Distribution patterns and diversity of Onosma in Iran: with emphasis on endemism conservation and distribution pattern in SW Asia

Geobotanical assessment of taxa with a high percentage of richness and endemism plays an important role on conservation plans. South-West Asia is one of the main biodiversity centers of the genus Onosma (Boraginaceae) comprising a high rate of species richness and endemism in Iran. Due to existing threatened factors to habitats and lack of sufficient data on conservation and distribution patterns the species of Onosma have been evaluated based on filed works and herbarium assessment by GIS. The results indicate that the most important hotspots and biodiversity centers of the genus in SW Asia are Caucasus mountains, Anatolian  plateau, Hindukush mountains as well as Zagros mountains. Sect. Protonosma showing a distribution mainly in sedimentary and volcanic-sedimentary rocks, whereas Sect. Podonosma in sedimentary rocks. Moreover, subsect. Onosma showing a distribution in wide spectra of substrate as follow sedimentary, volcanic-sedimentary, igneous and ophiolitic formations. In phytogeographical point of view, approximately 81.80 percent of taxa are belonging to Irano-Turanian region and 19.20 percent are biregional or multiregional western slopes of central Zagros and southern slopes of central Alborz are considered as the highest conservation priorities. Rare species have been mostly reported from one locality with single population, which majorities belong to subsections Hapolotricha and Heterotricha respectively. According to IUCN threatened categories, about 50% of species have been classified in critically endangred (CR) and endengred (En) categories. This study also showing some evidence on differentiation of Podonosma from Onosma which have been already done by the other biosystematics studies.