For example, Jacobs and Spencer (1994) did an experiment relating to the topic of natural selection and evolution. These scientists reviewed the natural space-use patterns and hippocampal size in kangaroo rats after undergoing evolution by natural selection. The size of the hippocampus, which is a forebrain structure that processes spatial information, correlates with the need to relocate food caches by passerine birds and with sex-specific patterns of space use in microtine rodents. However, the influences on hippocampal anatomy of sexual selection within species, and natural selection between species, have not yet been studied in concert. The researchers reported that natural space-use patterns predict hippocampal size within and between
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The hypoxic and cold environment at high altitudes requires that endothermic animals sustain high rates of oxygen (O2) consumption for both locomotion and thermogenesis while facing a diminished O2 supply. Recent evidence suggests that genes in the hypoxia inducible factor (HIF) pathway have been targeted by natural selection and have contributed to evolutionary adaptation to high altitudes in several species. In this project, these scientists examined the role of hypoxia signaling in high-altitude adaptation in deer mice (Peromyscus maniculatus). Maximal O2 consumption (VO2max) in hypoxia is augmented in high-altitude populations, underpinned by increases in pulmonary O2 extraction, arterial O2 saturation, cardiac output, and tissue O2 extraction compared to low-altitude populations. Highlanders also maintain higher heart rates during deep hypoxia at rest. Associated with the population differences in physiology is extreme allele frequency variation in a non-synonymous single nucleotide polymorphism in Epas1, the gene encoding HIF-2α. Transcriptome scans indicate that these differences in Epas1 allele frequency stem from a history of spatially varying selection between high and low altitudes. RNA-Seq measurements of gene expression in the left ventricle show that transcriptomic variation in HIF target genes is correlated to VO2max. Furthermore, comparisons of the hypoxia response between mice with different Epas1 genotypes show that the high-altitude Epas1 allele is associated with higher heart rates in deep hypoxia, but that it has no association with variation in breathing or blood haemoglobin content. These data results therefore conclude that changes in hypoxia signaling contribute to high-altitude adaptation in deer
The hypoxic and cold environment at high altitudes requires that endothermic animals sustain high rates of oxygen (O2) consumption for both locomotion and thermogenesis while facing a diminished O2 supply. Recent evidence suggests that genes in the hypoxia inducible factor (HIF) pathway have been targeted by natural selection and have contributed to evolutionary adaptation to high altitudes in several species. In this project, these scientists examined the role of hypoxia signaling in high-altitude adaptation in deer mice (Peromyscus maniculatus). Maximal O2 consumption (VO2max) in hypoxia is augmented in high-altitude populations, underpinned by increases in pulmonary O2 extraction, arterial O2 saturation, cardiac output, and tissue O2 extraction compared to low-altitude populations. Highlanders also maintain higher heart rates during deep hypoxia at rest. Associated with the population differences in physiology is extreme allele frequency variation in a non-synonymous single nucleotide polymorphism in Epas1, the gene encoding HIF-2α. Transcriptome scans indicate that these differences in Epas1 allele frequency stem from a history of spatially varying selection between high and low altitudes. RNA-Seq measurements of gene expression in the left ventricle show that transcriptomic variation in HIF target genes is correlated to VO2max. Furthermore, comparisons of the hypoxia response between mice with different Epas1 genotypes show that the high-altitude Epas1 allele is associated with higher heart rates in deep hypoxia, but that it has no association with variation in breathing or blood haemoglobin content. These data results therefore conclude that changes in hypoxia signaling contribute to high-altitude adaptation in deer