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Hokkaido Island (hokkaido + island)
Selected AbstractsSEQUENTIAL RAPID ADAPTATION OF INDIGENOUS PARASITOID WASPS TO THE INVASIVE BUTTERFLY PIERIS BRASSICAEEVOLUTION, Issue 8 2007Shingo Tanaka The introduction of a new species can change the characteristics of other species within a community. These changes may affect discontiguous trophic levels via adjacent trophic levels. The invasion of an exotic host species may provide the opportunity to observe the dynamics of changing interspecific interactions among parasitoids belonging to different trophic levels. The exotic large white butterfly Pieris brassicae invaded Hokkaido Island, Japan, and quickly spread throughout the island. Prior to the invasion, the small white butterfly P. rapae was the host of the primary parasitoid Cotesia glomerata, on which both the larval hyperparasitoid Baryscapus galactopus and the pupal hyperparasitoid Trichomalopsis apanteroctena depended. At the time of the invasion, C. glomerata generally laid eggs exclusively in P. rapae. During the five years following the invasion, however, the clutch size of C. glomerata in P. rapae gradually decreased, whereas the clutch size in P. brassicae increased. The field results corresponded well with laboratory experiments showing an increase in the rate of parasitism in P. brassicae. The host expansion of C. glomerata provided the two hyperparasitoids with an opportunity to choose between alternative hosts, that is, C. glomerata within P. brassicae and C. glomerata within P. rapae. Indeed, the pupal hyperparasitoid T. apanteroctena shifted its preference gradually to C. glomerata in P. brassicae, whereas the larval hyperparasitoid B. galactopus maintained a preference for C. glomerata in P. rapae. These changes in host preference may result from differential suitability of the two host types. The larval hyperparasitoid preferred C. glomerata within P. rapae to C. glomerata within P. brassicae, presumably because P. brassicae larvae attacked aggressively, thereby hindering the parasitization, whereas the pupal hyperparasitoid could take advantage of the competition-free resource by shifting its host preference. Consequently, the invasion of P. brassicae has changed the host use of the primary parasitoid C. glomerata and the pupal hyperparasitoid T. apanteroctena within a very short time. [source] Transport of subarctic large copepods from the Oyashio area to the mixed water region by the coastal Oyashio intrusionFISHERIES OCEANOGRAPHY, Issue 5 2009YUGO SHIMIZU Abstract The lateral transport of organic carbon in large grazing copepods (Neocalanus cristatus, Neocalanus flemingeri, Neocalanus plumchrus and Eucalanus bungii) from the Oyashio area to the mixed water region (MWR) by the coastal Oyashio intrusion was estimated using the data of VMPS (vertical multiple plankton sampler) and 1500 dbar-referred geostrophic transport from the CTD (conductivity temperature depth sensor) data of five cruises during June 2001 to April 2002 on a repeat observation section OICE (Oyashio Intensive observation line off Cape Erimo), which extends southeastward from Hokkaido Island, Japan. The transport to MWR by the coastal Oyashio intrusion was estimated to be 5.3 × 1011 g C for the four species. Data from profiling floats also indicated that the copepods were advected from OICE to MWR by the coastal Oyashio intrusion within about 2 months. This transport is considered to be one of the significant sources of organic carbon in MWR as it is larger than the amount of large zooplankton consumed by Pacific saury (Cololabis saira) in MWR, one of the dominant copepod predators in this region. [source] Relationship of topography to surface water chemistry with particular focus on nitrogen and organic carbon solutes within a forested watershed in Hokkaido, JapanHYDROLOGICAL PROCESSES, Issue 2 2006Akiko Ogawa Abstract We studied the relationships between streamwater chemistry and the topography of subcatchments in the Dorokawa watershed in Hokkaido Island, northern Japan, to examine the use of topography as a predictor of streamwater chemistry in a watershed with relatively moderate terrain compared with other regions of Japan. Topographic characteristics of the Dorokawa watershed and its subcatchments were expressed as topographic index (TI) values, which ranged from 4·5 to 20·4 for individual grid cells (50 × 50 m2), but averaged from 6·4 to 7·4 for the 20 subcatchments. Streamwater samples for chemical analyses were collected four times between June and October 2002 from 20 locations in the watershed. The pH of water that passed through the watershed increased from ,5·0 to 7·0, with major increases in Na+ and Ca2+ and marked decreases in NO3, and SO. Distinctive spatial patterns were observed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and NO3, concentrations of streamwater across the watershed. Statistical analyses indicated significant linear relationships between the average TI values of subcatchments and DOC, DON, and NO3, concentrations. Furthermore, the proportion of DOC in streamwaters in the wet season increased with TI values relative to other nitrogen species, whereas NO3, concentrations decreased with TI. The gradients of soil wetness and the presence of wetlands explained many of the observed spatial and temporal patterns of DOC, DON, and NO3, concentrations in the surface waters of the Dorokawa watershed. Our results suggest that the TI is especially useful for predicting the spatial distribution of DOC, DON and NO3, in the surface waters of Hokkaido, where topographical relief is moderate and wetlands more common than in other regions of Japan. Copyright © 2006 John Wiley & Sons, Ltd. [source] Contrasting patterns of nuclear microsatellite genetic structure of Fraxinus mandshurica var. japonica between northern and southern populations in JapanJOURNAL OF BIOGEOGRAPHY, Issue 6 2010Li-Jiang Hu Abstract Aim, The aim of this study is to detect extant patterns of population genetic structure of Fraxinus mandshurica var. japonica in Japan, and to provide insights into the post-glacial history of this species during the Holocene. Location, Hokkaido and Honshu islands, Japan (including the Oshima and Shimokita peninsulas). Methods, We examined nine polymorphic nuclear microsatellite loci to assess genetic variation within and among 15 populations across almost the entire range of the species in Japan. Extant patterns of geographical structure were analysed using Bayesian clustering, Monmonier's algorithm, analysis of molecular variance, Mantel tests and principal coordinates analysis. Recent bottlenecks within populations and regional genetic variation were also assessed. Results, Northern populations (Hokkaido Island and the Shimokita Peninsula) formed a single homogeneous deme, maintaining the highest level of allelic diversity on the Oshima Peninsula. By contrast, southern populations (Honshu Island) demonstrated strong substructure on both coasts. Specifically, populations on the Pacific side of Honshu exhibited significant bottlenecks and erosion of allelic diversity but preserved distinct subclusters diverging from widespread subclusters on the Japan Sea side of this island. Main conclusions, Genetic evidence and life history traits suggest that F. mandshurica occupied cryptic northern refugia on the Oshima Peninsula during the Last Glacial Maximum, which is reflected in the species' extant northern distribution. Strong geographical structure in southern populations, in agreement with fossil pollen records, suggests geographical isolation by mountain ranges running north,south along Honshu. Given that this tree species is cold-adapted and found in riparian habitats, populations on the Pacific side of Honshu probably contracted into higher-elevation swamps during warm post-glacial periods, leading to a reduction of effective population sizes and rare allelic richness. [source] Phylogeography of a northeast Asian spruce, Picea jezoensis, inferred from genetic variation observed in organelle DNA markersMOLECULAR ECOLOGY, Issue 16 2007M. AIZAWA Abstract Range-wide genetic variation of the widespread cold-temperate spruce Picea jezoensis was studied throughout northeast Asia using maternally inherited mitochondrial DNA and paternally inherited chloroplast DNA markers. This study assessed 33 natural populations including three varieties of the species in Japan, Russia, China, and South Korea. We depicted sharp suture zones in straits around Japan in the geographical distribution pattern of mitochondrial haplotypes (GST = 0.901; NST = 0.934). In contrast, we detected possible extensive pollen flow without seed flow across the straits around Japan during the past population history in the distribution pattern of chloroplast haplotypes (GST = 0.233; NST = 0.333). The analysis of isolation by distance of the species implied that by acting as a barrier for the movement of seeds and pollen, the sharp suture zones contributed considerably to the level of genetic differentiation between populations. Constructed networks of mitochondrial haplotypes allowed inference of the phylogeographical history of the species. We deduced that the disjunction with Kamchatka populations reflects range expansion and contraction to the north of the current distribution. Within Japan, we detected phylogeographically different types of P. jezoensis between Hokkaido and Honshu islands; P. jezoensis in Honshu Island may have colonized this region from the Asian continent via the Korean peninsula and the species in Hokkaido Island is likely to have spread from the Asian continent via Sakhalin through land bridges. Japanese endemism of mitochondrial haplotypes in Hokkaido and Honshu islands might have been promoted by separation of these islands from each other and from the Asian continent by the straits during the late Quaternary. [source] | ||||||||||