Tianhua He

Ex situ genetic conservation of endangered Vatica guangxiensis (Dipterocarpaceae) in China

RAPD polymorphisms were applied to check the efficiency of ex situ genetic conservation of endangered Vatica guangxiensis X. L. Mo. endemic to southwestern China. Low level of genetic variation was revealed in three remaining natural populations. Twenty random primers, each with 10 base pairs, generated 231 bands with 53.68% being polymorphic, and with an average of 32.46% being polymorphic in each natural population. Strong Population differentiation was revealed by AMOVA (analysis of molecular variance) and Gst value was 0.3764. The population ML ex situ conserved in the Xishuangbanna Tropical Botanical Garden contained an intermediate genetic variation compared with natural Populations. with 30.74% bands being polymorphic. Of the total 231 bands generated in V. guangxiensis, 204 bands were also detected in population M L, indicating that 88.31% of the total genetic variations of this species were conserved in ex situ population. If only the alleles with moderate to high frequency (P>0.05) were considered, 204 out of 209 bands (97.61%) occurred in ex situ population M L. RAPD analysis also detected one exclusive band in natural population NS, and five in natural population NP, three of these exclusive bands were generated in every samples of natural population (NP), and other three had moderate to high frequencies. While none of these exclusive bands were detected in ex situ conserved population ML. Our conclusions Lire that the ex situ conserved population ML contains representative genetic variation to maintain long-term survival and evolutionary process of V. guangxiensis, and that more extensive ex situ sampling in natural population NS and NP is needed to conserve more exclusive alleles in ex situ population. The tropical area in the Botanical Garden would play a more important role in the ex situ conservation of rare and endangered plants

Genetic spatial clustering : significant implications for conservation of wild soybean (Glycine soja: Fabaceae)

Knowledge of spatial patterns of genetic variation within populations of wild relative species has significant implications with respect to sampling strategies for exxa0situ and inxa0situ conservation. To study spatial genetic structure of wild soybean (Glycinexa0soja Sieb. et Zucc.) at the fine scale, three natural populations in northern China were analyzed using inter-simple sequence repeat (ISSR) fingerprints for estimating kinship coefficients. A regression analysis of kinship coefficients against spatial distances revealed that individuals occurring close together tended to be more genetically related. The Sp statistic further indicated a comparable spatial pattern among the three wild soybean populations with similar Sp values (mean = 0.0734, varied from 0.0645 to 0.0943) detected across the three populations. Genetic patches were on average ca. 20xa0m in size, and the effective neighborhood sizes varied between 10 and 15xa0m. The spatial genetic structure evident in the wild soybean populations may be attributed to the restricted seed dispersal and predominant inbreeding mating system of this species. The detection of family structure in the populations of wild soybean has a significant implication for the effective conservation of the important genetic resources.

Genetic evaluation of the efficacy of in situ and ex situ conservation of Parashorea chinensis (Dipterocarpaceae) in southwestern China

The majority of research in genetic diversity yields recommendations rather than actual conservation achievements. We assessed the efficacy of actual in situ and ex situ efforts to conserve Parashorea chinensis (Dipterocarpaceae) against the background of the geographic pattern of genetic variation of this species. Samples from seven natural populations, including three in a nature reserve, and one ex situ conservation population were studied. Across the natural populations, 47.8% of RAPD loci were polymorphic; only 20.8% on average varied at the population level. Mean population genetic diversity was 0.787 within natural populations and 1.410 for the whole species. Significant genetic differentiation among regions and isolation by distance were present on larger scales (among regions). AMOVA revealed that the majority of the among-population variation occurred among regions rather than among populations within regions. Regression analysis, Mantel test, principal coordinates analysis, and cluster analysis consistently demonstrated increasing genetic isolation with increasing geographic distance. Genetic differentiation within the region was quite low compared to that among regions. Multilocus spatial autocorrelation analysis of these three populations revealed random distribution of genetic variation in two populations, but genetic clustering was detected in the third population. The ex situ conserved population contained a medium level of genetic variation compared with the seven natural populations; it contained 77.1% of the total genetic variation of this species and 91% of the moderate to high frequency RAPD fragments (f > 0.05). Exclusive bands were detected in natural populations, but none were found in the ex situ conserved population. The populations protected in the nature reserve contained most of the genetic variation of the whole species, with 81.4% of the total genetic variation and 95.7% of the fragments with moderate to high frequency (f > 0.05) of this species conserved. The results show that the ex situ conserved population does not contain enough genetic variation to meet the need of release in the future, and that more extensive ex situ sampling in natural populations TY, NP, HK, and MG is needed. The in situ conserved population contains representative genetic variation to maintain long-term survival and evolutionary processes of P. chinensis.

Mating System of Ophiopogon xylorrhizus (Liliaceae), an Endangered Species in Southwest China

The mating system of Ophiopogon xylorrhizus Wang et Dai was studied in three natural populations with allozyme electrophoresis. The outcrossing rate was estimated by assaying eight enzyme loci. A mixed mating system model was used, and outcrossing rates were estimated for populations and families. The multilocus outcrossing rates in three populations were 0.467, 0.323, and 0.091. The extent of outcrossing in populations depended on the plant density (r = 0.9998; P < 0.02; df = 1). The frequency distribution of family outcrossing rates was slightly bimodal. A mixed mating system with considerable complete selfing and complete outcrossing was found in this species. Positive correlations were observed between family outcrossing rate and maternal heterozygosity (r = 0.70-0.98) and between family outcrossing rate and fecundity (r = 0.971; P < 0.0005; df = 7). Inbreeding depression was examined in populations P3 and P4, both of which had high outcrossing rates. Inbreeding depression was expressed mainly in seed production. Mating system pattern contributed to the high genetic variation in this species. Because of high inbreeding depression and habitat destruction, this species is threatened with extinction. Conservation in situ by protecting the habitat is the best way to conserve this species.

Generic relationships of Parashorea chinensis Wang Hsie (Dipterocarpaceae) based on cpDNA sequences

The systematic position of Parashorea chinensis (Dipterocarpaceae) was investigated by using maximum parsimony analysis of nucleotide sequences of matK, trnL intron, and trnL-trnF intergenic spacer region of chloroplast DNA. Previous studies have placed the taxon in Parashorea or Shorea. Analyses indicate that P. chinensis belongs within Parashorea (80% bootstrap) rather than within Shorea. Furthermore, P chinensis Wang Hsie and P. chinensis Wang Hsie var. kwangsiensis Lin Chi are further confirmed to be the same taxon.

Genetic Evaluation of in situ Conserved and Reintroduced Populations of Wild Rice (Oryza rufipogon: Poaceae) in China

We evaluated the genetic consequences and efficiency of conservation practices in Oryza rufipogon using microsatellite DNA markers. Spatial autocorrelation analysis from 12 microsatellite loci revealed that microsatellite alleles were exclusively distributed in patches within the population, indicating that large populations were unlikely to be homogeneous. An in situ conserved stand of O. rufipogon, which has been protected by a concrete wall from a large population, captured only 67.9% of the total genetic variation of the previous large population. The concrete wall was built to protect the wild rice, but it acted more as a physical barrier to gene exchanges between the two sides. An assignment test revealed only 11.1% putative seed exchanges across the wall. A reintroduced population was found to be genetically very diverse. About 76.3% of the total genetic variation detected in other populations was captured in this reintroduced population, and 24.8% of the total genetic variation in this population was not found in other populations. These results display two important findings for conservation of O. rufipogon. First, conserving one part of a large population of O. rufipogon will not preserve an adequate sample of the genetic variability, since populations are not homogeneous, and genotype distribution varies among localities. Second, a reintroduced population is not genetically depauperate, but it is too early to assess its long-term survival.

Note: Genetic Structure and Heterozygosity Variation Between Generations of Ophiopogon xylorrhizus (Liliaceae s.l.), an Endemic Species in Yunnan, Southwest China

Inbreeding depression and evolution of mating systems have been well discussed in the literature (Lande and Schemske, 1985; Schemske and Lande, 1985; Wolfe, 1993; Holsinger, 1988; Carr and Dudash, 1996). These studies all have a common assumption, i.e., homozygosity can cause deleterious recessive or partially recessive lethal alleles to show their effects on the phenotype, so heterozygotes are always more fit than homozygotes (Holtsford, 1996). This implies that inbreeding depression results from inbreeding and excessive homozygotes. Estimates of inbreeding depression usually depend on the fitness differences between selfed and outcrossed progeny. However, inbreeding depression has been generally underestimated, because it is difficult to measure at all possible stages of the life cycle (Charlesworth and Charlesworth, 1987). If inbreeding depression occurred in a species, it would lead to changes of homozygote frequency between seed populations and maternal populations or adult populations. The variation of homozygote frequency between generations may be a better parameter to describe inbreeding depression. Ophiopogon xylorrhizus Wang et Dai is a herbaceous perennial, endemic to Mengla County, Yunnan Province, Southwest China. Fewer than 1500 individuals located in eight disjunct populations cover an area of ca. 30× 20 km2 and the