PubMed · 6647399
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Y Beyeler. 1983-10-25. [The magic mountain].. https://pubmed.ncbi.nlm.nih.gov/6647399/
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Understanding the genetic bases and modes of adaptation to current climatic conditions is essential to accurately predict responses to future environmental change. We conducted a genome-wide scan to identify climate-adaptive genetic loci and pathways in the plant Arabidopsis thaliana. Amino acid-changing variants were significantly enriched among the loci strongly correlated with climate, suggesting that our scan effectively detects adaptive alleles. Moreover, from our results, we successfully predicted relative fitness among a set of geographically diverse A. thaliana accessions when grown together in a common environment. Our results provide a set of candidates for dissecting the molecular bases of climate adaptations, as well as insights about the prevalence of selective sweeps, which has implications for predicting the rate of adaptation.
Patterns of climatic adaptation in drosophila and other insects have largely been inferred from laboratory comparisons of traits that vary clinally. Here, we extend this research to comparisons under semi-natural conditions. To test for clinal variation in reproductive patterns and survival over winter, Drosophila melanogaster populations were initiated from seven collection sites along the eastern coast of Australia, ranging from tropical to temperate regions. The fecundity and survival of these populations were monitored in field cages at a temperate location until all adults had died more than 5 months later. Total fecundity showed a curvilinear relationship with latitude, due to higher egg production by high- and low-latitude populations. Adults from temperate locations survived winter conditions better than those from subtropical populations but not tropical ones. There was a linear cline in the timing of egg production: temperate populations produced eggs later than populations from lower latitudes. This cline is likely to be adaptive because egg-to-adult viability experiments indicated that only eggs laid in spring developed successfully to the adult stage. There was no evidence for climatic adaptation in the immature stages. The adult mortality rate increased gradually over winter, and in some populations was also correlated with the minimum ambient temperature. These results indicate that adaptation to winter conditions in D. melanogaster has involved shifts in reproductive patterns.
BACKGROUND: In chronic hypoxia, both heart rate (HR) and cardiac output (Q) are reduced during exercise. The role of parasympathetic neural activity in lowering HR is unresolved, and its influence on Q and oxygen transport at high altitude has never been studied. METHODS AND RESULTS: HR, Q, oxygen uptake, mean arterial pressure, and leg blood flow were determined at rest and during cycle exercise with and without vagal blockade with glycopyrrolate in 7 healthy lowlanders after 9 weeks' residence at >/=5260 m (ALT). At ALT, glycopyrrolate increased resting HR by 80 bpm (73+/-4 to 153+/-4 bpm) compared with 53 bpm (61+/-3 to 114+/-6 bpm) at sea level (SL). During exercise at ALT, glycopyrrolate increased HR by approximately 40 bpm both at submaximal (127+/-4 to 170+/-3 bpm; 118 W) and maximal (141+/-6 to 180+/-2 bpm) exercise, whereas at SL, the increase was only by 16 bpm (137+/-6 to 153+/-4 bpm) at 118 W, with no effect at maximal exercise (181+/-2 bpm). Despite restoration of maximal HR to SL values, glycopyrrolate had no influence on Q, which was reduced at ALT. Breathing FIO(2)=0.55 at peak exercise restored Q and power output to SL values. CONCLUSIONS: Enhanced parasympathetic neural activity accounts for the lowering of HR during exercise at ALT without influencing Q. The abrupt restoration of peak exercise Q in chronic hypoxia to maximal SL values when arterial PO(2) and SO(2) are similarly increased suggests hypoxia-mediated attenuation of Q.