Abstract
Understanding intraspecific genetic variation is one of the principal requirements for the evaluation of tree species capacity to cope with intensive climatic changes, as well as designing long-term conservation programs. Herein, we evaluated the genetic diversity and genetic structure of seven pedunculate oak (Quercus robur L.) populations, located at the southern margin of its distribution range on the Balkan Peninsula (Serbia). The objective of the study was to propose future in situ conservation measures aimed at protection of pedunculate oak adaptive and neutral genetic diversity at the species rear-edge. Genetic diversity and structure were estimated using twelve highly polymorphic simple sequence repeat (SSR) markers. The mean expected heterozygosity (He) was 0.769, allelic richness (AR) 9.63, and private allelic richness (pAR) 0.79, indicating high genetic diversity in the studied populations. Genetic differentiation among the populations was low (Fst = 0.032). Structure analysis, the unweighted pair group method with arithmetic mean (UPGMA) showed the existence of two gene pools unrelated to the populations’ area of occurrence. Taking into consideration the results of the current study and previous conservation activities on the pedunculate oak in Serbia, as well as the importance of rear-edge populations in the long-term conservation of the species genetic diversity, we suggested establishing three additional gene conservation units for securing long-term sustainability of the species.
Highlights
Pedunculate oak (Quercus robur L.) is widely distributed across Europe, from the Northern Iberian Peninsula, South Italy, and the Balkan Peninsula and Turkey to SouthernScandinavia, and from Scotland to Asia through the Ural and Caucasus Mountains [1].In Southern Europe, the Quercus species survived the last glacial period in micro- and macrorefugia, from which the species were spreading to the north and east depending on climate occurrences [2]
Relationships among the populations were estimated with Cavalli–Sforza and Edward’s chord genetic distances (DC) [52] using the INA method computed in FreeNA
Our study revealed that the studied pedunculate oak populations were characterized by a high level of genetic diversity, which is likely for Southern European tree populations as they are located in areas of glacial refugials [77]
Summary
Pedunculate oak (Quercus robur L.) is widely distributed across Europe, from the Northern Iberian Peninsula, South Italy, and the Balkan Peninsula and Turkey to SouthernScandinavia, and from Scotland to Asia through the Ural and Caucasus Mountains [1].In Southern Europe, the Quercus species survived the last glacial period in micro- and macrorefugia, from which the species were spreading to the north and east depending on climate occurrences [2]. Pedunculate oak (Quercus robur L.) is widely distributed across Europe, from the Northern Iberian Peninsula, South Italy, and the Balkan Peninsula and Turkey to Southern. According to Muir et al [4] results showed that in Europe Q. robur and Q. petraea hybridize extensively, the two species are separate taxonomic units; and populations from Serbia were close to populations from Slovenia. In Serbia, the majority of pedunculate oak stands is situated in the northern part of the country, along with the Sava and Danube rivers, and in Central Serbia (e.g., separate populations) [5,6]. Pedunculate oak forests in Europe have been subjected to numerous stress factors, such as low underground water level [7], drought stress [8], pest and diseases [9,10], and climate change [11]. Under the influence of intensive climate change, pedunculate oak forests may suffer significant damage from interacting causal agents, which have been shown to trigger a complex phenomenon of oak decline [13,14]
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