To clarify the evolutionary history of the Lilium maculatum–L. pensylvanicum complex in Japan and to improve the circumscription of its component taxa, we conducted phylogenetic analyses based on ...chloroplast and nuclear internal and external transcribed spacer (ITS, ETS) DNA sequences, a genome‐wide analysis of single‐nucleotide polymorphisms (SNPs) using multiplexed ISSR genotyping by sequencing (MIG‐seq), and morphological observations. Topological differences between the chloroplast and nuclear ITS + ETS phylogenies indicate that ancient hybridization or incomplete lineage sorting were involved in the origin of “maculatum”, but the relatively long length of relevant branches indicates that incomplete lineage sorting is implausible. The results of STRUCTURE analysis (K = 3, the highest delta K value) using MIG‐seq indicate that “maculatum” has already developed its own cluster and can be considered a species (L. maculatum) that originated through the hybridization of L. pacificum (sp. nov.) and L. pensylvanicum. MIG‐seq Neighbor‐Net and STRUCTURE analyses (K = 3), as well as chloroplast DNA phylogeny, reveal that populations in disjunct limestone areas (L. maculatum var. bukosanense) originated via the hybridization of L. maculatum and L. pacificum, whereas populations in the Sado‐Tobishima Islands (L. maculatum var. sadoense, var. nov.) originated via hybridization between L. maculatum and L. pensylvanicum. These taxa appear to be more or less genetically isolated from other populations based on the STRUCTURE analysis (K = 5), although we do not know whether this isolation resulted from geographic distance or reproductive barriers. Based on available MIG‐seq and morphological data, respectively, we consider the two hybrid‐origin populations to be independent varieties. Furthermore, the morphology of seaside populations of L. maculatum in East Tohoku District appears to have deviated slightly from that of mountain populations (L. maculatum f. monticola); as such, coastal populations merit recognition as a form of L. maculatum (L. maculatum f. spontaneum, comb. & stat. nov.). Other seaside populations of L. maculatum in the West Tohoku District appear to have originated from populations of L. pacificum, but have been successively taken over by L. maculatum through introgression, and have consequently evolved into a form of L. maculatum (L. maculatum f. maculatum). In addition, we found putative extant hybrid populations of L. maculatum × L. pensylvanicum. We recognize three species, two varieties, two forms, and one hybrid in the L. maculatum–L. pensylvanicum complex in Japan.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In den letzten Jahren sind wichtige Entwicklungen im Bereich der Schweißstromquellen und den Zusatzwerkstoffen für das Metall-Inertgas (MIG)-Schweißen von Magnesiumlegierungen gemacht worden. Diese ...Fortschritte führen zu einem wesentlich besseren Schweißprozeß und damit zu einem stark verbesserten Schweißergebnis. Von entscheidender Bedeutung für den Schweißprozeß ist die Energieeinbringung in den Draht. Die Schwierigkeiten resultieren aus den physikalischen Eigenschaften von Magnesium (Schmelzpunkt ca. 600 °C, Verdampfungspunkt ca. 1100 °C). Die Energiezuführung in den Draht muss so geregelt werden, dass es zwar zum Schmelzen, aber nicht zum Verdampfen des Drahtes kommt. Hierzu sind spezielle Stromquellenverläufe untersucht worden. Die Schwingfestigkeit der untersuchten Magnesiumlegierungen liegt im geschweißten Zustand bei ca. 50 % des Grundwerkstoffs. Bei abgearbeiteter Naht ergeben sich Festigkeiten von bis zu 75 % des Grundwerkstoff wertes.
Premise
Snow is an important environmental factor affecting plant distribution. Past changes in snowfall regimes may have controlled the demographies of snow‐dependent plants. However, our knowledge ...of changes in the distribution and demographies of such plants is limited because of the lack of fossil records.
Methods
Population genetic and landscape genetic analyses were used to investigate the response of population dynamics of Arnica mallotopus (Asteraceae)—a plant confined to heavy‐snow areas of Japan—to changes in snowfall regimes from the Last Glacial Period to the Holocene.
Results
The population genetic analysis suggested that the four geographic lineages diverged during the Last Glacial Period. The interaction between reduced snowfall and lower temperatures during this period likely triggered population isolation in separate refugia. Subpopulation differentiation in the northern group was lower than in the southern group. Our ecological niche model predicted that the current distribution was patchy in the southern region; that is, the populations were isolated by topologically flat and climatically unsuitable lowlands. The landscape genetic analysis suggested that areas with little snowfall acted as barriers to the Holocene expansion of species distribution and continued limiting gene flow between local populations.
Conclusions
These findings indicate that postglacial population responses vary among regions and are controlled by environmental and geographic factors. Thus, changes in snowfall regime played a major role in shaping the distribution and genetic structure of the snow‐dependent plant.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Geographical parthenogenesis, a phenomenon where parthenogens and their close sexual relatives inhabit distinct geographical areas, has been considered an interesting topic in evolutionary biology. ...Reports of geographical parthenogenesis from land and freshwater are numerous, but this occurrence has been rarely reported from the sea. Brown algae are mostly marine and are thought to include numerous obligate parthenogens; still, little is known about the distribution, origin and evolution of parthenogens in this group. Here we report a novel pattern of geographical parthenogenesis in the isogamous brown alga Scytosiphon lomentaria. Sex ratio investigation demonstrated that, in Japan, sexual populations grew in the coast along warm ocean currents, whereas female‐dominant parthenogenetic populations grew mainly in the coast along a cold ocean current. In the two localities where sexual and parthenogenetic populations were parapatric, parthenogens grew in more wave‐exposed areas than sexuals. Population genetic and phylogenetic analyses, including those based on genome‐wide single nucleotide polymorphism data, indicated that parthenogens have initially evolved at least twice and subsequent hybridizations between the parthenogens and sexuals have generated multiple new parthenogenetic lineages. The origin of the initial parthenogens is not clear, except that it would not be interspecies hybridization. Interestingly, we found that the production of sex pheromones, which attract male gametes, has been independently lost in the initial two parthenogenetic lineages. This parallel loss of the sexual trait may represent the direct origin of parthenogens, or the regressive evolution of a useless trait under asexuality.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The AA6082 aluminum alloy was welded by oscillating laser-MIG hybrid welding. By using beam oscillation, the porosity can be effectively suppressed in the range of 100−300 A arc current, especially ...at low arc current level. Percent porosity decreased greatly with the increase of the oscillating amplitude and frequency. The threshold frequency of porosity-free at different amplitudes were achieved. The effect of beam oscillation on porosity formation and suppression was studied by observing keyhole behavior via a “sandwich” high-speed video method. It was found that the porosity suppression depended on three reasons. Firstly, high-frequency oscillating keyhole can “capture” the bubbles or cavities in the molten pool and solidification front. Secondly, high-frequency oscillating keyhole can enlarge the diameter of keyhole and improve keyhole stability. Thirdly, beam oscillation can form stirring effect in molten pool, which can produce turbulence to reduce possibility of bubbles moving to the solidification front.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Molecular phylogenetic analysis was conducted using single-nucleotide polymorphism data from Chinese plants with pubescent stems, similar to Cassytha filiformis var. duripraticola, which has been ...known to distribute in Japan and Taiwan. The phylogenetic analysis demonstrated that the Chinese plants were included in the same clade with plants of C. filiformis var. duripraticola obtained from Japan and Taiwan. This study is the first report of C. filiformis var. duripraticola from Mainland China based on the morphological and molecular features.
Premise
Quaternary climatic fluctuations and long‐distance seed dispersal across the sea are critical factors affecting the distribution of coastal plants, but the spatiotemporal nature of population ...expansion and distribution change of East Asian coastal plants during this period are rarely examined. To explore this process, we investigated the genome‐wide phylogenetic patterns of Euphorbia jolkinii Boiss. (Euphorbiaceae), which grows widely on littoral areas of Japan, Korea, and Taiwan.
Methods
We used plastome sequences and genome‐wide single nucleotide polymorphisms in samples across the species range to reveal phylogeographic patterns and spatiotemporal distributional changes. We conducted ecological niche modeling for the present and the last glacial maximum (LGM).
Results
Genetic differentiation was observed between the northern and southern populations of E. jolkinii, separated by the major biogeographic boundary, the Tokara Gap. These two groups of populations differentiated during the glacial period and subsequently intermingled in the intermorainic areas of the central Ryukyu Islands after the LGM. Ecological niche models suggested that the potential range of E. jolkinii was restricted to southern Kyushu; however, it was widespread in the southern Ryukyu Islands and Taiwan during the LGM.
Conclusions
This study provides evidence of genetic differentiation among coastal plant populations separated by the prominent biogeographical boundary. Although coastal plants are typically expected to maintain population connectivity through sea‐drifted seed dispersal, our findings suggest that genetic differences may arise because of a combination of limited gene flow and changes in climate during the glacial period.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
