was a wide variation in frequencies for Di, Jk, and haptoglobin Hp¹. All tested for transferrins were classified as Tf C and all contained hemoglobin (A) as a major component. The following antigens were completely absent: Mi^a, Vw, p, P^k, r^y (CdE), K, and Le¹. Most notable is the unusual distribution of hereditary blood antigens among the Guayaki and Moro. The Guayaki had 100% P₁ and Fy^a; they were higher in R° (cDe), R¹ (CDe), and Jk^a; and lower in R² (cDE) and Hp¹ genes than other Indians; and Di was absent. The Guayaki differed from the other Indians also in having fair skin. The Moro were lower in the P¹ and Jk gene frequencies than is usually found in Amerinds, and the Di gene was absent. The Chamacoco also had an exceptionally low frequency for the P¹ gene (0.261).     

Distribution of hereditary factors in the blood of Indians of the Gila River, Arizona

This paper reports the distribution of blood groups, A-B-H secretors, haptoglobins, transferrins and hemoglobin types among Indians of the Gila River Valley in Arizona. Specimens were procured from the following putative full-bloods: 909 Pima, 37 Papago, and 124 Maricopa; and from the following known mixed-bloods: Pima-Papago 134, Pima-Maricopa 26, Pima-Other Indian 41, Pima-Caucasian 33. These 1304 samples were tested for factors in the A-B-O, M-N-S-s, P, Rh-Hr, Lutheran, Kell-Cellano, Lewis, Duffy, Kidd and Diego blood group systems, and for additional blood factors (Wr^a), Do^a, Vel, Yt^a, Co^a, Gy^a, Sav, and L. W. Serum samples were tested for haptoglobins and transferrins. Hemolysates, prepared from whole blood, were tested for hemoglobin types. The results are presented on appropriate tables as number and per cent of phenotypes for the various blood group antigens and their calculated allele frequencies. Locations of the populations from which blood samples were procured are shown on a map (fig. 1). Tests made by earlier workers on the blood of Arizona Indians and related tribes are presented for comparison and discussed. The usual high frequencies for allele O reported in Amerinds was found among the putatively full-blood Gila Indians; the 124 Maricopa presented the maximum frequency of 1.000. High frequencies were reported generally for M, s, P¹, R¹ (CDe), R² (cDE), k (100%) Fy, and Do^a alleles. Low frequencies were reported for N, S, r (cde), R° (cDe), fy, Le¹w and Di^a (Pima only). There was a wide variation in frequencies for jk, and Hp¹, and there were 17 Transferrin Tf B₁C observed in 270 Pima samples tested. All the remaining were classified as Tf C except two Tf B;C from mixed-bloods. All samples tested for Vel, Yt^a, Co^a, Sav, and Hemoglobin (A) showed the maximum frequency (1.000) for their genes. The following antigens were completely absent: Lu^a, Mi^a, Vw, Mt^a, p, P^k, r^y (CdE), K, and Wr^a. The results of this study suggests that the Papago tribe presents fewer genes of non-Indian origin than the Pima, and the Maricopa least of the three populations.     

Genetic status of the European bison Bison bonasus after extinction in the wild and subsequent recovery

• 1 The European bison Bison bonasus went through a severe bottleneck and became extinct in the wild 90 years ago. The lowland subspecies B. b. bonasus is the only one of three original subspecies that exists today. The entire species derives from only 12 founders, including a bull of the Caucasian subspecies B. b. caucasicus. Due to its presence among founders, there are two geographically separated genetic lines of European bison: the pure lowland (Bia?owie?a) line and the hybrid lowland‐Caucasian line.
• 2 The lowland line of the European bison originates from only seven founders with an extremely varying genetic contribution. Approximately 80% of the genes in contemporary populations come from just two founders.
• 3 A variety of genetic markers (mtDNA, microsatellites, single nucleotide polymorphism microchips) were applied to studies of the level of depletion of genetic variability in European bison.
• 4 The lowland line of the European bison, the most extensively studied, shows very low levels of genetic variation, and has just half the microsatellite heterozygosity of the closely related American bison Bison bison. The effective population size (N_e) for the highly genetically homogenous lowland line in the Polish part of the Bia?owie?a Forest is estimated to be 23.5, far less than the census population size of 450.
• 5 The average inbreeding level in lowland bison is almost 50%, although no signs of inbreeding depression have been observed. In contrast, inbreeding effects have been noticed in the lowland‐Caucasian line, which has a much lower average inbreeding level (28%). In spite of the apparently high fitness of the lowland bison, the lack of genetic variation and high level of inbreeding may present substantial threats in the future, especially in the context of potential epizootics.

     

Development of microsatellite markers for the white mangrove (Laguncularia racemosa C.F. Gaertn., Combretaceae)

We developed nine new microsatellite markers for the white mangrove (Laguncularia racemosa C.F. Gaertn.), a mangrove species widely distributed in the Western Hemisphere. The loci were developed from a sample collected in Baja California Sur, Mexico, and were screened for polymorphism in 108 individuals from the Pacific Coast of Mexico and Costa Rica. The level of polymorphism was relatively low, from two to four alleles. These are the first set of polymorphic markers described for L. racemosa and should be of value in studying regional genetic differentiation among natural populations of this species.     

Intra and intertribal genetic variation within a linguistic group: The Ge-speaking Indians of Brazil

A total of 562 individuals living in four villages of two Brazilian Indian tribes (Cayapo and Krahó) was studied in relation to blood groups ABO, MNSs, P, Rh, Lewis, Duffy, Kidd and Diego; haptoglobin, Gc, acid phosphatase and phosphoglucomutase types. These results were compared with those obtained previously among the Xavante, and the inhabitants of three other Cayapo villages, all of whom speak Ge languages; the ranges in gene frequencies observed in a representative series of South American Indians from all over the continent were also compiled. The Ge Indians are characterized by low frequencies ofR^z, medium frequencies ofR¹,R², R⁰, orr,Jk^a andPGM¹₁, and high frequencies ofGc² andACP^A when compared with other South American tribes. Genetic distance analyses based on six loci indicate that the intratribal variability observed among Cayapo is of the same order of magnitude as those obtained among the Xavante and Krahó, being much less pronounced than those observed among the Yanomama and Makiritare. The intertribal differences within this linguistic group are much less pronounced than those encountered among tribes that speak more differentiated languages.     

PHOSPHOGLUCONATE DEHYDROGENASE POLYMORPHISM AND SALINITY IN THE WHITE SANDS PUPFISH

The phosphogluconate dehydrogenase (Pgdh) locus is the only polymorphic allozyme locus observed among 37 loci examined in all four populations of a New Mexico state Endangered species, the White Sands pupfish (Cyprinodon tularosa). We report evidence suggesting that this polymorphism may be associated with salinity. Salinity levels vary widely within and between habitats occupied by White Sands pupfish. The frequency of the Pgdh¹⁰⁰ allozyme was correlated with salinity but not with temperature. Frequency of Pgdh¹⁰⁰ differed between low (3.76 parts per thousand (ppt)) and high (9.23 ppt) salinity sites at Malpais Spring despite no obvious barriers to fish movement. Frequencies of Pgdh¹⁰⁰ in two introduced populations differed from that of the presumptive founding stock and correlated with salinity in the current habitats.     

Small scale pH buffering in organic horizons of two boreal coniferous forest stands

Factors behind the small-scale variaton of pH were examined in O horizons (humus layers) developed under two stands of Picea abies (L.) Karst. (Site F and K) by combining data on the composition of the cation exchange complex with data from titrations of corresponding H⁺-saturated samples. Cations extractable in 0.5 M CuCl₂ (S=cmol_c kg^–1 [2Ca+2Mg+2Mn+K+Na]), aluminium extractable in 1.0 M KCl (Al_e=cmol_c kg^–1 [3Al]) and in 0.5 M CuCl₂ (Al_org=cmol_c kg^–1 [3Al]), as well as pH measured in 0.01 M CaCl₂ (pH_Ca) were analysed in one-cm-layers of 13 O horizon cores at each site. Composite samples representing each of the one-cm-layers at each site, as well as samples with two different levels of Al saturation at Site K, were H⁺ saturated and titrated with NaOH to chosen end points of pH_Ca=4.0 and 5.5 in a 0.01 M CaCl₂ ionic medium. The Acid Neutralisation Capacity (ANC) was estimated as the amount of base needed to increase pH_Ca of the composite H⁺-saturated samples to the mean pH_Ca of the corresponding natural samples. The ANC was found to be similar in magnitude or higher than the amount of sites binding S+Al_e, which suggests that 1.0 M KCl exchangeable Al ions are nonacidic in acid O horizons. The relative contribution from i) the capacity of acidic functional groups, ii) their acid strength and iii) their degree of neutralisation to differences in pH_Ca between sites, among cm-layers and between samples with different levels of Al saturation were estimated from titration curves adjusted to hold two out of three factors (i, ii and iii) to be constant. The degree of neutralisation explained most of the differences in pH_Ca between the two sites, as well as between samples with different levels of Al saturation at Site K. The pH_Ca decrease by depth at site F was, however, partly explained by an increasing acid strength. The study emphasizes the importance of examining not only changes in the degree of neutralisation, but also changes in the acid strength and the capacity of buffering functional groups before conclusions about causes behind acidification processes can be made. Difficulties of accurately estimating the degree of neutralisation (base saturation) of acidic functional groups from the composition of adsorbed cations, owing to the unknown acidity of adsorbed Al, was also demonstrated.     

Mitochondrial malic enzyme polymorphism among different ethnic groups in Singapore

Mitochondrial malic enzyme (EC 1.1.1.40; MEM) was examined by starch-gel electrophoresis on post-mortem brain samples from 453 unrelated subjects of either sex comprising 161 Chinese, 150 Indians and 113 Malays and 29 from other racial groups. The estimated gene frequencies of MEM1 were found to be 0.7111, 0.6100 and 0.6769 in Chinese, Indians and Malays, respectively. No significant deviation from the Hardy-Weinberg equilibrium was observed in Chinese and Malays. However, there was a significant deviation with a deficiency of heterozygotes among Indians. MES did not show any polymorphism.     

GENETIC AND PHENOTYPIC DIVERGENCE BETWEEN LOW‐ AND HIGH‐ALTITUDE POPULATIONS OF TWO RECENTLY DIVERGED CINNAMON TEAL SUBSPECIES

Spatial variation in the environment can lead to divergent selection between populations occupying different parts of a species’ range, and ultimately lead to population divergence. The colonization of new areas can thus facilitate divergence in beneficial traits, yet with little differentiation at neutral genetic markers. We investigated genetic and phenotypic patterns of divergence between low‐ and high‐altitude populations of cinnamon teal inhabiting normoxic and hypoxic regions in the Andes and adjacent lowlands of South America. Cinnamon teal showed strong divergence in body size (PC1; P_ST= 0.56) and exhibited significant frequency differences in a single nonsynonymous α‐hemoglobin amino acid polymorphism (Asn/Ser‐α9; F_ST= 0.60) between environmental extremes, despite considerable admixture of mtDNA and intron loci (F_ST= 0.004–0.168). Inferences of strong population segregation were further supported by the observation of few mismatched individuals in either environmental extreme. Coalescent analyses indicated that the highlands were most likely colonized from lowland regions but following divergence, gene flow has been asymmetric from the highlands into the lowlands. Multiple selection pressures associated with high‐altitude habitats, including cold and hypoxia, have likely shaped morphological and genetic divergence within South American cinnamon teal populations.