Markers associated with altitude and ecological factors in hexaploid Campeiostachys nutans (Griseb.) J. L. Yang, B. R. Baum et C. Yen and tetraploid Roegeneria nutans (Keng) Keng

The genetic basis of adaptation can be unraveled directly at the genome level, without regard to selectively advantageous genes or traits. Genetic variation and adaptation of polyploidy in the evolution of plants is becoming an area of intense interest. Whether hexaploid wheatgrass species has higher adaptability to altitude than tetraploid or not needs to be proofed by population genomic data. A fluorescence-based AFLP technique was used to investigate the allele share of hexaploid Campeiostachys nutans (Griseb.) J. L. Yang, B. R. Baum et C. Yen and tetraploid Roegeneria nutans (Keng) Keng as well as the genetic variation and natural selection in 22 natural populations and their association with ecological factors. Of all the AFLP bands, 84.29 % were found in common between two different ploidy wheatgrasses. In addition, we found that hexapoid C. nutans had 1.45 times the allelic frequency and more large-sized bands than tetraploid R. nutans. After genetic analyses, the next factor examined should be the effect of altitude on genetic variation. There were no significant inter-population genetic differentiations, suggesting that distance did not contribute to spatial isolation. Altitude and soil nutrient availability might play an important role in maintaining the genetic diversity. A certain percentage of positive selection loci were discovered in total genome allele. Hexaploid wheatgrass with higher ploidy numbers can show strong genetic adaptability to adverse high-altitude condition because of its complex genomic background with an additional H genome, which supports our hypothesis. Though this evolutionary process is believed to be the driving force behind sympatric speciation, we cannot forecast that hexaploid wheatgrass species will diversify into two species in the long term, but believe that diversification under local selection helps to increase the adaptability to the changes in altitude.