Life Sciences Commons^™

Adaptation Strategies: Ruminants, John B. Gaughan, Veerasamy Sejian, Terry L. Mader, Frank R. Dunshea

Department of Animal Science: Faculty Publications

• Growing populations and reduced access to arable land mean that animal production systems will either need to intensify and/or produce more from a reducing land and other resource base.

• Variable and unpredictable environmental conditions mean that animal production faces numerous challenges. In add- ition to climate, these challenges include increased disease risk, increased nutritional deficiencies, and lack of capital to support diversification.

• Predicted changes in climate will impose selection pressures on traits important for biological fitness (and production).

• Genetic adaptation is important for the future of livestock systems. Animal adaptation involves trade-offs, which must be considered when selecting animals for …

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Experimental Approaches To Evaluate The Contributions Of Candidate Protein-Coding Mutations To Phenotypic Evolution, Jay F. Storz, Anthony J. Zera

Jay F. Storz Publications

Identifying mechanisms of molecular adaptation can provide important insights into the process of phenotypic evolution, but it can be exceedingly difficult to quantify the phenotypic effects of specific mutational changes. To verify the adaptive significance of genetically based changes in protein function, it is necessary to document functional differences between the products of derived and wild-type alleles and to demonstrate that such differences impinge on higher-level physiological processes (and ultimately, fitness). In the case of metabolic enzymes, this requires documenting in vivo differences in reaction rate that give rise to differences in flux through the pathway in which the enzymes …

Integrating Evolutionary And Functional Approaches To Infer Adaptation At Specific Loci, Jay F. Storz, Christopher W. Wheat

Jay F. Storz Publications

Inferences about adaptation at specific loci are often exclusively based on the static analysis of DNA sequence variation. Ideally, population-genetic evidence for positive selection serves as a stepping-off point for experimental studies to elucidate the functional significance of the putatively adaptive variation. We argue that inferences about adaptation at specific loci are best achieved by integrating the indirect, retrospective insights provided by population-genetic analyses with the more direct, mechanistic insights provided by functional experiments. Integrative studies of adaptive genetic variation may sometimes be motivated by experimental insights into molecular function, which then provide the impetus to perform population genetic tests …

Molecular Evolution Of Cytochrome B In High- And Low-Altitude Deer Mice (Genus Peromyscus), E. J. Gering, J. C. Opazo, Jay F. Storz

Jay F. Storz Publications

Patterns of amino-acid polymorphism in human mitochondrial genes have been interpreted as evidence for divergent selection among populations that inhabit climatically distinct environments. If similar patterns are mirrored in other broadly distributed mammalian species, then adaptive modifications of mitochondrial protein function may be detected in comparisons among locally adapted populations of a single wide-ranging species, or among closely related species that have adapted to different environments. Here, we test for evidence of positive selection on cytochrome b variation within and among species of the ecologically diverse rodent genus Peromyscus. We used likelihood-based comparisons of synonymous and nonsynonymous substitution rates to …

Evidence For Contrasting Modes Of Selection At Interacting Globin Genes In The European Rabbit (Oryctolagus Cuniculus), R. Campos, Jay F. Storz, N. Ferrand

Jay F. Storz Publications

In hybrid zones between genetically differentiated populations, variation in locus-specific rates of introgression may reflect adaptation to different environments or adaptation to different genetic backgrounds. The European rabbit, Oryctolagus cuniculus, is well-suited to studies of such hybrid zone dynamics because it is composed of two genetically divergent subspecies that hybridize in a zone of secondary contact in central Iberia. A species-wide survey of allozyme variation revealed a broad range of locus-specific divergence levels (F_ST ranged from 0 to 0.54, mean F_ST = 0.16). Interestingly, the two loci that fell at opposite ends of the distribution of …

The Study Of Adaptation And Speciation In The Genomic Era, Jay F. Storz, Hopi E. Hoekstra

Jay F. Storz Publications

The availability of complete genome sequences and genetic linkage maps for a growing number of mammalian species is opening up exciting new opportunities for studies of evolutionary change in natural populations. For example, multilocus mapping approaches hold the promise of identifying the specific genetic changes that underlie ecological adaptation and reproductive isolation. The fact that many of the genomic resources that have been developed for Mus and Rattus are transferable to other muroid rodents means that roughly 25% of all mammalian species can now be considered ‘‘genome-enabled’’ study organisms to varying degrees. The transferability of genomic resources between model organisms …

Hemoglobin Function And Physiological Adaptation To Hypoxia In High-Altitude Mammals, Jay F. Storz

Jay F. Storz Publications

Understanding the biochemical mechanisms that enable high-altitude animals to survive and function under conditions of hypoxic stress can provide important insights into the nature of physiological adaptation. Evidence from a number of high-altitude vertebrates indicates that modifications of hemoglobin function typically play a key role in mediating an adaptive response to chronic hypoxia. Because much is known about structure– function relationships of mammalian hemoglobins and their physiological role in oxygen transport, the study of hemoglobin variation in high-altitude mammals holds much promise for understanding the nature of adaptation to hypoxia from the level of blood biochemistry to the level of …

Using Genome Scans Of Dna Polymorphism To Infer Adaptive Population Divergence, Jay F. Storz

Jay F. Storz Publications

Elucidating the genetic basis of adaptive population divergence is a goal of central importance in evolutionary biology. In principle, it should be possible to identify chromosomal regions involved in adaptive divergence by screening genome-wide patterns of DNA polymorphism to detect the locus-specific signature of positive directional selection. In the case of spatially separated populations that inhabit different environments or sympatric populations that exploit different ecological niches, it is possible to identify loci that underlie divergently selected traits by comparing relative levels of differentiation among large numbers of unlinked markers. In this review I first address the question of whether diversifying …

Functional Implication Of The Trna Genes Encoded In The Chlorella Virus Pbcv-L Genome, Da Young Lee, Michael V. Graves, James L. Van Etten, Tae-Jin Choi

James Van Etten Publications

The prototype Chlorella virus PBCV-l encodes 11 tRNA genes and over 350 protein-encoding genes in its 330 kbp genome. Initial attempts to overexpress the recombinant A189/192R protein, a putative virus attachment protein, in E. coli strain BL21(DE3) SI were unsuccessful, and multiple protein bands were detected on Western blots. However, the full-length A189/192R recombinant protein or fragments derived from it were detected when they were expressed in E. coli BL21 CodonPlus (DE3) RIL, which contains extra tRNAs. Codon usage analysis of the a1891192r gene showed highly biased usage of the AGA and AUA codons compared to genes encoded by E. …

Natural Selection Drives Altitudinal Divergence At The Albumin Locus In Deer Mice, Peromyscus Maniculatus, Jay F. Storz, Jean M. Dubach

Jay F. Storz Publications

In populations that are distributed across steep environmental gradients, the potential for local adaptation is largely determined by the spatial scale of fitness variation relative to dispersal distance. Since altitudinal gradients are generally characterized by dramatic ecological transitions over relatively short linear distances, adaptive divergence across such gradients will typically require especially strong selection to counterbalance the homogenizing effect of gene flow. Here we report the results of a study that was designed to test for evidence of adaptive divergence across an altitudinal gradient in a natural population of deer mice, Peromyscus maniculatus. We conducted a multilocus survey of …

Genome Scans Of Dna Variability In Humans Reveal Evidence For Selective Sweeps Outside Of Africa, Jay F. Storz, Bret A. Payseur, Michael W. Nachman

Jay F. Storz Publications

The last 50,000–150,000 years of human history have been characterized by rapid demographic expansions and the colonization of novel environments outside of sub-Saharan Africa. Mass migrations outside the ancestral species range likely entailed many new selection pressures, suggesting that genetic adaptation to local environmental conditions may have been more prevalent in colonizing populations outside of sub-Saharan Africa. Here we report a test of this hypothesis using genome-wide patterns of DNA polymorphism. We conducted a multilocus scan of microsatellite variability to identify regions of the human genome that may have been subject to continent-specific hitchhiking events. Using published polymorphism data for …

Natural Selection On Protein Polymorphism In The Rodent Genus Peromyscus: Evidence From Interlocus Contrasts, Jay F. Storz, Michael W. Nachman

Jay F. Storz Publications

The effects of natural selection are generally locus-specific, whereas migration, drift, and inbreeding are expected to have relatively uniform effects across the entire genome. This suggests that multilocus surveys of multiple populations can be used to distinguish selection from demographic effects. The purpose of this study was to test for evidence of selection on protein polymorphism in natural populations of mice in the genus Peromyscus. We analyzed published data from geographic surveys of allozyme variation and used a coalescent- based simulation model to identify specific loci that deviated from neutral expectations. Observed F_ST values generally exhibited a remarkably …