Relationships between floral morphology and pollinator fauna in insular and main island populations of Hosta longipes (Liliaceae)

We compared the floral morphologies and pollinator fauna and morphologies of Hosta longipes var. longipes on the main Japanese island of Honshu and var. latifolia on the Izu Islands to examine the differentiation processes of H. longipes in the island system. The corolla length was shorter on the southern Izu Islands than on the main island and northern Izu Islands. However, the size of other flower parts of H. longipes did not simply decrease across main island Honshu and the Izu Islands, unlike other Izu endemic plant species studied previously. Instead, the floral morphology showed a complicated variation pattern. Pollinator fauna of H. longipes on the Izu Islands varied more widely than those on the main island. The diverse pollinator fauna may have influenced the morphological differentiation of H. longipes on these islands.     

Assessment of genetic diversity of native species in Izu Islands for a discriminate choice of source populations: Implications for revegetation of volcanically devastated sites

In using native species for revegetation, it is necessary choose source populations carefully to reduce the risk of planting suboptimal germplasm. To make preliminary recommendations for native species to use in the revegetation of a volcanically devastated area on Miyake Is., Japan, we investigated the genetic variation of Alnus sieboldiana, Miscanthus sinensis ssp. condensatus, and Polygonum cuspidatum var. terminalis in the Izu Islands and on the Izu Peninsula based on chloroplast DNA (cpDNA) sequence variations and amplified fragment length polymorphisms (AFLPs). The amount and pattern of differentiation differ between organelle and nuclear markers, suggesting the necessity of evaluation based on both types of markers. Within-population diversity did not vary among populations, suggesting that it does not need to be considered in the choice of a source population. The pattern and degree of differentiation varied among species, and geographical proximity did not necessarily accord with genetic similarity, suggesting that the site of an appropriate source population varies among species and should be determined empirically rather than by assuming that close proximity predicts genetic similarity. The Izu Peninsula populations deviated from the island populations in all species. Comparison of cpDNA sequences with those of related species indicates the possibility of hybridization with related species on the Izu Peninsula, suggesting that seeds collected from populations where related species live sympatrically should not be used for revegetation. These findings indicate the need to assess the genetic diversity empirically by using organelle and nuclear markers to avoid unintended consequences of genetic mixing associated with revegetation.     

Distribution and species composition of juvenile and adult scombropids (Teleostei,Scombropidae) in Japanese coastal waters

Two scombropid fishes, Scombrops boops and Scombrops gilberti, are closely related and commercially important species in Japan. These species are often confused in commercial markets because of their morphological similarity. In this study, scombropid specimens collected from various Japanese coastal waters were subjected to polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis and phylogenetic analysis of the 16S rRNA gene in mitochondrial DNA. These analyses showed that all the scombropid specimens collected from localities in the Sea of Japan were identified as S. boops, whereas those from the Pacific Ocean included two species, S. boops and S. gilberti. Almost all juvenile (<200 mm standard body length, S_L) S. gilberti originated from the Pacific coastal waters of the northern Japan, whereas adults (>400 mm S_L) were found only in deep water off the Izu Peninsula to the Izu Islands. This suggests that S. gilberti might migrate extensively during its life cycle. In addition, differences in the number of specimens and the distribution between the two species suggest that S. gilberti is less abundant than S. boops in Japanese waters.     

Parapatric distribution of the lizards Plestiodon (formerly Eumeces) latiscutatus and P. japonicus (Reptilia: Scincidae) around the Izu Peninsula, Central Japan, and its biogeographic implications

The scincid lizard Plestiodon latiscutatus is found in the Izu Islands and Izu Peninsula of central Japan, whereas P. japonicus, a close relative, is found over the entire main island group of Japan, except the Izu Peninsula. The precise area of occupancy of these species was surveyed around the Izu Peninsula. Species identification was made through comparison of mitochondrial DNA partial sequences of specimens from the Izu Peninsula with those from the other regions, since morphological differences between these species have not yet been characterized. This study determined that these species are deeply diverged from each other in mitochondrial DNA sequence, and that the ranges of these species overlap only in a narrow zone. The results imply that gene flow between these species, if any, is restricted to a low level, without physical barriers. The boundary between the geographic ranges of these species was established as occurring along the lower Fuji River, Mt. Fuji, and the Sakawa River. This region is concordant with that of the old sea that is assumed to have separated the Izu Peninsula from other parts of the Japanese main island group until the middle Pleistocene. This pattern suggests that P. latiscutatus and P. japonicus were differentiated allopatrically before the connection of land areas of the Izu Peninsula and Honshu, the main island of Japan, and come into secondary contact through this connection. Thus, the species boundary is likely to have been maintained in situ, without physical barriers, since the secondary contact in the middle Pleistocene.     

Impact of geographical isolation on genetic differentiation in insular and mainland populations of Weigela coraeensis (Caprifoliaceae) on Honshu and the Izu Islands

Aim To provide insights into genetic differentiation between insular endemic Weigela coraeensis var. fragrans and its progenitor variety W. coraeensis var. coraeensis, the population genetic structure of both varieties was examined, and factors promoting genetic differentiation between the two taxa were explored. Location The natural range of W. coraeensis (sensu lato) throughout mainland Japan (Honshu) and the Izu Islands. Methods The analysis included 349 and 504 individuals across the mainland (Honshu) and the Izu Islands, respectively, using 10 allozyme and 10 microsatellite loci. The population genetic structure of W. coraeensis was assessed by analysing genetic diversity indices for each population, genetic differentiation among populations, model‐based Bayesian clustering or distance‐based clustering, and bottleneck tests. Results The level of genetic diversity in each of the populations on the Izu Islands was negatively correlated with geographical distance between each island and the mainland. The populations on the mainland and on the Izu Islands were genetically differentiated to a certain extent; however, the microsatellite analyses suggested that gene flow also occurred between the mainland and the islands, and among individual islands. These microsatellite analyses also suggested recent bottlenecks in several populations in both areas. Main conclusions The decrease in genetic diversity throughout the Izu Islands, which correlated with distance to the mainland, Honshu, may be the result of a repeated founder effect occurring at a series of inter‐island colonizations from north to south. The stepping stone‐like configuration of the islands may have played a role in the dispersal of the species. Geographical isolation by sea would effectively result in genetic differentiation of W. coraeensis between mainland Honshu and the Izu Islands, although some gene flow may still occur between Honshu and the northern Izu Islands. The differentiation process of the endemic plants on the Izu Islands is anagenetic but not completed, and the study of these plants will provide insightful knowledge concerning the evolution of insular endemics.     

Comparison of pollination characteristics between the insular shrub Clerodendrum izuinsulare and its widespread congener C. trichotomum

Impact of pollinator shift on differentiation of floral morphology has attracted the interest of naturalists for many years. A comparative investigation was conducted for determining the pollination characteristics, including pollinator assemblage, floral morphology, flowering phenology, and self‐compatibility, of two closely related Clerodendrum species—insular C. izuinsulare and widespread C. trichotomum. Japanese black swallowtail butterflies were the predominant flower visitors in mainland Japan, whereas diurnal hawk moths were predominantly found on the Izu Islands, a chain of oceanic islands located off the southeastern coast of the main Japanese island of Honshu in the west Pacific Ocean. The corolla tube of C. izuinsulare was longer than that of C. trichotomum, whereas the filaments and petals of C. izuinsulare were shorter than those of C. trichotomum. The flowering season of C. izuinsulare was later than that of C. trichotomum. The self‐compatibility of C. izuinsulare was higher than that of C. trichotomum. These differences might be associated with the low density of Japanese black swallowtail butterflies and dominance of diurnal hawk moths on the Izu Islands.     

Redescription of a rare callionymid fish,Paradiplogrammus corallinus,from Hawaii and Japan

Paradiplogrammus corallinus (Gilbert) has been represented by only two female specimens collected from the Hawaiian Islands. The species is redescribed on the basis of male and female specimens from the Hawaiian Islands and Hachijo-jima, Izu Islands, Japan. This species is unique amongParadiplogrammus in having a pair of supraorbital cirri.     

BIOGEOGRAPHY AND TAXONOMY OF BATRACHOSPERMUM HELMINTHOSUM (BATRACHOSPERMALES,RHODOPHYTA) IN JAPAN INFERRED FROM RBCL GENE SEQUENCES1

Twenty‐seven individuals of Batrachospermum helminthosum Bory were collected from various sites in Japan, from temperate Iwate Prefecture to subtropical Okinawa Prefecture. The chloroplast‐encoded rbcL gene was sequenced from each sample. Phylogenetic analyses were performed using these and previously published sequences of 12 samples from North America. There were five haplotypes among the Japanese samples. Haplotype 1 was collected throughout a large geographical area corresponding to most of the sampling range in this study and was represented by most individuals (21 individuals). The other haplotypes were represented by one to three individuals, respectively. These distributions of haplotypes suggest the occurrence of one large metapopulation and/or recent colonization over a wide geographical area in Japan. Phylogenetic analysis showed two well‐supported clades within B. helminthosum, one clade containing four haplotypes (1–4) from Japan and the other clade comprising five North American haplotypes. Such differences between Japanese and North American haplotypes might be a result of continental drift and subsequent isolation in the Mesozoic era. The position of haplotype 5 from Okinawa in Japan is poorly resolved, but it is not closely related to the other four Japanese haplotypes. It is suggested that several taxonomic characteristics (sexuality, point of origin of carpogonium‐bearing branches, and trichogynes with or without basal knobs or branching) is not fixed genetically but is affected by environmental conditions. Based on the results of the present study, B. coerulescens Sirodot and B. elegans Sirodot should be placed in synonymy with B. helminthosum.     

Erythroglossum latum sp. nov. (Delesseriaceae, Rhodophyta) from the east coast of Honshu, Japan

A new species, Erythroglossum latum, is described based on specimens from Fukushima Prefecture along the east coast of Honshu, Japan. This species differs from Erythroglossum pinnatum Okamura in having a broader main blade, a clear midrib and lateral branches that are smaller in size and not clearly constricted at the base.     

Rabaulichthys suzukii, a new anthiine fish from Japan

Rabaulichthys suzukii is described as a new species of anthiine fish, family Serranidae, from three specimens collected in 5–15 m off the Izu Peninsula, Shizuoka Prefecture, Japan in February 1999 and February 2000. It represents the third species of the genus, the most characteristic feature of which is the very high dorsal fin of the male. R. suzukii is most closely related to R. altipinnis Allen from New Britain, differing in its larger size (to 64.2 mm SL, compared to 45.5 mm for R. altipinnis), higher dorsal fin (29.3% SL, compared to 26.2% for R. altipinnis), lack of a filament on the caudal-fin lobes, 19 pectoral rays (modally 20 in R. altipinnis), 9–10 + 23 gill rakers (8–9 + 21–22 in R. altipinnis), and in color. Because the Izu Peninsula collection sites have been heavily dived for many years, the recent appearance of R. suzukii is believed to the result of transport of postlarvae from a population to the south. Received: April 20, 2000 / Revised: August 28, 2000 / Accepted: September 28, 2000     

ALLOZYME DIFFERENTIATION AND GENETIC STRUCTURE IN ISLAND AND MAINLAND JAPANESE POPULATIONS OF CAMPANULA PUNCTATA (CAMPANULACEAE)

Allozyme variation was investigated in 17 Japanese populations of Campanula punctata, ten from the Izu Islands and seven in the mainland (Honshu). The data indicate that there are two groups, a mainland group and an island one, and that the systematically problematic Oshima Island (northernmost Izu island) populations are closely related to those of the other islands. Nei's genetic identity values among islands and among mainland populations were 0.95 and 0.97, respectively, while the value between island and mainland populations was 0.84, suggesting that the island populations are an independent species. Total genetic variation was nearly the same among island and mainland populations. However, the apportionment of variation within and among populations was considerably different; 14% of gene diversity exists among mainland populations, while 31% of the diversity exists among island populations. Mean outcrossing rates of self-incompatible mainland and Oshima populations are 0.62–0.79, supporting xenogamy; those in self-compatible island populations are 0.37–0.57 in the northern islands, indicating a mixed mating system, and 0.16–0.25 in southern ones, indicating dominant inbreeding. Total genetic diversity in each island population decreased with distance from the mainland. Genetic and geological data suggest that the ancestors of insular populations were founded on northern islands in a relatively ancient period and that they dispersed progressively to the southern ones. Chromosome number (2n = 34) and isozyme numbers indicate gene duplications in this species, which suggests it is an ancient polyploid.     

Evolutionary effects of geographic and climatic isolation between Rhododendron tsusiophyllum populations on the Izu Islands and mainland Honshu of Japan

Geographic and environmental isolations of islands and the mainland offer excellent opportunity to investigate colonization and survival dynamics of island populations. We inferred and compared evolutionary processes and the demographic history of Rhododendron tsusiophyllum, in the Izu Islands and the much larger island Honshu, treated here as the mainland, using thousands of nuclear SNPs obtained by ddRAD-seq from eight populations of R. tsusiophyllum and three populations of R. tschonoskii as an outgroup. Phylogenetic relationships and their habitats suggest that R. tsusiophyllum had evolved and migrated from cold north to warm south regions. We detected clear genetic divergence among populations in three regions of Honshu and the Izu Islands, suggesting restricted migration between them due to isolated habitats on mountains even in the mainland. The three regions have different changes in effective population size, especially, genetic diversity and population size of the Izu Islands are small compared to the others. Further, habitats of populations in the Izu Islands are warmer than those in Honshu, suggesting that they have undergone adaptive evolution. Our study provides evidences of montane rather than insular isolation on genetic divergence, survival of populations and significance of adaptive evolution for island populations with small population size and low genetic diversity, despite close proximity to mainland populations.Subject terms: Genetic variation, Plant evolution, Conservation biology     

MORPHOLOGY AND MOLECULAR PHYLOGENY OF AUREOPHYCUS ALEUTICUS GEN. ET SP. NOV. (LAMINARIALES,PHAEOPHYCEAE) FROM THE ALEUTIAN ISLANDS1

A previously unknown species of kelp was collected on Kagamil Island, Aleutian Islands. The species can be easily distinguished from any known laminarialean alga: the erect sporophytic thallus is composed of a thin lanceolate blade attaining ～2 m in height and ～0.50 m in width, without midrib, and the edge of the blade at the transition zone is thickened to form a V‐shape; the stipe is solid and flattened, slightly translucent, attaining ～1 m in length; the holdfast is semidiscoidal and up to 0.15 m in diameter. Anatomically, the blade has the typical trumpet‐shaped hyphae characteristic of the Chordaceae and derived foliose laminarialean species (i.e., Alariaceae/Laminariaceae/Lessoniaceae). No hair pits or mucilaginous structures were observed on the blade or stipe. No fertile sporophytes were collected, but abundant juvenile sporophytes were observed in the field. In the molecular phylogenetic analyses using chloroplast rbcL gene, nuclear ITS1‐5.8S‐ITS2 rDNA, and mitochondria nad6 DNA sequences, the new species (Aureophycus aleuticus gen. et sp. nov.) showed a closer relationship with Alariaceae of conventional taxonomy, or the “Group 1” clade of Lane et al. (2006) including Alaria and related taxa than with other groups, although the species was not clearly included in the group. Aureophycus may be a key species in elucidating the evolution of the Alariaceae within the Laminariales. Because of the lack of information on reproductive organs and insufficient resolution of the molecular analyses, we refrain from assigning the new species to a family, but we place the new species in a new genus in the Laminariales.     

A time‐calibrated phylogenetic approach to assessing the phylogeography,colonization history and phenotypic evolution of snakes in the Japanese Izu Islands

Aim We infer the biogeography and colonization history of a dispersal‐limited terrestrial vertebrate, the Japanese four‐lined ratsnake (Elaphe quadrivirgata), to reveal the number of times mainland populations have invaded the Izu Archipelago of Japan, the mainland sources of these colonists, and the time‐scale of colonization. We compare these results with those of past studies in an attempt to uncover general biogeographical patterns. Moreover, we briefly examine the significance of colonization history when evaluating the evolution of body size and melanism of the Izu Island E. quadrivirgata populations. Location The Izu Islands (Oshima, Toshima, Niijima, Shikine, Kozu, Tadanae and Mikura), a volcanic archipelago off the Pacific coast of central Japan. Methods We obtained DNA sequences of the mitochondrial cytochrome b gene (1117 base pairs) from 373 individual snakes sampled from seven of the Izu Islands and 25 mainland localities. We employed partitioned Bayesian phylogenetic analyses assuming a relaxed molecular clock to estimate phylogenetic relationships among extant haplotypes and to give an explicit temporal scale to the timing of clade divergence, colonization history and tempo of body‐size evolution. Moreover, we employed model‐based biogeographical analysis to calculate the minimum number of times E. quadrivirgata colonized the Izu Islands. Results We found evidence that three separate regions of the Izu Archipelago have been colonized independently from mainland ancestors within the past 0.58–0.20 Ma. The Izu Peninsula plus Oshima and Mikura were both colonized independently from lineages inhabiting eastern mainland Japan. The Toshima, Niijima, Shikine, Kozu and Tadanae populations all derive from a single colonization from western mainland Japan. Oshima has been subject to three or possibly four colonizations. Main conclusions These results support the hypothesis that the extreme body‐size disparity among island populations of this ratsnake evolved in situ. Moreover, the fact that the dwarf, melanistic population inhabiting Oshima descends from multiple mainland colonization events is evidence of an extremely strong natural selection pressure resulting in the rapid evolution of this unique morphology. These results contrast with theoretical predictions that natural selection pressures should play a decreased role on islands close to the mainland and/or subject to frequent or recent immigration.     

Apterichtus keramanus, a new snake-eel from Okinawa, southern Japan (Ophichthinae, Ophichthidae)

A new snake-eel,Apterichtus keramanus, is described on the basis of a single 276-mm TL specimen trawled from the coast of Kerama Islands, Okinawa Prefecture, Japan. The species is unique in the genus in having the posterior nostril opening entirely inside the mouth and a dark band running from the anteroventral margin of the eye to the upper lip.     

First record of the genus Dudresnaya (Dumontiaceae,Rhodophyta) in New Zealand waters

The genus Dudresnaya is reported for the first time in New Zealand waters. Samples were collected in Bay of Islands, northern New Zealand, on rhodolith beds and at the edge of a rocky reef, between ?5 and ?10 m depth. The species was identified by morphological and anatomical characters as Dudresnaya capricornica and its identity was confirmed by molecular sequence data. This species is characterized by terete radial branches, outer cortical cells cylindrical, presence of hexagonal crystals, lack of annulation and mucilage coat on auxiliary cell branches, oblique division of carpogonium and cystocarps no cleft. The rbcL phylogenetic analysis showed the genus Dudresnaya is strongly supported and sister to taxa in the family Dumontiaceae. This family is also closely related to the families Rhizophillidaceae and Kallymeniaceae. This is the first record of the family Dumontiaceae in New Zealand.     

The Lek-like Mating System of Halichoeres melanochir (Pisces: Labridae) at Miyake-jima,Japan1

Reproductive behavior and social organization of the labrid fish Halichoeres melanochir were studied at Miyake-jima, Izu Islands, Japan. ♂♂ set up contiguous territories from early to mid-afternoon daily during the breeding season, with ♂♂ at the center of the spawning site experiencing significantly higher spawning success than those at the periphery. Unlike other labrids with lek-like mating systems previously reported, H. melanochir is sexually monochromatic and shows only minimal sexual size-dimorphism. The spawning behavior and mating system are described and compared with current theories on labrid reproductive strategies.     

A TAXONOMIC STUDY OF THE GENUS PADINA (DICTYOTALES,PHAEOPHYCEAE) INCLUDING THE DESCRIPTIONS OF FOUR NEW SPECIES FROM JAPAN,HAWAII, AND THE ANDAMAN SEA1

A taxonomic study of the genus Padina from Japan, Southeast Asia, and Hawaii based on morphology and gene sequence data (rbcL and cox3) resulted in the recognition of four new species, that is, Padina macrophylla and Padina ishigakiensis from Ryukyu Islands, Japan; Padina maroensis from Hawaii; and Padina usoehtunii from Myanmar and Thailand. All species are bistratose and morphologically different from one another as well as from any known taxa by a combination of characters relating to degree of calcification; the structure, position, and arrangement of hairlines (HLs) and reproductive sori; and the presence or absence of rhizoid‐like groups of hairs and an indusium. Molecular phylogenetic analyses demonstrated a close relationship between P. ishigakiensis, P. macrophylla, P. maroensis, and Padina australis Hauck. The position of P. usoehtunii, however, was not fully resolved, being either sister to a clade comprising the other three new species and P. australis in the rbcL tree or more closely related to a clade comprising several other recently described species in the cox3 tree. The finding of the four new species demonstrates high species diversity particularly in southern Japan. The following characters were first recognized here to be useful for species delimitation: the presence or absence of small rhizoid‐like groups of hairs on the thallus surface, structure and arrangement of HLs on both surfaces either alternate or irregular, and arrangement of the alternating HLs between both surfaces in equal or unequal distance. The evolutionary trajectory of these and six other morphological characters used in species delineation was traced on the phylogenetic tree.