Local adaptation to temperature and precipitation in naturally fragmented populations of Cephalotaxus oliveri, an endangered conifer endemic to China.

Cephalotaxus oliveri is an endangered tertiary relict conifer endemic to China. The species survives in a wide range from west to east with heterogeneous climatic conditions. Precipitation and temperature are main restrictive factors for distribution of C. oliveri. In order to comprehend the mechanism of adaptive evolution to climate variation, we employed ISSR markers to detect adaptive evolution loci, to identify the association between variation in temperature and precipitation and adaptive loci, and to investigate the genetic structure for 22 C. oliveri natural populations. In total, 14 outlier loci were identified, of which five were associated with temperature and precipitation. Among outlier loci, linkage disequilibrium (LD) was high (42.86%), which also provided strong evidence for selection. In addition, C. oliveri possessed high genetic variation (93.31%) and population differentiation, which may provide raw material to evolution and accelerate local adaptation, respectively. Ecological niche modeling showed that global warming will cause a shift for populations of C. oliveri from south to north with a shrinkage of southern areas. Our results contribute to understand the potential response of conifers to climatic changes, and provide new insights for conifer resource management and conservation strategies.

[Chemical properties and enzyme activities of rhizosphere and non-rhizosphere soils under six Chinese herbal medicines on Mt. Taibai of Qinling Mountains, Northwest China].

This paper studied the chemical properties and enzyme activities of rhizosphere and non-rhizosphere soils in different habitats of six Chinese herbal medicines, including Pyrola decorata, Cephalotaxus fortunei, Polygonatum odoratum, Potentilla glabra, Polygonum viviparum, and Potentilla fruticosa, on the Mt. Taibai of Qinling Mountains. In the rhizosphere soils of the herbs, the contents of soil organic matter, total nitrogen, available nitrogen, and available phosphorus and the soil cation exchange capacity (CEC) were higher, presenting an obvious rhizosphere aggregation, and the soil enzyme activities also showed an overall stronger characteristics, compared with those in non-rhizosphere soils. The soil organic matter, total nitrogen, and total phosphorus contents in the rhizosphere soils had significant positive correlations with soil neutral phosphatase activity, and the soil CEC had significant positive correlations with the activities of soil neutral phosphatase and acid phosphatase. In the non-rhizosphere soils, the soil organic matter and total nitrogen contents had significant positive correlations with the activities of soil urease, catalase and neutral phosphatase, and the soil CEC showed a significant positive correlation with the activities of soil urease, catalase, neutral phosphatase and acid phosphatase. The comprehensive fertility level of the rhizosphere soils was higher than that of the non-rhizosphere soils, and the rhizosphere and non-rhizosphere soils of P. fruticosa, P. viviparum, and P. glabra had higher comprehensive fertility level than those of P. decorata, P. odoratum and C. fortunei. In the evaluation of the fertility levels of rhizosphere and non-rhizosphere soils under the six Chinese herbal medicines, soil organic matter content and CEC played important roles, and soil neutral phosphatase could be the preferred soil enzyme indicator.