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Data supporting the occurrence of adaptive trait transfer (i.e. the transfer of genes and thus the phenotype of an adaptive trait through viral recombination, lateral gene transfer or introgressive hybridization) are provided in this review. Specifically, we discuss examples of lateral gene transfer and introgressive hybridization that have resulted in the transfer or de novo origin of adaptations. The evolutionary clades in which this process has been identified include all types of organisms. However, we restrict our discussion to bacteria, fungi, plants and animals. Each of these examples reflects the same consequence, namely that the transfer of genetic material, through whatever mechanism, may result in adaptive evolution. In particular, each of the events discussed has been inferred to impact adaptations to novel environmental settings in the recipient lineage.

Here we report our characterization of a widespread, highly selfing Mimulus allotetraploid formed by interspecific hybridization between M. nasutus and M. guttatus. Nucleotide variation at two nuclear loci (mCYCA and mAP3) within and among tetraploid populations resolves two haplotype clusters for each locus: one shares near identity with sequences from M. nasutus and the other group shares substantial variation with M. guttatus. With respect to the two loci studied, each allotetraploid individual is a 'fixed heterozygote' carrying sequences from both clusters. Moreover, mCYCA variation is consistent with at least two evolutionary origins for the Mimulus allotetraploid. We show that the allotetraploid is strongly reproductively isolated from M. nasutus and M. guttatus; interploidy crosses produce almost no viable seeds. By extension, we infer strong triploid block and argue that Mimulus allotetraploid formation might proceed in one step via the union of unreduced gametes in an M. nasutus-M. guttatus F(1) hybrid. We also discuss the potential roles of mating system and flowering asynchrony in allotetraploid establishment.

Aromatic compounds can form dimeric complexes in solution. Substituted aromatics tend to form parallel-stacked complexes, either aligned or offset. The HF-GIAO method in Gaussian 03 was employed to calculate the NMR isotropic shielding values of the proximal hydrogen of diatomic hydrogen probes above and below the center of the ring and above and below an unsubstituted ring carbon of 1,3,5-trimethylbenzene in a face-to-face pi-stacked aligned complex with 1,3,5-trinitrobenzene. The calculated isotropic shielding values for the aromatic hydrogens of each of the substituted rings were subtracted from the isotropic shielding values calculated for the comparable positions in the complex. Complexation results in each aromatic ring shielding the other ring. Also, the calculated isotropic shielding values for the proximal hydrogen of a diatomic hydrogen probe over (or under) each of the individual substituted benzenes were subtracted from the isotropic shielding values calculated for the comparable positions in the complex. The difference is the shielding increment due to complexation. Complexation results in increased NMR shielding of a hydrogen probe molecule on both sides of the pi-stacked complex, with slightly more shielding due to complexation on the side nearest 1,3,5-trimethylbenzene. The results are interpreted in terms of polarization of the pi cloud of the substituted benzenes by complexation and its NMR consequences. Finally, NMR shielding calculations were done on the optimized structure of N-phenylpyrrole dimer. The data were compared to concentration-dependent NMR shift data to estimate the percent dimer present.

In animal-pollinated plants, pollinator preferences for divergent floral forms can lead to partial reproductive isolation. We describe regions of plant genomes that affect pollinator preferences for two species of Louisiana Irises, Iris brevicaulis and Iris fulva, and their artificial hybrids. Iris brevicaulis and I. fulva possess bee and bird-pollination syndromes, respectively. Hummingbirds preferred I. fulva and under-visited both I. brevicaulis and backcrosses toward this species. Lepidopterans preferred I. fulva and backcrosses toward I. fulva, but also under-visited I. brevicaulis and I. brevicaulis backcrosses. Bumblebees preferred I. brevicaulis and F1 hybrids and rarely visited I. fulva. Although all three pollen vectors preferred one or the other species, these preferences did not prevent visitation to other hybrid/parental classes. Quantitative trait locus (QTL) mapping, in reciprocal BC1 mapping populations, defined the genetic architecture of loci that affected pollinator behavior. We detected six and nine QTLs that affected pollinator visitation rates in the BCIb and BCIf mapping populations, respectively, with as many as three QTLs detected for each trait. Overall, this study reflects the possible role of quantitative genetic factors in determining (1) reproductive isolation, (2) the pattern of pollinator-mediated genetic exchange, and thus (3) hybrid zone evolution.

Introduction: The spinocerebellar ataxias (SCAs), are rare neurodegenerative disorders caused by distinct genetic mutations. Clinically, the SCAs are characterised by progressive ataxia and a variety of other features, including cognitive dysfunction. The latter is consistent with a growing body of evidence supporting a cognitive as well as motor role for the cerebellum. Recent suggestions of cerebellar involvement in social cognition have not been extensively explored in these conditions. The availability of definitive molecular diagnosis allows genetically defined subgroups of SCA patients, with distinct patterns of cerebellar and extracerebellar involvement, to be tested comparatively using a common battery of tests of general, social and emotional cognition., Methods: : Nine patients with SCA6, and 6 with SCA3 were assessed using a comprehensive battery of neuropsychological instruments, encompassing domains of memory, language, visuo-spatial skills, calculation, attention and executive function, emotional processing and theory of mind (ToM)., Results: There were no deficits in visuo-spatial processing or calculation in either group, while individuals with naming and attentional difficulties were seen in both. Deficits in memory and executive function were present in both conditions, albeit more pronounced in SCA3. By contrast, both groups demonstrated consistently poor performance on ToM tests, and normal attribution of social and emotional responses., Conclusion: The data support the hypothesis that the cerebellum is important for cognitive as well as motor activity. The pattern of overlap of domain impairments provides tentative preliminary evidence that there is a cerebellar contribution to aspects of memory and executive function and ToM, and that other domains depend more on neural system outside the cerebellum. The findings relating to ToM are relevant to the possibility of cerebellar involvement in autism.

Despite the potential importance of divergent reproductive phenologies as a barrier to gene flow, we know less about the genetics of this factor than we do about any other isolating barrier. Here, we report on the genetic architecture of divergent flowering phenologies that result in substantial reproductive isolation between the naturally hybridizing plant species Iris fulva and I. brevicaulis. I. fulva initiates and terminates flowering significantly earlier than I. brevicaulis. We examined line crosses of reciprocal F1 and backcross (BC1) hybrids and determined that flowering time was polygenic in nature. We further defined quantitative trait loci (QTL) that affect the initiation of flowering in each of these species. QTL analyses were performed separately for two different growing seasons in the greenhouse, as well as in two field plots where experimental plants were placed into nature. For BCIF hybrids (BC1 toward I. fulva), 14 of 17 detected QTL caused flowering to occur later in the season when I. brevicaulis alleles were present, while the remaining 3 caused flowering to occur earlier. In BCIB hybrids (BC1 toward I. brevicaulis), 11 of 15 detected QTL caused flowering to occur earlier in the season when introgressed I. fulva alleles were present, while the remaining 4 caused flowering to occur later. These ratios are consistent with expectations of selection (as opposed to drift) promoting flowering divergence in the evolutionary history of these species. Furthermore, epistatic interactions among the QTL also reflected the same trends, with the majority of epistatic effects causing later flowering than expected in BCIF hybrids and earlier flowering in BCIB hybrids. Overlapping QTL that influenced flowering time across all four habitat/treatment types were not detected, indicating that increasing the sample size of genotyped plants would likely increase the number of significant QTL found in this study.

The HF-GIAO method in Gaussian 03 was employed to calculate the NMR isotropic shielding values of a diatomic hydrogen probe and to predict the through-space proton NMR shielding increment surfaces above benzene complexed with ammonium, lithium, sodium, potassium, magnesium or calcium ion. The sum of the calculated isotropic shielding values for the proximal hydrogen of a diatomic hydrogen probe over benzene and those calculated at appropriate positions relative to cations were subtracted from the isotropic shielding values calculated for the complexes. The result is a shielding increment for complexation. Complexation results in a synergistic effect on NMR shielding. Enhanced shielding was observed over the pi electron cloud of benzene upon complexation with the cations, more than the sum of the separate effects of the aromatic ring and the charge. The results are interpreted in terms of polarization of the pi cloud of benzene by the cation and its consequences.

Speciation often involves the evolution of numerous prezygotic and postzygotic isolating barriers between divergent populations. Detailed knowledge of the strength and nature of those barriers provides insight into ecological and genetic factors that directly or indirectly influenced their origin, and may help predict whether they will be maintained in the face of sympatric hybridization and introgression. We estimated the magnitude of pre- and postzygotic barriers between naturally occurring sympatric populations of Mimulus guttatus and M. nasutus. Prezygotic barriers, including divergent flowering phenologies, differential pollen production, mating system isolation, and conspecific pollen precedence, act asymmetrically to completely prevent the formation of F(1) hybrids among seeds produced by M. guttatus (F(1)g), and reduce F(1) hybrid production among seeds produced by M. nasutus (F(1)n) to only about 1%. Postzygotic isolation is also asymmetric: in field experiments, F(1)g but not F(1)n hybrids had significantly reduced germination rates and survivorship compared to parental species. Both hybrid classes had flower, pollen, and seed production values within the range of parental values. Despite the moderate degree of F(1)g hybrid inviability, postzygotic isolation contributes very little to the total isolation between these species in the wild. We also found that F(1) hybrid flowering phenology overlapped more with M. guttatus than M. nasutus. These results, taken together, suggest greater potential for introgression from M. nasutus to M. guttatus than for the reverse direction. We also address problems with commonly used indices of isolation, discuss difficulties in calculating meaningful measures of reproductive isolation when barriers are asymmetric, and propose novel measures of prezygotic isolation that are consistent with postzygotic measures.

The GIAO-HF method in Gaussian 03 was employed to calculate the isotropic NMR shielding values of a diatomic hydrogen probe above simple small-ring aromatic and antiaromatic hydrocarbons, including neutral and ionic examples. Subtraction of the isotropic shielding of diatomic hydrogen by itself allowed the prediction of through-space proton NMR shielding increment surfaces for these systems. Substantial shielding was observed above the center of aromatic rings, regardless of whether the ring was pi-aromatic or sigma-aromatic, and also regardless of the charge. In sharp contrast, deshielding was observed above the center of antiaromatic rings, regardless of whether the ring was pi-aromatic or sigma-aromatic, and also regardless of the charge. Shielding increment values at 2.5 angstrom above the ring centers were compared to NICS values at the same position. The shielding effects predicted by using diatomic hydrogen as a computational probe are diagnostic of whether a structure possesses aromaticity or antiaromaticity.

The GIAO-HF method in Gaussian 03 was employed to calculate the isotropic shielding values of a covalently bonded hydrogen probe and to predict the through-space proton NMR shielding increment surfaces near models of simple structures containing functional groups common to peptides. The functional groups examined include the carboxylate anion, carboxylic acid, amide, amino, ammonium and guanidinium groups. Our previously developed methodology involving the use of diatomic hydrogen as a probe of through-space shielding effects was employed. Substantial shielding or deshielding effects were observed only in the cases of the charged (ionic) groups, each of which displayed shielding or deshielding effects of greater than 1 ppm at distances comparable to those observed in peptides. Equations for predicting the shielding increments of these groups as a function of the Cartesian coordinate position of the affected proton were determined. The validity of using simple structures as models of shielding by comparable functional groups in peptides was confirmed by computing the shielding effects at selected positions above a model of glycylglycylglycine and its hydrogen-bonded dimer. Knowledge of these through-space shielding effects should aid in the tertiary structure determination of peptides by NMR.

Psychophysiological science proposes close interactions between cognitive processes and autonomic responses, yet the consequences of autonomic failure on cognitive functioning have not been documented. This pilot study investigates, for the first time, the cognitive profile of 14 patients with Pure Autonomic Failure (PAF). Each patient was administered a comprehensive battery of neuropsychological tests and neuroimaging investigation. A number of patients (n = 6) presented with cognitive impairment. The two most frequent types of impairment were: deficits of speed and attention, and executive functioning. Impairments of free recall memory, intellectual functioning, nominal and calculation functions were also documented, albeit in a much lower frequency. These cognitive changes were not always associated with white matter abnormalities. We speculate that the cognitive impairments associated with PAF represent consequences of systemic hypotension with cerebral underperfusion. However, a failure in integrated bodily arousal responses during cognitive behaviours may also contribute to some of the observed deficits.

The idea that natural hybridization has served as an important force in evolutionary and adaptive diversification has gained considerable momentum in recent years. By combining genome analyses with a highly selective field experiment, we provide evidence for adaptive trait introgression between two naturally hybridizing Louisiana Iris species, flood-tolerant Iris fulva and dry-adapted I. brevicaulis. We planted reciprocal backcross (BC1) hybrids along with pure-species plants into natural settings that, due to a flooding event, favored I. fulva. As expected, I. fulva plants survived at much higher rates than I. brevicaulis plants. Backcross hybrids toward I. fulva (BCIF) also survived at significantly higher rates than the reciprocal backcross toward I. brevicaulis (BCIB). Survivorship of BCIB hybrids was strongly influenced by the presence of a number of introgressed I. fulva alleles located throughout the genome, while survivorship in the reciprocal BCIF hybrids was heavily influenced by two epistatically acting QTL of opposite effects. These results demonstrate the potential for adaptive trait introgression between these two species and may help to explain patterns of genetic variation observed in naturally occurring hybrid zones.

Iris fulva and I. brevicaulis are long-lived plant species known to hybridize where they coexist in nature. Year-to-year survival contributes significantly to overall fitness for both species and their hybrid derivatives, and differences in hybrid survivability may have important consequences to interspecific gene flow in nature. We examined the genetic architecture of long-term survivorship of reciprocal backcross I. fulva x I. brevicaulis hybrids in a common-garden, greenhouse environment. Differences in mortality were found between the two backcross (BC1) hybrid classes, with hybrids crossed toward I. fulva (BCIF) revealing twice the mortality of those hybrids backcrossed toward I. brevicaulis (BCIB). Using genomic scans on two separate genetic linkage maps derived from the reciprocal hybrid populations, we found that hybrid survivorship is influenced by several genetic regions. Multiple interval mapping (MIM) revealed four quantitative trait loci (QTLs) in BCIF hybrids that were significantly associated with survivorship. Introgressed I. brevicaulis DNA increased survivorship at three of the four QTLs. For the fourth QTL, introgressed I. brevicaulis DNA was associated with decreased survivorship. No QTLs were detected in BCIB hybrids; however, single-marker analysis revealed five unlinked loci that were significantly associated with survivorship. At all five markers, survivorship was positively associated with introgressed I. fulva DNA. The present findings have important implications for the evolutionary dynamics of naturally occurring hybrid zones. Regions of the genome that increase survivorship when in a heterozygous (i.e., hybrid) state should have an increased likelihood of passing across species boundaries, whereas those that decrease survivorship will be less likely to introgress.

In a strong magnetic field, covalently bonded hydrogen nuclei located over the plane of an anisotropic pi bond-containing functional group experience magnetic shielding (or deshielding) that results from the combined effect of the magnetic anisotropy of the functional group and other nearby covalent bonds plus other intramolecular shielding effects. These effects can now be calculated with reasonable accuracy using ab initio methods. We have investigated several computational probes of the magnetic shielding surface near anisotropic functional groups and compared the results to previous reports of experimental observations in example structures. GIAO-HF in Gaussian 03 was employed to calculate isotropic shielding values and to predict the net NMR shielding increment for several computational probes: methane, diatomic hydrogen, a hydrogen atom, a helium atom, or a ghost atom, each held in various positions over simple test molecules (ethene, ethyne, benzene and HCN) that contain the functional groups studied. Also, the effect of performing single point calculations versus constrained geometry-optimized calculations was examined. In addition, the effect of the angle of the orientation of the probe molecule (in the case of CH(4) and H(2)) relative to the pi bond in the test molecule was studied. Finally, the atomic charges in the molecular probes (CH(4) and H(2)) were computed to investigate the nature of the interaction of the probe with the test molecule. The optimal, most economical computational results were obtained using single point calculations of a diatomic hydrogen probe oriented perpendicular to the surface (or axis) of the test molecule.

Covalently bonded hydrogen nuclei located over the plane of a carbonyl group in a strong magnetic field experience magnetic shielding (or deshielding) that results from the combined effect of the magnetic anisotropy of the carbon-oxygen double bond and various other intramolecular shielding effects. GIAO-HF in Gaussian 98 was employed to calculate isotropic shielding values and to predict the net proton NMR shielding increment for a simple model system: the proximate proton of methane held in various positions over formaldehyde. The net shielding increments of the proximate proton of methane, plotted against its Cartesian coordinates relative to the center of the carbon-oxygen double bond, led to the development of a single empirical equation for predicting the NMR shielding experienced by a covalently bonded proton over the plane of a carbonyl group. The predictive capability of this equation has been validated by calculating the shielding increments of protons over the plane of a carbonyl group in known structures, using this as a correction to the chemical shift estimated by subtituent effects and comparing the result to experimentally observed chemical shifts. Shielding is predicted by this equation for protons located in the region from over the center of the carbon-oxygen double bond to beyond the carbon atom; deshielding is predicted for protons located above and beyond the oxygen atom. This prediction differs from those made by the long-held "shielding cone" model found in nearly every textbook on NMR, but is consistent with experimental observations. The algorithm for predicting the shielding increment for a proton over a carbonyl group can be used in a spreadsheet or incorporated into software that estimates chemical shifts using additive substituent constants or a database of structures. Its use can improve the accuracy of the estimated chemical shift of a proton in the vicinity of a carbon-oxygen double bond, and thus assist in spectral assignments and in correct structure determination.

In a strong magnetic field, covalently bonded hydrogen nuclei located over a pi bonded functional group experience magnetic shielding (or deshielding) that results from the combined effect of the magnetic anisotropy of the pi bond and various other intramolecular shielding effects. Gauge including atomic orbital (GIAO)-HF in Gaussian 98 was employed to calculate isotropic shielding values and to predict the net through-space proton NMR shielding increment for a simple model system: the proximate proton of methane held in various positions over simple molecules that contain a carbon-carbon triple bond, a carbon-nitrogen triple bond, or a nitro group. These net shielding increments of the proximate proton of methane, plotted against their Cartesian coordinates, led to the development of a single empirical equation for predicting the NMR shielding experienced by a covalently bonded proton over each group. The predictive capability of each equation has been validated by calculating shielding increments of protons over the functional group in known structures. These shielding increments are then used to adjust predicted chemical shifts for through-space shielding effects, and the adjusted values are compared to experimentally observed chemical shifts. The algorithms for predicting the shielding increment for a proton over these functional groups can be used in a spreadsheet or incorporated into software that estimates chemical shifts using additive substituent constants or a database of structures. Their use can substantially improve the accuracy of the estimated chemical shift of a proton in the vicinity of these functional groups, and thus assist in spectral assignments and in correct structure determination.

GIAO-HF and IGLO-DFT computations of isotropic magnetic shieldings were used to map the NMR shielding environments of small molecules exemplifying selected organic functional groups. Two different probes were employed: a methane molecule and NICS (nucleus-independent chemical shifts) based on computed absolute isotropic shieldings. The reason for the different results obtained using these two probes is perturbation of the wave function by the proximity of methane to the pi bond, as analyzed by the localized orbital contributions to the shieldings. [structure: see text]

In a strong magnetic field, hydrogen nuclei located over an aromatic ring experience a reduced magnetic field as a result of the induced magnetic field associated with circulating pi electrons. We used GIAO-SCF, an ab initio subroutine in Gaussian 94 to calculate isotropic shielding values and to determine the proton nuclear magnetic resonance (NMR) shielding increment for a simple model system: methane held at various positions over a substituted benzene ring. The NMR shielding increments experienced by the proximal protons of methane have been mapped as a function of their position X, Y, and Z relative to the center of aniline and, separately, nitrobenzene. A mathematical function of the same form has been fit to the three-dimensional shielding increment surface at each of five distances from the face of each aromatic ring. In addition, a single mathematical equation has been developed for predicting the shielding caused by either substituted aromatic ring. The chemical shifts predicted by using the results of this equation in conjunction with additive substituent increments are compared to observed values.

Hydrogen nuclei located over a carbon-carbon double bond in a strong magnetic field experience NMR shielding effects that result from the magnetic anisotropy of the nearby double bond and various other intramolecular shielding effects. We have used GIAO, a subroutine in Gaussian 98, to calculate isotropic shielding values and to predict the proton NMR shielding increment for a simple model system: methane held in various orientations, positions, and distances over ethene. The average proton NMR shielding increments of several orientations of methane have been plotted versus the Cartesian coordinates of the methane protons relative to the center of ethene. A single empirical equation for predicting the NMR shielding experienced by protons over a carbon-carbon double bond has been developed from these data. The predictive capability of this equation has been validated by comparing the shielding increments for several alkenes calculated using our equation to the experimentally observed shielding increments. This equation predicts the NMR shielding effects more accurately than previous models that were based on fewer geometries of methane over ethene. In fact, deshielding is predicted by this equation for protons over the center and within about 3 A of a carbon-carbon double bond. This result is in sharp contrast to predictions made by the long-held McConnell "shielding cone" model found in nearly every textbook on NMR, but is consistent with experimental observations. The algorithm for predicting the (de)shielding increment for a proton over an alkene can be used in a spreadsheet on a PC or incorporated into software that estimates chemical shifts using additive substituent constants or a database of structures. In either application its use can substantially improve the accuracy of the estimated chemical shift of a proton in the vicinity of a carbon-carbon double bond, and thus assist in spectral assignments and in correct structure determination.