Philip Hedrick

..Fourth, the changes at both loci in a short-term selection experiment for low weight gain were in the opposite direction than the changes in the contemporaneous related population selected for high weight gain...

..Based on population-specific markers and a quantitative evaluation of ancestry using a likelihood approach, it appears that ancestry from each of the source populations was retained in both populations...

..Population genetics can be used to determine the amount and pattern of selection in the past and predict selection in the future for other malaria resistance variants as they are discovered...

..This is not to say that some heterozygote advantage loci do not have important adaptive functions, but that their role in overall evolutionary change might be more of an unusual phenomenon than a major player in adaptation...

..This asymmetry may result in a lower standing genetic variation for inbreeding depression than expected from mutation rates and contemporary population size data...

..Overall, it generally appears that allele C will quickly replace the S allele in malarial environments. Explicit population genetic predictions suggest that this replacement may occur within the next 50 generations in Burkina Faso...

..This finding appears robust when there is a large proportion of families with exactly two progeny or when there is random variation in progeny numbers among these families...

....

..The implications of these findings are briefly discussed...

..Interestingly, the extent of heterozygosity, differentiation across populations and linkage disequilibrium in the CCR5 region is not dissimilar to other human genomic regions, challenging claims of recent positive selection...

....

..Examination of population genetic factors, singly and jointly, provides insight into the establishment and maintenance of this unusual polymorphism...

..Overall, this population genetic examination provides an evolutionary framework for understanding the worldwide frequency of α thalassemia and the deletions that cause it in both nonmalarial and malarial environments...

....

..The evolutionary explanations for sex-specific differences for each factor are multifaceted and, in addition, explanations may include chance, nonadaptive differences, or mechanistic, nonevolutionary factors...

..However, population reintroductions of both Mexican and red wolves appear to have reached numbers well below the generally recommended number for recovery and there is no current effort to re-establish other populations...

..Here I review and evaluate this situation and provide recommendations for the reduction of cattle ancestry, avoidance of inbreeding depression, and maintenance of genetic variation in the conservation herds of bison...

..Although the mechanism of sex determination may ultimately prove more complex, simple genetic mechanisms can account for the broad features of sexual maturation in oyster families and the stability of sex ratios in populations...

..Further examination of the cattle genome in bison may shed light on whether these markers, or their associated regions, are indeed neutral...

..Resistance to pathogens is an important aspect of the management and long-term survival of endangered taxa, such as the Mexican wolf...

..As a result, maintenance of these variants should be considered as a goal in the captive breeding program of the Arabian oryx...

..The approach given here could be applied to retain genetic variation in other endangered species in a captive broodstock until they have stable natural populations of adequate size...

....

..Examination of the known dog sequences for this locus showed that one of the Mexican wolf alleles was found in dogs and that the allele found in both grey and red wolves is also found in dogs...

....

..In addition, there appeared to have been a duplication of the MHC locus that was present in most of the fish in six of the natural populations of the Gila topminnow...

..We suggest that the measure be examined theoretically to determine when (and how much) the predictive value of the measure is different from that of heterozygosity for inbreeding or outbreeding levels in a variety of different scenarios...

....

..Overall, resistance conferred by specific alleles to temporally variable pathogens may contribute to the observed polymorphism at MHC genes and other similar host defense loci...

....

..This revised classification should be considered in future assessment and management of California sea lion populations in Mexican waters...

..Disequilibrium values are calculated and tested for statistical significance. High levels of disequilibrium are found between all pairs of major histocompatibility complex (MHC) loci and between MHC and a linked microsatellite locus...

..Examination of the level and pattern of linkage disequilibria between pairs of sites suggest that the heterozygosity, substitution and frequencies at individual amino acids are not highly dependent upon each other...

....

..Rapid genetic analysis of captured spawners and a new rearing facility on the Sacramento River should alleviate these problems and their negative effect on the effective population size in future years...

..To reconcile the species and gene trees for the 104 sequences examined, 95 'deep coalescent' events were necessary, illustrating the importance of balancing selection maintaining variation over speciation events...

..Because other organisms have extensive variation at homologous loci, the Przewalski's horse may have quite low variation in this important adaptive region...

..For three or more alleles, the model has the qualities of a traditional balancing selection model...

..In nearly all cases, HLA-sharing proportions were very close to those expected from random mating, suggesting strong negative-assortative mating for MHC is not present in these South Amerindians...

..This continent-island model gives results that well describe the system. Issues fundamental to the differences between X-linked and haplodiploid genetic systems and diploid genetic systems are also discussed...

..This suggests that other loci, presumably other MHC loci, play a significant role in transplantation success in fishes, as they do in mammals...

..The low litter and pack sizes observed in the wild population are consistent with this genetic load, but it appears that there is still potential to establish vigorous wild populations...

..Inference of the nature of the selection events that create such signals should be approached with caution. However, a combination of tests on different time scales may overcome such problems...

..Our modeling approach may prove generally useful in providing insight into situations involving complex species interactions when data are few...

..Our results illustrate the importance of distinctly defining hybrid classes in studies of reproductive isolation. To our knowledge, this is the first such detailed evolutionary analysis in endangered fish taxa...

..This scenario is consistent with historical information and with results from population genetics theory...