Genetic (RAPD) Diversity Across Species Range: Core vs. Peripheral Populations of Wild Barley in Israel and Turkmenistan

Populations of wild barley,Hordeum spontaneum, were collected in two countries, Israel and Turkmenistan, in environments representing two similar sharp clines of aridity. This allowed us to use the same criteria to define species core and periphery in the two regions. Plants from 21 Israeli and 11 Turkmenian populations were analyzed for 59 putative loci by randomly amplified polymorphic DNA. Extent of variation was similar in populations at species border (periphery) and in populations inhabiting favorable environments away from the border (core). In contrast, the two regions (Israel and Turkmenistan) differed in extent of genetic diversity as estimated by mean number of alleles per locus, the proportion of polymorphic loci, and the percent of expected heterozygosity, with Israel harboring more variation than Turkmenistan. The genetic population structure revealed by RAPDs did not differ between species core and periphery in each region and between the two regions. The pattern of RAPD variation corresponded to inter-population mosaic structure characterized by genetic differentiation over short geographic distances.The major conclusion of this study is that there is no simple relationship between neutral genetic variability and population location with respect to the species range (core vs. periphery).