Distribution Patterns and Endemism of the genus Onosma L. (Boraginaceae) in Central Alborz

The evaluation as well as data banking of distribution patterns are considered as the most important management action for the conservation of biodiversity. Iran is considered as one of the most important of diversity centers of Onosma L. and includes a high rate of endemism. Due to the lack of adequate data on conservation and distribution patterns of the genus at local scale, the current study was conducted in Central Alborz, as an important diversity and endemism centers in Iran, based on field and herbarium assessments, using Geographic Information System. Sampling was performed as a survey of reported points as well as other parts of the region. For physico-chemical analysis of soils, pH, nitrogen (N), phosphorus (P), potassium (K), organic carbon (C) and soil texture of each habitat were measured from the surface to the depth of plant roots. Results indicated that studied species are mainly distributed at the elevation range of 1257 to 3060 m.a.s.l. Members of Haplotricha subdivision are scattered at an altitude of 307 to1257 m and Heterotricha subdivision at an altitude of 2880-1589 m. Dominantly, the studied species are distributed in semi-arid and Mediterranean climates. However, some species are distributed in semi-humid climate. Generally, most of the species are distributed in habitats with an average annual rainfall of about 250 to 500 mm, on sedimentary, sedimentary-volcanic, igneous and rarely on quaternary deposits. Soils` pH ranged between 7.13 (O. gaubae) and 8 (O. dichroantha). Studied species are often on loamy clay sandy soils. Less than 50% of the populations of various Onosma species, across the study area, are located in protected areas. In addition, O. gaubae is classified as a rare taxon with a priority for conservation, due to its very small population size and geographical range. The current study has also analyzed the distribution patterns of Onosma in Central Alborz region, based on geo-botanical factors. Findings of this study can be used as an important step to improve the distribution patterns of the genus in Iran and the southwest Asia.