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Stipa steppes are considered to be an important model ecosystem in arid land ecology owing to their wide geographical distribution and their strong association with human activities. This paper presents data on the seed germination of four Jordanian Stipa species (Stipa capensis, Stipa parviflora, Stipa arabica and Stipa lagascae) that are widespread throughout various phytogeographical regions in Jordan. We studied variation in seed germination under laboratory conditions among populations and under various temperature regimes. There was significant variation in seed germination with temperature in all four species and seed provenance was significant for three out of the four species. The temperature levels that were most suitable for germination varied from low (8/4 degrees C and 20/10 degrees C) for S. lagascae to high (20/10 degrees C and 32/20 degrees C) for S. capensis; S. arabica and S. parviflora germinated equally well at all three temperature regimes. Variations among populations were species specific, but populations with the highest seed germination were always of arid and Saharan Mediterranean origin. Thus, seed germination was negatively correlated with annual precipitation. Such flexibility among temperatures and populations could be interpreted as an efficient survival strategy for species growing under unpredictable environmental conditions. Where artificial reseeding is necessary, differences among species and also among different seed provenances should be taken into account.