Population assignment in autopolyploids.

Understanding the patterns of contemporary gene dispersal within and among populations is of critical importance to population genetics and in managing populations for conservation. In contrast to diploids, there are few studies of gene dispersal in autopolyploids, in part due to complex polysomic inheritance and genotype ambiguity. Here we develop a novel approach for population assignment for codominant markers for autotetraploids and autohexaploids. This method accounts for polysomic inheritance, unreduced gametes and unknown allele dosage. It can also utilise information regarding the origin and genotype of one parent for population assignment of maternal or paternal parents. Using simulations, we demonstrate that our approach achieves high levels of accuracy for assignment even when population divergence is low (FST~0.06) and with only 12 microsatellite loci. We also show that substantially higher accuracy is achieved when known maternal information is utilised, regardless of whether allele dosage is known. Although this novel method exhibited near identical levels of accuracy to Structure when population divergence was high, it performed substantially better for most parameters at moderate (FST=0.06) to low levels of divergence (FST=0.03). These methods fill an important gap in the toolset for autopolyploids and pave the way for investigating contemporary gene dispersal in a widespread group of organisms.

The dynamics of resource allocation and costs of reproduction in a sexually dimorphic, wind-pollinated dioecious plant.

Sexual dimorphism in resource allocation is expected to change during the life cycle of dioecious plants because of temporal differences between the sexes in reproductive investment. Given the potential for sex-specific differences in reproductive costs, resource availability may contribute to variation in reproductive allocation in females and males. Here, we used Rumex hastatulus, a dioecious, wind-pollinated annual plant, to investigate whether sexual dimorphism varies with life-history stage and nutrient availability, and determine whether allocation patterns differ depending on reproductive commitment. To examine if the costs of reproduction varied between the sexes, reproduction was either allowed or prevented through bud removal, and biomass allocation was measured at maturity. In a second experiment to assess variation in sexual dimorphism across the life cycle, and whether this varied with resource availability, plants were grown in high and low nutrients and allocation to roots, aboveground vegetative growth and reproduction were measured at three developmental stages. Males prevented from reproducing compensated with increased above- and belowground allocation to a much larger degree than females, suggesting that male reproductive costs reduce vegetative growth. The proportional allocation to roots, reproductive structures and aboveground vegetative growth varied between the sexes and among life-cycle stages, but not with nutrient treatment. Females allocated proportionally more resources to roots than males at peak flowering, but this pattern was reversed at reproductive maturity under low-nutrient conditions. Our study illustrates the importance of temporal dynamics in sex-specific resource allocation and provides support for high male reproductive costs in wind-pollinated plants.

Source population characteristics affect heterosis following genetic rescue of fragmented plant populations.

Understanding the relative importance of heterosis and outbreeding depression over multiple generations is a key question in evolutionary biology and is essential for identifying appropriate genetic sources for population and ecosystem restoration. Here we use 2455 experimental crosses between 12 population pairs of the rare perennial plant Rutidosis leptorrhynchoides (Asteraceae) to investigate the multi-generational (F(1), F(2), F(3)) fitness outcomes of inter-population hybridization. We detected no evidence of outbreeding depression, with inter-population hybrids and backcrosses showing either similar fitness or significant heterosis for fitness components across the three generations. Variation in heterosis among population pairs was best explained by characteristics of the foreign source or home population, and was greatest when the source population was large, with high genetic diversity and low inbreeding, and the home population was small and inbred. Our results indicate that the primary consideration for maximizing progeny fitness following population augmentation or restoration is the use of seed from large, genetically diverse populations.

Patterns of hybridization and asymmetrical gene flow in hybrid zones of the rare Eucalyptus aggregata and common E. rubida.

The patterns of hybridization and asymmetrical gene flow among species are important for understanding the processes that maintain distinct species. We examined the potential for asymmetrical gene flow in sympatric populations of Eucalyptus aggregata and Eucalyptus rubida, both long-lived trees of southern Australia. A total of 421 adults from three hybrid zones were genotyped with six microsatellite markers. We used genealogical assignments, admixture analysis and analyses of spatial genetic structure and spatial distribution of individuals, to assess patterns of interspecific gene flow within populations. A high number of admixed individuals were detected (13.9-40% of individuals), with hybrid populations consisting of F(1) and F(2) hybrids and backcrosses in both parental directions. Across the three sites, admixture proportions were skewed towards the E. aggregata genetic cluster (x=0.56-0.65), indicating that backcrossing towards E. aggregata is more frequent. Estimates of long-term migration rates also indicate asymmetric gene flow, with higher migration rates from E. aggregata to hybrids compared with E. rubida. Taken together, these results indicate a greater genetic input from E. aggregata into the hybrid populations. This asymmetry probably reflects differences in style lengths (E. rubida: ~7 mm, E. aggregata: ~4 mm), which can prevent pollen tubes of smaller-flowered species from fertilizing larger-flowered species. However, analyses of fine-scale genetic structure suggest that localized seed dispersal (<40 m) and greater clustering between hybrid and E. aggregata individuals may also contribute to directional gene flow. Our study highlights that floral traits and the spatial distributions of individuals can be useful predictors of the directionality of interspecific gene flow in plant populations.

Validation of parameters for assessing Obscure Auditory Dysfunction--robustness of determinants of OAD status across samples and test methods.

About 5% of those presenting at an ENT clinic with ear or hearing complaints are found to have normal pure-tone thresholds. Many of this group complain specifically of difficulties understanding speech in background noise. We have termed this complaint 'Obscure Auditory Dysfunction' (OAD). Previous research on OAD (Saunders and Haggard, 1992) on a sample of 50 patients and 50 matched controls showed that 83% of the deviance (binary variance) in membership of group (OAD/control) could be explained by four variables, with three underlying factors. These four variables are performance threshold in noise for speech; discrepancy between this and a self-adjusted signal-to-noise ratio value (i.e. a measure of auditory confidence); dichotic listening performance; and performance on a psychoacoustic test, the threshold for detecting a tone in a spectrally notched noise. This paper reports a study on a further 59 new OAD patients and 64 unmatched controls, using the tests in the form present in the test package, plus certain others. For routine practice, slightly differing implementations of the auditory test techniques were used. Compared to the earlier sample, the new sample had poorer measures of speech reception threshold in noise and they considered themselves more handicapped by their OAD state; however there was no significant difference between the two samples on the other performance variables. Overall, the results demonstrate the robustness of the conclusions reached from the previous study, as the test-variable determinants of OAD status (i.e. case-control differences) were similar. The items on the OAD interview questionnaire which had shown significant differences between OADs and controls were also similar for the two OAD samples, giving a consistent picture of patient profile. These were: difficulties learning to read or write as a child (which relates to dichotic listening scores); adult ear problems; and tinnitus (which relate to the psychoacoustic scores). This necessary replication confirms the validity of the three-factor model of OAD status and the utility of the clinical test package based upon it.

A clinical test battery for obscure auditory dysfunction (OAD): development, selection and use of tests.

Obscure auditory dysfunction (OAD) is defined as convincing self-report of auditory disability accompanied by normal pure-tone thresholds. This has been increasingly recognized as a clinical problem, but until now there has not been a standard clinical procedure for dealing with such patients. This paper summarizes a demographic and clinical characterization of a sample of 50 OAD patients, reports new norms on the tests in the version issued, and describes a test package developed from a case-control research study that can be routinely used with OAD patients. The package enables clinicians: (i) to confirm, or otherwise, OAD as the appropriate classification for individuals presenting with OAD-like symptoms; (ii) to elucidate the underlying basis of OAD in such individuals and hence in most cases to provide explanations that are justified by test findings; and (iii) to counsel cases in a fashion appropriate for each individual. The package consists of four performance tests, a specialized clinical interview and a brief questionnaire to determine the severity of OAD. The assessment takes approximately 37 min and can be run using a two-channel audiometer and a cassette recorder.

Limitations of chest pain follow-up from an urban teaching hospital emergency department.

Close outpatient follow-up of chest pain patients released from the emergency department (ED) has been suggested as an important means of detecting atypical presentations of cardiac ischemia. Urban teaching hospital patient populations often have limited private physician follow-up options and rely upon standard teaching hospital clinic systems. We analyzed the follow-up of 318 patients 30 or more years of age with nontraumatic chest pain released from the ED of a large urban teaching hospital. The planned disposition of the released patients was as follows: a medical clinic (136), another clinic or a private physician (76), or ED "as needed" (98); in addition, some patients left against medical advice (AMA) (8). The medical clinics received only 38% (51/136) of planned referrals. No subsequent record could be found for 13% (17/136) of referred patients. Only 17% (23/136) of referred patients were reevaluated within seven days. Two of the patients referred to medical clinics were admitted to the hospital within 24 hours for unstable angina and another was admitted from a medical clinic 16 days after ED evaluation with an acute myocardial infarction. Of patients with ED follow-up "as needed," one patient required admission for unstable angina 27 days after ED evaluation. Of the patients who left AMA, only two were reevaluated within 30 days. These findings suggest that specific measures to enhance follow-up must be instituted at urban teaching hospitals if chest pain patients are to be closely followed after ED release.