Genetic structure and conservation status of Astragalus subrecognitus (Fabaceae): a very rare and narrow endemic species

Abstract

Background and aims – Narrow endemics, characterized by small distribution areas and small effective population sizes are prone to extinction due to low genetic variation caused by genetic bottlenecks and drift together with the danger of habitat loss. Astragalus subrecognitus is an endemic species that only occurs in northwestern Iran in mountain steppe at higher elevations above the Qezel Ozan River in the province Zanjan. Methods – In this study, we investigated the genetic structure of the populations of A. subrecognitus using inter simple sequence repeats (ISSR) and sequence-related amplified polymorphism (SRAP) as molecular markers.Key results – We detected two genetic groups, which do however not concur with the geographic origins east and west of the Qezel Ozan River. Extant gene flow between these populations is rather unlikely given their distance of c. 70 km and the lack of suitable habitats for this species in lower areas of the valley in between. Conclusions – From this we conclude that we see an older pattern of geographic isolation that was followed by an exchange of genotypes during a time when migration through the valley was possible. Still, admixture between both genetic clusters was found only in one individual, indicating that broadening of allelic diversity by hybridization between individuals belonging to different genetic clusters might be a slow process. Due to the small size of the population, sparse inhabited area, and also very slow or even lack of regeneration in some places we consider A. subrecognitus according to IUCN Red List criteria as ‘endangered’ species.