Ecotype variation in the endemic tree Callicarpa subpubescens on small oceanic islands: genetic, phenotypic, and environmental insights.

Callicarpa subpubescens, endemic to the Ogasawara Islands, is suggested to have multiple ecotypes in the Hahajima Islands, specifically in the central part of the Ogasawara Islands. In this study, associations between genetic groups and spatial distribution, habitat, leaf morphology, size structure, and flowering time of each genetic group were investigated on Hahajima and the satellite Imoutojima Islands. Genetic groups were identified using EST-SSR markers, revealing four ecotypes named based on morphological features: Dwarf (D), Glabrescent (G), Tall (T), and Middle (M), with M being a result of the hybridization of G and T. Ecotype D, adapted to dry environments, is characterized by small tree size, dense thick leaves with abundant hairs, and is distributed in dry scrub. Ecotype G, adapted to understory of mesic forests, lacks leaf hairs. Ecotype T, adapted to the canopy of mesic forests, has hairy leaves and is tall in tree height. Ecotype M, adapted to the canopy of mesic scrub or edges of mesic forests, has hairy leaves but with a shorter tree height than ecotype T. Flowering peaks differed among all ecotype pairs except G and M, but the flowering times more or less overlapped among all ecotypes, suggesting that pre-mating isolation among ecotypes is not perfect. Post-mating isolation is considered absent, as there were no differences in the results, germination, and survival rates of one-year seedlings among inter- and intra-ecotype crossings. The existence of such ecotypes provides valuable insights into the ongoing speciation processes adapting to the oceanic island environments.

Contrasting genetic diversity between Planchonella obovata sensu lato (Sapotaceae) on old continental and young oceanic island populations in Japan.

Genetic diversity of plant populations on islands is likely to be influenced by characteristics such as island origin (oceanic or continental) and their age, size, and distance to continental landmasses. In Japan, Planchonella obovata sensu lato which is found on both continental and oceanic islands of varying age, size, and distance to East Asian continental areas-is an ideal system in which to investigate the factors influencing genetic diversity of island plant species. In this study, we examined the genetic diversity of P. obovata s.l. populations, in the context of the species population genetic structure, demography, and between island migration, from 668 individuals, 28 populations and 14 islands including both continental (the Yaeyama Islands) and oceanic islands (the Daito, Bonin, and Volcano Islands) using 11 microsatellite markers. The Yaeyama and Volcano Islands respectively had the highest and lowest genetic diversity, and island origin and age significantly affected genetic diversity. Clustering analysis revealed that populations were grouped into Bonin, Volcano, and Yaeyama + Daito groups. However, Bonin and Volcano groups were distinct despite the relatively short geographical distance between them. Approximate Bayesian Computation analysis suggested that the population size was stable in Bonin and Yaeyama + Daito groups, whereas population reduction occurred in Volcano group, and migration between groups were very limited. Younger oceanic islands showed lower genetic diversity, probably due to limited gene flow and a lack of time to accumulate unique alleles. Genetic structure was generally consistent with the geographic pattern of the islands, but in Volcano, a limited number of founders and limited gene flow among islands are likely to have caused the large genetic divergence observed.

Multiple origins of two Ochrosia (Apocynaceae) species endemic to the Bonin (Ogasawara) Islands.

The genus, Ochrosia, is widely distributed from the West Indian Ocean throughout tropical Asia to the Middle Southern Pacific region. Ochrosia comprises many island-endemic species, suggesting that long-distance dispersal and isolation after migration are key factors for clarifying the diversification process. However, the phylogeny and biogeography of endemic Ochrosia species have not been evaluated well due to the difficulty of adequate sampling from the entire distribution range of the genus. In this study, we focused on two Ochrosia species endemic to the Bonin (Ogasawara) Islands in the northwest Pacific. The Bonin Islands are of volcanic origins and consist of two islands groups, the Ogasawara and Volcano Islands groups, approximately 300 km apart. Ochrosia nakaiana is endemic to the Ogasawara Islands group, whereas O. hexandra is endemic to the Volcano Islands group. To elucidate the phylogenetic positions of these two endemic Ochrosia species, we conducted molecular phylogenetic studies with dating and biogeographic analyses including other Ochrosia species. The phylogenetic trees showed that the two endemic species had distinct origins; O. nakaiana was closely related to O. oppositifolia and O. iwasakiana, whereas O. hexandra was related to O. mariannensis. Based on the chloroplast DNA phylogeny, the genus, Ochrosia, divided into two major lineages 36.6 million years ago. Further, the two endemic species of the Bonin Islands were independently derived approximately 1-2 million years ago. Ochrosia nakaiana originated from the Southeast Asia, New Caledonia, or other Pacific Islands, while O. hexandra derived from O. mariannensis in Micronesia. We demonstrated different origins of the two endemic Ochrosia species on the Bonin Islands. This study provided an excellent example of the complex origins and speciation of flora in the oceanic islands.

Cochlear Implantation in Cases of Inner Ear Malformation: A Novel and Simple Grading, Intracochlear EABR, and Outcomes of Hearing.

OBJECTIVE: To propose a simple grading of inner ear malformation (IEM) and investigate intracochlear electrical auditory brainstem response (EABR) and outcomes for hearing in terms of the novel grading system. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Sixty patients with IEMs who received cochlear implants. INTERVENTION: Grading according to observation of modiolus deficiency and/or internal auditory canal (IAC) cochlear nerve deficiency (CND). MAIN OUTCOME MEASURE: Intracochlear EABR and categories of auditory performance (CAP) scores were assessed; children in school were categorized according to the type of school attended. RESULTS: Among 60 patients, 38% were classified as Grade I (modiolus present + normal cochlear nerve), 22% as grade II (modiolus deficiency + normal cochlear nerve), 33% as grade III (modiolus present + IAC CND), and 7% as grade IV (modiolus deficiency + IAC CND). During the operation, 93% of Grade I, 36% of Grade II, 23% of Grade III, and 50% of Grade IV patients showed typical EABR waves. CAP scores of 4 or more were obtained from 91% of Grade I, 62% of Grade II, 35% of Grade III, and 25% of Grade IV. Whereas none of children in Grades III and IV entered main stream school, 55% of Grade I and 25% of Grade II entered mainstream schools. CONCLUSIONS: Outcomes of hearing with cochlear implantations in IEM children depend on the severity of IEM and IAC CND. Our novel grading of IEM is simple and can be useful for understanding the severity of IEM.

Genetic diversity, structure, and demography of Pandanus boninensis (Pandanaceae) with sea drifted seeds, endemic to the Ogasawara Islands of Japan: Comparison between young and old islands.

Pandanus boninensis, endemic to the Ogasawara Islands, Japan, is distributed on both the older Bonin and younger Volcano Islands. In this study, we conducted population genetic analyses of P. boninensis on these islands to examine the population diversity and structure across old and young islands, to assess potential differences in population demography with island age, and to collect any evidence of migration between old and young islands. We found that the genetic diversity of expressed sequence tag (EST)-based microsatellite (SSR) markers, the nucleotide diversity of nuclear DNA sequences, and the haplotype diversity of chloroplast DNA on young islands were lower than those on old islands. Clustering analyses of EST-SSR indicated that populations on old islands were strongly diverged from those on young islands. Approximate Bayesian computation analysis of EST-SSR suggested that population expansion occurred on old islands while population reduction occurred on young islands. We also found evidence of migration among old islands (mostly from south to north), while it appears that there have been very few migration events between old and young islands. These differences could be due to the fact that young islands tend to be geographically isolated and support smaller populations that began a shorter time ago from limited founders. The P. boninensis populations on the Volcano Islands are interesting from an evolutionary perspective as they constitute a classic example of the early stages of progressive colonization on oceanic islands with small effective population sizes and low genetic diversity.

Strong genetic structure revealed by microsatellite variation in Callicarpa species endemic to the Bonin (Ogasawara) Islands.

Adaptive radiation is the diversification of a founding population into multiple taxa that are differentially adapted to diverse ecological niches. The three Callicarpa (Lamiaceae) species endemic to the Bonin Islands are considered to represent an example of adaptive radiation on oceanic islands. All three species are distributed in the Chichijima Island Group and grow in different habitats, while only one species, C. subpubescens, is distributed among other island groups. Particularly, in the Hahajima and Mukojima Island Groups, C. subpubescens grows in various habitats and shows relatively high morphological variation. We investigated genotypes of the three Callicarpa species at 14 microsatellite markers to elucidate genetic differentiation within and between species or island groups and between different habitats or morphologies. We found that genetic differentiation within C. subpubescens in the Hahajima and Mukojima Island Groups was equally as high as that between the three species in the Chichijima Island Group, while differentiation within C. subpubescens in the Chichijima Island Group was much lower. Analyses such as a Bayesian clustering analysis showed that genetically distinct groups were associated with the three species in the Chichijima Island Group, whereas they showed strong genetic structure within C. subpubescens in the Hahajima and Mukojima Island Groups among different habitats and morphologies. These results indicated that ecological diversification occurred in the Hahajima and Mukojima Island Groups. Meanwhile, high genetic differentiation among different island groups was also observed, reflecting isolation by distance. It implies that non-ecological factors such as geographic isolation also played important roles in genetic differentiation in Callicarpa species in the Bonin Islands. These findings suggest that the Callicarpa species in the Bonin Islands are differentiated into multiple genetic groups by both ecological and non-ecological factors.

Molecular and karyological data confirm that the enigmatic genus Platypholis from Bonin-Islands (SE Japan) is phylogenetically nested within Orobanche (Orobanchaceae).

Molecular phylogenetic studies have greatly improved our understanding of phylogenetic relationships of non-photosynthetic parasitic broomrapes (Orobanche and related genera, Orobanchaceae), but a few genera have remained unstudied. One of those is Platypholis, whose sole species, Platypholis boninsimae, is restricted to the Bonin-Islands (Ogasawara Islands) about 1000 km southeast of Japan. Based on overall morphological similarity, Platypholis has been merged with Orobanche, but this hypothesis has never been tested with molecular data. Employing maximum likelihood and Bayesian analyses on a family-wide data set (two plastid markers, matK and rps2, and three nuclear markers, ITS, phyA and phyB) as well as on an ITS data set focusing on Orobanche s. str., it is shown that P. boninsimae Maxim. is phylogenetically closely linked to or even nested within Orobanche s. str. This position is supported both by morphological evidence and by the newly obtained chromosome number of 2n = 38, which is characteristic for the genus Orobanche s. str.

Development of SSR markers for Psychotria homalosperma (Rubiaceae) and cross-amplification in four other species.

PREMISE OF THE STUDY: Twenty-six microsatellite (simple sequence repeat [SSR]) markers were characterized in Psychotria homalosperma (Rubiaceae), an endemic evergreen tree in the Bonin Islands, Japan, to investigate the genetic structure and gene flow of the species. METHODS AND RESULTS: Using next-generation sequencing, we developed 26 SSR markers for P. homalosperma with perfect motifs from di- to pentanucleotide repeats. Of these, the Chichijima and Hahajima island populations of P. homalosperma had mean allele numbers of 6.50 and 6.81, respectively. The mean expected heterozygosities were 0.578 and 0.606, respectively. In addition, 10 and eight of these markers were successfully amplified for P. boninensis and P. serpens, respectively, occurring in the same or adjacent areas. CONCLUSIONS: The SSR markers developed in this study will be useful for future studies concerning the population genetics of P. homalosperma and will facilitate the development of a conservation strategy.

Genetic differentiation in Elaeocarpus photiniifolia (Elaeocarpaceae) associated with geographic distribution and habitat variation in the Bonin (Ogasawara) Islands.

Gene flow between populations in different environmental conditions can be limited due to divergent natural selection, thus promoting genetic differentiation. Elaeocarpus photiniifolia, an endemic tree species in the Bonin Islands, is distributed in two types of habitats, dry scrubs and mesic forests. We aim to elucidate the genetic differentiation in E. photiniifolia within and between islands and between the habitat types. We investigated genotypes of 639 individuals from 19 populations of E. photiniifolia and its closely-related E. sylvestris at 24 microsatellite loci derived from expressed sequence tags. The data revealed genetic differentiation (1) between E. photiniifolia and E. sylvestris (0.307 ≤ F ST ≤ 0.470), (2) between the E. photiniifolia populations of the Chichijima and Hahajima Island Groups in the Bonin Islands (0.033 ≤ F ST ≤ 0.121) and (3) between E. photiniifolia populations associated with dry scrubs and mesic forests in the Chichijima Island Group (0.005 ≤ F ST ≤ 0.071). Principal coordinate analysis and Bayesian clustering analysis also showed that genetically distinct groups were associated with the habitat types, and isolation by distance was not responsible for the genetic differentiation. These findings suggest that E. photiniifolia is divided into genetically differentiated groups associated with different environmental conditions in the Bonin Islands.

Development of EST-SSR markers for Elaeocarpus photiniifolia (Elaeocarpaceae), an endemic taxon of the Bonin Islands.

PREMISE OF THE STUDY: Expressed sequence tag (EST)-derived microsatellite markers were developed for Elaeocarpus photiniifolia, an endemic taxon of the Bonin Islands. METHODS AND RESULTS: Initially, a complementary DNA (cDNA) library was constructed by de novo pyrosequencing of total RNA extracted from a seedling. A total of 267 primer pairs were designed from the library. Of the 48 tested loci, 25 loci were polymorphic among 41 individuals representing the entire geographical range of the species, with the number of alleles per locus and expected heterozygosity ranging from two to 14 and 0.09 to 0.86, respectively. Most loci were transferable to a related species, E. sylvestris. CONCLUSIONS: The developed markers will be useful for evaluating the genetic structure of E. photiniifolia.

A study of electron scattering from benzene: excitation of the 1B1u, 3E2g, and 1E1u electronic states.

We report results from measurements for differential and integral cross sections of the unresolved (1)B(1u) and (3)E(2g) electronic states and the (1)E(1u) electronic state in benzene. The energy range of this work was 10-200 eV, while the angular range of the differential cross sections was ∼3°-130°. To the best of our knowledge there are no other corresponding theoretical or experimental data against which we can compare the present results. A generalized oscillator strength analysis was applied to our 100 and 200 eV differential cross section data, for both the (1)B(1u) and (1)E(1u) states, with optical oscillator strengths being derived in each case. The respective optical oscillator strengths were found to be consistent with many, but not all, of the earlier theoretical and experimental determinations. Finally, we present theoretical integral cross sections for both the (1)B(1u) and (1)E(1u) electronic states, as calculated within the BEf-scaling formalism, and compare them against relevant results from our measurements. From that comparison, an integral cross section for the optically forbidden (3)E(2g) state is also derived.

Electron excitation of the Schumann-Runge continuum, longest band, and second band electronic states in O2.

We report measurements of differential and integral cross sections for electron excitation of the Schumann-Runge continuum, longest band, and second band electronic states in molecular oxygen. The energy range of the present study is 15-200 eV, with the angular range of the differential cross section (DCS) measurements from 2 to 130°. A generalized oscillator strength analysis is then employed in order to derive integral cross sections (ICSs) from the corresponding DCSs, and these ICSs are compared with relevant energy and oscillator strength scaled Born cross section (BEf-scaling [Y.-K. Kim, J. Chem. Phys. 126, 064305 (2007)]) results determined as a part of this investigation. Interestingly, while the present Schumann-Runge continuum and second band ICSs were in reasonable agreement with the respective BEf-scaling results, agreement for the longest band was poor below 100 eV with a possible reason for this apparently anomalous behavior being canvassed here. Finally, where possible all present data are compared with the results from earlier measurements and calculations with the level of agreement found being very good in some cases and marginal in others.

Origin and diversification of Hibiscus glaber, species endemic to the oceanic Bonin Islands, revealed by chloroplast DNA polymorphism.

Abstract Two woody Hibiscus species co-occur in the Bonin Islands of the northwestern Pacific Ocean: Hibiscus glaber Matsum. is endemic to the islands, and its putative ancestral species, Hibiscus tiliaceus L., is widely distributed in coastal areas of the tropics and subtropics. To infer isolating mechanisms that led to speciation of H. glaber and the processes that resulted in co-occurrence of the two closely related species on the Bonin Islands, we conducted molecular phylogenetic analyses on chloroplast DNA (cpDNA) sequences. Materials collected from a wide area of the Pacific and Indian Oceans were used, and two closely related species, Hibiscus hamabo Siebold Zucc. and Hibiscus macrophyllus Roxb., were also included in the analyses. The constructed tree suggested that H. glaber has been derived from H. tiliaceus, and that most of the modern Bonin populations of H. tiliaceus did not share most recent ancestry with H. glaber. Geographic isolation appears to be the most important mechanism in the speciation of H. glaber. The co-occurrence of the two species can be attributed to multiple migrations of different lineages into the islands. While a wide and overlapping geographical distribution of haplotypes was found in H. tiliaceus, localized geographical distribution of haplotypes was detected in H. glaber. It is hypothesized that a shift to inland habitats may have affected the mode of seed dispersal from ocean currents to gravity and hence resulted in geographical structuring of H. glaber haplotypes.

Ant-colonized domatia on fruits of Mucuna interrupta (Leguminosae).

Domatia of myrmecophytes have been reported only in vegetative organs so far. In this paper, we report the first record of domatia formed on the legume surface of Mucuna interrupta. The domatium consists of 12-16 vertical lamellae which traverse the fruit surface obliquely to form long, narrow hollows, providing two ant species with a nest site.