| Genetic diversity is the foundation and core of biological diversity, study on geneticdiversity is critical for the understanding of evolutionary history (the origin of themanner and time) of species or populations, it can also provide insights for theevolutionary potential and future destiny and important data for its protection strategy.Natural hybridization is an important evolutionary mechanism of angiosperms, whichis the hot topic in the plant evolutionary biology today. The research of the relativefitness of hybrids and their parents of the hybrid zone which formed from twosympatric species'hybridization is significant to the maintenance mechanism and theevolutionary dynamics of the hybrid zone. Hippophae, the pioneer species ofcommunity succession, has important ecological and economic value, which presenthigh genetic diversity and great clone reproduction, its clone reproduction maybe hasan important influence on the fitness of hybrids (H. goniocarpa ssp.goniocarpa) andparents(H. rhamnoides ssp. sinensis and H. neurocarpa ssp.neurocarpa). In presentstudy, the variation of fruit characteristics of 7 populations both of the H. tibetana andH. neurocarpa ssp.neurocarpa, which are the endemic species of Hippophae in thehigh altitude area of Qinghai-Tibet Plateau and Himalayas, were analyzed statisticallyin order to study their variation level and geographic variation patterns, and thegenetic variance of 11 populations of H. neurocarpa ssp.neurocarpa were analyzedstatistically using ISSR marker in order to study their variation level and adaptationpatterns to the alpine environment, meanwhile the clone fitness of hybrids and theirparents on the hybrid zone of Gongbaiwan and Babaohetan in Qilian County ofQinghai Province, were compared using ISSR marker in order to provide evidence tothe maintenance mechanism of hybrid zone in Hippophae. The main results andconclusions are as follows:1. There were great diversities in the fruit characters of H. tibetana, The resultsshowed that very significant variation existed among and within populations(p<0.01)of the 5 fruit characters, except the fruit ornamentation length amongpopulations(p<0.05). Coefficient of variation(CV) ranged between 11.19% and45.03%, the length of fruit stalk presented the greatest variation (CV was 45.03%), thefollowing was fruit ornamentation length (CV was 31.97%), and fruit width presented the least variation(CV was 11.19%). Phenotypic differentiation coefficients ofvariation (Vst) ranged from 0.2133 to 0.6299 and the mean of it was 0.4895. Both ofthe variation among and within populations accounted for a half of the fruit variation.Breeding system, geographic isolation, and gene flow influenced the phenotypicdifferentiation of H. tibetana. Correlations analysis indicated that there were verysignificant correlations among the fruit characteristics (p<0.01) except the fruit lengthand the length of fruit stalk, fruit width and fruit ornamentation length. There werealso very significant correlations between characteristics and geographical factors(p<0.01) except fruit length and altitude, fruit width and latitude and longitude. Somefruit characteristics showed geographic variation gradient. Cluster analysis indicatedthat 7 populations clustered according to the geographical distance.2. There were great diversities in the fruit characters of H. neurocarpa ssp.neurocarpa.The results showed that very significant variation existed among and withinpopulations (p<0.01) of the 4 fruit characters , Coefficient of variation(CV) rangedbetween 11.75% and 61.82%, the length of fruit stalk presented the greatest variation(CV was 61.82%), the following were indexes of fruit shape(CV was 18.22%) andfruit width(CV was 17.96%), and fruit length presented the least variation(CV was11.75%). Phenotypic differentiation coefficients of variation (Vst) ranged from 0.3280to 0.7179 and the mean of it was 0.4710.The variation among populations accountedfor 47.1% of the phenotypic variation, which meant the variation among populationswas only slightly less than variation within populations, and the phenotypicdifferentiation of H. neurocarpa ssp.neurocarpa influenced by breeding system,geographic isolation, and gene flow. Correlations analysis indicated that there werevery significant correlations among the fruit length and fruit width and indexes offruit shape(p<0.01). There was significant correlation between fruit length and thelength of fruit stalk. There were also very significant correlations between fruit widthand the length of fruit stalk and latitude and longitude(p<0.01), and significantcorrelations between the length of fruit stalk and longitude(p<0.05).3. 179 polymorphic bands of total 183 bands were generated from 181 individuals of11 populations of H. neurocarpa ssp.neurocarpa using 11 ISSR primers. Atsubspecies level, the percentage of polymorphic bands (PPB) was 97.81%, Nei's gene diversity(h) was 0.2830 and Shannon's index(I) was 0.4326. At population level threeindexes (PPB , h , I) were 56.78%, 0.2096 and 0.3109, respectively. Both subspeciesand population level indicated great genetic diversity of H. neurocarpa ssp.neurocarpa. Coefficient of gene differentiation(Gst)was 0.2181 from POPGENE,slightly higher than the mean value of outcrossing plant, showed that most of thevariation existed within populations. And this conformed to the breedingcharacteristics of Hippophae . There was some gene flow among populations(Nm=1.4275) . Nm of H. neurocarpa ssp. neurocarpa is far lower than the mean ofother wind-pollinated, outcrossing long-lived woody plants. Mental tests amonggenetic distances and geographic distances and altitude distances of 11 populationindicated that existed very positive significant correlations between genetic distancesand geographic distances(r=0.48540,p=0.0005<0.01)and negative significantcorrelations between genetic distances and altitude distances(r= -0.40155,0.01<p=0.0230<0.05). Coefficient of gene differentiation of 4 subpopulations ofpopulation N89B indicated small-scale genetic differentiation still strong (Gst =0.1768).4. Comparison of clone fitness was made between hybrids (H. goniocarpassp.goniocarpa) and their parents (H. rhamnoides ssp. sinensis and H. neurocarpassp.neurocarpa) of Gongbaiwan and Babaohetan hybrid zones using 12 ISSR primers.The results showed high clone diversity of hybrids and their parents of 2 hybridzones(N/G=1.0606～1.3464,PD=0.8800～0.9600,D=0.9867～0.9967), and the clonereproduction was low(the number of clones in each population was 1-3 ). Extensioncapacity of ramets was slightly different between hybrids and their parents of 2 hybridzones. Extension capacity of hybrids ramets was higher than their parents inGongbaiwan hybrid zone, however, the Babaohetan's situations in the opposite,andhybrids ramets'extension capacity was far lower than their parents, indicated that thehybrid and parental fitness of the clonal reproduction existed certain differences. And trade-offbetween sexual and clonal reproduction had a certain extent . Environment had acertain influence on clone reproduction of hybrids and their parents. As very fewramets were found using ISSR marker, these laws were going to be verified by othermarkers, such as co-dominant markers SSR, AFLP, etc. |
PDF Full Text Request