Phylogenetic And Reproductive Studies Of Cyatheaceae In China

As the only relict tree-fern in Jurassic,Cyatheaceae has important significance in the evolution of woody ferns.This group has a unique form and has always been the focus of botanists and gardeners.They have extremely important research value and ornamental value.However,the fragmentation and loss of habitats make them endangered,but in the same living environment,the endangered degree of the Cyatheaceae is very different,and there has been much controversy in the classification and evolution of this group.In order to solve the phylogenetic problems of Cyatheaceae at the genus and species level in China,the differences between morphological and molecular studies of some species are explored,revealing the natural hybridization and evolution of species and the problems in reproduction.In this paper,through extensive sampling,GBS simplified genome sequencing technology was used to obtain SNP for phylogenetic tree construction and analysis of principal components,combined with genetic structures,and statistical analysis of morphological characteristics such as leaves,scales and spores,as well as,observation of spore development.The following results are obtained:1.The 200 samples of Cyatheaceae collected in this study were classified into three groups by phylogenetic tree analysis and principal component analysis,namely Sphaeropteris,Gymnosphaera and Alsophila.At the same time,the morphological observation and statistical analysis show that each of the three groups has unique and highly recognizable features.2.The natural hybridization phenomenon of Cyatheaceae in China is very common,and the purebred species is less than 1/2 of the total number.The Gymnosphaera austro-yunnanensis and the Alsophila costularis are interspecific hybrid species.The difference in the morphology and molecular research of G.austro-yunnanensis is caused by hybridization.The largest proportion of genetic material is G.podophylla,followed by the species of Alsophila.And there are also different ratios of G.gigantea and G.denticulata introgression in different samples.3.Both G.metteniana var.subglabra and G.metteniana are hybrids of G.giganteaand G.denticulata.They are difficult to separate in genetic analysis,but the morphological features such as small pinnas and spores have significant differences,reaching the conditions of the morphological species concept and should be restored.4.Gymnosphaera andersonii has a significant difference in leaf morphology from G.gigantea,but in the analysis of molecular phylogeny,the genetic difference between G.andersonii and G.gigantea is lower,and Structure analysis shows that there is a gene flow from unknown species in G.andersonii samples,thus expanding its genetic difference from G.gigantea.At the same time,this unknown gene flow appears in G.metteniana samples with diverse degrees.This gene is possibly related to genes regulating the morphology of pinna and the spores of G.metteniana var.subglabra,and this unknown species may be an extinct ancient plant.5.The Sphaeropteris brunoniana samples collected from Hainan and Yunnan have two different genotypes,and there are significant differences in the three leaf traits of the logarithm of the split,the aspect ratio of the small feathers and the logarithm of the veins.Geographical segregation has resulted in the species differentiation of S.hainanensis,which are significantly different from the oranges in both niche and genotypes,satisfying the conditions of ecological and genetic species concepts,so the status of S.hainanensis should be restored.6.The spores of the hybrid G.metteniana and A.costularis collected in the wild is able to germinate and grow normally,which proves that the hybridization events in the Cyatheaceae occur earlier,so that the hybrid progeny have become stable and inheritable species.In addition,there are still hybrid offspring that are constantly appearing.Three samples of Alsophila are hybrids of A.spinulosa and A.latebrosa.Whether these samples are F1 or have formed fertile and heritable hybrids still require further in-depth research.