PubMed · 16431353
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Jochen Zeil, Jan M Hemmi, Patricia R Y Backwell. 2006-01-24. Fiddler crabs.. https://doi.org/10.1016/j.cub.2006.01.012
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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.
Chronic low back pain (CLBP) patients achieve postural stability during challenging stance conditions by increasing sway speed. We investigated the mechanisms underlying this behavior, and whether postural strategy selection may be influenced by short-term experience of postural perturbation. Thirteen CLBP patients and thirteen age-matched controls underwent posturography tests. Subjects were asked to stand quietly: (a) with eyes open and eyes closed, and (b) while expecting a series of four backward translations of the support surface. Data from condition (a) was subjected to sway density analysis (SDA). This computes the number of consecutive spaces and respectively time samples during which center of pressure (COP) displacements remained inside a 2.5 mm radius. Three parameters of this analysis were considered: the mean number of peaks (MP), reflecting the time spent by COP in regions of stability, the mean time between peaks (MT) relating to the rate of production of posturographic commands, and the mean spatial distance (MD), reflecting the distance between stable regions. In condition (b) the mean COP positions were analyzed during the time (500 ms) preceding each translation. The MD was significantly increased in the CLBP group as compared to controls (P < 0.01), while the MP and MT did not present any significant difference. The expectation of backward translations initially produced a different COP positioning between the two groups (P < 0.0001) which decreased with repetition of platform translations (controls: PDelta1-4 < 0.002; patients: PDelta1-4 < 0.005). The findings show that the timing and the rate of the balance motor commands is comparable between the two groups. On the other hand, there is greater distance between regions of stability in the patient group. Such modification of motor control patterns might be the consequence of a reweighting of sensory input, possibly due to a deterioration of its reliability. Platform translation findings show that both groups aimed at optimizing their posture selection strategy based on prior testing experience. CLBP patients make use of a different postural motor strategy to maintain quiet stance. This is probably the consequence of an imprecise internal estimate of body sway, due to reduced accuracy in the sensory integration process.