Genetic evidence for central‐marginal hypothesis in a Cenozoic relict tree species across its distribution in China

Abstract

Aim This study tests predictions of the central‐marginal (C‐M) hypothesis using geographical patterns of genetic variation in a Cenozoic relict tree species Euptelea pleiospermum. Additionally, we explore the extent to which post‐glacial recolonization and landscape barriers created by topographical heterogeneity shape spatial genetic variation. Location South‐west and central subtropical China. Methods Using microsatellite data of 678 individuals from 21 populations, we documented geographical patterns of genetic diversity and population genetic structure, supplemented with current and past (Last Glacial Maximum, LGM) distributions based on species distribution models (SDMs). Genetic structure was determined by non‐spatial and spatially sensitive Bayesian clustering, analysis of molecular variance, barrier analysis and a multivariate population graphing approach. We also examined both historical and contemporary gene flow. Results Genetic diversity significantly declined with distance from centre and showed unimodal patterns along both latitude and longitude. The C‐M pattern of genetic diversity along latitudinal gradient is high‐latitude‐skewed, with the peak at higher portion of the species' latitudinal extent. The Sichuan Basin divided individuals into south and north clusters, whereas the Qinba Mountains did not. The general shape of the predicted distribution during the LGM is strongly similar with that of current distribution, except the Sichuan Basin. Main conclusions Our study provides genetic evidence for the C‐M hypothesis in a Cenozoic relict tree species across its distribution in China. The Sichuan Basin, rather than the Qinba Mountains, acts as dispersal barrier for a mountain tree species. Our results suggest that in situ refugia were maintained across southwest and central China during the LGM. The slight post‐glacial northward expansion and asymmetrical south–north historical‐gene flow did not result in a low‐latitude‐skewed C‐M pattern of genetic diversity. Instead, complex topography in combination with the C‐M dispersal dynamics shaped the latitudinal pattern of genetic diversity.

Genomic insights into historical population dynamics, local adaptation, and climate change vulnerability of the East Asian Tertiary relict Euptelea (Eupteleaceae)

“…In this study, we applied stringent filtering methods to generate a high-quality SNP dataset for phylogeographic inference. Consistent with previous results using nuclear microsatellites (440 samples and 8 microsatellites, Cao et al, 2016; 678 samples and 7 microsatellites, Wei et al, 2016), our analyses of RADseq datasets identified two classic phylogeographic breaks across the East China Sea and between the Sino-Himalayan and Sino-Japanese Forest subkingdoms (Cao et al, 2016;Wei et al, 2016). However, we were also able to detect three subclusters (SW1-3) within the SW lineage of E. pleiosperma from our RADseq data ( Figures S3b, S4b), suggesting that RADseq can recover finer population structure than microsatellites, despite including only 17.7-38.6% of the individual samples in previous studies.…”

“…Likewise, irrespective of whether or not we filtered out SNPs with MAF < 1%, our results recovered the same general phylogeographical pattern, suggesting that our inferences of population structure were less affected by minor allele frequency thresholds. Clearly, our RADseq datasets with fewer samples but many more loci recovered finer population structure and inferred a more detailed evolutionary history in Euptelea, when compared to microsatellites (Cao et al, 2016;Wei et al, 2016). Moreover, we were able to use the thousands of genomic SNPs contained in our RADseq datasets, along with environmental data, to provide insights into its local adaptation and genomic vulnerability to future climate change in this system.…”

Pronounced genetic differentiation in Fokienia hodginsii revealed by simple sequence repeat markers

“…This phenomenon agreed with previous reports that most populations in Vietnam harbor low genetic diversity ( H T = 0.0970 ± 0.0101, ISSR markers used by Tam et al, ). It is possible that China serves as the central distributional area of F. hodginsii , such that its genetic diversity decreased as it dispersed from its central area to its marginal areas, such as Vietnam (Wei, Sork, Meng, & Jiang, ). Tam et al () also indicated that, as a result of human disturbance, the F. hodginsii habitat in Vietnam has been degraded and fragmented, which may also serve as a good explanation for the low genetic variability in Vietnam, as signals of bottleneck events were also detected in these two populations.…”

Geological effects influence population genetic connectivity more than Pleistocene glaciations in the water strider Metrocoris sichuanensis (Insecta: Hemiptera: Gerridae)

“…Sun et al, 2014;Wei, Sork, Meng, & Jiang, 2016) and vertebrates (e.g. Sun et al, 2014;Wei, Sork, Meng, & Jiang, 2016) and vertebrates (e.g.…”

“…Sichuan Basin have mainly focused on plants (e.g. Sun et al, 2014;Wei, Sork, Meng, & Jiang, 2016) and vertebrates (e.g. Li, Zhao, Wei, Luo, & Wu, 2015;Lu, Bi, & Fu, 2014).…”