Elevated mutation and selection in wild emmer wheat in response to 28 years of global warming

Abstract

Global warming has been documented to threaten wild plants with strong selection pressures, but how plant populations respond genetically to the threats remains poorly understood. We characterized the genetic responses of 10 wild emmer wheat (Triticum dicoccoides Koern.; WEW) populations in Israel, sampling them in 1980 and again in 2008, through an exome capture analysis. It was found that these WEW populations were under elevated selection, displayed reduced diversity and temporal divergence, and carried increased mutational burdens forward. However, some populations still showed the ability to acquire beneficial alleles via selection or de novo mutation for future adaptation. Grouping populations with mean annual rainfall and temperature revealed significant differences in most of the 14 genetic estimates in either sampling year or over the 28 y. The patterns of genetic response to rainfall and temperature varied and were complex. In general, temperature groups displayed more temporal differences in genetic response than rainfall groups. The highest temperature group had more deleterious single nucleotide polymorphisms (dSNPs), higher nucleotide diversity, fewer selective sweeps, lower differentiation, and lower mutational burden. The least rainfall group had more dSNPs, higher nucleotide diversity, lower differentiation and higher mutational burden. These characterized genetic responses are significant, allowing not only for better understanding of evolutionary changes in the threatened populations, but also for realistic modeling of plant population adaptability and vulnerability to global warming.