@article {178, title = {Multiple glacial refugia for cool-temperate deciduous trees in northern East Asia: the Mongolian Oak as a case study}, journal = {Molecular Ecology}, year = {2015}, pages = {n/a-n/a}, abstract = {

In East Asia, temperate forests are predicted to have retracted southward to c. 30\º N during the last glacial maximum (LGM) based on fossil pollen data, whereas phylogeographic studies have often suggested glacial in situ survival of cool-temperate deciduous trees in their modern northern ranges. Here we report a study of the genetic diversity and structure of 29 natural Mongolian oak (Quercus mongolica) populations using 19 nuclear simple sequence repeat (nSSR) loci and four chloroplast DNA fragments. Bayesian clustering analysis with nSSRs revealed five groups, which were inferred by approximate Bayesian computation (ABC) to have diverged in multiple refugia through multiple glacial-interglacial cycles. Analysis of chloroplast DNA variation revealed four lineages that were largely but incompletely geographically disjunct. Ecological Niche Modelling (ENM) indicated a southward range shift of the oak\&$\#$39;s distribution at the LGM, although high suitability scores were also evident in the Changbai Mts. (Northeast China), the Korean Peninsula, areas surrounding the Bohai Sea, and along the coast of the Russian Far East. In addition, endemic chloroplast DNA haplotypes and nuclear lineages occurred in high-latitude northern areas where the ENM predicted no suitable habitat. The combined evidence from nuclear and chloroplast DNA, and the results of the ENM clearly demonstrate that multiple northern refugia, including cryptic ones, were maintained across the current distributional range of the Mongolian oak during the LGM or earlier glacial periods. Though spatially limited, postglacial expansions from these refugia have led to a pattern of decreased genetic diversity with increasing latitude. This article is protected by copyright. All rights reserved.

}, keywords = {East Asia ecological niche modelling molecular variation northern refugia Quaternary glaciations temperate forest}, author = {Zeng, Yan-Fei and Wang, Wen-Ting and Liao, Wan-Jin and Wang, Hong-Fang and Zhang, Da-Yong} } @article {175, title = {Variation in morphological traits in a recent hybrid zone between closely related Quercus liaotungensis and Q. mongolica (Fagaceae)}, journal = {Journal of Plant Ecology}, volume = {8}, year = {2015}, pages = {224-229}, abstract = {

Aims Hybridization usually leads to gene introgression between related species in hybrid zones, associated with complex patterns of morphological variation. Nevertheless, previous studies have tended to ignore the effects of geographic variation in hybridization rates on species taxonomy. This study aims to investigate the variation of morphological traits between two sympatric and taxonomically confused oak species, Quercus liaotungensis and Q. mongolica, and reveal the effects of hybridization rates on morphological traits and the taxonomic boundary.Methods We used seven microsatellite loci to evaluate species status and measured 15 morphological traits in 26 trees in the recent hybrid zone between Q. liaotungensis and Q. mongolica, and we characterized the differences between the two oak species and their hybrids for the investigated traits.Important Findings Molecular analyses indicated that 74\% of 78 sampled maternal trees were hybrids between Q. liaotungensis and Q. mongolica although the observed morphological variation suggested that they had remained distinct species. Across all of the differentiated leaf and reproductive traits, the hybrids expressed patterns similar to Q. liaotungensis, which may suggest dominant expression of parental characters. These results are consistent with our expectation that hybrids will be difficult to distinguish from parental species in a recent hybrid zone.

}, author = {Wei, Lai and Li, Yue-Fei and Zhang, Han and Liao, Wan-Jin} } @article {131, title = {Exploring Species Limits in Two Closely Related Chinese Oaks}, journal = {PLoS ONEPLoS ONE}, volume = {5}, number = {11}, year = {2010}, pages = {e15529}, publisher = {Public Library of Science}, abstract = {Background

The species status of two closely related Chinese oaks, Quercus liaotungensis and Q. mongolica, has been called into question. The objective of this study was to investigate the species status and to estimate the degree of introgression between the two taxa using different approaches.

Methodology/Principal Findings

Using SSR (simple sequence repeat) and AFLP (amplified fragment length polymorphism) markers, we found that interspecific genetic differentiation is significant and higher than the differentiation among populations within taxa. Bayesian clusters, principal coordinate analysis and population genetic distance trees all classified the oaks into two main groups consistent with the morphological differentiation of the two taxa rather than with geographic locations using both types of markers. Nevertheless, a few individuals in Northeast China and many individuals in North China have hybrid ancestry according to Bayesian assignment. One SSR locus and five AFLPs are significant outliers against neutral expectations in the interspecific FST simulation analysis, suggesting a role for divergent selection in differentiating species.

Main Conclusions/Significance

All results based on SSRs and AFLPs reached the same conclusion: Q. liaotungensis and Q. mongolica maintain distinct gene pools in most areas of sympatry. They should therefore be considered as discrete taxonomic units. Yet, the degree of introgression varies between the two species in different contact zones, which might be caused by different population history or by local environmental factors.

}, author = {Zeng, Yan-Fei and Liao, Wan-Jin and Petit, R{\'e}my J. and Zhang, Da-Yong} }