Genetic (allozyme) divergence in wild barley, Hordeum spontaneum at a microsite: "Evolution Canyon", Lower Nahal Oren, Mt. Carmel, Israel
Genetic (allozyme) divergence in wild barley, Hordeum spontaneum at a microsite: "Evolution Canyon", Lower Nahal Oren, Mt. Carmel, Israel
 Eviatar Nevo, Iris Apelbaum-Elkaher and Avigdor Beiles
Institute of Evolution, University of Haifa,
Haifa 31905, Israel

Allozymic diversity was studied electrophoretically in proteins encoded by putative 28 loci in 170 plants of wild barley, Hordeum spontaneum from Lower Nahal Oren microsite, Mt. Carmel, Israel, designated by us "Evolution Canyon" (for technical and electrophoretic data see Nevo et al., 1979 and 1996). The samples of wild barley were collected from six stations: 3 (upper, middle, lower) on the South-facing slope (S-slope), and 3 (lower, middle, upper) on the North-facing slope (N-slope). We estimated allelic polymorphisms (P), mean number of alleles per locus (A), observed heterozygosity (H) and gene diversity (He) by Biosys-1 (Swofford and Selander, 1989). The results appear in Figure 1.

The results indicate: (i) The highest genetic diversity was at the upper South-slope station; (ii) a cline, especially in P, of decreasing diversity from the upper to the lowest station on the S-slope; and (iii) the between stations diversity is higher on the S-slope than on the N-slope (Figure 1).

The S-slope is ecologically more heterogeneous and stressed by drought in space and time than its N-slope counterpart (Nevo, 1995). This is a direct result of the higher solar radiation on the S- (up to 300%) than on the N-slope. Thus, the S-slope is ecologically more variable and stressful than the N-slope. Furthermore, solar radiation, hence temperature nd drought are highest in station 1, the uppermost station on the S-slope. Runoff water from station 1 to 3 and 7 to 5 cause milder and less drought-stress in the lower station on both slopes. Polymorphism and allele diversity increased in parallel upward that slope towards the highest stress at station 1 on this slope.

At "Evolution Canyon", as predicted, multilocus genetic (allozymic) diversity was higher in subpopulations on the more stressful S-slope (Nevo, 1995; Nevo et al., 1996). Natural selection appears the only major evolutionary driving force able to cause the observed intra and interslope genetic differences. These results have important implications for sampling and utilization of the wild gene pool for barley improvement.

References:

Nevo, E. 1995. Asian, African and European biota meet at "Evolution Canyon", Israel: Local tests of global biodiversity and genetic diversity patterns. Proc. Roy. Soc. Biol. (in press).

Nevo, E., Zohary, D., Brown, A.H.D. and Haber, M. 1979. Genetic diversity and environmental associations of wild barley, Hordeum spontaneum, in Israel. Evolution 33:815-833.

Nevo, E., Apelbaum-Elkaher, I., Garty, J. and Beiles, A. 1996. Natural selection causes microscale allozyme diversity in wild barley and a lichen at "Evolution Canyon", Mt. Carmel, Israel (submitted).

Swofford, L.D. and Selander, R.B. 1989. BIOSYS-1 computer program for the analysis of allelic variation in population genetics and biochemical systematics. Release 1.7. D.L. Swofford, Illiois Natural History Survey, Champaign, Illiois.


Fig. 1 Genetic diversity inter- and intraslope divergence of wild barley Hordeum spontaneum subpopulations on opposite slopes at "Evolution Canyon", Lower Nahal Oren, Mount Carmel, Israel. P = polymorphism (1%), A = allele diversity; H/e/ = genic diversity. S - South-facing slope; N - North-facing slope; three stations on each slope: S Upper (= station 1); S Middle (=2); S Lower (=3); N Lower (=5); N Middle (=6); N Upper (=7).