Abstract/Summary

Wild olive (Olea europaea subsp. cuspidata (Wall. & G. Don) Cif.) are common, but scattered, throughout the mountains of Oman. They are vulnerable to disturbance from biotic and abiotic stresses. One hundred and eighty-four trees of wild olive, from eight locations in the three mountain ranges of Oman (Western Hajar, Eastern Hajar in the north; Dhofar Mountains in the south), were assessed. Almost all trees were damaged: only 5% showed little damage, with 53% showing moderate, 29% high, and 13% severe damage. Trees in Jabal Akhdar were least damaged and those in Jabal Hatt most damaged (both in Western Hajar mountains). Leaves, fruits and stones from the eight locations were imaged and measured. The size and shape of wild olive leaves and stones distinguished the Dhofar mountain populations from those to the north in the Eastern and Western Hajar mountains, whereas fruit size and shape were unique to each of these three mountain ranges. Morphological variations were correlated with environmental and geographical factors, indicating future climate change may affect fruit and stone characteristics, which may affect the germination and future decline of olive in Oman. Low levels of genetic diversity and high genetic differentiation were detected in the wild olive between northern and southern Oman which can affect the ability of wild olive to adapt to various environmental change and increasing the risk of extinction. Genetic diversity, studied using nuclear SNP markers, varied amongst Oman, United Arab Emirates, Saudi Arabia, Yemen, Iran, and South Africa. The Oman populations were grouped into two genetic clusters (all individuals from the Eastern and Western Hajar mountains; and all from Dhofar). The former group was associated with wild olive populations from the United Arab Emirates and Iran; the latter with those from Saudi Arabia, Yemen, and South Africa. In a further study, no genetic admixture was detected between cultivated olive and wild olive at Jabal Akhdar in Oman, except with D-statistic test. The study identified considerable genetic diversity in wild olive in Oman, but that this diversity in wild olive is at risk due to anthropogenic factors, and conservation is required.