Homoploid Hybrid Origin Of Hippophae Goniocarpa Subsp.Goniocarpa

The homoploid hybrid origin prevailed in plant kingdom, but they were very difficult to identify traditionally, and now it becomes the research hot in ecology and evolutionary biology. In order to test the hypothesis that Hippophae goniocarpa subsp. goniocarpa is the homoploid hybrid between H. rhamnoides subsip.sinensis and H. neurocarpa subsp. neurocarpa and detect the direction of gene introgression in process of hybrid origin of the Qinghai Qilian natural population, 6 species 10 taxon of the genus Hippophae, including 2 of Qinghai Qilian population and 2 of the putative parent that one is sympatric and another is allopatric were selected , and two methods that could convince the hybrid hypothesis were performed, which one is based on the hybrid behave on phylogenetic trees and the other is the incongruence between gene trees, both of them come from the molecular phylogenetic analysis using genes from two different genomes (chloroplast - maternal, nuclear - biparental).1 Chloroplast DNA analyses1.1 trnL-FThe sequence of trnL-F in the genus was relatively conservative, its length after alignment is 868bp, and there are 22 information sites in it. 11 strict consensus of most parsimonious trees were detected with PAUP*4.0 when exclude two putative hybrid individuals, H. salicifolia was the basal lineage in cladogram, and the tree was apparently divided into two branches, that one was S-branch which included H. rhamnoides subsp. sinensis and its close relative subspecies, the other was N-branch which included H. neurocarpa subsp.neurocarpa and so on. 15 trees were obtained and the topological structure of cladogram had little difference, when two putative hybrid individuals were involved in analysis, which were placed in two branchs as the sister taxon of sympatric H. rhamnoides subsp. sinensis and H. neurocarpa subsp. neurocarpa respectively. 1.2 trnS-GThe variation of trnS-G was rather large, and the length after alignment was 711 bp, which had 41 information sites. 69 trees were detected without hybrid individuals in analysis and 131 trees were obtained and the topological structure ofcladogram had no change with two hybrid individuals in analysis, and they performed the same behave as in trnL-F, but both of the cladogram showed the genus was polyphyly that may not be the true. Additionally, trnS-G sequence analysis indicated that H. salicifolia had been derived from the genus Elaeagnus with a simple repeat of 40bp motif.In a word, the result of chloroplast DNA analyses of the genus implied that there was little impact of topological structure of gene trees when H. goniocarpa subsp. Goniocarpa was in analysis, but its two individuals had different position in cladogrm strongly supported the hypothesis of its hybrid origin and suggested there was bidirectional gene introgression during the process.2 Nuclear ncpGS gene analysis2.1 ncpGS gene phylogenetic analysisAfter alignment, the sequence length of ncpGS gene in the genus was 677bp, which included 13 information sites. 15 trees were detected without putative hybrid in analysis, the tree was directly divided into two branches, one liked S-branch which included H. tibetana^ H.rhamnoides svfosp.sinensis and its close relative subspecies, the other was like N-branch which included H.salicifolia> H. neurocarpa subsp. neurocarpa and so on. With one putative hybrid individual in analysis, 32 trees were obtained, and the position of putative hybrid was not in S-branch as the sister taxon of H. rhamnoides subsp. Sinensis as in trnL-F tree, it was placed in N-branch as its basal lineage.Especially, PCR-sequencing signal of putative hybrid individual was disorder, and the overlap peaks were serious in many sites. It implied that there were heterozygous alleles in genome and it was necessary to take a further measure of clone sequencing.2.2 Clone sequencing and analysis of hybrid ncpGS geneThere were 8 sequences available after molecular clone of one hybrid individual ncpGS gene, which were sorted into two kinds of haplotype after cluster analysis, both of them were homozygou...