Abstract
Oak trees (Quercus L.) are important models for estimating abiotic impacts on the population structure and demography of long life span tree species. In this study, we generated genetic data for 17 nuclear microsatellite loci in 29 natural populations of Quercus fabri to estimate the population genetic structure. We also integrated approximate Bayesian computation (ABC) and ecological niche analysis to infer the population differentiation processes and demographic history of this oak species. The genetic analyses indicated two genetic clusters across the 29 populations collected, where most approximately corresponded to the intraspecific differentiation among populations from western and eastern China, whereas admixed populations were mainly found in central mountains of China. The best model obtained from hierarchical ABC simulations suggested that the initial intraspecific divergence of Q. fabri potentially occurred during the late Pliocene (ca. 3.99 Ma) to form the two genetic clusters, and the admixed population group might have been generated by genetic admixture of the two differentiated groups at ca. 53.76 ka. Ecological analyses demonstrated clear differentiation among the Q. fabri population structures, and association estimations also indicated significant correlations between geography and climate with the genetic variation in this oak species. Our results suggest abiotic influences, including past climatic changes and ecological factors, might have affected the genetic differentiation and demographic history of Q. fabri in subtropical China.
Highlights
Historical and ecological factors have left complex imprints on the genetic structure and demographic history of extant species (e.g., Petit et al, 2002; Chen et al, 2008; Zhang et al, 2019)
Previous studies have suggested that local adaptation to varying climate or ecological niches was a major driver of the geographical patterns and current genetic structure of plant species (Ortego et al, 2015; Hipp et al, 2018)
To evaluate the ecological distance, we selected six bioclimatic factors that contributed to the phylogenetic patterns and geographic distribution of Quercus species (Xu et al, 2013, 2016; Qian and Sandel, 2017; Yang et al, 2018): annual mean temperature (BIO1), temperature seasonality (BIO4), mean temperature of coldest quarter (BIO11), annual precipitation (BIO12), precipitation seasonality (BIO15), and precipitation of the driest quarter (BIO17)
Summary
Historical and ecological factors have left complex imprints on the genetic structure and demographic history of extant species (e.g., Petit et al, 2002; Chen et al, 2008; Zhang et al, 2019). These factors include geographical and/or climatic processes, such as the uplift of the mountains, morphological reconstruction, and climatic oscillations associated with ice ages. The interactions among these processes over varying temporal scales may have led to the non-random distributions of plant species within or throughout landscapes (Eiserhardt et al, 2011). Various ecological factors such as precipitation and temperature may have been responsible for driving intraspecific differentiation (Yang et al, 2018; Li et al, 2019)
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