Studies on the transferrins of goats. 3. Evidence for a third transferrin allele

A new allele Tf ^c in serum transferrin of goats is postulated. It was considered that serum transferrins in goats classified into six phenotypes are genetically controlled by three codominant alleles, Tf ^A, Tf ^B and Tf ^c. Frequencies of Tf ^c were low in native goats in Korea, Philipines and Thailand, and this allele is yet to be observed in other breeds of goats.     

Polymorphism of mannose-6-phosphate isomerase in cattle

Enzymo-electrophoresis and enzymo-electrofocusing of white cells and of muscular extracts of cattle has revealed four kinds of phenotypic patterns. Evidence presented here indicates that three of these phenotypes are controlled by two codominant, autosomal alleles, MPI ^B and MPI ^C. The allele MPI ^C occurs with a frequency of about 0.10 in most of the breeds studied and of about 0.03 in the Charolais breed. The fourth, very rare, two-banded phenotype, encountered mostly in purebred and crossbred Charolais, is believed to be under the dependence of a third allele MPI ^A but the breeding tests are lacking.     

Genetic polymorphism of the sixth component of complement (C6) in the pig

Summary
Using agarose gel isoelectric focusing and immunoblotting with rabbit anti-rabbit C6, a genetic polymorphism has been found in the sixth component of complement (C6) in six breeds of pigs. The C6 locus was highly polymorphic. Family data indicated that pig C6 pheno-types were inherited by means of five codomonant alleles named C6 ^A, C6 ^B, C6 ^C, C6 ^D and C6 ^E at a single autosomal locus. C6 deficiency in two of 241 individuals tested was found, which suggested the presence of a null allele in pig populations. Marked breed differences among the gene frequencies and heterozygosities at C6 locus were observed.     

Habitat fragmentation and the structure of genetic diversity within disjunct isolates of Anthericum ramosum L. (Anthericaceae) in Scandinavia

The lilioid herb, Anthericum ramosum , occurs in four geographically-isolated regions (Sjælland, Skåne, Öland and Gotland) in Denmark and southern Sweden. We investigated allozyme variation at nine polymorphic loci in A. ramosum from 16 sites (33 populations) in the four regions. There was no clear overall geographic pattern of differentiation between the regions, but the southernmost Gotland and the Öland populations had similar allele frequencies, suggesting that they have had a common history. The total genetic diversity (H_10t) was 0.458 and the between-region, site- and population components of diversity accounted, respectively, for 13%, 10% and 2% of the total diversity. The species is restricted to grassland habitats. Such habitats have become increasingly rare in the Sjælland and Skåne regions, where A. ramosum now has a highly fragmented distribution. Within three of the regions (Sjælland, Skane and Öland) there was a negative relationship between the extent of grassland habitat and the between-site components of genetic diversity. Öland, with its extensive grassland habitats and low levels of population disjunction, showed litde allelic differentiation between sites and the lowest between-site component of diversity (3%), suggesting that there is (or has been) extensive gene flow between sites. The between-site components of diversity were higher within Skåne (7%) and Sjaelland (12%). The high within-region G_ST (25%) for the fourth region, Gotland, cannot be explained in terms of recent habitat disjunction but is, instead, interpreted in terms of the restricted distribution of limestone bedrock on Gotland and the fact that die southern and northern Godand populations appear to have had different origins.     

Microgeographic variation in allozyme and shell characters in Littorina saxatilis Olivi (Prosobranchia: Littorinidae)

Twenty-three enzymes and five shell parameters were screened in 11 subpopulations of Littorina saxatilis Olivi (= L. rudis Maton) occupying different habitats over a 1 km stretch of coastline. Shell morphology varied considerably and consistently with respect to degree of exposure, and since there is evidence that such morphology is at least partly under genetic control, it is likely that natural selection selects particular genotypes at particular locations. There was significant allozyme heterogeneity between neighbouring subpopulations, sometimes only metres apart, but little of the allozyme variability could be related directly to environmental pressures. Thus, with the exception of the Odh locus, the considerable morphological differentiation between snails from exposed and sheltered sites was not reflected in differentiation of those genes coding for electrophoretically assayed enzymes. At the Odh locus, virtually all the genetic differentiation between subpopulations was attributable to differentiation between habitat types. Two loci, Sod-1 and Aat-1, showed highly significant genetic disequilibrium, and possible reasons for this are explored. The population structure as assessed electrophoretically accords well with the stepping-stone model which permits greater differentiation of neighbouring populations than the island model, and which seems realistic in the ovoviviparously reproducing L. saxatilis, where the greater part of gene flow is likely to occur through the occasional migration of adults between contiguous populations.     

Polymorphism of 6-phosphogluconate dehydrogenase in the leucocytes of cattle

By means of starch gel electrophoresis the polymorphism of the 6-phosphogluconate dehydrogenase (6PGD) has been found in cattle leucocytes. The phenotypes (A, AB and B) and allele frequencies ( 6PGD ^A= 0.425; 6PGD ^B= 0.575) are demonstrated in families of German Friesian cattle.     

Haemoglobin synthesis in Daphnia magna Straus (Crustacea: Cladocera): ecological differentiation between neighbouring populations

SUMMARY. 1. Variations in the haemoglobin index of two neighbouring populations of Daphnia magna were recorded over a range of dissolved oxygen concentrations (0.5–4.0ml O₂ 1⁻¹, 20°C). Reciprocal transfer experiments between habitats compared haemoglobin synthesis in situ.
2. An inverse relationship was found between the oxygen content of pond water and the haemoglobin indices of laboratory and natural populations.
3. Significant genetic differences in the synthesis of haemoglobin were found between the two populations. Animals from the poorly oxygenated habitat (0.8±0.18ml O₂ 1⁻¹) had consistently higher haemoglobin contents (maximum HI, 87.7±4.5) at all experimental and in situ oxygen levels. D. magna from the well oxygenated pond (4.3±0.59 ml O₂1⁻¹) had a lowered physiological ability to synthesize haemoglobin (maximum HI, 48.3±4.2). The process of ecological differentiation in Daphnia populations is discussed.     

Genetic control of urea resistant esterase of liver extracts in chicken

Starch gel electrophoresis according to Okada & Sasaki (1970) revealed six regions of esterase activity designated I to VI. Further genetic variation was found in esterase region III in this study. Two phenotypes, A and O, were observed by means of urea denaturation of chicken liver extracts. These were genetically controlled by an autosomal locus, designated as Es-9 , with a completely dominant ( Es-9 ^A) and a completely recessive ( Es-9 °) alleles.
Es-9 ^A was the most frequent allele in White Plymouth Rock, New Hampshire and Australorp strains and rare in White Leghorn strains.     

Genetic polymorphism of leucine aminopeptidase in canine plasma

Genetic polymorphism was found in the isozymes of leucine aminopeptidase in the canine plasma. Analysis of parentage records of the dogs examined revealed that the phenotypic variation of leucine aminopeptidase isozymes was controlled by one autosomal locus, designated Lap , with two codominant gene alleles, Lap ^A and Lap ^B, though individuals of homozygous B type were not found in the specimen used. The gene frequencies were 0.97 for Lap ^A and 0.03 for Lap ^B in most of the dog breeds examined. Higher frequencies for Lap ^B (0.11–0.25) were obtained in breeds such as Pointer, Doberman pinscher, Boxer, Borzoi and San'in-Shiba (a Japanese native breed), while in German shepherd, Collie, and two of the Japanese native breeds, Akita and Kishu, phenotype of the isozyme seemed to be fixed to homozygous A ( Lap ^A/ Lap ^A).     

Polymorphism of adenosine deaminase in the pig: allelic variation in erythrocytes

Within the frame of our investigations on genetic variation of pig red cell enzymes, by means of enzymo-electrophoresis and spectrophotometric measurements, four kinds of adenosine deaminase phenotypic patterns were identified in haemolysates from 542 Belgian Landrace and 502 Pietrain pigs. Segregation data are consistent with the hypothesis that these phenotypes are determined by two codominant alleles ADA ^A and ADA ^B and a recessive silent allele ADA ^O, at an autosomal locus. Differences in gene frequencies between the two breeds are highly significant.     

Influence of woodlot floor topography on microbial decomposer distribution

The distribution of microbial populations that decomposed sugar, cellulose and lignin-related substrates was examined in a beech Fagus grandifolia Ehrh. and maple Acer saccharum Marsh. dominated woodlot developed on glacial till. The topography of the woodlot, characterized by rises, depressions and more extensive level areas about 1 m in diameter with a 0.5 m vertical maximum, produced a mosaic of decomposer habitats designated as high, level and low sites.
In general, populations of sugar, cellulose and lignin decomposing organisms (based on ten estimates made from April to October) were two to four times higher in litter and soil samples from low sites than those from high sites. Sugar decomposing bacteria in litter were most abundant at all topographic sites. 135 × 10⁶ g⁻¹ dry litter at high sites, 396 × 10⁶ g⁻¹ at level sites and 456 × 10⁶ g⁻¹ at low sites; lignolytic fungi were least abundant, 391 × 10² g⁻¹ dry litter at high sites. 700 × 10⁶ g⁻¹ at level sites and 954 × 10² g⁻¹ at low sites. Numbers of microbial decomposers in the topographic sites were correlated with organic matter content. Distribution of fungal genera did not appear to be related to topographic site. Most populations examined showed two numerical peaks, one in late May or June and one in late September or October. It is suspected that these peaks were influenced by the coincident timing of favourable physical conditions and priming by soluble nutrients leached from litter.     

Natural and sexual selection against immigrants maintains differentiation among micro‐allopatric populations

Local adaptation to divergent environmental conditions can promote population genetic differentiation even in the absence of geographic barriers and hence lead to speciation. But what mechanisms contribute to reproductive isolation among diverging populations? We tested for natural and sexual selection against immigrants in a fish species inhabiting (and adapting to) nonsulphidic surface habitats, sulphidic surface habitats and a sulphidic cave. Gene flow is strong among sample sites situated within the same habitat type, but low among divergent habitat types. Our results indicate that females of both sulphidic populations discriminate against immigrant males during mate choice. Furthermore, using reciprocal translocation experiments, we document natural selection against migrants between nonsulphidic and sulphidic habitats, whereas migrants between sulphidic cave and surface habitats did not exhibit increased mortality within the same time period. Consequently, both natural and sexual selection may contribute to isolation among parapatric populations, and selection against immigrants may be a powerful mechanism facilitating speciation among locally adapted populations even over very small spatial distances.     

Genetic structure,allozyme-habitat associations and reproductive fitness in Gypsophila fastigiata (Caryophyllaceae)

Relationships between allozyme differentiation, habitat variation and individual reproductive success were examined in local populations of a perennial herb, Gypsophila fastigiata, on the Baltic island of Öland (Sweden). Relatively little (c. 2%) of the total allozyme diversity in this largely outcrossing species is explained by differentiation between sites tens of kilometres apart. The low level of geographic differentiation suggests that gene flow between sites is, or has recently been, extensive. Yet the component of allozyme diversity due to differentiation between plots (only tens of meters apart) within sites is 3 times larger than the between-site component of diversity. Allozyme variation, especially at the Pgi-2 locus, is significantly associated with habitat variation within sites. Different allele x habitat combinations for the Pgi-2 locus are associated with differences in individual reproductive fitness. Differential selection in different local habitats may thus contribute to the fine-scale structuring of genetic diversity within sites.     

Habitat-dependent song divergence in the little greenbul: an analysis of environmental selection pressures on acoustic signals

Abstract.— Bird song is a sexual trait important in mate choice and known to be shaped by environmental selection. Here we investigate the ecological factors shaping song variation across a rainforest gradient in central Africa. We show that the little greenbul ( Andropadus virens ), previously shown to vary morphologically across the gradient in fitness-related characters, also varies with respect to song characteristics. Acoustic features, including minimum and maximum frequency, and delivery rate of song notes showed significant differences between habitats. In contrast, we found dialectal variation independent of habitat in population-typical songtype sequences. This pattern is consistent with ongoing gene flow across habitats and in line with the view that song variation in the order in which songtypes are produced is not dependent on habitat characteristics in the same way physical song characteristics are. Sound transmission characteristics of the two habitats did not vary significantly, but analyses of ambient noise spectra revealed dramatic and consistent habitat-dependent differences. Matching between low ambient noise levels for low frequencies in the rainforest and lower minimal frequencies in greenbul songs in this habitat suggests that part of the song divergence may be driven by habitat-dependent ambient noise patterns. These results suggest that habitat-dependent selection may act simultaneously on traits of ecological importance and those important in prezygotic isolation, leading to an association between morphological and acoustic divergence. Such an association may promote assortative mating and may be a mechanism driving reproductive divergence across ecological gradients.     

Does secotioid inertia drive the evolution of false-truffles?

Secotioid inertia is a model implemented to explain the prevalence of highly derived false-truffles with no obvious connection to the Homobasidiomycetes. The model accommodates the apparent lack of epigeous sister taxa for some highly derived hypogeous lineages by assuming that gasteromycetation in some fungi leads to the extinction of their epigeous sister population. The derived state of some hypogeous lineages suggests that they arose early in the evolution of Homobasidiomycetes and that those groups were subject to conditions that favoured hypogeous lineages such that the hypogeous fruit body form became the predominant form for some lineages. The directional selection component of secotioid inertia, termed secotioid drive, led to the extinction of their epigeous sister taxon. Morphological and molecular data from Russulaceae are used to model the evolutionary stages of secotioid inertia. The resulting phylogenetic results are compared with data from the order Leucogastrales, and the genus Destuntzia. The implications of secotioid drive are discussed with reference to gasteromycete phylogenetics, evolution, and conservation. Specifically, secotioid inertia can be used to account for reversals in fruit body morphology and instability in mycorrhizal formation.     

Seasonal biomass and diversity of estuarine fishes coupled with tropical habitat heterogeneity (southern Gulf of Mexico)

Nekton dynamics were studied in two contrasting habitats in Terminos Lagoon, Mexico. Over an annual cycle, a total of 83 fish species used the high-salinity fringing mangrove/ Thalassia testudinum habitat and biomass ranged from 0.43 to 3.43 g m⁻². The highest biomass occurred during the dry season when aquatic primary production was highest (i.e. 333 g C m⁻² year⁻¹). By contrast, 65 species used the freshwater and low-salinity riverine mangrove/Crassostrea virginica/Vallisneria habitat and biomass ranged from 0.57 to 1.48 g m⁻² with the highest biomass occurring during the wet season, the time of highest primary production in this habitat (i.e. 219 g C m⁻² year⁻¹). The high- and low-salinity habitats serve as ecological bridges between freshwater areas and the sea. Fish life histories have evolved to utilize these habitats for spawning, feeding and nursery grounds in a manner which generally leads to the use of different habitats during the periods of highest primary productivity.     

Studies on bovine serum amylase; evidence for two loci

Two genetically controlled polymorphic systems of amylase enzymes are described in sera from Friesian, Jersey, Guernsey, Hereford, Ayrshire and Charolais cattle. One of these Ami has been described previously and is controlled by two codominant alleles in British cattle, AmI ^B and AmI ^C. Evidence presented here suggests that it could be a gamma.amylase. The other enzyme which is described here for the first time has many of the properties of an alpha amylase. It is also polymorphic and controlled by two codominant alleles AmII ^A and AmII ^B. AmII ^A is only present in low frequency. The inheritance of both enzyme systems has been studied in 419 families.