Diversity, distribution, ecology and description rates of alpine endemic plant species from Iranian mountains

Mountain ranges cover around one-half of the territory of Iran. Although it is well-known that these mountains are characterized by high levels of endemism, no assessment of vascular plant endemism of Iranian mountains has been made. Here, we undertake a first analysis of the diversity and biogeography of high-altitude (=taxa, whose elevational distribution ranges are entirely or largely above 2500 m a.s.l.) endemic vascular plant species restricted to Iran. In total, our data set includes 569 endemic vascular plant taxa (incl. 43 subendemic taxa which slightly extend into adjacent countries), which correspond to 62 % of the entire alpine flora. The highest number of alpine endemics occurs in the Zagros, followed by Alborz, and the NW Iranian mountains. Screes, rocks and thorn-cushion grasslands are the most important habitats for the alpine endemics. The altitudinal distribution of Iranian endemic alpine plant taxa peaks at high altitudes at c. 3000 m a.s.l. Below and above this altitude, there is a steep decrease in endemic alpine species numbers. The analysis of description histories in time-to-event analysis framework suggests that the rate by which new Iranian endemic alpine plant species are described does not seem to level off. Therefore, the proportion of species that still remain to be described is difficult to estimate. However, time-to-event analysis shows that at least 7 % of the extant Iranian alpine endemic species are not yet known to science. In addition, on average, the time lag between the year of collection and species description was 18 years. We conclude that there is a need for a continued botanical exploration in particular of under-sampled mountain ranges and for taxonomic revisions of genera rich in endemics which have been insufficiently studied yet.