Yu-bao Gao

RAPD diversity of Stipa grandis populations and its relationship with some ecological factors

The genetic diversity of Stipa grandis P.Smirn and its relationship with the climatic variables were studied using the RAPD technique for 90 genes from five natural populations sampled in the Xilingol steppe, China. Sixteen oligonucleotides screened from 100 random primers were used to amplify 310 trackable RAPD loci, which were all polymorphic. By analyzing the RAPD data using POPGENE software, different geographic S. grandis populations were studied, which indicated a high level of genetic diversity, and the maximum variation was observed within the populations with a 28% variation observed among the populations. Using Pearson correlation analysis, significant (P < 0.05) or highly significant (P < 0.01) relationships were found between gene diversity indexes and temperature factors (≥10°C cumulative temperature in a year, annual mean temperature and mean temperature in January). Mantels tests showed that there was no significant correlation between Neis unbiased genetic distance and the geographic distance of S. grandis populations (r = 0.184, P = 0.261). However, there were significant or highly significant correlations between Neis genetic distance and the several climatic divergences in pairwise S. grandis populations. All results indicated that natural selection resulting from variations in water and temperature was responsible for the adaptive eco-geographical differentiation indicated by the RAPD markers of different S. grandis populations, and that immigration and gene drift did not play an important role in affecting the differentiation of S. grandis populations.

Genetic diversity and population differentiation of the dominant species Stipa krylovii in the Inner Mongolia Steppe.

Random amplified polymorphic DNA was used to assess the level of genetic diversity and genetic structure of Stipa krylovii (Gramineae), an important dominant species in the northern grasslands of China. Genetic diversity was low within S. krylovii populations, and diversity at the population level was associated with precipitation and cumulative temperature variations. There was much genetic differentiation among populations and among habitats as well. A Mantel test indicated no significant correlation between genetic distance and geographic distance of populations. A nonmetric multidimensional scaling analysis revealed some spatial relationships among the 90 individuals in a two-dimensional plot. Habitat fragmentation and degradation throughout the geographic range of S. krylovii could account for the low genetic diversity and high genetic differentiation of the species. Such information will be useful for conservation managers trying to plan an effective strategy to protect this important species.

Genetic variation among Stipa grandis P. Smirn populations with different durations of fencing in the Inner Mongolian Steppe

The genetic structure of a population should be carefully considered in ecological restoration because it may play a critical role in maintaining the persistence of a restored ecosystem. In the present study, we examined genetic diversity and genetic structure of Stipa grandis P. Smirn populations from fenced and grazed plots using amplified fragment length polymorphism markers. Molecular genetic variation showed that the genetic diversity of the fenced populations was greater compared with the overgrazed population. There was a significant variation among the populations (Fst = 0.3689, P < 0.001) by AMOVA analysis, and the gene flow was 0.4039 among the populations. The results from a comparison of limited morphological characteristics and from an unweighted pair group method with arithmetic mean cluster analysis and non-metric multi-dimensional scaling analysis suggested that genetic differentiation had occurred between the fenced populations and the grazed populations. The largest genetic diversity was in the moderately grazed population, which might be related to higher population density and greater sexual reproduction due to less disturbances in the plots. The genetic diversity of the long-term (24 years) fenced population was similar to that of a short-term fenced population (fenced for 11 years). These results suggested that the genetic diversity in the overgrazed population might be increased to some extent through fencing, but this effect did not occur beyond 11 years.

Ecophysiological response in leaves of Caragana microphylla to different soil phosphorus levels

Phosphorus (P) is one of the limiting mineral nutrient elements in the typical steppe of Inner Mongolia, China. In order to find out the adaptive strategy of Caragana microphylla to low soil P status, we grew plants in P-deficient soil in April 2009 and gave a gradient of P addition ranging from 0 to 60 mg(P) kg−1(soil) from May 2010. Leaf traits were measured in September 2010. Both leaf growth and light-saturated photosynthetic rate (Pmax) were similar among different groups. Leaf nitrogen (N):P ratio indicated that the growth of C. microphylla was not P-limited in most of the Inner Mongolia typical steppe, which had an average soil available P content equal to 3.61 mg kg−1. The optimal P addition was 20 mg(P) kg−1(soil) for two-year-old plants of C. microphylla. Leaf mass area (LMA) and leaf dry matter content (LDMC) were enhanced with low P, and significantly negatively correlated with photosynthetic N-use efficiency (PNUE). Photosynthetic P-use efficiency (PPUE) increased with decreasing soil P and increasing leaf inorganic P (Pi): organic P (Po) ratio, and showed no significant negative correlation with LMA or LDMC. Pmax of C. microphylla did not decline so sharply as it was anticipated. The reason for this phenomenon might be due to the increased PPUE through regulating the leaf total P allocation. C. microphylla had high P-use efficiency via both high PPUE and long P-retention time at low-P supply. The adaptation of C. microphylla to low-P supply provided a new explanation for the increased distribution of the species in the degraded natural grassland in Inner Mongolia, China.