Areas of endemism in the high-mountain flora of Iran

Alpine habitats are biodiversity hotspots that host a considerable number of endemic species. At the same time, alpine habitats are considered to be among the most strongly affected by global change. Whereas the high mountain flora for temperate and boreal mountains is comparatively well studied, much less is known about mountain ranges elsewhere. This is also the case for SW Asian mountain ranges, which harbor a considerable fraction of plant diversity in this region. For instance, around 10% of the Iranian flora occurs in alpine habitats and more than 50% of the alpine flora of Iran are endemic or subendemic to this country. The concept of endemism, i.e., the state of being restricted to a particular area, is central to biogeography. Areas of endemism, i.e., areas of non-random distributional congruence among different taxa, are fundamental entities of analysis in evolutionary biogeography, as they are the units compared in the investigation of earth history according to biological patterns. Biogeographers and evolutionary biologists are interested in explaining the causes for the occurrence of areas of endemism, such as ecological factors or historical reasons (e.g., vicariance, speciation in isolation); ecologists are interested in areas of endemism due to their importance in devising conservation priorities. Here we will identify areas of endemism and their ecological and/or historical correlates in the Iranian high-mountain flora as the basis for a better understanding of its fate under global change and for determining the habitats with conservation priorities. Specifically, using several complementary techniques for identifying areas of endemism (Endemicity Analysis; Sympatry Inference and Network Analysis; Delimitation of Biogeographic Regions Using Fuzzy Logic), we will address the following questions: (i) Where are the areas of endemism of the Iranian alpine flora? (ii) What are the roles of historical, physical and/or ecological factors in shaping areas of endemism of the Iranian alpine flora? (iii) Which areas of endemism have conservation priorities? By assembling data on Iranian alpine endemics and their publication in appropriate online databases, the proposed research will provide the necessary (publicly available) basis for recognition and prioritization of conservation areas and their distinguishing species. Furthermore, knowledge on areas of endemism provides a valuable basis for future research on the phylogeography of the thus far grossly understudied Iranian biodiversity hotspot. Finally, because analyses including some of the newer and conceptually different approaches for inferring areas of endemism are at best rare, the proposed research is expected to be of broader interest for the biogeography and the evolutionary biology community.

Understanding patterns of how endemic species (i.e., species restricted in their distribution to an area) are distributed is relevant both for evolutionary biologists, who are interested in explaining the underlying causes of these patterns (e.g., ecological factors, historical reasons), and for ecologists, who are interested in those patterns as these can help devising conservation priorities. Nevertheless, our knowledge on patterns of endemism is still limited even in widely recognized global biodiversity hotspots, including the Irano-Anatolian hotspot in southwestern Asia. Focusing on Iran, which covers large parts of the Irano-Anatolian hotspot, we found that areas of endemism are strongly associated with high mountain ranges. Specifically, the number of endemic species peaks at mid-elevations, whereas the percentage of endemism gradually increases with elevation. This is likely due to high environmental heterogeneity and strong geographic isolation among and within mountain ranges. The same association between endemism and mountain ranges, although based on geographically less dense data, could be identified for Turkey. Biodiversity loss due to human activities has dramatically increased over the last decades, and increased efforts to protect threatened species are needed. This is also the case for Iran, where we found that hotspots of vascular plant endemism suffer from significant conservation gaps, as centres of unique plant diversity often are not within protected areas. Specifically, priority hotspots (i.e., centres of endemism congruently identified by all used biodiversity indices) harbour about half of the Iranian endemic plant species on only about 5% of the Iranian surface area, still half of those priority hotspots are not covered by nature reserves. In light of the growing pressure on these areas due to, for instance, global climate change or increasing anthropogenic land use establishment of new nature reserves and increased management efficacy of existing reserves is urgently needed. An up-to-date account of diversity and distribution of the endemic species of Iran, based on data of more than 2500 species, emphasizes the importance of the Irano-Anatolian biodiversity hotspot (harbouring 84% of all endemic species) and of mountain ranges (harbouring three fourths of all endemic species) in general. Although the precise numbers will change over time due to taxonomic work (including the description of new species, as done within the project for the Shirkuh Mountains in central Iran), the overall patterns certainly will hold.