PubMed · 13480176
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L DELIUS. 1957-11-15. [Changed reactivity & adaptation].. https://doi.org/10.1055/s-0028-1117024
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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.
The object of this study was to analyse the synaptic interactions of slow-adapting type II (SAII) afferent terminals in laminae III-V of the rat spinal cord. The axons of SAII afferents were physiologically characterized by intracellular recording before injection with neurobiotin and preparation for electron microscopy. Axon terminals were serially sectioned and immunolabelled with antibodies against gamma-aminobutyric acid (GABA) or glycine by using a postembedding immunogold procedure. Computer-aided reconstruction was used to reveal the relative distribution of different types of synapses on terminal and en passant synaptic boutons. Eighty-nine percent of boutons received axoaxonic synaptic contacts, the mean number of contacts per bouton being 3.5. Fifty-nine percent of presynaptic axons were immunoreactive for both GABA and glycine and 45% for GABA alone. Most boutons (95%) made axodendritic contacts, and the mean number of dendrites contacted was 1.6. More than half of the postsynaptic dendrites were greater than 1 microm in diameter. Twenty-three percent were immunoreactive for glycine, and 71% were not immunoreactive for either antibody. Synaptic triads in which an axon presynaptic to the afferent was also in contact with a dendrite postsynaptic to the afferent were seen at 63% of boutons. These results are discussed in the light of similar studies of other low-threshold mechanoreceptive afferent terminals in the rat and cat and in the context of what is known of the sensory interneurones carrying information from slow- and rapid-adapting mechanoreceptors.