Optimizing purebred selection for crossbred performance using QTL with different degrees of dominance

A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing.     

Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle

Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle.     

Echoortung bei der Fledermaus Chilonycteris rubiginosa

Zusammenfassung Chilonycteris rubiginosa erzeugt in allen Orientierungsituationen dreiteilige Ortungslaute. Im Anfangsteil steigt die Frequenz um etwa 1–2 kHz an. Der folgende Mittelteil hat eine konstante Frequenz von etwa 57 bis 57,6 kHz. Im Endteil fällt die Frequenz um etwa 8 kHz ab. Die Laute werden in Folgen von Lautgruppen ausgesendet.CR erzeugt pro Flügelschlag eine Lautgruppe. Im freien Flug zeigt CR Gruppen mit 2 Lauten von etwa 17–23 msec Dauer. Landende Fledermäuse senden in der Annäherungsphase Gruppen mit einer zunehmenden Zahl immer kürzerer Laute und in der Schlußphase eine längere Gruppe mit vielen kurzen Lauten.Fliegende Tiere senken die Frequenz des konstantfrequenten Mittelteils immer um etwa den Betrag der durch die Fluggeschwindigkeit bedingten Dopplereffekte ab, so daß die von den Tieren gehörte Echofrequenz nahezu konstant in Höhe der vor dem Flug ausgesendeten Frequenz gehalten wird.CR zeigt Kopf- und Ohrbewegungen. Die Ohrbewegungen stehen in Beziehung zur Lautaussendung.

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Echolocation by the bat Chilonycteris rubiginosa

Summary Chilonycteris rubiginosa (CR) produces tripartite ultrasonic sounds in all orientation situations. During the first part the frequency rises by 1–2 kHz. The following middle part has a constant frequency of about 57–57,6 kHz. In the terminal part the frequency decreases by about 8 kHz. The sounds are emitted as a sequence of groups of sounds.In flight they produce per wingbeat one group of sounds at a repetition rate of 10–11 Hz. In free flight CR emits groups of 2 sounds of about 17–23 msec duration. During the approach landing bats emit groups consisting of an increasing number of sounds of decreasing duration. During the terminal phase the group is longer in duration and consists of many short sounds.Flying CR lower the frequency of the middle part by an amount which compensates for Doppler shifts caused by the flight velocity. The frequency heard by the bats is, thus, always kept constant and equal to a frequency which is about 100–150 Hz above the medium frequency emitted before the flight. CR shows head and ear movements. The ear movements are correlated to the sound emission.

     

Successional status of trees in gallery forest along the river Rhine

Abstract. 20 alluvial forest stands of different ages along the river Rhine in central Alsace, France, are described. A natural complex landscape occurs which is formed by erosion activity of the river. Recent human impact (canal construction, cutting) has affected river hydrology: flooding is eliminated over large areas and the underground water levels are stabilized. The forest vegetation varies in species diversity and structure, from young pioneer to older, mid-successional forests. The forests were classified into four associations: Salici-Populetum nigrae, Ligustro-Populetum nigrae, Fraxino-Populetum albae and Querco-Ulmetum minoris. The first three communities are ‘softwood’ because of the dominance of Salix and Populus, the fourth, dominated by Quercus robur, Fraxinus excelsior and Ulmus minor, is ‘hardwood’. Differences in structure, species composition and diversity in 10 widely varying stands in 30-yr and 150-yr old forests are quantified and interpreted in relation to the processes and gradients (moisture and texture) involved. A model of forest succession is developed as follows:

• 1 Whatever the topographic level, Salix and Populus species are the most competitive in colonizing bare sediments.
• 2 Under natural conditions, pioneer softwoods are generally replaced by hardwoods in less than 100 yr.
• 3 Old Querco-Ulmetum is basically the terminal stage of the alluvial succession.
• 4 Old softwood forests result from an interruption of the natural course of succession. Softwoods may be an intermediate or late-successional phase depending on the interruption.
• 5 Successional processes change according to hydrological and edaphic gradients.
• 6 Allogenic processes of flooding are fundamental in the space-time species pattern.
• 7 Allogenic processes are responsible for the high species and community diversity.

     

Fledermäuse im Windkanal

Zusammenfassung In einem Windkanal wurde für eine Myotis lucifugus die Abhängigkeit der Fluggeschwindigkeit (v_F) und der Geschwindigkeit über Grund (v_G) von der Windgeschwindigkeit (v_W) bestimmt. Die Fledermaus flog bei Windstille mit einer mittleren v_F von etwa 4,5 m/sec. Bei zunehmenden Gegenwinden erhöhte sie v_F und verringerte v_G, um bei v_W=7,7 m/sec für kurze Zeit stationären Flug (v_G=0) zu erreichen. Die Flügelschlagfrequenz lag bei Gegenwinden von 0–7,7 m/sec zwischen 10–11/sec. Bei zunehmenden Rückenwinden wurde der Flug immer mehr dem Rüttelflug ähnlich und die Flügelschlagfrequenz stieg bis 16/sec an. Die v_G blieb nahezu konstant in einem Bereich zwischen 4,5–5 m/sec. Bei Myotis lucifugus, Chilonycteris rubiginosa, Carollia perspillicata und Rhinolophus ferrum-equinum wurde die Flügelstellung während der Lautaussendung ermittelt. Alle Arten erzeugten entweder einen Einzellaut oder eine Gruppe von Lauten pro Flügelschlag.

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Bats in the wind tunnel

Summary In an experimental wind tunnel air speed (v_F) and ground speed (v_G) of a Myotis lucifugus were measured as a function of wind speed (v_W). The bat had a v_F of about 4,5 m/sec in still air. With head winds it increased v_F and lowered v_G to reach stationary flight (v_G=0) at a v_W of 7,7 m/sec. The rate of wing motion remained at about 10–11/sec at head winds from 0–7,7 m/sec. With tail winds the bat changed to a semi-hovering flight with wing beat frequencies rising to about 16/sec and v_F dropping to almost zero at 4–5 m/sec tailwinds. The v_G remained nearly constant between about 4,5–5 m/sec. (Figs. 2 and 3). The wing positions during which orientation sounds were emitted were determined for Myotis lucifugus (Fig. 4), Chilonycteris rubiginosa, Carollia perspillicata and Rhinolophus ferrum-equinum (Fig. 5). All bats emitted either one single sound or a group of sounds per wing beat.

     

A study on the minimum number of loci required for genetic evaluation using a finite locus model

For a finite locus model, Markov chain Monte Carlo (MCMC) methods can be used to estimate the conditional mean of genotypic values given phenotypes, which is also known as the best predictor (BP). When computationally feasible, this type of genetic prediction provides an elegant solution to the problem of genetic evaluation under non-additive inheritance, especially for crossbred data. Successful application of MCMC methods for genetic evaluation using finite locus models depends, among other factors, on the number of loci assumed in the model. The effect of the assumed number of loci on evaluations obtained by BP was investigated using data simulated with about 100 loci. For several small pedigrees, genetic evaluations obtained by best linear prediction (BLP) were compared to genetic evaluations obtained by BP. For BLP evaluation, used here as the standard of comparison, only the first and second moments of the joint distribution of the genotypic and phenotypic values must be known. These moments were calculated from the gene frequencies and genotypic effects used in the simulation model. BP evaluation requires the complete distribution to be known. For each model used for BP evaluation, the gene frequencies and genotypic effects, which completely specify the required distribution, were derived such that the genotypic mean, the additive variance, and the dominance variance were the same as in the simulation model. For lowly heritable traits, evaluations obtained by BP under models with up to three loci closely matched the evaluations obtained by BLP for both purebred and crossbred data. For highly heritable traits, models with up to six loci were needed to match the evaluations obtained by BLP.     

Origin of volatile organic compound emissions from subarctic tundra under global warming

Warming occurs in the Arctic twice as fast as the global average, which in turn leads to a large enhancement in terpenoid emissions from vegetation. Volatile terpenoids are the main class of biogenic volatile organic compounds (VOCs) that play crucial roles in atmospheric chemistry and climate. However, the biochemical mechanisms behind the temperature‐dependent increase in VOC emissions from subarctic ecosystems are largely unexplored. Using ¹³CO₂‐labeling, we studied the origin of VOCs and the carbon (C) allocation under global warming in the soil–plant–atmosphere system of contrasting subarctic heath tundra vegetation communities characterized by dwarf shrubs of the genera Salix or Betula. The projected temperature rise of the subarctic summer by 5°C was realistically simulated in sophisticated climate chambers. VOC emissions strongly depended on the plant species composition of the heath tundra. Warming caused increased VOC emissions and significant changes in the pattern of volatiles toward more reactive hydrocarbons. The ¹³C was incorporated to varying degrees in different monoterpene and sesquiterpene isomers. We found that de novo monoterpene biosynthesis contributed to 40%–44% (Salix) and 60%–68% (Betula) of total monoterpene emissions under the current climate, and that warming increased the contribution to 50%–58% (Salix) and 87%–95% (Betula). Analyses of above‐ and belowground ^12/13C showed shifts of C allocation in the plant–soil systems and negative effects of warming on C sequestration by lowering net ecosystem exchange of CO₂ and increasing C loss as VOCs. This comprehensive analysis provides the scientific basis for mechanistically understanding the processes controlling terpenoid emissions, required for modeling VOC emissions from terrestrial ecosystems and predicting the future chemistry of the arctic atmosphere. By changing the chemical composition and loads of VOCs into the atmosphere, the current data indicate that global warming in the Arctic may have implications for regional and global climate and for the delicate tundra ecosystems.