Comparative phylogeography in Iranian high mountain ranges

Mountains are biodiversity hotspots, harboring a considerable proportion of terrestrial plant and animal diversity and high levels of range-restricted species. These habitats are known to be among the most severely impacted ecosystems by global climate change. High mountain ranges bordering the Iranian Plateau, SW Asia, comprise major parts of the Irano-Anatolian biodiversity hotspot, which is characterized by high levels of endemism. Despite this high relevance for global patterns of biodiversity, little is known about the diversification of mountain species of this region and their response to Pleistocene climate oscillations. Such questions can be addressed within the framework of phylogeography, which in the last years has strongly changed methodologically and technically, moving it from a descriptive science towards a hypothesis-testing one. One of these approaches is the Integrative Distributional, Demographic and Coalescent (iDDC) approach, which uses spatially-explicit demographic models that can be translated into coalescent models testable by Approximate Bayesian Computation (ABC) techniques. This approach has already been successfully used to test hypothesis about Pleistocene range shifts in a number of different biomes, including mountain biota. Using the iDDC approach on 12 species, each characteristic for one of the four elevational zones (montane, subalpine, alpine, subnival), we will address the following questions: (1) What is the impact of Pleistocene climate oscillations on phylogeographic differentiation of Iranian mountain species in different elevational zones? (2) What is the directionality of range shifts between major mountain ranges? (3) Is there congruence between the putative glacial refugia identified by phylogeographical inferences with areas and centres of endemism identified by floristic data in the mountains of Iranian Plateau? The proposed project will fill our knowledge gap with respect to the response of mountain species from SW Asian mountain ranges, being part of a global biodiversity hotspot, to Peistocene climate change in this region. Furthermore, identification of glacial refuge areas is of fundamental interest to set priorities for conservation and management of genetic resources. The herein obtained genetic data will facilitate identifying Evolutionary Significant Units or genetically highly variable populations and will thus help prioritizing nature conservation activities. Setting sensible conservation priorities is especially important since mountain habitats of the study area are under extreme anthropogenic pressure. The planned study will attract the interest of the scientific community to these diverse mountains, and will encourage the scientists to work on this less known region.

The impact of climate change on biodiversity has become one of the most important topics in biodiversity research and conservation biology in the last decades. Understanding the reaction of species to past climate changes, especially during glacial (cold) and interglacial (warm) periods of the Pleistocene (from 2.6 million to 11,700 years ago), will help us to predict the impact of the ongoing climate change on species. These climatic oscillations have had strong impacts on distribution ranges, population sizes and local persistence or extinctions of plant and animal species. Phylogeographic methods, using genetic data of different populations of many species, can show us the biogeographic history of these species in the context of climate change. In this project, we were looking for the impacts of glacial and post-glacial periods on the biogeographic history of mountain species of the Iranian Plateau in South-West Asia. The study area is located in the Irano-Anatolian global biodiversity hotspot, which harbours a high amount of endemic species, but at the same time its natural habitats are strongly threatened by human activities. Using nine mountain species restricted to the Iranian Plateau that were categorized in two elevational belts (four montane and five alpine species), we assessed population responses of these species to Pleistocene climate oscillations. We tested the hypotheses that during glacial periods montane species possessed smaller population sizes due to restriction in lowland refugia, whereas alpine species had larger population sizes due to expansion into suitable lower elevations. Our study rejected this hypothesis, as most of the alpine species showed post-glacial expansion (larger population sizes in warmer periods) and glacial contraction (smaller population sizes in colder periods). As all alpine species showing larger population sizes during warmer periods are restricted to habitats with very short snow cover and longer growing seasons, this suggests that in the alpine zone of the study area microhabitats play a determining role on how species respond to climate change. Data gathered during the course of this project contributed to the description of three alpine species new to science. One of those species constitutes a genus new to science with a very small distribution area restricted to a narrow belt (3850-4050 m a.s.l.) close to the summit of an isolated mountain in central Iran surrounded by deserts. Moreover, we worked on alpine plant diversity in South-West Asia. We found that bioregionalization is largely determined by species restricted to the study region. Additionally, hotspots of alpine plant diversity and their conservation gaps (species-rich areas that are not protected) were identified. As more than 50% of the identified hotspots are not protected, our results can be very useful to establish new protected areas.