J Syst Evol ›› 2020, Vol. 58 ›› Issue (2): 189-199.DOI: 10.1111/jse.12489

• Research Articles • Previous Articles    

Phenology and polyploidy in annual Brachypodium species (Poaceae) along the aridity gradient in Israel

Shira Penner1,2, Barak Dror1,2†, Iris Aviezer1,2‡, Yamit Bar-Lev1,2, Ayelet Salman-Minkov2, Terezie Mandakova3, Petr Šmarda4, Itay Mayrose2, and Yuval Sapir1,2*   

  1. 1Tel Aviv University Botanical Garden, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
    2School of Plant Sciences and Food Security, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
    3Central European Institute of Technology (CEITEC), and Faculty of Science, Masaryk University, Brno, CZ-62500, Czech Republic
    4Department of Botany and Zoology, Masaryk University, Brno, CZ-61137, Czech Republic
  • Received:2018-08-08 Accepted:2019-02-20 Online:2019-03-03 Published:2020-03-01


Local adaptation of plants along environmental gradients provides strong evidence for clinal evolution mediated by natural selection. Plants have developed diverse strategies to mitigate stress, for example, drought escape is a phenological strategy to avoid drought stress, while polyploidy was proposed as a genomic adaptation to stress. Polyploidy as an adaptation to aridity (an environmental parameter integrating temperature and precipitation) was previously documented in annual Brachypodium spp. (Poaceae) in the Western Mediterranean. Here, we examined whether polyploidy or phenology are associated with aridity in annual Brachypodium spp. along the aridity gradient in the Eastern Mediterranean. Using flow cytometry, we determined ploidy levels of plants from natural populations along the Israeli gradient, spanning ∼424 km from mesic Mediterranean to extreme desert climates. In a common garden we recorded time of seedling emergence, flowering and senescence. We tested whether the proportion of allotetraploids in the populations and phenological traits were associated with aridity. Contrary to a previous study in the Western Mediterranean, we found no effect of aridity on the proportion of allotetraploids and diploids within populations. Interestingly, phenology was associated with aridity: time of emergence was later, while flowering and senescence were earlier in desert plants. Our results indicate that in the Eastern Mediterranean, adaptation of Brachypodium to aridity is mediated mainly by phenology, rather than ploidy level. Therefore, we suggest that genome duplication is not the main driver of adaptation to environmental stress; rather, phenological change as a drought escape mechanism may be the major adaptation.

Key words: abiotic stress, adaptation,  Brachypodium, climatic gradient, polyploidy