Quantitative comparison of foliage development amongDryopteris monticola,D. tokyoensis and a putative hybrid,D. kominatoensis in Northern Japan

Developmental leaf architecture was quantitatively described in terms of measurements of various parameters on leaf blade from different size of sporophytes inDryopteris monticola, D. tokyoensis and a putative hybrid,D. kominatoensis in the natural site of Hokkaido, to compare the ontogenetic differentiation in foliage structure among allied ferns. The morphological stage of leaf and sporophyte was tentatively quantified by the number of midrib branches of the leaf (NV, number of veins), which exhibited a significant correlation to the leaf-shape complexity from a circle (DI=marginal length/2×(3.14×square)^1/2) of leaf blade. D. kominatoensis showed intermediate values between others in following characters; DI increase, maximum NV (also blade length), maximum number of costa branches of pinnae (NVMP), number of costa branches of the lowest pinna (NVLP), difference between NVMP and NVLP (NVMP-NVLP), during heteroblastic leaf development. A larger number of leaves per sporophyte was found inD. kominatoensis than in others. The fertility rate (%) and initiation of fertility (IF) in the relative developmental stage (RDS) ofD. kominatoensis shifted to that ofD. tokyoensis, while the order of pinnae with NVMP shifted to that ofD. monticola. Even in the intermediate characters inD. kominatoensis, slight shifts in characters to those of putative parents were found during heteroblastic leaf development. Contribution No. 3145 from the Institute of Low Temperature Science, Hokkaido University.     

A quantitative estimation of sequential foliage development and fertility inDryopteris crassirhizoma

The foliage development ofDryopteris crassirhizoma Nakai was quantitatively estimated by measurements of shape and size of leaves from different developmental stages of sporophytes, to lead to an understanding of the life history characteristics of the species. The number of midrib branches (NV, number of veins) of the leaf corresponds to the leaf-shape complexity (DI, dissection index; shape complexity from a circle) and length of leafblade (BL). Some quantitative characters, such as leaf uniformity (decrease in NV variation), changes in shape and increase in number of leaves, vary progressively during foliage formation. The sequence of foliage development can be quantified using the parameter NV: for example, 15-NV for leaf uniformity, 30-NV for leaf-shape change from triangular to oblanceolate, 60-NV for increase in leaf number and leaf fertility in the course of sporophyte ontogeny. Contribution No. 3297 from the Institute of Low Temperature Science, Hokkaido University.     

Life history characteristics ofPolystichum tripteron with special reference to its leaf venation

An intra-species comparison of the life history of various populations ofPolystichum tripteron was undertaken in Hokkaido and Honshu in Japan with respect to some leaf-size characters and fertility during sporophyte development. The developmental process of sporophytes was quantitatively estimated by counting the number of venation (NV: number of midrib branches of the leaf). The mean NV of the fertile leaves decreased slightly with increasing altitude on Mt. Teine near Sapporo and with increasing latitudes from Honshu to Hokkaido. The blade length was longer at any NV in Hokkaido populations than in those of southern Honshu. Longer blade (BL) and pinna length (PL) and lesser number of pinnules of the lowest pinna (NPLP) versus NV were observed in leaf populations from Hokkaido than in those from southern Honshu. The maximum values of lowest pinna length (LPL), NV, number of costa branches (NVLP) and number of pinnule (NPLP) were larger in southern Honshu than in Hokkaido. In the course of leaf-shape formation represented by the ratio of PL to BL versus NV, the Kyoto population seemed to be more differentiated into long-lanceolate fronds than did the Hokkaido population. Initiation of fertility in the sporophyte development and the maximum NV seemed to decrease with increasing altitudes and latitudes in Japan. Contribution No. 2885 from the Institute of Low Temperature Science, Hokkaido University.     

Estimation of chronological age for sporophyte maturation in three semi-evergreen ferns in Hokkaido

To elucidate the life cycle time schedule of semi-evergreen ferns at natural sites in Sapporo, the chronological age for sporophyte maturation was estimated from the increase in the number of veins (NV, number of midrib branches) from overwintered to newly expanded leaves. The measurements were conducted on populations ofPolystichum braunii, Polystichum tripteron andDryopteris crassirhizoma at altitudes of 50–650 m on Mt. Teine to compare the interspecific maturation age of sporophytes. The mean age for sporophyte maturation was estimated to be 7.6 yr forP. braunii, 16.5 yr forP. tripteron and 12.6 yr forD. crassirhizoma. The minimum ages (1% fertility rate) for sporophyte maturation ofP. braunii, P. tripteron andD. crassirhizoma were 5.8, 11.0 and 7.9 yr, respectively. The maturation age was shortest forP. braunii and longest forP. tripteron. The maturation age of a species thus seems to differ according to altitude and habitat, and that of the present three species seems to be influenced by the geographical location of the species distribution. Contribution No. 3315 from the Institute of Low Temperature Science, Hokkaido University.     

Comparative life history of five HokkaidoPolystichum ferns with reference to leaf development in relation to altitudinal distribution

The temperate fernsPolystichum craspedosorum, P. retroso-paleaceum, P. tripteron, P. braunii andP. microchlamys are distributed widely in Hokkaido: on 13 Hokkaido mountains their average altitudinal distributions are 450, 479, 570, 689 and 964 m above sea level, respectively. The developmental stage of the sporophytic leaf is expressed by the “number of venation” (NV, the number of veins branching from the midrib of the leaf), which, inPolystichum ferns, is itself a qualitative expression of the phase-change from sterile to fertile leaf production and is more discriminatory than leaf area, length or dry weight. Usually, the developmental stage structure of the fertile leaf expressed by NV in the fivePolystichum ferns showed a normal distribution. Among the fourPolystichum ferns that grow in the forest understory of Hokkaido's cool temperate regions, a good correlation was found between the mean altitude of vertical distribution and the maximum NV of the leaf (r=−0.993) and the initiation of maturity in the relative developmental stage (r=0.991) of the ferns.Polystichum craspedosorum found on cliffs, however, matures at much earlier stage and has the smallest maximum NV. In the developmental stage expressed by the NV, the initiation of fertility and maximum NV seem to be correlated with altitudinal distribution and habitat in populations ofPolystichum ferns in Hokkaido. Contribution No. 2694 from the Inst. of Low Temp. Sci., Hokkaido University.     

Life history characteristic ofCyrtomium falcatum around the natural northern boundary in Hokkaido,with reference to the alternation of generations

To understand the life history characteristic for expanding the distributional area to colder climates, developmental age structure of population ofCyrtomium falcatum was observed along southwestern coasts of Hokkaido at the natural northern boundary of its distribution, with reference to the alternation of generations. The length and number of pinna of fertile leaves ofCyrtomium falcatum decrease towards the northern part of Japan. In southwestern Hokkaido, typically dwarf fertile leaves and gametophytes were observed growing together on cliffs nearby the sea. To estimate the developmental ages of small and dwarf leaves, the number of venation (NV: branching number of vein from midrib) of leaves was counted on each sporophyte. The sporophyte with leaves at the simple pinna stage ranging from 0–25NV, is predominant in the population of southwestern coasts of Hokkaido. The fertility of the sporophyte seems to be achieved more than five years after the germination. The gametophytes were also observed at the location to be almost equal in number to sporophytes. The number of gametophytes and sporophytes decreases with advancement of developmental stages. In the same location at Okushiri Isl. with slight gradiency of humidity, the gametophyte is predominant on the drier cliff, while the sporophyte is predominant on the humid hole. The population ofCyrtomium falcatum at the natural northern boundary in Hokkaido, seems to have the life history characteristic with alternation of generations. Contribution No. 2557 from the Inst. of Low Temp. Sci.     

Quantitative expression of fern leaf development and fertility inPolystichum tripteron (Aspidiaceae)

To elucidate the quantitative and qualitative expression of fern development, various features of leaf-size and morphology were examined on leaves ofPolystichum tripteron (Aspidiaceae) in Japan. Among ten parameters, the number of branches of the leaf midrib (NV) proved to be the most successful for discrimination between fertile and sterile leaf populations. In the phase-change from sterile to fertile leaves, the NV parameter also gave the strongest correlation, increasing with fertility (r = 0.983), and is therefore a useful tool for research into the life history characteristics of ferns.Contribution no. 2751 from the Institute of Low Temperature Science, Hokkaido University.     

Comparative life history of aspidiaceous ferns in northern Japan with reference to fertility during sporophyte development in relation to habitats

The life-cycle characteristics of ferns, in particular reproductive characteristics in relation to alternation of generations, have been studied in populations of 19 species of aspidiaceous ferns native to Hokkaido. The developmental age of the sporophyte was quantitatively expressed by the number of midrib branches of the leaf (NV; number of venation). The maximum developmental age (MNV) of the aspidiaceous ferns in Hokkaido ranged from 49 to 113. The initiation of fertility (IF) in the relative developmental age (RDA), percentages of any NV to the maximum NV of the leaf population) ranged from 15 to 65%. Ferns occurring on rocky cliffs initiated fertility at 15–21%, while ferns occurring on the forest floor initiated fertility at 41–65% in the RDA of a leaf population. Further observations were undertaken on 26 ferns of other families and revealed that there were correlations between habitat and maximum NV, and habitat and IF in the RDA. Ferns occurring on cliffs, on mossy rocks and on tree trunks, had lower maximum NV of the leaf and earlier initiation of fertility in the RDA, than those of ferns occurring on the forest floor, edge of forests and on grassland in Hokkaido. Ferns occurring in the exposed habitat seemed to behave as a r-strategist, while ferns occurring in the forest floor seemed to behave as a K-strategist.     

Evidence for intergeneric incompatibility in ferns

The archegonial mucilage ofAthyrium filix-femina andA. distentifolium paralyses spermatozoids ofDryopteris filix-mas (and in one caseD. inaequalis) before they penetrate the archegonial venter. The archegonial mucilage ofDryopteris filix-mas has a weak positive chemotactic influence on the spermatozoids of the twoAthyrium species. The spermatozoids ofDryopteris were never observed in the archegonia ofAthyrium. Incompatibility was not observed within and between the twoAthyrium species, withinDryopteris filix-mas or betweenAthyrium filix-femina and twoAsplenium species.Contribution No. 327.     

Seasonal changes in polar lipids in fronds of the ferns Dryopteris filix-mas and Matteuccia struthiopteris

The distribution pattern of total lipids, glyco- and phospholipids, and one betaine lipid (DGTS) in the fronds of the ferns Dryopteris filix-mas and Matteuccia struthiopteris was studied. The lipid composition of the embryo leaflets forming a bud, or treble clef, and that of fully opened leaves changed throughout the growth season. The maximum amount of DGTS in clefs and mature leaves was detected at the beginning of the season. By midsummer, the DGTS content decreased, dropping to zero in the fully opened leaves, and then increased again. The amount of DGTS in the clefs collected in October versus those collected in May was somewhat higher in the case of Dryopteris filix-mas and almost twofold lower in the case of Matteuccia struthiopteris. The ratio between polar lipids contained in the clefs and mature leaves throughout the growth season was determined.     

Chemotaxonomic studies onArachniodes (dryopteridaceae) I. Phloroglucinol derivatives of japanese species

Twelve species ofArachniodes from Japan were examined for phloroglucinol derivatives and glandularity of rhizome and petiole bases. For comparison 3 species ofDryopteris, 1 species ofCtenitis, 4 species ofPolystichum, and 1 species ofAcystopteris were also investigated. Phloroglucinol derivatives were detected for the first time by sensitive TLC in the followingArachniodes, Dryopteris andPolystichum species:A. amabilis, A. dimorphophylla, A. exilis, A. hasseltii, A. maximowiczii, A. miqueliana, A. mutica, A. nipponica, A. okinawensis, A. simplicior incl. var.major, D. hayatae, D. sparsa, andP. tsus-simense. On the other hand,A. pseudo-aristata, A. standishii, P. polyblepharum, P. pseudomakinoi, P. retroso-paleaceum, Ctenitis maximowicziana, andAcystopteris japonica were totally lacking phloroglucinols. The phloroglucinol containing species ofArachniodes andPolystichum contained external glands, whereas those ofDryopteris contained internal and/or external glands. External glands are common inDryopteris sect. Nephrocystis. In taxa lacking phloroglucinols no glands were present. The homologous iso-aspidins BB and AB were detected in ferns for the first time.     

Phenology and wintering capacity of sporophytes and gametophytes of ferns native to northern Japan

Summary To investigate life history adaptations to cold climates, the leaf development, sporulation period, growing stage of gametophytes, and the frost and drought resistance of sporophytes and gametophytes of 67 fern species native to Kokkaido were studied. Most ferns common in Hokkaido are summer-green with leaves developing during late May to June and decaying during October. Most of the ferns in Hokkaido sporulate during August to early September. Spores dispersed from June to September germinate before winter begins, forming vegetative prothallia. Gametophytes mature only in the following summer. Thus in Hokkaido the gametophytes as well as perennial sporophytes are exposed to severe winter conditions. In order to correlate the life cycles of temperate ferns with winter cold stress, frost resistance of gametophytes, rhizomes, and leaves of sporophytes were determined. Maximal frost resistance of rhizomes reflects the stress conditions of their habitats: rhizomes of forest understory ferns are damaged at-5°to -17.5°C, epiphytic ferns and ferns of habitats exposed to severe frost sustained temperatures of -20° to-40°C. The leaves of winter-green and evergreen ferns resist frost ranging from -25° to -40°C. The leaves of summer-green ferns are killed by late frost below -5°C. With some exceptions, gametophytes of ferns growing on the forest floor resist frost to -40°C and are much hardier than sporophytes. These results suggest the possible restrictive effects of cold climate on the life span of leaves as well as on the sporulation period. If winter cold is one of the decisive factors for seasonality expression and habitat distribution of ferns, the sensitive generation must be the sporophyte rather than the gametophyte. The hardier gametophyte is therefore able to colonize habitats in which the sporophyte is excluded by frost if mechanisms of vegetative propagation are evolved.Contribution No. 2451 from The Institute of Low Temperature Science     

Lomariopsis ×farrarii: a new hybrid fern between L. japurensis and L. vestita (Lomariopsidaceae) from Costa Rica

A new hybrid,Lomariopsis ×farrarii, is illustrated and described from the La Selva Biological Station, Costa Rica. It is intermediate between its parents,L. japurensis andL. vestita in length and color of the rhizome scales, shape and number of the pinnae, and size and division of the juvenile leaves in a heteroblastic series.     

Reiterative growth in the complex adaptive architecture of the Paleozoic (Pennsylvanian) filicalean fern Kaplanopteris clavata

Reiteration is a widespread component of plant growth whose evolutionary importance in ferns is not recognized widely. We introduce and discuss the growth architecture of Kaplanopteris clavata, a fossil filicalean fern from the Pennsylvanian (ca. 305 million yeas old), focusing on types of reiteration exhibited by this species and on the adaptive and phylogenetic significance of reiteration for ferns in general. Kaplanopteris clavata combines two types of reiterative growth where growth modules are borne on fronds: (1) entire fronds derived from primary pinnae, and (2) epiphyllous plantlets. This combination of reiterative pathways, unique among fossil and living ferns, allowed K. clavata to explore ecospace through an opportunistic combination of scrambling, climbing and epiphytic growth. Kaplanopteris clavata underscores the organographic importance of fronds (as opposed to stems) in the adaptive architecture of ferns, emphasizing functional convergences between the different Baupla̋ne of ferns and angiosperms. This unique combination of reiterative pathways is interpreted as a derived condition illustrating the structural and developmental complexity achieved by some filicaleans during the first major evolutionary radiation of leptosporangiate ferns.     

Genetic variation and differentiation of the two river sculpins,Cottus nozawae andC. amblystomopsis,deduced from allozyme and restriction enzyme-digested mtDNA fragment length polymorphism analyses

Genetic differentiation of the two sibling species,Cottus nozawae andC. amblystomopsis, from the northern part of Japan (Hokkaido Island and the Tohoku District) was investigated using allozyme variations and restriction fragment length polymorphisms of mitochondrial DNA. Although the two species are morphologically very similar, previously being thought to be a single species, they have different life-cycles;C. nozawae has a fluvial life-cycle with a small number of large-sized eggs, whereasC. amblystomopsis is an amphidromous species with a large number of small-sized eggs. Four populations ofC. amblystomopsis from Hokkaido Island and 24 populations ofC. nozawae (22 from Hokkaido Island and 2 from the Tohoku District) were sampled and examined Intrapopulational differentiation in the two species was measured by examining several indexes, including proportion of polymorphic loci (P), mean heterozygosity (H) and nucleotide diversity (π). All measurements were higher in theC. amblystomopsis populations, suggesting that intrapopulational variation inC. nozawae was less than inC. amblystomopsis and reflecting the difference in effective population sizes between them. Cluster analyses were performed using the UPGMA method, based on the data matrices of genetic distance (D) and the net nucleotide difference (δ) between populations. TheC. nozawae andC. amblystomopsis populations from Hokkaido Island composed a large cluster (Hokkaido group), while theC. nozawae populations from the Tohoku District composed a different cluster (Tohoku group). Bootstrap probabilities deduced from 1000 bootstrap replications for presence or absence of restriction sites showed that the mtDNA haplotypes detected within the Tohoku Group occurred in 99.9% of the bootstrap replicates outside the mtDNA haplotypes of the Hokkaido group, while those within the Hokkaido group occurred in 3.5–64.9% of bootstrap replicates. Consequently, the Hokkaido populations of the two species (Hokkaido group) were genetically close to each other, whileC. nozawae from the Tohoku District (Tohoku group) were distant from the Hokkaido group. These results suggest that the ancestral populations of the two species on Hokkaido Island shared the same gene pool, even after becoming geographically isolated from the ancestral population ofC. nozawae in the Tohoku District by the formation of the Tsugaru Straits.     

Hybridization involving independent gametophytes in the Vandenboschia radicans complex (Hymenophyllaceae): a new perspective on the distribution of fern hybrids

To test our hypothesis of hybrid formation involving the ‘independent gametophyte’ phenomenon in ferns, we identified the genomic formulae and ploidy level of gametophytes of the Vandenboschia radicans complex at the periphery of a sporophyte population. We identified haploid gametophytes of V. kalamocarpa (one of the two putative parents of V.×stenosiphon) in a hybrid sporophyte population in Japan that lacks fertile non‐hybrid individuals. Furthermore, diploid sporophytes of the species were not found within a 50‐km radius. This finding supports a hypothesis of hybridization involving the ‘independent gametophyte’ phenomenon and provides a new perspective on the geographical distribution of fern hybrids.     

A revision of the genusCyathorachis in Japan

Cyathorachis, a genus of Cretaceous tree fern rachises is revised. In addition to the type specimens of the sole species,C. fujiiana Ogura, two specimens collected near the type locality were examined histologically. The histological data being used for the taxonomical comparison were obtained from anatomical studies on the rachises of extant tree ferns. As a result of the study three species are recognized, two of which are new. As a result of this study, it appears that species differentiation of the tree ferns in the late Cretaceous age of Hokkaido was rather high, as it is now in tropical and subtropical regions. Contributions from the Laboratory of Phylogenetic Botany, Chiba University, No. 74.     

Induced apogamous sporophytes inPteris dispar andP. semipinnata,and the meiotic behavior in their sporocytes

Spores ofPteris dispar andP. semipinnata were aseptically cultured in flasks for apogamous sporophyte induction. Calli or cell colonies similar to calli were induced in cultures supplemented with hormones. Sporophytic leaves subsequently developed from them in hormone-free medium and the young sporophytes were raised into plants with sporangia. Since the wild-type plants having 116 chromosomes are tetraploid, the sporophytic plants originating from spores would appear to be diploid (dihaploid). In induced sporophytes ofP. semipinnata, non-homologous chromosomes (58 univalents) were found during the meiotic process in sporocytes. InP. dispar, however, the meiotic cells showed many bivalent chromosomes (maximum 29ll). These results suggest thatP. semipinnata is allotetraploid, whereasP. dispar is autotetraploid.     

Hybridization and speciation in the genusDryopteris (Pteridophyta:Dryopteridaceae) on Pico Island in the Azores

The cytology of wild hybrids ofDryopteris from Pico, Azores has been examined. This has confirmed the parentage of the hybrids, and provided evidence to support the view that the tetraploid speciesD. crispifolia has evolved in the Azores from two diploid species,D. aemula andD. azorica, by hybridization and polyploidy.     

Cytogenetic and phytochemical investigations in hybrids of MacaronesianDryopteris (Pteridophyta: Aspidiaceae)

The cytology and phloroglucinol composition of wild and synthesized hybrids of MacaronesianDryopteris species have been examined. Both cytological and chemical evidence suggest that the tetraploidD. guanchica has arisen from the diploid speciesD. aemula andD. maderensis by hybridization and chromosome doubling. However, the formation of the characteristic fully aromatic compounds inD. aemula appears to be suppressed in most of the hybrids involving this species, and inD. guanchica.