Geographical isolation and environmental heterogeneity contribute to the spatial genetic patterns of Quercus kerrii (Fagaceae)

Abstract

Southwest China is one of the major global biodiversity hotspots. The Tanaka line, extending within southwestern China from its northwest to its southeast, is an important biogeographical boundary between the Sino-Japanese and Sino-Himalayan floristic regions. Understanding the evolutionary history of the regional keystone species would assist with both reconstructing historical vegetation dynamics and ongoing biodiversity management. In this research, we combined phylogeographic methodologies and species distribution models (SDMs) to investigate the spatial genetic patterns and distribution dynamics of Quercus kerrii, a dominant evergreen oak inhabiting southwest China lowland evergreen-broadleaved forests (EBLFs). A total of 403 individuals were sampled from 44 populations throughout southwest China. SDMs and mismatch distribution analysis indicated that Q. kerrii has undergone northward expansion since the Last Glacial Maximum (LGM). Quantitative analysis revealed that the range expansion of Q. kerrii since the LGM exceeded that of the sympatric mid-elevation species Quercus schottkyana, likely owing to their contrasting distribution elevations and habitat availabilities. The historical climate change since the LGM and the latitude gradient of the region played an important role in shaping the genetic diversity of Q. kerrii. The genetic differentiation index and genetic distance surface of Q. kerrii populations east of the Tanaka line exceeded those to its west. The long-term geographic isolation and environmental heterogeneity between the two sides of the Tanaka line might increase species divergence patterns and local adaptation. This study provides new insights into the historical dynamics of subtropical EBLFs and the changing biota of southwest China.

Ancient events and climate adaptive capacity shaped distinct chloroplast genetic structure in the oak lineages

“…Coordinates of these specimens were then used to extract 19 BIOCLIM variables from WorldClim 1.4: Current conditions (~ 1960–1990) [128] using the raster [129] and dismo packages [129] in R. Geographic records of sections Cyclobalanopsis , Ilex and Quercus were obtained from our field collection database, Chinese Virtual Herbarium (http://www.cvh.ac.cn), Global Biodiversity Information Facility (https://www.gbif.org) and National Herbarium of the Netherlands (http://herbarium.naturalis.nl/nhn/explore). Additional geographic occurrence data were added from previous studies for section Cyclobalanopsis [36–38, 130], section Ilex [39, 43, 47, 131], and section Quercu s [29, 50, 130, 132–134]. The sampling records of sections Ilex and Quercus were uneven, which would have affect climate analysis.…”

“…Oak plastome haplotypes have been widely sampled, particularly in three major clades: sections Cyclobalanopsis and Ilex , which have an East and Southeast Asian and Eurasian (sub) tropical distribution, respectively; and section Quercus , which is widely distributed in the Northern Hemisphere [27]. Recent phylogeographic studies of the species of section Cyclobalanopsis [36–38] indicated that landscape, climate and local adaptation shape regional genetic diversity patterns. Similarly in section Ilex , geomorphological and climate changes from the Neogene onward have been demonstrated to have shaped the genetic structure [39–47].…”

Geographic isolation and climatic variability contribute to genetic differentiation in fragmented populations of the long-lived subalpine conifer Pinus cembra L. in the western Alps

“…Fluctuating environmental conditions, including variation in the local or regional climate, can induce severe stress that can considerably alter the genetic variation of a species through divergent selection processes [15], and may lead to increased genetic differentiation between populations on a spatial scale [16]. Environmental variability (or heterogeneity) has long been recognized as an important driver of genetic variation and differentiation [17, 18], and several studies have also shown statistical associations between neutral genetic variation and environmental heterogeneity [19–22]. The latter correlations may be interpreted as evidence of diversifying selection acting over whole genomes, including on putatively neutral loci, and allows us to infer the long-term effects of environmental conditions on genetic variation [19, 23].…”

Spatial Genetic Patterns and Distribution Dynamics of the Rare Oak Quercus chungii: Implications for Biodiversity Conservation in Southeast China

“…Forests play crucial roles in both the regional ecology and economy, including maintaining species diversity, regulating climate, conserving water and soil, and providing timber and food [1,2]. A great deal of research is still required to better understand and untangle the biotic and abiotic factors that drive speciation, genetic differentiation, and the distribution dynamics of trees [3][4][5][6]. The demographic history and distribution dynamics of trees can be reconstructed based on a species genetic diversity, paleontology data, and a species distribution model, or the combination of these data [7,8].…”