Development and Application of Genomic Resources in an Endangered Palaeoendemic Tree, Parrotia subaequalis (Hamamelidaceae) From Eastern China.

Parrotia subaequalis is an endangered palaeoendemic tree from disjunct montane sites in eastern China. Due to the lack of effective genomic resources, the genetic diversity and population structure of this endangered species are not clearly understood. In this study, we conducted paired-end shotgun sequencing (2 × 125 bp) of genomic DNA for two individuals of P. subaequalis on the Illumina HiSeq platform. Based on the resulting sequences, we have successfully assembled the complete chloroplast genome of P. subaequalis, as well as identified the polymorphic chloroplast microsatellites (cpSSRs), nuclear microsatellites (nSSRs) and mutational hotspots of chloroplast. Ten polymorphic cpSSR loci and 12 polymorphic nSSR loci were used to genotype 96 individuals of P. subaequalis from six populations to estimate genetic diversity and population structure. Our results revealed that P. subaequalis exhibited abundant genetic diversity (e.g., cpSSRs: Hcp = 0.862; nSSRs: HT = 0.559) and high genetic differentiation (e.g., cpSSRs: RST = 0.652; nSSRs: RST = 0.331), and characterized by a low pollen-to-seed migration ratio (r ≈ 1.78). These genetic patterns are attributable to its long evolutionary histories and low levels of contemporary inter-population gene flow by pollen and seed. In addition, lack of isolation-by-distance pattern and strong population genetic structuring in both marker systems, suggests that long-term isolation and/or habitat fragmentation as well as genetic drift may have also contributed to the geographic differentiation of P. subaequalis. Therefore, long-term habitat protection is the most important methods to prevent further loss of genetic variation and a decrease in effective population size. Furthermore, both cpSSRs and nSSRs revealed that P. subaequalis populations consisted of three genetic clusters, which should be considered as separated conservation units.

Microsatellite markers for the critically endangered elm species Ulmus gaussenii (Ulmaceae).

The Anhui elm Ulmus gaussenii is listed as a critically endangered species by the International Union for Conservation of Nature and is endemic to China, where its only population is restricted to Langya Mountain in Chuzhou, Anhui Province. To better understand the population genetics of U. gaussenii, we developed 12 microsatellite markers using an improved technique. The 12 markers were polymorphic, with the number of alleles per locus ranging from two to nine. Observed and expected heterozygosities ranged from 0.021 to 0.750 and 0.225 to 0.744, respectively. The inbreeding coefficient ranged from -0.157 to 0.960. Significant linkage disequilibrium was detected for two pairs of loci, and significant deviations from Hardy-Weinberg equilibrium were found in nine loci. These microsatellite markers will contribute to the studies of population genetics in U. gaussenii, which in turn will contribute to species conservation and protection.

Development and characterization of polymorphic microsatellite markers (SSRs) for an endemic plant, Pseudolarix amabilis (Nelson) Rehd. (Pinaceae).

Pseudolarix (Pinaceae) is a vulnerable (sensu IUCN) monotypic genus restricted to southeastern China. To better understand levels of genetic diversity, population structure and gene flow among populations of P. amabilis, we developed five compound SSR markers and ten novel polymorphic expressed sequence tags (EST) derived microsatellites. The results showed that all 15 loci were polymorphic with the number of alleles per locus ranging from two to seven. The expected and observed heterozygosities varied from 0.169 to 0.752, and 0.000 to 1.000, respectively. The inbreeding coefficient ranged from -0.833 to 1.000. These markers will contribute to research on genetic diversity and population genetic structure of P. amabilis, which in turn will contribute to the species conservation.

Species and biogeochemical cycles of organic phosphorus in sediments from a river with different aquatic plants located in Huaihe River Watershed, China.

The results of phosphorus fractionation in the sediments from a contaminated river containing different aquatic plants, analyzed by solution 31P-NMR for Organic Phosphorus, showed that the concentration of Inorganic Phosphorus dominated in all species and Organic Phosphorus accounted for over 20% of Total Phosphorus. In general, orthophosphate was dominant in all the sampling sites. The proportion of Organic Phosphorus accounting for the Total Phosphorus in the sediments with different plant decreased in the following order: Paspalum distichum>Typha orientalis>Hydrilla verticillata. Phosphorus-accumulation ability of Paspalum distichum was obviously stronger than Typha orientalis and Hydrilla verticillata. The Organic Phosphorus was in aquatic plants dominated by humic-associated P (Hu-P), which converted to Inorganic Ohosphorus more significantly in submerged plants than in emerged plants. The sediment dominated by Paspalum distichum abundantly accumulated Organic Phosphorus in the orthophosphate monoester fraction. The degradation and mineralization of orthophosphate monoester was the important source of high Inorganic Phosphorus concentration and net primary productivity in Suoxu River. The Organic Phosphorus derived from Typha orientalis and Hydrilla verticillata was dramatically converted to Inorganic Phosphorus when the environmental factors varied.