The Comparison of Climatic Niches, Plant Functional Traits and the Late Quaternary Refugia of Oaks (Quercus) Distributed in Different Biomes of the Western Palearctic Region

Abstract

Various factors have impacts of species’ distributions on a global scale. The genus Quercus (oaks) has many widespread species whose distributionhas changed significantly with the global climate changes that occurred in the late Quaternary period. However, the fact that it has many subspecies, high hybridization capacity, and the fact that many species are sympatric in the same area shows that apart from climate the plant functional traits shaped by environmental differences also contribute to their geographical distribution. The objectives of this thesis are to determine the differentiation of oak species distributed in the Western Palearctic region between different climate zones and to determine the differences in plant functional traits among these climate zones and among sections, to interpret their climatic niches in the Western Palearctic oak species, and to reveal the biogeographic patterns of these species. For this purpose, we used ecological niche modeling to test both wide-ranged and endemic species' response to climate fluctuations, also revealed their possible refugia during the late Quaternary refugia. Additionally, we assessed the variabilities in ten functional plant traits among 23 oak species under the four oak sections (Quercus, Ilex, Cerris, Ponticae) in three different climatic conditions by using general linear mixed models. The results of the functional traits analyses show that Mediterranean zone species’ response patterns against climatic changes, and trait variabilities has a difference compared to other climatic zone species. Therefore, climate zone shapes trait variability in oaks of the western Palearctic, but the evolutionary legacy in plant traits may have also played a role. Our results reveal out that the distribution ranges and functional traits of Mediterranean oak species are more conservative under climate changes and this pattern is important to consider climatic zones in conservation and management plannings. Our findings contributed to the scientific literature regarding the climatic niche variability of oak species in the western Palearctic region and contributed the effects of the plant functional traits shaping the species distribution ranges, and the importance of Anatolia as a host for the diverse of oak species.