Due to the relatively high environmental importance of endemic species on the regional ecosystems of Southern Sinai, to consider a taxon as endemic without specifying a geographic range is meaningless. Because the ranges of taxa change over time, time must also be specified, or at least understood. Changes in the ranges of species, either by invasion (range extension) or by range contraction, change the percentage endemism within a given area. Changes in endemism also occur by extinction and speciation, although the rate of speciation is much slower than the rate at which taxa change their ranges. The eco-physiological studies provide the most suitable tool for the appropriate comprehensive understanding of low environmental and physiological processes that interact to determine the performance of the growth of plant species. The analysis of species–environment relationship has always been a central issue in ecology. For over a century, ecologists have attempted to determine the factors that control plant species distribution and variation in vegetation composition.