PubMed · 8858596
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D J Savic. 1996. Adaptive mutations: an additional view.. https://doi.org/10.1046/j.1365-2958.1996.01377.x
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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.
Light and electron microscopic techniques were used to examine the structure and innervation of the mystacial vibrissal follicle-sinus complex (F-SC) in the Australian water rat. The F-SCs of this semiaquatic rodent show the same morphologic elements described in terrestrial rats but differ in size, structure, and innervation. Most striking is the size of the water rat's caudal F-SCs, measuring 6.3 mm in length and 2.4 mm in diameter. The sinus system is divisible into a ring sinus and a cavernous sinus and shows a distinct asymmetry. At the highest level of the cavernous sinus, the outer root sheath forms a ridge in the direction of the trabeculae, which bind the ridge to the capsule. A ringwulst is present only in small and medium-sized F-SCs. The mean number of myelinated axons counted in the deep vibrissal nerve (DVN) of most caudal F-SCs was 537, indicating an innervation density of the water rat's vibrissal system at least 2.5 times as high as that of terrestrial rats. The total number of nerve fibers of the small superficial nerves was less than 10% of that of the DVN. These fibers innervate almost exclusively the area of the inner conical body. Structural specializations of the water rat F-SC are discussed as an analogous development in mammals adapted to the aquatic environment, primarily in terms of thermoregulation, whereas its high degree of innervation is assessed to lend support to the hypothesis that the vibrissal system is of special significance in aquatic mammals.