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Aegagropila linnaei is a freshwater green alga of the order Cladophorales, which is well known as ‘Marimo’ in Japan for its beautiful spherical form as lake balls in Lake Akan. Lake Akan is the only lake in which spherical ‘Marimo’ is found in Japan, but the species also grows as floating or epilithic filaments which appear in several other Japanese lakes. The spherical growth form usually reproduces vegetatively, and it is not known if the species also reproduces sexually or whether transformation between different growth forms happens in natural populations. In this study, the genetic diversity of A. linnaei in Japan was investigated using isozyme analysis. Apart from one colony in Lake Ogawara, each colony was genetically homogeneous, which suggests that asexual reproduction is dominant. All the non-epilithic (spherical aggregations, floating filaments, and floating tufts) colonies in Lake Akan were genetically similar, regardless of the location of sites within the lake, while epilithic colonies have different genetic structures. Therefore, transformation or gene flow between epilithic and non-epilithic forms is not evident in natural populations. Because the genetic diversity largely depends on epilithic algae in Lake Akan, it is important to conserve epilithic- as well as spherical-colonies.

The karyotype of diploid Aster iinumae is morphologically similar to that of diploid Aster ageratoides var. ageratoides, however, its chromosome size is apparently smaller (S-type chromosomes versus L-type chromosomes, respectively). The hybrid origin of tetraploid Aster microcephalus var. ovatus (LS-type chromosomes) has previously been suggested by cytogenetics and chloroplast DNA (cp DNA) data. The cp DNA phylogeny also implies that the S-type chromosome is apomorphic, which means that genome size reduction occurred on the evolutionary way to A. iinumae. In this study, we have demonstrated that the chromosome size difference does not depend on the intensity of chromosome condensation but on the DNA content. The simultaneous genomic in situ hybridization (GISH) results show the similarity between S-type chromosomes of A. iinumae and A. microcephalus var. ovatus, and between L-type chromosomes of A. ageratoides and A. microcephalus var. ovatus, which provide additional evidence for A. microcephalus var. ovatus being a tetraploid amphidiploid produced by hybridization between S-type chromosomes and L-type chromosomes. The distribution patterns of Ty1-copia-like retrotransposons were similar in L- and S-type chromosomes. The copies of this retrotransposon dispersed uniformly on all chromosomes, and it is not yet apparent how the Ty1-copia-like retrotransposon affects the size difference between them.

Thirteen new species of the genusStevia are described and illustrated from Mexico:S. chilapensis, S. coahuilensis, S. crassifolia, S. ecatepecana, S. filodecaballoana, S. mascotensis, S. mexicana, S. oaxacana, S. oligophylla, S. potosina, S. rotundifolia, S. scabrelloides, andS. viejoana. In addition, two varieties,Stevia aschenborniana Sch. Bip. ex Klotzsch var.occidentalis Grashoff andS. palmeri A. Gray var.constricta Grashoff are herein redefined as being distinct species,S. occidentalis andS. constricta stat. nov.Stevia mexicana resemblesStevia trifida Lagasca but differs in the habit.

RFLPs of cpDNA were examined for 18 species ofAster, six species ofKalimeris, two species ofMiyamayomena and one species and one variety ofHeteropappus from Japan, using 16 restriction endonucleases. Approximately 275 restriction sites were surveyed, and a total of 74 restriction site mutations was detected, and 31 of these were phylogenetically informative. Sixteen most parsimonious trees constructed from Wagner parsimony analysis indicated the polyphyly ofKalimeris andMiyamayomena sensu Kitamura;K. miqueliana belongs to a different clade from the remaining species ofKalimeris, and two species ofMiyamayomena did not make a single clade. This result suggests that the shortening or loss of pappus have happened parallelly in different evolutionary lineages. We must be careful to assess the pappus character in taxonomy and phylogeny, and it is desirable to examine their phylogenetic relationships using a molecular data.

The genusPittosporum includes about 160 species. Four species ofPittosporum occur in the Bonin Islands, and all of these are endemic to the islands. Electrophoretic studies of the four endemic species,P. tobira, from the Japanese mainland, andP. lutchuense var.denudatum from the Ryukyu Islands, were used to determine the origin and speciation pattern of the endemic species.

RFLPs of cpDNA of five species and one variety ofKalimeris, and elght species ofAster from Japan were investigated. Approximately 290 restriction sites were surveyed using 16 restriction enzymes. A total of 52 restriction site mutations was detected, and 21 of them were phylogenetically informative. Wagner parsimony analysis resulted in only one most parsimonious tree. In the tree obtained,Kalimeris sensu Kitamura is a colyphyletic group;K. miqueliana belongs to a different clade than the remaining species ofKalimeris. This result suggests that the shortening of the pappus has occurred in parallel in different evolutionary line. Thus, it is not appropriate to extend the generic circumscription ofKalimeris to includeK. miqueliana, based on pappus length. The sister group ofKalimeris, exceptK. miqueliana, is theAster ageratoides group.Aster ovatus is included in theKalimeris clade and it is suggested that it represents an amphidiploid with someKalimeris species as its maternal parent.

To study the origin and speciation of plants in oceanic islands, electrophoretic analyses have been done on three endemic species ofSymplocos in the Bonin Islands as well as on three other species;S. kuroki, S. nakaharae andS. tanakae which are considered to be closely related to the Bonin endemics. There occur three species:S. kawakamii, S. pergracilis andS. boninensis in Bonin. The genusSymplocos is one which is considered to be diversified in the Bonin Islands.

Genetic differentiation was examined betweenAdiantum capillus-veneris L. andA. ogasawarense Tagawa. A total of 136 individuals from two populations ofA. ogasawarense and three populations ofA. capillus-veneris were sampled. Allozymes encoded by 19 putative loci for nine enzyme systems were observed. The populations ofA. ogasawarense are genetically differentiated from those ofA. capillus-veneris; conspecific populations cluster together. However, genetic identity between two species was estimated to be 0.815, and indicates that the degree of allozyme differentiation is lower than those between endemic flowering plants and their progenitors. It is possible that the low genetic differentiation observed betweenA. ogasawarense andA. capillus-veneris results from a recent origin of the endemic species,A. ogasawarense.

TheAster leiophyllus complex is complicated taxonomically and includes many related taxa representing polyploid series. It has been reported that this group is diversified throughout the Kanto district, central Japan, and there are three taxa endemic to the Kanto district. However, as neither morphological variation range nor distribution pattern is sufficiently investigated, taxonomic confusion sometimes occurs. In this study, morphological variation was examined in relation to the ploidy level, and taxonomic consideration was given. As a result, four morphologically recognized taxa occur in the Kanto district;A. leiophyllus (2x, 6x),A. leiophyllus var.sawadanus (2x, 3x, 4x),A. semiamplexicaulis (2x), andA. sugimotoi (4x, 5x). The distribution ranges ofA. leiophyllus var.sawadanus, A. semiamplexicaulis andA. sugimotoi are small, whileA. leiophyllus is distributed over most of the Kanto district. Morphological and cytological observations indicate that one of the reasons of the taxonomic confusion is the presence of presumed hybridization betweenA. leiophyllus and other taxa.

The mode of initiation and development of integuments was investigated in six species of five genera in Menispermanceae, which have bitegmic and unitegmic ovules. The species investigated have similar integumentary structures at maturity in each of the bitegmic and unitegmic ovules. In bitegmic ovules (e.g.Cocculus), both integuments are for the most part two-cell layered. The initiation of inner integument (ii) begins with divisions of dermal cells of the nucellar primordium. The initiation of the outer integument (oi) commences with divisions of subdermal cells. In unitegmic ovules (e.g.Stephania), the integument is initiated by periclinal divisions of dermal cells, and cells of subdermal origin (which may represent the oi in case of bitegmy) form a small swelling on the raphal side and, on the antiraphal side, are included in the base of the single integument. Unitegmy of Menispermanceae (at least in the case of the genera investigated) seems to have been derived through elimination of oi, rather than through “integumentary shifting” (Bouman and Calis, 1977), a process suggested for explanation of unitegmy as in Ranunculaceae.

Thirty species and one variety of Symplocos (Symplocaceae), including all taxa distributed in Japan, were phylogenetically analyzed with DNA sequence data. The evolution of morphological characters is discussed on the basis of the phylogenetic relationships obtained. All species were Asian, except one, S. austromexicana, from Mexico. The nuclear ribosomal internal transcribed spacer (ITS) region and two intergenic spacer regions, between trnL and trnF, and between trnH and psbA of chloroplast DNA were used. The topologies of trees obtained from ITS and the chloroplast intergenic spacers are largely congruent. S. sonoharae, the representative of the subgenus Symplocos in Asia, was sister to all other species. The position of the American species, S. austromexicana, which also belongs to the subgenus Symplocos, was not well resolved. The phylogenetic tree based on combined sequence data largely supports the monophyletic origin of the infrageneric sections proposed earlier. However, the phylogenetic relationship between them is not well resolved, probably due to rapid diversification. The section Palura, a deciduous group, is well defined in the DNA analysis, suggesting its independent status in the genus Symplocos. In spite of their morphological divergence, the three endemic species of the Bonin Islands are monophyletic. The occurrence of curved seeds seems to be homoplastic, scattered over the phylogenetic tree without showing a particular infrageneric relationship.