Study On Molecular Ecology Of Elaeagnus Mollis In Shanxi

Elaeagnus mollis is one of the larger shrubs and dwarf trees, being an endemic to China and one of the China protected two-grade rare and endangered plants. Because of the restriction of geographic factors, there are only two or three disjuncted populations distributed in the southwest of Shanxi. E. mollis is vulnerable to extinction because of its rarity, endangerment, and limited distribution. First, the morphology, physiology of seed, biological traits, geographic distribution, ecological and community characteristics, karyotypes, nitrogenase activity of root nodules and chemical constituents of E. mollis were reviewed, respectively. Second, the population genetic structure and genetic diversity of E. mollis were studied by using allozyme eletrophoresis and the electrophoretic data for 6 loci from 3 populations being Xiangning, Yicheng and Pinglu populations in Shanxi were got. The level of polymorphism was relatively higher than that of the insect- pollinated outcrossing species (He=0.375 ). The average number of alleles per locus (A), percentage polymorphic loci (P), observed heterozygosity (Ho) and Wright's fixation index (F) is 2.2, 77.9, 0.433, -0.138, respectively. The species also had higher variation than that of the other woody angiosperms widespread. Moreover, E. mollis has higher population genetic variation than that of 26 long-lived woody endemics with narrow geographic distributions.E. mollis had higher genetic diversity among populations, and the reason may be as follows:(1) Those populations are generally large and are not subject to significant loss of variation through small-population effects such as random genetic drift and inbreeding coupled with selection. (2) The mechanism of pollination off. mollis.(3) E. mollis is a long-lived species,(4) A feature of the flora in the southwest of Shanxi is its antiquity associated with prolonged geographical stability and no obvious extinction episodes caused by recent glaciations.Genetic divergence over all populations was very low (FsT=0.019). The result are not in line with the general finding of Hamrick and Godt (1989) that species with narrow geographic distributions show as much interpopulation divergence as geographically widespread species. The mechanism of pollination may influence the interpopulation divergence. The result of UPGMA suggests that Xiangning population was similar to Yicheng population and apart from Pinglu population. Gene flow estimates among populations were higher even though the minimum geographical distance between any pair of populations is over 60km and could be attributed to the activity of bee-pollinators locally. We show the reason of high gene flow (Nm=37) that it mayresult from the mechanism of pollination of E. mollis. It may be suggested that notall types of rarity have die same genetic implications from these results.Based on these results, the strategies for conservation E. mollis population to preventthe isolation and fragment of the populations and maintain the high genetic variationamong the populations. Moreover, it should be avoid the decline of gene flow wasresulted from the isolation of the populations so that resulted in the differentiationand genetic decline of the population. Finally, it should be adopt some method tospread continuous distribution and extend genetic diversity of the population.