New insights into the evolution and local adaptation of the genus Castanea in east Asia.

Chestnut plants (Castanea) are important nut fruit trees worldwide. However, little is known regarding the genetic relationship and evolutionary history of different species within the genus. How modern chestnut plants have developed local adaptation to various climates remains a mystery. The genomic data showed that Castanea henryi first diverged in the Oligocene ~31.56 million years ago, followed by Castanea mollissima, and the divergence between Castanea seguinii and Castanea crenata occurred in the mid-Miocene. Over the last 5 million years, the population of chestnut plants has continued to decline. A combination of selective sweep and environmental association studies was applied to investigate the genomic basis of chestnut adaptation to different climates. Twenty-two candidate genes were associated with temperature and precipitation. We also revealed the molecular mechanism by which CmTOE1 interacts with CmZFP8 and CmGIS3 to promote the formation of non-glandular trichomes for adaptation to low temperature and high altitudes. We found a significant expansion of CER1 genes in Chinese chestnut (C. mollissima) and verified the CmERF48 regulation of CmCER1.6 adaptation to drought environments. These results shed light on the East Asian chestnut plants as a monophyletic group that had completed interspecific differentiation in the Miocene, and provided candidate genes for future studies on adaptation to climate change in nut trees.

[Current distribution of Schisandra chinensis in China and its predicted responses to climate change].

With integration of literature data, specimens records, and field surveys, the current distribution map of Schisandra chinensis in China was drawn, and, based on this map and considering 21 environmental factors, the future distribution of S. chinensis in China in the 2050s and 2080s under the IPCC A2 and A1B climate change scenarios was predicted by using Maxent software. Currently, the S. chinensis in China occurred in 15 provinces, involving 151 counties, and its distribution area decreased with decreasing latitude and longitude. The main distribution area included Heilongjiang, Liaoning, Inner Mongolia, and Jilin. The potential distribution area of S. chinensis in China was 145.12 x 10(4) km2, 48.6% of which were the favorable habitat area, mainly distributed in Changbai Mountains, Xiaoxing'anling Mountains, Daxing'anling Mountains, and the regions between Hebei and Liaoning provinces. The most favorable habitat area only accounted for 0.3%, and was mainly in the Kuandian Manchu Autonomous County, Benxi Manchu Autonomous County, and Huanren Manchu Autonomous County of Liaoning Province, the Antu County and Helong County of Jilin Province, and the Yakeshi City of Inner Mongolia. Under the two climate change scenarios, the potential future distribution area of S. chinensis in China would have a gradual decrease, and the decrement would be larger under A2 than under A1B scenario. By 2050, the distribution area of the S. chinensis under A1B and A2 scenarios would be moderately decreased to 84.0% and 81.5% of the current distribution area, respectively; by 2080, the distribution of S. chinensis under A2 scenario would be dramatically decreased to only 0.5% of the current range, and that under A1B scenario would be decreased to 1/2 of the current range.

Adaptive evolution in the GAF domain of phytochromes in gymnosperms.

The GAF domain of phytochrome is essential for photoconversion and signal transduction. In gymnosperms, it exists in all members of the phytochrome family that experience gene duplication. Maximum-likelihood models of codon substitution can provide a framework for constructing likelihood ratio tests of changes in selective pressure and make clear predictions about patterns of genetic change following gene duplication. In this study, 68 gymnosperm GAF sequences were analyzed to identify lineages and sites under positive selection. Our results indicate that (1) positive selection at a few sites (3.6%), rather than relaxation of selective constraints, has played a major role in the evolution of the gymnosperm GAF domain; (2) strong positive selective pressure tends to occur in the recent PHYP lineages of cogeneric species, but is absent in old lineages consisting of distantly related species; and (3) the selective pressure indicated by the omega ratio varies greatly among lineages and sites in the GAF domain.

Genetic diversity and population differentiation of chestnut blight fungus, Cryphonectria parasitica, in China as revealed by RAPD.

Seventeen Cryphonectria parasitica populations sampled from six regions in China were investigated using RAPD. Across all 169 isolates from the 17 populations evaluated, 52 of the 71 markers (73%) were polymorphic, total genetic diversity (h) was 0.1463, and Shannon's index was 0.2312. Diversity within populations accounted for 74% of total genetic diversity, and genetic differentiation among populations was 0.26 (G (ST) = 0.26). Gene flow was 1.4 among the populations; higher gene flow was found among populations within regions and among regions [N (m) (G (SR)) = 2.8 and N (m) (G (RT)) = 3.5]. The unweighted pair group mean analysis (UPGMA) dendrogram revealed two distinct clusters: the northern China group and the southern China group. The spatial autocorrelation analysis revealed that the variation at most loci was randomly distributed and lacked spatial structure, but several loci and closer distances were spatially structured. Human activity and habitat could also be important factors affecting genetic structure among C. parasitica populations in China. Genetic diversity was highest in Southwest China, descending in an orderly fashion to Northeast China. This pattern indicated that Southwest China might be the center of origin of C. parasitica in China. The present study provides useful information for understanding the origin and spread of chestnut blight fungus in China and valuable data for formulating relevant strategies for controlling the disease in China.

[Interspecific association between understory species in a southern highland plantation].

Based upon 2 x 2 contingency table, chi2 test and association coefficient were used to determine the interspecific association between understory species in a southern highland plantation, and to analyze the restoration degree and the stability of southern highland vegetations originated from plantation. The Qianyanzhou in Taihe County of Jiangxi Province, a typical sample of southern highland plantation, was chosen to make the study. The results showed that both in shrub layer and in herb layer, species pair with chi2 reaching significant level (P <0.05) was few in number. In shrub layer, 12 species pairs' association was highly significant (P < 0.01), 19 pairs' was significant (P < 0.05), and other 200 pairs' was nonsignificant, while in herb layer, 11 pairs' was highly significant, 11 pairs' was significant and other 83 pairs' was nonsignificant. According to interspecific association and correlation, shrub layer was divided into two species groups: Group I . Adinandra bockiana, Syzygiumn grijsii, Vaccinium bracteatunm, Ilex aculeolata, Smilax ferox, Eurya muricata and Group II . Lespedeza davidii, Serissa serissoides, Vitex negundo var. cannabifolia. Many species in Group I had a significantly negative association with the species in Group II, and dominant species always played a key role in the relationships among species. The three dominant species in herb layer, Wooduardia japonica, Dryopteris atrata and Adiantun flabellulaturn, had a highly significant positive correlation between each other, and moreover, had a significant or highly significant positive association with many other herbaceous species. Similarily, dominant species in shrub layer played a key role on the interspecific association in the two species groups. The ratios of positive and negative association indicating the species compositions of the two layers were fluctuating, which was 125/106 in shrub layer and 42/63 in herb layer. Several shortcomings of interspecific association method were pointed out, with some proposals put forward.