Breeding success and direction of animal crossing in the hybrid russet (Spermophilus major) and yellow (Spermophilus fulvus) ground squirrel population

Reproductive relations between animals in the hybrid settlement of the russet and yellow ground squirrels are panmictic and are characterized by the absence of assortative crossings and by the presence of multimale pairings in females with evidently heterospermic broods. Maximum breeding success was observed for hybrid animals proving the fertility of hybrids. However, the hybrid breeding potential (young animal survival rate) is significantly lower as compared with russet and yellow ground squirrels, but the survival rate of the hybrid progeny in the hybrid population is not lower than in specific settlements.     

Decay instability of a lower hybrid wave

A study is made of the decay instability of a lower hybrid wave with a finite wave vector (k ₀≠0) and a large amplitude such that the oscillatory velocity of the electrons with respect to the ions cannot be neglected. It is shown that, depending on the angle between the propagation direction of the lower hybrid wave and the external magnetic field and the angle through which the wave is scattered, the decay instability is primarily governed either by the oscillatory electron motion with respect to the ions or by the nonlinear response of the plasma to the lower hybrid wave propagating in it. The role of the nonlinear frequency shift in the saturation of the lower hybrid decay instability is clarified.     

A test of ecological selection against young-of-the-year hybrids of sympatric sticklebacks

Ecological selection against hybrids, the reduction in hybrid fitness attributed solely to environmental factors, was tested by introducing young-of-the-year benthic, limnetic and F₁ hybrid sticklebacks Gasterosteus aculeatus to divided experimental ponds and lake enclosures. The frequency of hybrids in samples taken at the end was significantly lower than their frequency at introduction. Hybrid survival was significantly lower in pond-sides in which they were initially the most common cross type than in pond-sides in which they were initially rare, suggesting that hybrid survival may be frequency-dependent. Growth rate of F₁ hybrids was marginally lower than benthic growth rates, being significantly lower than in ponds and not different in lake enclosures. The diet of hybrids overlapped with both parent species in ponds and with benthic diets in lake enclosures. The results suggest that ecological selection is acting against young-of-the-year hybrid sticklebacks.     

Reduction of allergenic proteins by the effect of the ripening inhibitor (rin) mutant gene in an F1 hybrid of the rin mutant tomato

The ripening inhibitor (rin) mutant tomato yields non-ripening fruit, and the rin hybrid fruit (RIN/rin) shows an intermediate phenotype between the wild and mutant fruit, that is, red-ripe and extended shelf life. We found by a microarray analysis that the genes encoding possible allergenic proteins were expressed at a significantly lower level in the rin hybrid fruit than in the wild-type fruit. These allergenic proteins, which were beta-fructofuranosidase and polygalacturonase 2A (PG-2A), were confirmed to accumulate at a lower level in the rin hybrid fruit than in the wild-type fruit. The immunoglobulin E (IgE) in serum from a tomato-allergic patient showed lower reactivity to the extract of the rin hybrid fruit than to that of the wild fruit. These results suggest that the rin gene has the potential to regulate allergen accumulation in tomato fruit.     

Excitation of inertial Alfvén waves via modulational interaction with lower hybrid waves

The concept of modulational instability, which results from the coupling of waves modes of very different time and space scales, was introduced to plasma physics through an elegant paper by Vedenov and Rudakov in 1964 [1]. Our paper is devoted to the theory of modulational instability resulting from the interaction of lower hybrid waves and slow density perturbations associated with inertial Alfvén waves. The nonlinear set of equations describing the modulational coupling of these two types of waves is constructed. The lower hybrid wave trajectories are analyzed within predefined density structures and it is shown that these waves can be trapped in the vicinity of the density extremum. The density modulations, originally being associated with inertial Alfvén waves, deepen due to the trapping of lower hybrid waves; this leads to modulational instability. A dispersion relation describing the modulational instability is constructed and analyzed. The threshold intensity of the lower hybrid waves for the onset of instability is obtained and it is shown that instability can serve as an efficient mechanism for the excitation of inertial Alfvén waves in the auroral ionosphere.     

Suppression of the current instability by decay processes

A study is made of the instability of lower hybrid waves in an isothermal magnetized current-carrying plasma. It is assumed that the dynamic suppression of the current instability is associated with the excitation of a quasi-monochromatic wave near the instability threshold and its subsequent decay into two strongly damped lower hybrid waves. It is shown that the decay process results in the onset of either a quasi-periodic or stochastic nonlinear stabilization regime involving a small number of modes. The anomalous resistance is estimated.     

Effect of the radial electric field on lower hybrid plasma heating in the FT-2 tokamak

Conditions for efficient ion heating in the interaction of lower hybrid waves with plasma are experimentally determined. Experiments show that efficient lower hybrid heating stimulates a transition to the improved confinement mode. The formation of internal and external transport barriers is associated with strong central ion heating, which results in a change of the radial electric field E _r and an increase in the shear of the poloidal plasma velocity. The improved confinement mode in the central region of the discharge is attained under the combined action of lower hybrid heating and an additional rapid increase in the plasma current. A new mechanism for the generation of an additional field E _r is proposed to explain the formation of a transport barrier.     

转 Bt 基因水稻对三化螟自然种群的影响

为了了解水稻重要害虫三化螟 Scirpophaga incertulas（Walker）对转 Bt 基因水稻产生抗性的潜在风险,本文利用自然种群生命表,研究了第 3 代三化螟在转Bt基因杂交稻汕优 63 及非转 Bt 基因杂交稻汕优 63 上的种群参数。结果表明：在 Bt 稻上1～2 龄幼虫的存活率为 4.03%,极显著低于非转基因 SY63（55.76%）;Bt 稻上幼虫为害率为1.75%,极显著低 于非转基因 SY63（5.98%）;Bt 稻上存活的幼虫发育历期明显长于非转 Bt SY63。     

A New Hybrid Strain of an Oxytetracycline-producing Organism, Streptomyces rimosus

A new strain, Streptomyces rimosus LS-T hybrid, characterized by a lower level of foaming and higher antibiotic activity as compared to the other active strains of S. rimosus, is obtained as a result of selection among prototrophic recombinant forms of strains LS-T293 and BS-21. The studies on strain LS-T hybrid show the possibilities of combining properties of different strains of S. rimosus in the hybrid forms. The occurrence of new properties in the hybrid forms is detected.     

Genetic analysis of the hybrid male rescue locus of Drosophila

Several hybrid rescue mutations-alleles that restore the viability of normally lethal hybrids-have been discovered in Drosophila melanogaster and its relatives. Here we analyze one of these genes, Hybrid male rescue (Hmr), asking two questions about its role in hybrid inviability. (1) Does the wild-type allele from D. melanogaster (Hmr(mel)) cause hybrid embryonic inviability? (2) Does Hmr(mel) cause hybrid larval inviability? Our results show that the wild-type product of Hmr is neither necessary nor sufficient for hybrid embryonic inviability. Hmr(mel) does, however, appear to lower the viability of hybrid larvae. The data further suggest (though do not prove) that Hmr(mel) acts as a gain-of-function poison in hybrids. These findings support previous claims that hybrid embryonic and larval lethalities are genetically distinct and suggest that Hmr(mel) is at least one of the proximate causes of hybrid larval inviability.     

Male and female gamete abortions,and reduced affinity between the uniting gametes as the causes for sterility in an indica/japonica hybrid in rice

Hybrid sterility frequently occurs in crosses between indica and japonica subspecies of Asian cultivated rice. In this study, we investigated the cytological processes involved in formation and development of male and female gametes as well as their interactions in fertilization, using an indica/japonica hybrid in comparison with an indica/indica hybrid. It was found that more than 50% of the microspores generated in the indica/japonica hybrid could not develop into functional pollen. The abortion rate of microspores in the indica/japonica hybrid was much higher than that in the indica/indica hybrid. Abortive embryo sacs made up roughly 70% of the embryo sacs examined in the indica/japonica hybrid, which was also much higher than that detected in the indica/indica hybrid. Moreover, the amount of pollen adherence on stigmas of the indica variety upon hand-pollination with pollen from the japonica variety was much lower than the indica/indica pollination, and the number of pollen adhered on the stigmas by natural self-pollination was much greater in the indica/indica hybrid than in the indica/japonica hybrid. The indica/japonica hybrid also encountered difficulties in pollen tube growth after pollination, and the fertilization rate of the indica/japonica hybrid was much lower than that of the indica/indica hybrid. These results clearly illustrate the complexity of the mechanisms underlying inter-subspecific hybrid sterility in rice involving both pre- and post-zygotic reproductive isolation mechanisms.     

Plasma Turbulence near the Lower Hybrid Resonance

Plasma turbulence at frequencies near the lower hybrid resonance is studied experimentally with the KROT device. Nonlinear effects during the interaction of intense lower hybrid waves with a magnetoactive plasma are investigated, with the focus on the formation and evolution of nonlinear plasma structures (cavitons). Macroscopic consequences of plasma turbulence are considered, including nonlinear plasma heating, particle acceleration, and its effect on transport processes.     

Stability of hybrid modes of a single-component electron plasma containing an admixture of background gas ions

The spectrum of eigenmodes of a waveguide completely filled with a cold electron plasma containing a small admixture of ions produced due to electron-impact ionization of background gas atoms is calculated numerically. The calculations were performed within the entire range of allowable values of the radial electric and longitudinal magnetic fields for both magnetized and unmagnetized ions by using the earlier derived nonlocal dispersion relation [Plasma Phys. Rep. 36, 563 (2010)]. The spectrum consists of three families of electron modes with frequencies equal to the Doppler-shifted upper and lower hybrid frequencies and modified ion cyclotron (MIC) modes. When the Doppler shift caused by electron rotation in the crossed electric and magnetic fields compensates for the hybrid frequency, the electron modes become low-frequency modes and interact with the ion modes. For m = 1, only the lower hybrid modes can be low-frequency ones, whereas at m ≥ 2, both lower and upper hybrid modes can be low-frequency ones. The spectrum of modes having the azimuthal number m = 2 is thoroughly analyzed. It is shown that, in this case, the lower hybrid modes behave similar to the m = 1 modes. The dispersion curves of the upper hybrid modes intersect with all harmonics of the MIC frequency (positive, negative, and zero) and are unstable in the vicinities of the intersections. The maximum value of the instability growth rate is several times higher than the ion plasma frequency. The MIC modes are unstable within a wide range of the field strengths, and their growth rates are two orders of magnitude slower. Instabilities are caused by the relative motion of electrons and ions (the transverse current) and the anisotropy of the ion distribution function.     

Impact of plant resistance on southwestern corn borer (Lepidoptera: Crambidae) biology and plant damage

Southwestern corn borer, Diatraea grandiosella Dyar (Lepidoptera: Crambidae), is a major insect pest of corn, Zea mays L., in the southern United States. Germplasm lines with resistance to southwestern corn borer have been developed and released by the USDA-ARS. Two single-cross hybrids produced by crossing germplasm lines with resistance to southwestern corn borer and a susceptible single-cross hybrid were infested with southwestern corn borer larvae in a 2-yr field test conducted in Mississippi. The susceptible hybrid sustained significantly more leaf damage and stalk tunneling than either resistant hybrid. The number of tunnels and the length of tunneling were significantly lower on the resistant hybrids. In 2003, up to 15 times more tunneling was observed on the susceptible hybrid. Larvae feeding on the resistant hybrids were delayed in their movement from the whorl to the stalk and larval survival was 50% lower on the resistant hybrids than on the susceptible hybrid. Larvae recovered from the susceptible hybrid 7-14 d after infestation weighed twice as much as those recovered from the resistant hybrids. Similar differences in larval weight were observed in the laboratory when larvae were reared on diets prepared from lyophilized tissue from the three hybrids. These results provide a foundation for other investigations designed to identify and determine the roles of specific genes and gene families associated with southwestern corn borer resistance in corn.     

Comparison of kinetic properties of the ATPase reaction of arterial smooth muscle myosin with skeletal muscle myosin

Myosin was prepared from arterial smooth muscle, and a hybrid actomyosin was formed from arterial myosin and rabbit skeletal muscle F-actin. We performed kinetics on the ATPase reaction [EC 3.6.1.3] of arterial myosin and the hybrid actomyosin at high ionic strength, and compared the kinetic properties of arterial myosin ATPase with those of skeletal muscle myosin ATPase. No significant difference was found between these two myosins in the size of the initial Pi burst, the amount of bound nucleotides, and the rates of various elementary steps in the ATPase reaction. On the other hand, two important differences were observed between the hybrid actomyosin and skeletal muscle actomyosin: (i) The amounts of ATP necessary for complete dissociation of the hybrid and skeletal muscle actomyosins were 2 and 1 mol/mol of myosin, respectively. (ii) The rate of dissociation of the hybrid actomyosin induced by ATP was much lower than that of skeletal muscle actomyosin and also was lower than that of fluorescence enhancement.     

Hemoglobin oxygen affinity in Mesocricetus auratus hamsters of different ages

Studies have been made on the amino acid composition of electrophoretically homogeneous albumin and its main isoelectrically homogeneous fraction in two strains of hens and their hybrid. Serum albumin of hen and hybrid is characterized by higher total content of Asp and Glu residues as compared with that of the cock (137, 121, and 116 respectively) and lower content of Lys (59 against 66). The acidity of albumin increases in the line cock-hen-hybrid. With respect to its amino acid composition, the maternal serum albumin stands close to the hybrid one.     

Behavior of meiotic chromosomes in Pinus wallichiana, P. strobus and their hybrid and nrDNA localization in pollen mother cells of the hybrid by using FISH

The complete process of meiosis was investigated in Pinus wallichiana, P. strobus and their artificial hybrid （F1） using microsporocytes. It is revealed that there were slightly lower chiasma frequency, lower ring bivalent frequency, lower meiotic index and distinctly higher frequency of aberrance （chromosomal bridges, fragments or micronuclei） in pollen mother cells （PMCs） of the hybrid （F1） than those of the parental species, which showed a certain degree of differentiation between homologous chromosomes of the two parents. However, relatively higher frequency of ring bivalents and higher meiotic index in all the three entities indicate the great stability of genomes of parental species, and the differentiation of genomes between the two parents must have been slight. Total nineteen signal loci of 18S rDNA were observed in nine bivalents of the hybrid （F1）, among which one bivalent bears two loci, while the others have only one. It is suggested that distinct differentiation at genetic level existed in homologous chromosomes of the two parental species, whereas only slight differentiation at karyotypic and genomic levels take place between the parent species.     

Interspecific mating in the Piriqueta caroliniana (Turneraceae) complex: effects of pollen load size and composition

Two taxa of Piriqueta (P. caroliniana and P. viridis) form a broad hybrid zone that extends over much of the central Florida peninsula. We used genetic markers to examine the strength of the isolation barriers between these taxa and the patterns of mating at the initial stages of hybridization. Regression models were employed to analyze the effects of pollen load size and the proportions of intra- and interspecific pollen on the frequency of first-generation (F1) hybrid formation. Overall, the postpollination mating barriers between these two taxa were relatively weak. However, there were significant effects of pollen load composition and size on the patterns of hybridization in both taxa with frequency-dependent responses to composition in both taxa. The frequency of F1 hybrid formation was generally lower than expected based on the frequency of each pollen type on the stigma for P. caroliniana recipients. The lower frequencies of F1 seeds in this taxon were apparently due to a greater competitive ability for intraspecific pollen, since hybrid seed formation decreased with increasing pollen load size. Pollen from P. caroliniana donors was also competitively superior on P. viridis recipients, leading to higher than expected frequencies of hybrid seed formation. Pollen from P. caroliniana did suffer higher rates of pollen-tube attrition than intraspecific pollen on P. viridis recipients, so the frequency of hybrid seed formation would be lower when pellen load sizes were small. In general, reproductive isolation mechanisms were stronger in P. caroliniana, suggesting that introgression should occur into P. viridis when these taxa come into close contact. Comparison of these expected patterns of mating to the distribution of hybrid genotypes in Florida provides insights into the relative roles of mating and selection in the evolution of hybrid populations of Piriqueta.     

The influence of hybridization between African and European honeybees, Apis mellifera, on asymmetries in wing size and shape

Abstract We examined the possible role of hybridization in the invasion process of the African honeybee by testing two hypotheses regarding fluctuating asymmetry (FA), a measure of developmental stability, in wing characteristics: (1) FA should be higher in hybrid versus parental genotypes of African and European races; (2) FA should be lower in African bees compared to hybrid and European workers. Parental and reciprocal hybrid worker genotypes were cross fostered in common-hive rearing environments. We did not find greater FA for wing size and shape in the hybrids compared to both parental types. However, we did find significantly lower FA of shape in the African workers compared to the European and hybrid workers, suggesting that European bees and their hybrids may have compromised fitness relative to African bees. We also found that the two hybrid genotypes significantly differed in overall wing size and shape. If these differences affect wing aerodynamics, then the paternity of hybrids may influence worker performance and could potentially contribute to the loss of European matrilines. Hybridization had few consistent effects on directional asymmetry for wing size and shape. Genotypic factors played a far greater role in determining the effect of hybridization on wing morphology than did differences in rearing environment. Thus, African bees may have lower FA for wing shape (and by inference greater developmental stability) relative to European and hybrid workers, which may contribute to the ability of African bees to displace European honeybee races in invaded regions.     

Intensity of infection with intracellular Eimeria spp. and pinworms is reduced in hybrid mice compared to parental subspecies

Genetic diversity in animal immune systems is usually beneficial. In hybrid recombinants, this is less clear, as the immune system could also be impacted by genetic conflicts. In the European house mouse hybrid zone, the long‐standing impression that hybrid mice are more highly parasitized and less fit than parentals persists despite the findings of recent studies. Working across a novel transect, we assessed infections by intracellular protozoans, Eimeria spp., and infections by extracellular macroparasites, pinworms. For Eimeria, we found lower intensities in hybrid hosts than in parental mice but no evidence of lowered probability of infection or increased mortality in the centre of the hybrid zone. This means ecological factors are very unlikely to be responsible for the reduced load of infected hybrids. Focusing on parasite intensity (load in infected hosts), we also corroborated reduced pinworm loads reported for hybrid mice in previous studies. We conclude that intensity of diverse parasites, including the previously unstudied Eimeria, is reduced in hybrid mice compared to parental subspecies. We suggest caution in extrapolating this to differences in hybrid host fitness in the absence of, for example, evidence for a link between parasitemia and health.