PubMed · 14289242
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R J KAHANA. 1964. LONGEVITY AND ADAPTATION.. https://doi.org/10.1093/geront%2F4.1.41
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Local adaptation represents a pivotal theme in evolutionary biology. The Opisthopappus genus, comprising Opisthopappus longilobus and O. taihangensis, thrives on the cliffs of the Taihang Mountains. During their evolutionary history, two species are hypothesized to have locally adapted to their cliff habitats. In the present study, we employed a combined approach of whole-genome sequencing of O. taihangensis and population genomic analysis from both species to gain deeper insights into their patterns of local adaptation. Our results revealed that the expansive genome of O. taihangensis (3010.18 Mb), a consequence of a whole-genome duplication (WGD) event, coupled with a high proportion of repetitive sequences (82.70%), was postulated as one of its adaptive strategies. A clear differentiation between O. taihangensis and O. longilobus was observed, with the two species diverging approximately 17.57 million years ago (Mya), with O. longilobus serving as the ancestor. Since their divergence, limited gene flow was observed between the two species. Post-divergence, the effective population sizes of both species expanded, yet underwent a dramatic reduction at approximately 0.07 Mya. Furthermore, a total of 798 adaptive genes were identified, of which 207 overlapped with expanded genes, and eight genes were found to be under positive selection. These genes primarily regulated the growth and development of both species via pathways such as oxidation-reduction and ubiquitin-proteasome, enabling them to withstand climate changes. These findings provide profound insights into the local adaptation of Opisthopappus species to the cliff environments and offer valuable clues for further exploring the local adaptation among various cliff-dwelling organisms.
In this report, we examine the hypothesis that the drivers of latitudinal selection observed in the eastern US Drosophila melanogaster populations are reiterated within seasons in a temperate orchard population in Pennsylvania, USA. Specifically, we ask whether alleles that are apparently favoured in northern populations are also favoured early in the spring, and decrease in frequency from the spring to autumn with the population expansion. We use SNP data collected for 46 metabolic genes and 128 SNPs representing the central metabolic pathway and examine for the aggregate SNP allele frequencies whether the association of allele change with latitude and that with increasing days of spring-autumn season are reversed. Testing by random permutation, we observe a highly significant negative correlation between these associations that is consistent with this expectation. This correlation is stronger when we confine our analysis to only those alleles that show significant latitudinal changes. This pattern is not caused by association with chromosomal inversions. When data are resampled using SNPs for amino acid change the relationship is not significant but is supported when SNPs associated with cis-expression are only considered. Our results suggest that climate factors driving latitudinal molecular variation in a metabolic pathway are related to those operating on a seasonal level within populations.
Although transcriptional factors are known to play important roles in synaptic plasticity, their role in olfactory adaptation has not been studied well. Here we report that Ce-TBX-2, the TBX2/TBX3 transcriptional factor homologue of the nematode Caenorhabditis elegans, is involved in olfactory adaptation. Two missense hypomorphic mutations in this gene confer abnormality in adaptation, but not chemotaxis, to all the odorants sensed by AWC olfactory neurons. The Ce-tbx-2 gene is expressed in AWB, AWC, ASJ, and many pharyngeal neurons, but expression in AWC neurons is sufficient for normal adaptation. Unexpectedly, the protein product is localized mostly in cytoplasm. The AWC neurons in the mutants retain their characteristic morphology and many marker gene expressions, suggesting that the mutants are abnormal in neural functions rather than neuronal differentiation. The results of this study imply that some of the mammalian T-box family proteins, which play central roles in embryonic development, may also control functions like neural plasticity in differentiated neurons.