Abstract 6
Pavlíček, T. and Nevo, E. 1994: Genetic diversity of the beetle Oxythyrea noemi in a microsite: A test of correlation in nature between genetic diversity and environmental unpredictability. Zool. Jb. Syst. 121: 505-513.
The prediction of the niche-width variation hypothesis of positive correlation between niche width and genetic diversity was tested on the beetle Oxythyrea noemi Rche. (Coleopterea, Scarabeidae) from microclimatically contrasting slopes at a Mediterranean microsite, at Nahal Oren, Mount Carmel, Israel. The Nahal Oren canyon consists of two opposing slopes varying drastically in microclimate, flora and fauna, but sharing geology and macroclimate. The South-facing slope (S-slope) receives greater radiation and is warmer, drier and climatically more variable than the North-facing slope (N-slope).

We predicted that the subpopulation living on the S-slope are selected for higher genetic diversity due to a wider ecological microclimatic niche in space and time as compared to the N-facing slope. To test our prediction we compared the levels of genetic diversity of the beetles from the opposing slopes.

We examined totally 88 individuals of O. noemi, 51 individuals from the S-slope, 16 individuals from the N-slope, and 21 individuals from the bottom (B) of the canyon, each tested from 22 putative allozyme loci. Genetic diversity indices A, P, and He were higher on the S-slope as compared to the N-slope, as predicted, and H was the same on both slopes. Four loci (IDH, G6PD, EST-2, and XDH) showed a significant higher diversity on the S-slope while 2 loci (HBD, and ALD-1) showed a significant opposite trend. On average, 3.4% of the total diversity was between the slopes. A general large paucity of heterozygotes has been found. The significant excess of heterozygotes in the AO locus suggests selection for advantage of heterozygotes at this locus. The differences in genetic indices between the slopes were not significant in O. noemi. However they are in line with results obtained in six other species, all displaying higher genetic diversity on the S-slope, supporting the niche-width variation hypothesis. We found that the number of alleles per locus (A) is significantly higher on the S-slope than on the N-slope. A similar trend, but not significant, is indicated also for H, He and P. We believe that our results in O. noemi and in Carabus hemprichi (Coleoptera), Tetrarthrosoma syriacum Diplopoda), Buliminus labrosus (Mollusca), Sphincherochtila zonata (Mollusca) and S. propetharum support the niche width genetic variation hypothesis, or more generally, the environmental theory of genetic diversity.




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