title: Indehiscent sporangia enable the accumulation of local fern diversity at the Qinghai-Tibetan Plateau.
abstract: BACKGROUND
  Indehiscent sporangia are reported for only a few of derived leptosporangiate ferns. Their evolution has been likely caused by conditions in which promotion of self-fertilization is an evolutionary advantageous strategy such as the colonization of isolated regions and responds to stressful habitat conditions. The Lepisorus clathratus complex provides the opportunity to test this hypothesis because these derived ferns include specimens with regular dehiscent and irregular indehiscent sporangia. The latter occurs preferably in well-defined regions in the Himalaya. Previous studies have shown evidence for multiple origins of indehiscent sporangia and the persistence of populations with indehiscent sporangia at extreme altitudinal ranges of the Qinghai-Tibetan Plateau (QTP).
  
  
  RESULTS
  Independent phylogenetic relationships reconstructed using DNA sequences of the uniparentally inherited chloroplast genome and two low-copy nuclear genes confirmed the hypothesis of multiple origins of indehiscent sporangia and the restriction of particular haplotypes to indehiscent sporangia populations in the Lhasa and Nyingchi regions of the QTP. In contrast, the Hengduan Mountains were characterized by high haplotype diversity and the occurrence of accessions with and without indehiscent sporangia. Evidence was found for polyploidy and reticulate evolution in this complex. The putative case of chloroplast capture in the Nyingchi populations provided further evidence for the promotion of isolated but persistent populations by indehiscent sporangia.
  
  
  CONCLUSIONS
  The presented results confirmed the hypothesis that indehiscent sporangia promote the establishment of persistent population in different regions of the QTP. These results are consistent with the expectations of reproductive reassurance by promotion of self-fertilization that played a critical role in the assembly of populations in isolated locations and/or extreme habitats.
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Harald
authors.initials: H
authors.lastname: Schneider
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Wu
authors.forename: Lijuan
authors.initials: L
authors.lastname: He
authors.forename: Xianchun
authors.initials: X
authors.lastname: Zhang
authors.forename: Qiaoping
authors.initials: Q
authors.lastname: Xiang
mesh_terms: D000531:Altitude; D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D029624:Ferns / Q000145:classification / Q000235:genetics* / Q000502:physiology; D014644:Genetic Variation; D005828:Genetics, Population; D054628:Genome, Chloroplast / Q000235:genetics; D005843:Geography; D006239:Haplotypes; D008969:Molecular Sequence Data; D010802:Phylogeny; D057945:Self-Fertilization; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D058432:Sporangia / Q000235:genetics* / Q000502:physiology; D018609:Tibet
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant