PubMed · 12815130
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Nerys Williams. 2003. Monitor.. https://doi.org/10.1093/occmed%2Fkqg079
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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.
Because of their resistance to environmental degradation, polychlorinated biphenyls (PCBs) are among the most widespread environmental contaminants. PCBs have high bioaccumulation potential and may affect a number of biological/physiological processes including disruption of the endocrine system function, lipid metabolism and reproduction. The objective of this study was to test whether conditioning sexually immature oysters with PCB-contaminated algal diets affects their subsequent reproductive success. Sexually immature oysters were conditioned in individual containers and fed daily with 0.7 g algal paste containing 0, 0.35 or 3.5 microg PCBs for up to 76 days. The impact of sediment load on PCB accumulation in oysters was also tested by exposure of a subset of oysters to clay particles. Oysters in different treatments were sampled 56 days after conditioning with PCB-contaminated algal diets to determine uptake and distribution of PCBs in gonad, digestive gland, mantle, gill and muscle, and the presence of gametes. Tissues from oysters exposed to PCBs alone for 56 days were also analyzed for lipid and fatty acid composition. Following 61 and 76 days of PCB exposure, remaining oysters from all treatments were induced to spawn via thermal stimulation. Non-spawned oysters were stripped to determine if sexual products were present. Oysters exposed to PCBs alone and PCBs plus clay particles showed similar trends in PCB accumulation, but concentrations were generally lower in the latter. PCB accumulation in oysters increased with an increase in algal-associated PCB concentrations, varied with organ types and was correlated with lipid content. The highest PCB concentration was in the gonad and the lowest in gill and muscle. PCB-153, -138/158, -118, -90/101 and -149 were the dominant congeners in all tissue compartments, except the muscle where PCB-28/31 was the dominant congener pair. PCB exposure appeared to impair both lipid metabolism and reproductive success. Although PCB exposure produced only slight changes in the lipid class composition in the oysters, decreases in phospholipids were observed in gonad, muscle and mantle of oysters exposed to 3.5 microg PCBs daily for 56 days. After 56 days of conditioning with PCB-sorbed algal paste, no well-developed mature eggs were observed in any of the oysters examined for the presence of sexual products. No significant difference was noted in reproductive success (production of spawned females and males) between sediment-treated and non-treated groups after 76 days of PCB exposure compared to controls, PCB-exposed oysters produced fewer spawned females, but no dose-dependent relationship was observed.