Soil microfungi of the negev desert, israel - adaptive strategies to climatic stress

We present here the results of our mycological studies conducted in the soils of the Negev desert covering near 60% of the territory of Israel in its southern part with annual rainfall ranging from more than 300 mm in the northwest to about 25 mm in the extreme south. In spite of hostility, the soils of the desert were found to be inhabited by a comparatively rich fungal diversity - more than 360 identified microfungal species. The present study showed that soil mycobiota of the Negev desert has evolved under highly stressful climatic and edaphic conditions. The mycobiota displayed remarkable adaptive strategies to harsh desert stress reflected in diverse phenotypic and biological traits: (i) dominance or superdominance of species with dark-colored, large, thick-walled and multi-celled conidia (Ulocladium atrum, U. botrytis, Alternaria alternata, and A. chlamydospora); (ii) combination of true soil and plant (animal) inhabiting species; (iii) aspergilli (mainly Aspergillus fumigatus) and sexual ascomycetes comprising a basic part of thermotolerant mycobiota; (iv) relatively small spatiotemporal variation of community structure in most hostile environments of central and southern Negev, but drastic fluctuations in microfungal densities with high-positive dependence on organic matter content; (v) much more significant differences between the open crust and shrub localities, separated only by a few meters in northern and central Negev than between the crust or shrub localities in the distance of tens of kilometers which indicates that microenvironmental factors (soil moisture, temperature, organic matter content) influenced the development of studied communities more essentially than macroenvironmental (rainfall amount) factors; (vi) decreasing biodiversity level (heterogeneity, evenness) in microclimatically extreme localities and climatically extreme seasons. The most remarkable phenomenon of desert mycobiota is it unique adaptive complex of melanism, sexuality, drought and UV resistant morphology.