Ecological studies of Commiphora genus (myrrha) in Makkah region, Saudi Arabia.

Commiphora, myrrha, is a pantropical genus and perform well in arid and semi-arid environments. This genus has economic importance. Distribution of Commiphora species and their associated species in Saudi Arabia has not been studied to date. The current study report on (a) characterization and distribution of plant communities including Commiphora species and (b) assessment of factors influencing ecological preferences of these species. Five species of Commiphora are recorded inhabiting mountain slopes, steep escarpments or hills consisting of igneous rocks, either granites or basalt with drought prone shallow soil. One hundred and twenty-six plant species belonging to 95 genera and 35 families were found associated with different Commiphora species. Therophytes showed the most frequent life form class and Sudanian region elements recorded the highest phytogeographical units (28%) followed by Tropical elements. Field study showed that Commiphora gileadensis and C. quadricincta preferred granite and basalt rocks exposed to erosion, while C. myrrah, C. kataf and C. habessinica grow on resistant coarse pink granite. The analysis of 240 sampling stands with TWINSPAN revealed the vegetation of Commiphora habitats into eight vegetation groups; each group represented a distinct microhabitat. Dendrogram obtained from a hierarchical classification showed that habitats of C. gileadinsis and C. quadricincta are more similar than those of other species. This similarity was confirmed by Jaccard and Sorenson similarity indices and by Pearson correlation coefficient. This investigation compiled the information/data to facilitate future range management of Commiphora species.