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PubMed2002

Mating signal variation and bimodality in a mosaic hybrid zone between Chorthippus grasshopper species.

The grasshoppers Chorthippus brunneus and Chorthippus jacobsi are easily distinguished by male calling song and the number of stridulatory pegs on the hind femur, and form a mosaic hybrid zone in northern Spain. In this paper, we fit a two-dimensional cline to variation in male calling song characters, which are of particular interest as they are likely to be involved in mate choice by females. As with variation in peg number, local habitat makes only a small contribution in explaining deviations in mean song score from clinal expectations. However, the fitted width of the cline for song characters is significantly narrower than for peg number, suggesting that mating signals may be associated with reduced hybrid fitness in the field and that recombination rates are sufficient to allow clines for different characters to diverge in width. Despite this, estimates for the overall elevation in linkage disequilibrium at the zone center, based on covariance between peg and song characters, reveal a substantial overrepresentation of parental genotypes at the cline center relative to the expectations of a tension zone of similar width. Examination of covariance at individual sites reveals that this inflated estimate of linkage disequilibrium is caused by several sites where the distribution of phenotypes is effectively bimodal. This substantial variation in linkage disequilibrium at the cline center could result from local variation in the strength of assortative mating or selection against hybrids, or may reflect the long-distance colonization of empty habitat from outside the hybrid zone, which would continually create new contacts between parental genotypes at the cline center. Hybrid zones like this, in which strong linkage disequilibrium occurs in some situations but not in others, are of particular relevance to speciation research and allow investigation of the spread of combinations of alleles through different genetic and ecological backgrounds.

Animals↗
PubMed2003

Socially mediated speciation.

We employ a simple model to show that social selection can lead to prezygotic reproductive isolation. The evolution of social discrimination causes the congealing of phenotypically similar individuals into different, spatially distinct tribes. However, tribal formation is only obtained for certain types of social behavior: altruistic and selfish acts can produce tribes, whereas spiteful and mutualistic behaviors never do. Moreover, reduced hybrid fitness at tribal borders leads to the selection of mating preferences, which then spread to the core areas of the respective tribes. Unlike models of resource competition, our model generates reproductive isolation in an ecologically homogeneous environment. We elaborate on how altruistic acts can lead to reproductive isolation, but also predict that certain types of competition can lead to the speciation effect. Our theory provides a framework for how individual-level interactions mold lineage diversification, with parapatric speciation as a possible end product.

Social Behavior↗
PubMed2006

Influence of hydrogeographic history and hybridization on the distribution of genetic variation in the pupfishes Cyprinodon atrorus and C. bifasciatus.

The evolutionary importance of hybridization in animals has been subject of much debate. In this study, we examined the influence of hydrogeographic history and hybridization on the present distribution of nuclear and mitochondrial DNA variation in two pupfish species, Cyprinodon atrorus and Cyprinodon bifasciatus. Results presented here indicate that there has been limited introgression of nuclear genes; however, mtDNA introgression has been substantial, with complete replacement of the C. bifasciatus mitochondrial genome by that of C. atrorus. Subsequent to this replacement, there has been diversification of mitochondrial haplotypes along major geographic regions in the basin. Evidence was also found that mitochondrial replacement follows a predictable, cyclical pattern in this system, with isolation and diversification followed by re-contact and replacement of C. bifasciatus mitochondrial haplotypes by those of C. atrorus. This pattern is best explained by a combination of a numeric bias towards C. atrorus and mating site selection rather than selection for C. atrorus mitochondrial genome. These results demonstrate the important role hybridization can play in evolution.

Animals↗
PubMed2005

Preliminary observations on the effect of parity on first day ultrasonic detection of embryo and its organs in bovine.

The aim of this study was to determine the effect of parity on the first day of ultrasonic detection of embryo and its organs using 8 MHz frequency. For this purpose, six nulliparous heifers, five primiparous cows and six multiparous cows of the Holstein breed were selected and mated by a single bull from the herd. From day 16 after mating, cows and heifers were examined by ultrasonography thrice weekly for the day of first detection of the embryo and its organs. The mean of first-day detection in heifers, primiparous and multiparous cows was as follows, respectively: allantois on days 22.3, 23 and 25.8; embryo proper on days 21.8, 23 and 27; heartbeat of embryo on days 26.1, 26.6 and 31.1; amnion on days 31, 31 and 30.8; limb buds on days 29.5, 28.8 and 30.6; stomach (abomasum) on days 32.2, 38.6 and 36.8; spinal column on days 32.6, 33.4 and 37.3; placentomes on days 33.3, 37 and 35.3; eyes on days 35.1, 35.4 and 38.6 and lens on days 40, 41.4 and 44. Although the mean of first day observation of all structures in heifers tends to be earlier than in the other groups, statistically, allantois, the embryo proper and its heartbeat in heifers and primipara were visualized significantly earlier than in multiparous cows. However, there were no differences between heifers and primiparous cows.

Animals↗
PubMed1986

Phenotypic resemblance in birth weight between first cousins.

Birth weight data on 72,078 liveborn singletons representing 5981 paternal and 7036 maternal single first cousin kinships were assembled by computerized record linkage from all marriages and livebirths registered in Hawaii during a 38-year period from 1942 to 1979. These kinships represented incrosses of five selected racial groups. An additional 15,536 livebirths from 1134 paternal and 1679 maternal cousin kinships provided data on outcrossing between racial groups, and 28,952 livebirths from 2379 paternal and 3538 maternal cousin kinships provided data on both incrossing and outcrossing within kinships. Phenotypic resemblance in birth weight between single first cousins was estimated by the covariance and intraclass correlation. The covariances between maternal cousins were generally much higher than those between paternal cousins. Neither heterogeneity in maternal genotypes nor heterogeneity in newborn genotypes had any significant effect on the resemblance between first cousins. These observations have led to the conclusion that maternal influences of non-hereditary origin are of primary importance in determining birth weight in man. The observed non-zero correlation in several groups of paternal cousins was explained in part by the process of preferential selection of mates within and among racial groups by brothers, and probably by the similarity in some maternal characteristics associated with age at childbearing among their wives.

Asian People↗
PubMed1989

Cloning and characterization of a Bacteroides conjugal tetracycline-erythromycin resistance element by using a shuttle cosmid vector.

The Bacteroides conjugal tetracycline resistance (Tcr) elements appear not to be plasmids. In many cases, resistance to erythromycin (Emr) is cotransferred with Tcr. Using a newly constructed shuttle cosmid, pNJR1, we cloned 44 to 50 kilobase pairs of a conjugal Tcr Emr element on overlapping cosmid clones. Cosmid libraries were made in Escherichia coli with DNA from the original clinical Bacteroides thetaiotaomicron DOT strain containing Tcr Emr-DOT or from a Bacteroides uniformis Tcr Emr-DOT transconjugant strain. The cosmid clones were mobilized from E. coli into B. uniformis in groups of 10 to 20 per filter mating, with selection for Tcr or Emr transconjugants. The Tcr and Emr genes were cloned both separately and together on 30-kilobase-pair fragments. Several of the Tcr clones also contained transfer genes that permitted self-transfer of the cosmid from B. uniformis donors to E. coli or B. uniformis recipients. Neither the Tcr nor the Emr gene conferred resistance on E. coli, and the transfer-proficient clones did not self-transfer out of E. coli. Southern blot analysis was used to compare DNA from independently isolated Bacteroides strains carrying conjugal Tcr or Tcr Emr elements and their respective B. uniformis transconjugants. Results of these analyses indicate that there are large regions of homology, including regions outside the Tcr and Emr genes, but that the elements are not identical. Some Tcr clones contained a region which hybridized to chromosomal DNA from the wild-type B. uniformis recipient strain that did not carry the Tcr Emr-DOT element. This region of homology appeared not to be a junction fragment. It was not required in a Bacteroides recipient for successful transfer of the Tcr Emr element. Although we are not sure we have cloned a junction fragment between the Tcr Emr-DOT element and the B. uniformis chromosome, the preliminary function and restriction map appears to be linear.

Bacteroides↗
PubMed1989

Intergeneric conjugation between Escherichia coli and Streptomyces species.

We have constructed Escherichia coli-Streptomyces shuttle plasmids which are capable of conjugal transfer from E. coli to Streptomyces spp. These plasmids contained the pBR322 and pIJ101 origins of replication and the RK2 (IncP) origin of transfer. The transfer of plasmid was specifically dependent the presence of a 760-base-pair, cis-acting, oriT-containing fragment and on RP4 (IncP) functions supplied in trans. Conditions of mating and selection of exconjugants were analyzed with Streptomyces lividans as recipient. Plasmid transfer to other Streptomyces species was also demonstrated.

Conjugation, Genetic↗
PubMed1998

Intermarriage and homogamy: causes, patterns, trends.

"Although many characteristics play a role in the choice of a spouse, sociologists have most often examined endogamy and homogamy with respect to race/ethnicity, religion, and socioeconomic status.... I summarize empirical research by answering four questions: (a) To what extent are groups endogamous and how do groups differ in this respect? (b) How has endogamy changed over time? (c) Which factors are related to endogamy? (d) How do various dimensions of partner choice coincide? [I then] discuss strengths and weaknesses of past research."

Culture↗
PubMed1995

Do you need to shop around? Age at marriage, spousal alternatives, and marital dissolution.

"This article attempts to shed light on the oft-observed relationship between age at marriage and marital dissolution by first deriving a hypothesis from marital search theory that relates both variables to the supply of spousal alternatives in the local marriage market. This hypothesis states that, relative to people who marry later in life, persons who marry at comparatively young ages will be especially susceptible to divorce when confronted with abundant alternatives to their current spouse. Marital history data from the National Longitudinal Survey of Youth were then merged with aggregated data from the Public Use Microdata Samples of the 1980 U.S. census to test this hypothesis." The author finds that "discrete-time event history analyses offer no support for this hypothesis. Although the risk of marital dissolution is highest where either husbands or wives chance numerous spousal alternatives, the impact of age at marriage on divorce is significantly weaker in marriage markets containing abundant remarriage opportunities. Some of the effect of age at marriage on marital dissolution is attributable to the detrimental impact of early marriage on educational attainment."

Americas↗
PubMed1997

Mate availability, women's marriage prevalence, and husbands' education.

"We predict that marriage prevalence and husbands' education for Black women [in the United States] vary directly with mate availability. We also predict that marriage prevalence and husbands' education will be lower for Black women with less than a high school education than for other Black women. We test these predictions using data on marriage and husbands' education for a national sample of individuals and data on aggregate-level marriage prevalence and husbands' education for a sample of large metropolitan areas. The results support our predictions, and they help to explain how low mate availability for Black women helps to create and maintain an underclass that is disproportionately composed of less-educated Black women and their children."

Black or African American↗
PubMed1995

Two groups of diabetic KK-CAy mice specifically bred for high and low sensitivity to exogenous acetylcholine and beta 1-adrenergic stimulation: interaction of higenamine and aconitine on pulse rate.

Diabetic KK-CAy mice were specifically bred for high and low sensitivity to the addition of exogenous acetylcholine (ACh). The sensitivity to ACh was measured by the change in pulse rate 2 min after the administration of ACh (10 mg/kg, s.c.). The two groups of mice, with high and low sensitivity to ACh, were specially selected and mated sequentially until the 12th filial generation. Although higenamine (100 micrograms/kg, i.p.), a beta 1-adrenergic agonist (a compound derived from aconite), had no effect per se, it inhibited aconitine (another compound derived from aconite extract)-induced bradycardia within 30 s of administration in ACh-low sensitive mice but not in ACh-high sensitive mice. The effects of aconitine and higenamine alone did not differ between these two groups of mice. This demonstrates that the high muscarinic and high beta 1-adrenergic sensitive mice may be stratified into two groups based upon an antagonistic interaction between higenamine and aconitine.

Acetylcholine↗
PubMed2006

Genomic reconstruction by serial mitotic recombination of yeast artificial chromosomes.

DNA cloned in yeast artificial chromosomes (YACs) is a valuable resource for functional experiments in cell culture as well as whole animal systems. Where the size or chimerism of a YAC clone are limiting factors it may be desirable to generate recombinant YAC clones. One such approach is based on mitotic recombination, and we describe the development of a methodology that allows multiple recombination cycles for serial reconstruction of overlapping YACs. This approach employs retrofitting with standard plasmid vectors, transfer of YACs to a common haploid host by Kar1 mating, and selection for recombination with 5-fluoro-orotic acid.

Chromosomes, Artificial, Yeast↗
PubMed1990

Covariances among sire by breed group of dam interaction effects in multibreed sire evaluation procedures.

In multibreed populations, bulls need to be evaluated for additive and nonadditive genetic effects. When the nonadditive genetic effects associated with a bull are defined as sire x breed-group-of-dam interactions, they can be expressed as linear combinations of interactions between alleles of one or more breeds at one or more loci. If these specific allelic interactions are assumed to be independent, then variances and covariances between sire x breed-group-of-dam interaction subclasses can be shown to be linear combinations of variances and covariances of specific intra- and interlocus intra- and interbreed allelic interactions. Furthermore, covariances between sire x breed-group-of-dam interactions due to specific interactions at one, two, or more loci are zero. If dams are assumed to be unrelated to bulls and among themselves, except through their sires and maternal grandsires, efficient procedures to compute the inverse of the covariance matrices of nonadditive genetic effects can be devised, both in subclass and in regression models. Recursive procedures developed make possible the evaluation of large numbers of bulls for nonadditive genetic effects using mixed-model methodology. For completeness, recursive procedures to compute nonadditive covariance matrices in subclass and in regression models also were developed. The prediction of nonadditive genetic values for bulls, in addition to their additive genetic values, will help plan matings, make selection decisions more accurate and, possibly, make economic projections better.

Alleles↗
PubMed2006

Genetic analysis of calf market weight and carcass traits in Japanese Black cattle.

Heritabilities of and genetic correlations between additive direct and maternal genetic effects for calf market weight, and additive direct genetic effects for carcass traits, were estimated for Japanese Black cattle by REML procedures under 2-trait animal models. Data were collected from calf and carcass markets in Hyogo and Tottori prefectures and analyzed separately by prefecture. Calf market weight was measured on 42,745 and 23,566 calves in Hyogo and Tottori, respectively. Only the fattening animals with calf market weight were extracted from the carcass database and used for estimation. The carcass traits analyzed were carcass weight, ribeye area, rib thickness, subcutaneous fat thickness, yield estimate, beef marbling score, and 4 meat characters (color, brightness, firmness, and texture). Direct and maternal heritabilities for calf market weight were estimated to be 0.22 and 0.07 in Hyogo, and 0.37 and 0.15 in Tottori, respectively. The estimates of heritabilities for carcass traits were moderate to high in both prefectures. The estimates of direct-maternal genetic correlations for calf market weight were positive (0.17) in Hyogo and negative (-0.63) in Tottori. The direct effect for calf market weight was positively correlated with the direct effect for carcass weight (0.87 and 0.56 in Hyogo and Tottori, respectively) but negatively correlated with the direct effect for beef marbling score (-0.10 in both prefectures). The estimates of genetic correlations between the maternal effect for calf market weight and the direct effects for carcass traits varied from -0.13 to 0.34 in Hyogo and from -0.14 to 0.15 in Tottori. Because direct and maternal genetic effects for early growth traits can be evaluated from calf market weight data in the production system of Japanese Black cattle, this information should be incorporated into selection and mating schemes of the breed.

Animals↗
PubMed1984

Interethnic marriages in the USSR in the mid-1930s.

"The present article will attempt to determine the extent of interethnic marriage in the Soviet Union in the mid-1930s, utilizing materials from the Central Statistical Administration of the USSR." Interethnic marriage is analyzed according to Union Republic, rural or urban area, and socioeconomic and cultural development.

Culture↗