Geobotany of the genus Onosma L. (Boraginaceae) in the middle part of the Central Zagros: A conservation approach

Onosma is one of the most diverse genera of Boraginaceae. The areas of endemism as well the main diversity centers of the genus cover the Iranian as well Anatolian plateaus and the Mediterranean region. The present study has been conducted to determine the distribution patterns, centers of diversity, endemism centers as well as assessment the endangered species in the middle part of the Central Zagros. During the field studies, 75 populations of 10 species of Onosma were collected in the target area. The studied species showing an elevation range of 803- 2952 m. Additionally, the species are distributed in habitats with semi-humid, Mediterranean, and semi-arid climates and in alkaline soils (8/48-37/48. (The altitude and content of potassium in soil are the most important environmental variables affecting diversity as well species distribution in the studied area. Our results showing that half of the species in the studied area are located in the threatened categories. Finally, the results of this study emphasize the need for ex-situ conservation in some highly endangered species.