Allelic and haplotypic diversity at the major histocompatibility class II within domesticated Australian Atlantic salmon (Salmo salar L.)

Variation within the major histocompatibility (MH) class II alpha gene ( Sasa-DAA ) was compared between domesticated Australian Atlantic salmon and their ancestral Canadian population. The level of Sasa-DAA and MH class II beta gene ( Sasa-DAB ) sequence variation was also examined within the Australian population and compared with that published for European Atlantic salmon populations. In contrast to variation previously reported for non-coding microsatellite loci, a high level of MH class II allelic variation has been maintained within the domesticated Australian populations. Furthermore, a high level of Sasa-DAA and Sasa-DAB allele sequence diversity was also observed and exceeded that reported for other cultured Atlantic salmon populations. The number of Sasa-DAB allele sequences (14) surpassed the number of Sasa-DAA allele sequences (9) to produce 14 unique class II haplotypes. We conclude that the Australian Atlantic salmon populations show high MH class II allelic and haplotypic variation compared with both its ancestral Canadian population and other cultured Atlantic salmon populations.     

Semiochemical compounds of preen secretion reflect genetic make-up in a seabird species

Several vertebrates choose their mate according to genetic heterozygosity and relatedness, and use odour cues to assess their conspecifics' genetic make-up. In birds, although several species (including the black-legged kittiwake) exhibit non-random mating according to genetic traits, the cues used to assess genetic characteristics remain unknown. The importance of olfaction in birds' social behaviour is gaining attention among researchers, and it has been suggested that, as in other vertebrates, bird body scent may convey information about genetic traits. Here, we combined gas chromatography data and genetic analyses at microsatellite loci to test whether semiochemical messages in preen secretion of kittiwakes carried information about genetic heterozygosity and relatedness. Semiochemical profile was correlated with heterozygosity in males and females, while semiochemical distance was correlated with genetic distance only in male-male dyads. Our study is the first to demonstrate a link between odour and genetics in birds, which sets the stage for the existence of sophisticated odour-based mechanisms of mate choice also in birds.     

Reed bunting females increase fitness through extra-pair mating with genetically dissimilar males

Females of many socially monogamous species accept or even actively seek copulations outside the social pair bond. As females cannot increase the number of offspring with promiscuous behaviour, the question arises why they engage in extra-pair mating. We used microsatellite data to determine paternity, heterozygosity and genetic relatedness in the reed bunting (Emberiza schoeniclus), a species with high levels of extra-pair paternity (EPP). We found that extra-pair young (EPY) were more heterozygous than within-pair young (WPY). The high heterozygosity of the EPY resulted from a low genetic similarity between females and their extra-pair mates. EPY were heavier and larger when compared with their maternal half-siblings shortly before they left the nest. Recapture data indicated a higher fledgling survival of EPY compared with WPY. Our data suggest that reed bunting females increase the viability of their offspring and thus fitness through extra-pair mating with genetically dissimilar males.     

Major histocompatibility complex class II compatibility,but not class I,predicts mate choice in a bird with highly developed olfaction

Mate choice for major histocompatibility complex (MHC) compatibility has been found in several taxa, although rarely in birds. MHC is a crucial component in adaptive immunity and by choosing an MHC-dissimilar partner, heterozygosity and potentially broad pathogen resistance is maximized in the offspring. The MHC genotype influences odour cues and preferences in mammals and fish and hence olfactory-based mate choice can occur. We tested whether blue petrels, Halobaena caerulea, choose partners based on MHC compatibility. This bird is long-lived, monogamous and can discriminate between individual odours using olfaction, which makes it exceptionally well suited for this analysis. We screened MHC class I and II B alleles in blue petrels using 454-pyrosequencing and quantified the phylogenetic, functional and allele-sharing similarity between individuals. Partners were functionally more dissimilar at the MHC class II B loci than expected from random mating (p = 0.033), whereas there was no such difference at the MHC class I loci. Phylogenetic and non-sequence-based MHC allele-sharing measures detected no MHC dissimilarity between partners for either MHC class I or II B. Our study provides evidence of mate choice for MHC compatibility in a bird with a high dependency on odour cues, suggesting that MHC odour-mediated mate choice occurs in birds.     

Smelling right: the scent of male lemurs advertises genetic quality and relatedness

Sexual selection theory predicts that competitors or potential mates signal their quality or relatedness to conspecifics. Researchers have focused on visual or auditory modes of signal transmission; however, the importance of olfactory indicators is gaining recognition. Using a primate model and a new integrative analytical approach, we provide the first evidence relating male olfactory cues to individual genome-wide heterozygosity and to the genetic distance between individuals. The relationships between male semiochemical profiles and genetic characteristics are apparent only during the highly competitive and stressful breeding season. As heterozygosity accurately predicts health and survivorship in this population, we identify scrotal olfactory cues as honest indicators of male quality, with relevance possibly to both sexes. Beyond showing that semiochemicals could underlie kin recognition and nepotism, we provide a putative olfactory mechanism to guide male–male competition and female mate choice.     

Genetic variability in arrhenotokous and thelytokous forms ofMesochorus nigripes [Hym.: Ichneumonidae]

Electrophoresis of isozymes was carried out to determine the degree of genetic variability in arrhenotokous and thelytokous forms ofMesochorus nigripes. Although the over-all heterozygosity (H_a) for 12 loci in 10 enzyme systems was 0.187 for the arrhenotokous form and 0.103 for the thelytokous form, a paired comparison t-test showed no significant difference. Nei's coefficient of genetic identity between these 2 forms I=0.982.

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Résumé Afin de déterminer le degré de variabilité génétique chez les formes arrhénotoques et thélytoques deMesochorus nigripes, les isozymes ont été étudiés par électrophorèse. Bien que le taux d'hétérozygotie (H_a), calculé à partir de 12 loci appartenant à 10 systèmes enzymatiques, soit de 0,187 chez la forme arrhénotoque et de 0,103 chez la forme thélytoque, aucune différence significative n'existe selon le test ≪t≫. Le coefficient d'identité génétique de Nei entre ces deux formes est: I=0,982.

     

Biochemical genetic variation in the genus Littorina (Prosobranchia:Mollusca)

The genus Littorina has been subject to many studies of electrophoretically detectable variation, mostly aimed either at clarifying questions concerned with population structure, or at clarifying difficult taxonomic/systematic problems. This paper reviews many of these studies. Topics covered include Hardy-Weinberg deviations, the extent of genetic differentiation among populations within species, founder effects and the effects of human introductions on genetic variation, the biological significance of allozyme variation, and the uses of allozyme variation in Littorina systematics.     

Genetic variation in Australian Merino sheep

Variation at 22 gene loci was investigated in a flock of Australian Merino sheep using restriction fragment length polymorphism (RFLP) analysis. Polymorphism was observed at 20 loci, including loci for wool keratin, hormone and immunoglobulin light chain genes. Eleven loci yielded unambiguous genotypes suitable for population data analysis. Average heterozygosity, determined from these and two monomorphic loci, was estimated as 0.107 (SE = 0.024). Average heterozygosity excluding all monomorphic data was estimated as 0–377 (SE = 0.031), which is comparable with human RFLP heterozygosities for loci chosen in the same way that we selected sheep loci.     

Lack of concordance between genetic diversity estimates at the molecular and quantitative-trait levels

In many applications of population genetics, particularly in the field of conservation biology, estimates of molecular diversity are used as surrogate indicators of less easily acquired measures of genetic variation for quantitative traits. The general validity of this approach to inferring levels of quantitative genetic variation within populations is called into question by the demonstration that estimates of molecular and quantitative-genetic variation are essentially uncorrelated in natural populations of Daphnia, one of the few organisms for which multiple estimates of both quantities are available. On the other hand, molecular measures of population subdivision seem to give conservatively low estimates of the degree of genetic subdivision at the level of quantitative traits. This suggests that although molecular markers provide little information on the level of genetic variation for quantitative traits within populations, they may be valid indicators of population subdivision for such characters.     

Subunit size of enzymes and genetic heterozygosity in vertebrates

There is a small but significant positive correlation between individual locus estimates of heterozygosity and subunit molecular weight in vertebrate dimeric enzymes. This correlation is smaller than that previously shown to exist for Drosophila dimers, and some possible reasons for this are explored. Data for vertebrate tetrameric enzymes are less extensive but appear to give similar trends to those shown by dimers. It is concluded that enzyme heterozygosity is influenced by both subunit size and quaternary structure.     

Genetic characterization in four sciaenid species from the Arabian Sea

Four sciaenid species Johnieops dussumieri, Kathala axillaris, Pennahia macropthalmus and Otolithes ruber were analysed electrophoretically for genetic variation at 18 loci (16 in P. macropthalmus and O. ruber ). Twelve loci were polymorphic in J. dussumieri , 10 in K. axillaris , three in P. macropthalmus and 12 in O. ruber ( P <0·99). Average heterozygosity ranged from 0·033 ± 0·100 to 0·070 ± 0·122. The allele frequencies of 14 loci were used to estimate Nei's genetic distance (). The values ranged from 0·334 to 0·612. Three isozyme loci ( LDH-B*, MDH-2* and G3PDH-1* ) were found to be the most reliable species-specific markers.     

Genetic distance analysis among nine endogamous population groups of Maharashtra,India

Genetic distance analysis based on 16 biochemical markers, following Nei's distance measure has been performed on nine endogamous groups of Maharashtra: Nava Budha, Maratha, Deshastha Rigvedi Brahmin, Chitpavan Brahmin, Chandrasenya Kayastha Prabhu, Parsis, Bhil, Pawara and Katkari. The distances between these groups are small as compared to the within group heterogeneity. The average heterozygosity per gene per locus is high for all the populations (in the range of 20–22%). The observed clusterings among these nine groups, in general, are compatible with the known ethnic history of Maharashtra.     

我国特有树种长叶榧树的生物学特性与保护问题研究

在持续１０余年对我国特有珍贵树种长叶榧树的分布区、生长环境、生物学特性调查研究基础上,全面系统地提出了该树种保护措施与开发利用意见。