Kunio Iwatsuki

A TAXONOMIC REVISION OF HYMENOPHYLLACEAE

SUMMARY A new classification of Hymenophyllaceae, consisting of nine genera (Hymenophyllum, Didymoglossum, Crepidomanes, Polyphlebium, Vandenboschia, Abrodictyum, Trichomanes, Cephalomanes and Callistopteris) is proposed. Every genus, subgenus and section chiefly corresponds to the mono phyletic group elucidated in molecular phylogenetic analyses based on chloroplast sequences. Brief descriptions and keys to the higher taxa are given, and their representative members are enumerated, including some new combinations.

Phylogeny of gymnosperms inferred fromrbcL gene sequences

Partial nucleotide sequences of the large subunit of ribulose-1,5-bisphosphate carboxylase (rubisco) gene (1333 base pairs: about 90% of the gene) from several seed plants were determined. Phylogenetic trees based on amino acid sequences were inferred by using the neighbor joining and maximum likelihood methods. The results indicate (1) monophyly of gnetum group (Ephedra, Gnetum, Welwitschia), (2) monophyly of extant gymnosperms containing gnetum group, which contradicts the results of morphological data.

Phylogenetic relationships in gnetophyta deduced fromrbcL gene sequences

Part of the large subunit of the ribulose-1,5-bisphosphate carboxylase gene (rbcL) was sequenced (1333 base pairs) from three species of gymnosperms:Ephedra sinica Gnetum parvifolium, Welwitschia mirabilis. Phylogenetic trees inferred from the neighbor joining, Wagner parsimony and maximum likelihood methods showed thatGnetum andWelwitschia were more closely related to each other than either is toEphedra within Gnetophyta, and the result supports previous cladistical analysis of morphological data.

Cytotaxonomic study of ferns of Yunnan, southwestern China

A cytotaxonomic study was made of 90 fern species of Yunnan, southwestern China, based on collections from northwestern, central, and southwestern Yunnan and a few Chengs collections. The results verified most of the formerly reported basic chromosome numbers of Chinese genera, and recorded for the first time the basic numbers ofGymnogrammitis andSorolepidium and Chinese members of several other genera. Cytotaxonomy of some problematical genera was discussed. Biogeographical relationships between Japanese, Chinese, and Himalayan ferns were compared with special reference to local cyto-reproductive variations inConiogramme, Deparia, Onychium, andPteris cretica. The present evidence indicates that most triploid species examined are agamosporous, as general in filicalean ferns, and also suggests the sexual 32-spored sporogenesis inHypodematium crenatum andSorolepidium graciale as in Lindsaeaceae.

Chloroplast DNA from Adiantum capillus-veneris L., a fern species (Adiantaceae); clone bank, physical map and unusual gene localization in comparison with angiosperm chloroplast DNA

SummaryWe cloned all of Adiantum capillus-veneris chloroplast DNA PstI fragments longer than 1.0 kb, which cover 98% of the genome. These cloned fragments were used to construct a physical map for five restriction enzymes. The genome of A. capillus-veneris is approximately 153 kb long and contains a 24 kb inverted repeat. Mapping of 12 chloroplast DNA genes and heterologous hybridization, involving A. capillus-veneris chloroplast DNA and angiosperm chloroplast DNA probes, demonstrated that chloroplast DNA of A. capillus-veneris has a different gene order from typical angiosperm cpDNA (e.g., tobacco) in the inverted repeat region and the flanking segment of the large single copy region.

Diploid and triploid offspring of triploid agamosporous fern Dryopteris pacifica

A cytological and reproductive study of the diploid and triploid agamosporousDryopteris pacifica was made to elucidate the origin of its infraspecific cytotypes. Some triploids produced 16 spore mother cells (SMCs) sometimes with n=41II+41I chromosomes, in addition to eight SMCs with n=123II, in each sporangium. In the former case the 16 SMCs usually underwent abnormal meiosis to give rise to some 50 spores, some of which were regular-shaped; in the latter the eight SMCs multiplied into 32 spores by normal meiosis. We found that spores from one of the triploid plants developed into either diploid or triploid gametophytes, which further apogamously produced diploid or triploid sporophytes, respectively. This novel mechanism of ploidy reduction is discussed in relation to the origin of diploid agamosporous ferns, the taxonomic complexity of the species, and the correlation of agamospory with polyploidy. The mechanism is also compared to that operating in agamospermous angiosperms.

Genetic variation in the ‘Japanese apogamous form’ of the fernAsplenium unilaterale Lam.

Genetic variation was examined in the Japanese apogamous and sexual forms ofAsplenium unilaterale by electrophoretic analysis of eight enzyme systems. The apogamous form consisted of four biotypes (A, B, C, and D) which show different band patterns. Biotypes C and D were distinguished from biotype A by a difference at only one locus each:Mdh-1 andPgi-2, respectively. Biotypes A, C, and D were sufficiently differentiated from the sexual form (Neis genetic distance (D)=0.50). This suggests that the apogamous form is not directly derived from the sexual form. However, biotype B expressed the combined band pattern of biotype C and the sexual form, leading to the conclusion that biotype B probably originated by hybridization between those two.

Genetic variation in agamosporous fern Pteris cretica L. in Japan

The genetic variation of an agamosporous fern, Pteris cretica L., was examined by enzyme electrophoresis. Five diploid and six triploid clones were distinguished by differences at five polymorphic enzyme loci. Among the triploids, four clones were characterized by two alleles, Hkd and Pgi-2a, which were not found in either the 2x clones or the two other 3x clones.These two alleles, Hkd and Pgi-2a were also found in diploid sexual relative of P. cretica, P. kidoi. This evidence suggests that the 3x clones with these alleles originated through fertilisation of reduced eggs of P. kidoi by unreduced spermatozoids of 2x clones P. cretica and three different 2x clones of P. cretica appear to have participated in crosses with P. kidoi to produce 33 clones. Thus recurrent hybridizations contribute toward generating genetic variation among agamosporous species, P. cretica.

Gene localization on the chloroplast DNA of the maiden hair fern;Adiantum capillus-veneris

Gene maps were constructed for the inverted repeat region and for the adjacent large single copy region of the chloroplast genome of the maiden hair fern,Adiantum capillus-veneris L. Gene order and organization was very different from the typical angiosperm chloroplast genome (e.g. tobacco). Elongation of inverted repeat and a minimum of two inversions must be postulated to account for the unusual genome structure.

Electrophoretic variation of the apogamousDryopteris varia group (Dryopteridaceae)

A total of 35 electrophoretic variants were detected in four apogamous species of theDryopteris varia group: 14 variants inD. bissetiana triploids, 7 inD. sacrosancta triploids, 6 inD. varia triploids, 3 inD. pacifica triploids, and 5 in apogamous diploids. The variants differed from each other in various combinations of a few alleles which were common in some of the variants, suggesting recurrent origin.Dryopteris insularis var.insularis (2x) and var.chichisimensis (3x), other members of the group, were electrophoretically monomorphic, suggesting single origin. Banding patterns infer that triploids ofD. bissetiana andD. sacrosancta may have originated from hybrids whose parent is the sexualD. saxifraga, whereas this species was not involved in the origin of the other apogamous triploids and the apogamous diploids. The other parent was also discussed and we proposed a hypothesis that diploid offsprings fromD. pacifica triploids hybridized withD. saxifraga giving rise to triploids ofD. bissetiana andD. sacrosancta.