Associations of stream geomorphic conditions and prevalence of alternative reproductive tactics among sockeye salmon populations.

In many species, males may exhibit alternative life histories to circumvent the costs of intrasexual competition and female courtship. While the evolution and underlying genetic and physiological mechanisms behind alternative reproductive tactics are well studied, there has been less consideration of the ecological factors that regulate their prevalence. Here, we examine six decades of age composition records from thirty-six populations of sockeye salmon (Oncorhynchus nerka) to quantify associations between spawning habitat characteristics and the prevalence of precocious sneakers known as 'jacks'. Jack prevalence was independent of neutral genetic structure among stream populations, but varied among habitat types and as a function of continuous geomorphic characteristics. Jacks were more common in streams relative to beaches and rivers, and their prevalence was negatively associated with stream width, depth, elevation, slope and area, but positively related to bank cover. Behavioural observations showed that jacks made greater use of banks, wood and shallows than guard males, indicating that their reproductive success depends on the availability of such refuges. Our results emphasize the role of the physical habitat in shaping reproductive tactic frequencies among populations, likely through local adaptation in response to variable fitness expectations under different geomorphic conditions.

Major histocompatibility complex diversity is positively associated with stream water temperatures in proximate populations of sockeye salmon.

Local adaptation to heterogeneous environments generates population diversity within species, significantly increasing ecosystem stability and flows of ecosystem services. However, few studies have isolated the specific mechanisms that create and maintain this diversity. Here, we examined the relationship between water temperature in streams used for spawning and genetic diversity at a gene involved in immune function [the major histocompatibility complex (MHC)] in 14 populations of sockeye salmon (Oncorhynchus nerka) sampled across the Wood River basin in south-western Alaska. The largest influence on MHC diversity was lake basin, but we also found a significant positive correlation between average water temperature and MHC diversity. This positive relationship between temperature and MHC diversity appears to have been produced by natural selection at very local scales rather than neutral processes, as no correlation was observed between temperature and genetic diversity at 90 neutral markers. Additionally, no significant relationship was observed between temperature variability and MHC diversity. Although lake basin was the largest driver of differences in MHC diversity, our results also demonstrate that fine-scale differences in water temperature may generate variable selection regimes in populations that spawn in habitats separated by as little as 1 km. Additionally, our results indicated that some populations may be reaching a maximum level of MHC diversity. We postulate that salmon from populations in warm streams may delay spawning until late summer to avoid thermal stress as well as the elevated levels of pathogen prevalence and virulence associated with warm temperatures earlier in the summer.

Estimating contemporary effective population size in non-model species using linkage disequilibrium across thousands of loci.

Contemporary effective population size (Ne) can be estimated using linkage disequilibrium (LD) observed across pairs of loci presumed to be selectively neutral and unlinked. This method has been commonly applied to data sets containing 10-100 loci to inform conservation and study population demography. Performance of these Ne estimates could be improved by incorporating data from thousands of loci. However, these thousands of loci exist on a limited number of chromosomes, ensuring that some fraction will be physically linked. Linked loci have elevated LD due to limited recombination, which if not accounted for can cause Ne estimates to be downwardly biased. Here, we present results from coalescent and forward simulations designed to evaluate the bias of LD-based Ne estimates ([Ncirc ]e). Contrary to common perceptions, increasing the number of loci does not increase the magnitude of linkage. Although we show it is possible to identify some pairs of loci that produce unusually large r(2) values, simply removing large r(2) values is not a reliable way to eliminate bias. Fortunately, the magnitude of bias in [Ncirc ]e is strongly and negatively correlated with the process of recombination, including the number of chromosomes and their length, and this relationship provides a general way to adjust for bias. Additionally, we show that with thousands of loci, precision of [Ncirc ]e is much lower than expected based on the assumption that each pair of loci provides completely independent information.

Safety of fenbendazole in Chinese ring-necked pheasants (Phasianus colchicus).

Ring-necked pheasants raised on propagation farms can be severely parasitized with Syngamus trachea (gapeworm) and other parasitic worms. Fenbendazole is a highly effective benzimidazole-class anthelmintic that is not currently approved for game bird species in the United States. The objective of this work was to provide target animal safety data to support a label claim for fenbendazole in pheasants at 100 parts per million (ppm) in the feed for 7 consecutive days. Demonstration of safety in young pheasants and a separate demonstration of reproductive safety in adult birds were required. In the young bird study, 160 Chinese ring-necked pheasants (Phasianus colchicus, 80 males and 80 females) were fed a commercial game bird starter ration containing no antibiotics, growth promoters, or coccidiostats until day 0 of the study (approximately 21 days of age). On day 0 the birds were placed on their respective study diets containing fenbendazole at 0, 100, 300, and 500 ppm for 21 days (three times the normal treatment duration). Clinical observations were recorded twice daily. Feed consumption, feed conversion rate, and body weights were determined for each pen. Three birds from each pen were randomly selected for necropsy, histopathology, and clinical pathology. Birds were carefully examined for feathering abnormalities immediately following euthanasia. The remaining birds in each pen were submitted for drug concentration analysis so that concentrations (for low vs. high treatment levels) could be correlated with clinical observations, clinical pathology, and histologic findings. There no morbidities or mortalities after study day--1. There were no statistically significant treatment-related differences in feed consumption, feed conversion rates, body weights, serum biochemistry profiles, hematologic profiles, gross necropsy findings, histopathologic examination, and feathering. Allowable liver and muscle concentrations of fenbendazole sulfone in turkeys are 6 and 2 ppm, respectively, with a 6-hr feed withdrawal. Analysis of fenbendazole concentrations in kidney, liver, leg/thigh, and breast muscle and skin with associated fat revealed that, even at the highest dose level used and with no feed withdrawal, fenbendazole concentrations were relatively low in these tissues. These findings indicate that fenbendazole has a relatively wide margin of safety in young pheasants and that the proposed dose of 100 ppm in the feed for 7 consecutive days is well within the margin of safety. In the reproductive safety study, two large game bird farms fed fendbendazole at 100 ppm for 7 days and collected data on hatching percentage of pheasant eggs before and after treatment. Reproductive performance in hen pheasants was not adversely affected.

Safety evaluation of lasalocid use in Chinese ring-necked pheasants (Phasianus colchicus).

Coccidiosis remains a significant threat to the welfare of game farm-reared pheasants in the United States. Although lasalocid has been demonstrated to be effective against pheasant specific coccidia, information regarding its safety in this species is lacking. The purpose of this study was to gather data on the safety of lasalocid when fed to Chinese ring-necked pheasants at one, two, and three times the recommended high dose of lasalocid used for prevention of coccidiosis in other poultry at three times the normal treatment period. Pheasant chicks (approximately 1 day-old; n = 160) were randomly blocked by sex into four treatment groups and given their respective diets continuously for 6 wk. No significant differences were observed in overall feed consumption, weight gain, feed conversion rates, clinical pathology measurements, or tissue gross and histopathologic evaluations between controls and treatment groups associated with lasalocid administration. Based on the results of this study it appears that lasalocid fed at the recommended rate of 125 ppm is safe in Chinese ring-necked pheasants.

The threat of soil erosion to long-term crop production.

National increases in row crops at the expense of hay and pasture crops, particularly on steeper slopes, have made the control of erosion a difficult prospect. Management practices that fit the various field conditions are needed to accomplish effective erosion control. These measures should be selected on the basis of soil characteristics, landscape type, and the amount of ongoing erosion. The maintenance of a cropland base adequate to our needs must be a primary national goal.

Hematology and Serum Biochemistry Reference Intervals for Six-Week-Old, Farm-Reared Chinese Ring-Necked Pheasants ( Phasianus colchicus ) from Minnesota.

Chinese ring-necked pheasants ( Phasianus colchicus ) are commonly farmed in intensive operations for purposes such as meat production, hunting preserves, or research. Under these conditions, pheasants frequently suffer medical ailments such as bacterial, viral, and parasitic infections or nutritional or metabolic disorders. Relatively little scientific information exists regarding clinical pathology reference intervals (RIs) for farm-reared pheasants. The objective of this study was to determine RIs for hematologic and serum biochemical variables for Chinese ring-necked pheasants from Minnesota at 6 wk of age. Blood samples from 119 clinically healthy Chinese ring-necked pheasants were analyzed using standard techniques. Reference intervals were generated in Microsoft® Excel® 2013 (Microsoft, Redmond, WA) using Reference Value Advisor freeware version 2.1 (Microsoft). Ninety-five percent RIs were determined using nonparametric methods that followed Clinical and Laboratory Standards Institute guidelines. These RIs will be useful for the monitoring of health and diagnosis of disease in confined Chinese ring-necked pheasant populations that are approximately 6 wk old.

An integrated linkage map reveals candidate genes underlying adaptive variation in Chinook salmon (Oncorhynchus tshawytscha).

Salmonids are an important cultural and ecological resource exhibiting near worldwide distribution between their native and introduced range. Previous research has generated linkage maps and genomic resources for several species as well as genome assemblies for two species. We first leveraged improvements in mapping and genotyping methods to create a dense linkage map for Chinook salmon Oncorhynchus tshawytscha by assembling family data from different sources. We successfully mapped 14 620 SNP loci including 2336 paralogs in subtelomeric regions. This improved map was then used as a foundation to integrate genomic resources for gene annotation and population genomic analyses. We anchored a total of 286 scaffolds from the Atlantic salmon genome to the linkage map to provide a framework for the placement 11 728 Chinook salmon ESTs. Previously identified thermotolerance QTL were found to colocalize with several candidate genes including HSP70, a gene known to be involved in thermal response, as well as its inhibitor. Multiple regions of the genome with elevated divergence between populations were also identified, and annotation of ESTs in these regions identified candidate genes for fitness related traits such as stress response, growth and behaviour. Collectively, these results demonstrate the utility of combining genomic resources with linkage maps to enhance evolutionary inferences.

Employment-seeking experiences of residents in 1996: a window into the neurology marketplace.

OBJECTIVE: To assess career choice and employment-seeking experience of senior neurology residents in 1996. METHODS: Graduating residents in adult and pediatric neurology (n = 573) were surveyed to obtain career plans, initial job selection, health care attitudes, and demographic information. Results were compared with 1996 data on all United States neurologists and data from an American Medical Association (AMA) resident survey regarding the employment status of new physicians. RESULTS: Survey response rate was 71%. There was a significant increase in international medical graduates and women entering neurology compared with the current workforce. Seventy-four percent of graduates planned to enter a fellowship position; 19%, private practice; 5%, an academic position; and 2%, a career outside of clinical medicine. Neurology residents differ from aggregate national data because only 28% of residents responding to an AMA survey across all specialties applied to fellowships in 1996. Overall, 44% of neurology graduates planned an academic career. CONCLUSIONS: Changing demographics and career choice of recent graduates may require continued monitoring and could be important in neurology workforce planning. The high rate of fellowship training and plans for academic careers in 1996 is of interest and may reflect both resident response to new demands in the changing health care market and a need to modify residency programs to enhance academic training and competitiveness of neurology graduates.

US neurologists in the 1990's: trends in practice characteristics.

BACKGROUND: The American Academy of Neurology (AAN) conducts periodic surveys of its members to profile and monitor changes in the characteristics of US neurologists and their practices. OBJECTIVE: To assess neurologists' characteristics, geographic distribution, practice arrangements, professional activities, practice volume, procedures performed, sources of revenue, involvement with managed care and capitation, and other selected topics. METHODS: The AAN Member Census survey was sent to US neurologists in the fall of 1996 (response rate = 89%), and the Practice Profile survey was sent to a random sample of 1,986 US neurologists in the summer of 1997 (response rate = 55%) who had completed a Member Census survey. The results of the Practice Profile survey were compared with those of two prior surveys conducted in 1991 to 1992 and 1993 to 1994. RESULTS: The mean age of US neurologists is 48 years, 18% are women, 93% are US citizens, and 24% are international medical graduates. The proportion of neurologists in solo practices, group practices, and medical schools/universities has not changed. The weekly hours worked has remained stable (58 hours), but the time spent in administrative activities has increased (p < 0.001). The average number of patient visits per week to neurologists appears to have increased (p < 0.001), as has the proportion of neurologists performing procedures (p < 0.05). The majority of neurologists have contracts with managed care organizations (82%), and a minority (32%) have capitated payment arrangements. Medicare continues to be the largest source of clinical revenue. Nearly 50% of all respondents have experience in developing clinical practice guidelines or critical pathways, and >20% of respondents employed physician extenders to assist in their practices. CONCLUSION: Neurologists are spending more time in administrative activities, are performing or interpreting more procedures, and are seeing more patients. Neurologists' involvement with capitation is comparable with that in a nationally representative sample of physicians, and they are exploring innovative ways, such as developing practice guidelines and using physician extenders, to improve the quality and efficiency of providing neurologic care.

Relationships between motor-unit number estimates and isometric strength in distal muscles in ALS/MND.

Measurement of progression in amyotrophic lateral sclerosis/motor neuron disease (ALS/MND) is useful for charting the natural history and assessing efficacy in drug trials. Common measures are maximal voluntary isometric contraction (MVIC) which mainly focuses on-proximal muscles, and electrophysiologic measures of the compound muscle action potential (CMAP) and motor-unit number estimation (MUNE) which focus on distal muscles. We have undertaken a study to compare the relationships between MVIC, CMAP and MUNE recorded in intrinsic hand muscles of 10 subjects with ALS/MND. Grip and pinch (between the first and fifth digits) MVIC were recorded. The CMAP and MUNE (determined by the multipoint stimulation technique) were recorded from thenar and hypothenar muscle groups. To facilitate comparisons between strength and electrophysiologic measures, the MUNE values and the CMAP values from the thenar and hypothenar muscle groups were each summed. Test-retest correlations were high for all measures (r = 0.75-0.99). Pinch and grip MVIC were highly correlated (r = 0.83). However, MVIC measures showed weaker correlations with summed MUNE values (pinch r = 0.56, grip r = 0.64) and summed CMAP values (pinch r = 0.58 and grip r = 0.65). The weak correlations between MVIC and electrophysiologic measures are due to two factors. First, grip and pinch MVIC are correlated through co-activation of agonist muscle groups, for we recorded strong concomitant muscle activity from forearm flexor muscles during pinch. In contrast, CMAP and MUNE reflect measurement from isolated muscle groups in the hand. Second, MVIC and the CMAP are affected by collateral reinnervation and only indirectly assess motor-unit loss, while MUNE is uninfluenced by reinnervation and directly addresses the degree of motor-unit loss. These factors determine the information available from endpoint measures. We offer guidelines for choosing useful measures based upon the goals of a given study.

Disabled stereopsis may be the norm among well-educated people.

Most well-educated people, where the author lives, have lost the ability to perceive the third dimension in space during everyday life. This has passed unnoticed because poor depth perception is not a serious handicap in an urban environment and because clinical depth perception tests have not been designed to detect this deficit. The author's hypothesis is that disabled stereopsis is a global phenomenon. A simple way of testing for disabled stereopsis is presented, in the hope that investigators in other parts of the world will test a sample of their local population and send the results to the author.