Natural selection causes microscale allozyme diversity in wild barley and a lichen at ‘Evolution Canyon’, Mt. Carmel, Israel

Abstract

Allozymic diversity was studied for proteins encoded by 28 putative loci in 170 plants of wild barley, Hordeum spontaneum, and for 13 loci in 78 different thalli of the lichen Caloplaca aurantia, from the Lower Nahal Oren microsite, Mt. Carmel, Israel, designated by us ‘Evolution Canyon’. The samples of wild barley were collected from six stations: three (upper, middle, lower) on the south-facing slope (SF-slope) and three (lower, middle, upper) on the north-facing slope (NF-slope). The samples of C. aurantia were collected from three stations: two (middle and upper) on the SF-slope and one (upper) on the NF-slope. Higher solar radiation on the SF- than on the NF-slope makes it warmer, drier, spatiotemporally more heterogeneous, and climatically more fluctuating and stressful. Consequently, it exhibits an open park forest representing an ‘African’ savanna landscape. Significant inter- and intraslope allozymic differentiation was found in both organisms with generally higher polymorphism, heterozygosity, allele and gene diversity on the more variable and stressful upper station of the SF-slope, as expected by the niche-width variation hypothesis, and the environmental theory of genetic diversity. Solar radiation, temperature and aridity stress caused interslope and intraslope differences on the SF-slope in genotypes and phenotypes of wild barley and the lichen at the ‘Evolution Canyon’ microsite, as was the case for beetles, diplopods and earthworms tested at the site. Diversifying natural (microclimatic) selection appears to be the major evolutionary driving force causing interslope and SF-intraslope adaptative genetic divergence. ‘Evolution Canyon’ proves an optimal model for unravelling evolution in action, across life and organizational levels.