Concordance of Nuclear and Mitochondrial DNA Markers in Detecting a Founder Event in Lake Clark Sockeye Salmon

Genetic bottleneck effects can reduce genetic variation, persistence probability, and evolutionary potential of populations. Previous microsatellite analysis suggested a bottleneck associated with a common founding of sockeye salmon Oncorhynchus nerka populations of Lake Clark, Alaska, about 100 to 400 generations ago. The common founding event occurred after the last glacial recession and resulted in reduced allelic diversity and strong divergence of Lake Clark sockeye salmon relative to neighboring Six Mile Lake and Lake Iliamna populations. Here we used two additional genetic marker types (allozymes and mtDNA) to examine these patterns further. Allozyme and mtDNA results were congruent with the microsatellite data in suggesting a common founder event in Lake Clark sockeye salmon and confirmed the divergence of Lake Clark populations from neighboring Six Mile Lake and Lake Iliamna populations. The use of multiple marker types provided better understanding of the bottleneck in Lake Clark. For example, the Sucker Bay Lake population had an exceptionally severe reduction in allelic diversity at microsatellite loci, but not at mtDNA. This suggests that the reduced microsatellite variation in Sucker Bay Lake fish is due to consistently smaller effective population size than other Lake Clark populations, rather than a more acute or additional bottleneck since founding. Caution is urged in using reduced heterozygosity as a measure of genetic bottleneck effects because stochastic variance among loci resulted in an overall increase in allozyme heterozygosity within bottlenecked Lake Clark populations. However, heterozygosity excess, which assesses heterozygosity relative to allelic variation, detected genetic bottleneck effects in both allozyme and microsatellite loci

Ecological, morphological, genetic, and life history comparison of two sockeye salmon populations, Tustumena Lake, Alaska

Thesis (Ph. D.)--University of Washington, 1998Populations can differ in both phenotypic and molecular genetic traits. Phenotypic differences likely result from differential selection pressures in the environment, whereas differences in neutral molecular markers result from genetic drift associated with some degree of reproductive isolation. Two sockeye salmon, Oncorhynchus nerka, populations were compared using both phenotypic and genotypic characters, and causal factors were examined. Salmon spawning in a short (<3 km), shallow (<21 cm), clear, homogenous spring-fed study site spawned later, were younger, smaller, and produced fewer and smaller eggs than salmon spawning in a longer (∼80 km), deeper, stained, diverse, precipitation-dominated stream. Run timing differences were associated with differences in stream thermal regimes. Age and size at maturity differences are likely due to differences in age-specific mortality rates. Fish in the shallow spring-fed system suffered higher adult predation rates and exhibited greater egg to fry survival compared to fish in the precipitation-fed system. Salmon in both streams exhibited non-random nest site selection for deeper habitats and smaller substrates (≥2 to <64 mm mean diameter) relative to available habitat; fish from the precipitation system avoided low velocity habitats containing fine (<2 mm) substrates. Genetic comparisons of six microsatellite loci indicated that run time was a more effective reproductive isolating mechanism than geographical distance. Differences between and within the tributary spawning populations are discussed in terms of selection, genetic drift, and the homogenizing effects of gene flow. This study indicates important adaptive differences may exist between proximate spawning groups of salmon which should be considered when characterizing populations for conservation or management purposes

NO WARRANTY

Use of any trademarks in this report is not intended in any way to infringe on the rights of the trademark holder. Internal use. Permission to reproduce this document and to prepare derivative works from this document for internal use is granted, provided the copyright and “No Warranty ” statements are included with all reproductions and derivative works. External use. Requests for permission to reproduce this document or prepare derivative works of this document for external and commercial use should be addressed to the SEI Licensing Agent

Sustaining Software-Intensive Systems

As today's systems become increasingly reliant on software, the issues surrounding sustainment become increasingly complex. The risks of ignoring these issues can potentially undermine the stability, enhancement, and longevity of fielded systems. Questions about sustaining new and legacy systems include 1. What does it mean to perform sustainment from a software perspective? 2. What types of development and acquisition activities are required to sustain software-intensive systems? 3. Although the Department of Defense (DoD) has a technical definition of sustainment, does the DoD typically consider sustainment as maintenance? 4. How does the increased use of commercial-off-the-shelf software complicate sustainment? This technical note discusses these questions and presents definitions, related issues, future considerations, and recommendations for sustaining software-intensive systems. Sustainment done well leads to well-supported software-intensive systems and reduced total ownership costs and should help organizations meet current and new mission area and capabilities requirements. The information contained in this technical note is based on information that the Software Engineering Institute gathered during work with Air Force software-intensive systems. While the information is pertinent and can be applied to systems in the commercial sector, keep in mind minimal effort was made to convert "DoDspeak" into commercial sector language

AFS Position Paper and Policy on Mining and Fossil Fuel Extraction

Following a four-year period of writing, member comment, and multiple revisions, the AFS Position Paper and Policy on Mining and Fossil Fuel Extraction was approved unanimously by the membership at the Society\u27s annual business meeting August 19, 2015, in Portland, Oregon. The entire document can be read at fisheries.org/policy_statements; a brief summary follows

Analysis of Outcomes in Ischemic vs Nonischemic Cardiomyopathy in Patients With Atrial Fibrillation A Report From the GARFIELD-AF Registry

IMPORTANCE Congestive heart failure (CHF) is commonly associated with nonvalvular atrial fibrillation (AF), and their combination may affect treatment strategies and outcomes