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.

The small genusPisumis composed of two annual species,P.fulvumand the domesticated peaP.sativum. The domesticated pea has two main wild-type taxa:P.elatiusandP.humile. Members of the genusPisumare not well defended from herbivory by high levels of toxins like the seeds of many other legume species. We studied the color patterns in the pods and seeds of these three wild taxa (P.fulvum,P.elatiusandP.humile) in order to examine their potential for defensive coloration (camouflage and Batesian mimicry). All three taxa are polymorphic concerning pod and seed coloration. The mature pods of many individuals ofP.humileandP.elatiusmimic aposematic caterpillars, but some are plain green. The pods of some individuals ofP.elatiushave a zigzag or straight red marking along them that resembles the conspicuous dorsal markings of the local common venomous viper, potentially mimicking it. The pods of many individuals ofP.fulvumhave dark blotches that when compared to such patterns in animals, potentially function as camouflage. The seeds of all three species are camouflaged by either: (1) color matching with that of soil (especiallyP.fulvumandP.elatius), (2) disruptive coloration (especiallyP.humile), (3) variability in seed-coat color that may undermine the use of search images by visually oriented granivores that look for cryptic seeds (all taxa). The mature pods ofP.fulvumare also defended in many inflorescences by degenerated flowers that develop into sharp thorns. It seems that this species is still in the process of evolving this mechanical defense as the response to millennia of strong grazing pressure.