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.     

Polistes formosanus (Hymenoptera: Vespidae), a good species supported by both morphological and molecular phylogenetic analyses, and a key social wasp in understanding the historical biogeography of the Nansei Islands

Polistes formosanus Sonan, 1927 is closely related to P. japonicus de Saussure, 1858, and has been treated variously as a good species or subspecies or synonym of P. japonicus. We designate the lectotype of P. formosanus. Detailed examination of morphological characters of specimens from continental Asia, Taiwan, the Nansei Islands and main islands of Japan showed that P. formosanus is a good species different from P. japonicus. Molecular phylogenetic analyses using mitochondrial genes also supported this conclusion. Polistes formosanus is distributed in northern and central Taiwan and in the Nansei Islands and extends northward to the Amami Islands, while P. japonicus occurs in continental Asia, central Taiwan, Korean Peninsula, Honshu to Kyushu of Japan and the Osumi Islands (Yakushima and Tanega-shima Island) of the Nansei Islands. The speciation and biogeography of P. formosanus are briefly discussed.     

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.     

Phytogeographic aspects of Lysionotus pauciflorus sensu lato (Gesneriaceae) in the China, Japan and Taiwan regions: phylogenetic and morphological relationships and taxonomic consequences

Comparison of leaf morphometric variation and phylogenetic analyses based on nrITS and partial trnC-D cpDNA sequences were conducted for samples of Lysionotus pauciflorus sensu lato collected from China, Japan and Taiwan. In the morphometric comparison, leaves of plants from Japan proper and those from Taiwan proper were not significantly distinguishable by their leaf length to width ratio. In phylogenetic analyses, monophyly of L. pauciflorus s. l. samples was strongly supported, and Japanese and Taiwanese samples fell into a clade separate from Chinese samples. In the Japan?CTaiwan clade, plants from Japan proper formed a sister clade to those from Okinawa Island (Japan) and Taiwan. The present results suggest that (1) the L. pauciflorus s. l. samples from China, Japan and Taiwan must be treated as a single species; (2) L. pauciflorus s. l. originated in China; (3) a single dispersal event, dispersal via a land-bridge during low sea levels in a Pleistocene glacial maximum, from China to Taiwan and Japan is proposed; (4) three oversea dispersal events, probably through anemochory, to Japan proper, across the Tokara Gap, to Okinawa islands crossing the Kerama Gap, and from Taiwan to Lanyu Island are proposed. The study gives further insight into the biogeographical dynamics between the Ryukyus and surrounding areas.     

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.     

Distribution of S-alleles in island populations of flowering cherry, Prunus lannesiana var. speciosa

We surveyed the distribution of S-alleles in natural island populations of Prunus lannesiana var. speciosa sampled from seven sites on the Izu Peninsula and six Izu islands, Japan. The S-genotypes of sampled individuals were determined by Southern analysis of RFLPs generated by restriction enzyme digestion of genomic DNA, using cDNA of the S-RNase gene as a probe. All individuals were heterozygous, as expected under gametophytic self-incompatibility (GSI). Sixty-three S-alleles were observed in the species, but 12 private to the Izu Peninsula population seemed to be derived from related species, giving a total of 75. The estimated number of S-alleles in each population ranged from 26 to 62, and was inversely correlated with the respective population's distance from the Izu Peninsula, the closest point in the mainland to the islands. This geographical cline in the estimated numbers of S-alleles suggests that gene flow to and from the distant island populations was less frequent, and that the studied species has migrated from the mainland to the Izu islands. The genetic relationship at the S-locus among populations also gave an "isolation by distance" pattern. The genetic differentiation at the S-locus among the populations was very low (F(ST) = 0.014, p < 0.001). The number of S-alleles in the species did not seem to depend on genetic differences associated with population subdivisions. This might be due to the greater effective migration rates of S-alleles, as expected under balancing selection in GSI.     

Multiple origins of Locusta migratoria (Orthoptera: Acrididae) in the Japanese Archipelago and the presence of two major clades in the world: evidence from a molecular approach

Phylogenetic relationships among migratory locust (Locusta migratoria) populations in different climatic regions were analysed by sequencing four mitochondrial DNA regions, with special reference to the origin of Japanese populations. The populations are clearly separated into two clades: one consists of individuals from temperate and cold‐temperate areas of Japan and the Chinese continent, and the other comprises those from subtropical islands of Japan, Hainan Island in China, Timol Leste, Australia, Ethiopia, France, and some individuals from Tsushima Island and Honshu of Japan. The divergence time between the two clades is estimated to be 0.86–1.89 Mya. The phylogenetic analysis revealed that Japanese L. migratoria populations were composed of individuals of six different origins: (1) Hokkaido populations possibly from the Russian continent; (2) Honshu–Kyushu populations from the Chinese continent; (3) Southwest Island populations from Hainan Island or adjacent areas; (4) Ogasawara populations that might have originated from Micronesia; (5) part of the Tsushima population that originated from somewhere in the Asian tropics; and (6) a possible relict population of ancient southern haplotypes that exists in western areas of northern Honshu. The Tsugaru Straits and Tokara Straits have acted as effective geographical barriers, as in other organisms, isolating locust populations for a few thousand years. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 570–581.     

Possible domestic dispersal of Bactrocera dorsalis during 2015 occurrence on the small islands of south‐western Japan

Although Japan has maintained the state of eradication of the oriental fruit fly, Bactrocera dorsalis Hendel complex (Diptera: Tephritidae) since 1986, B. dorsalis complex are occasionally trapped within a limited area and short time period on Japan's small south‐western islands. Trapping events occurred on Amamioshima Island, Kagoshima Prefecture, in 2015, and male adults were also caught in surveillance traps on neighbouring Tokunoshima (south of Amamioshima) and Yakushima (north of Amamioshima) islands as well as on several islands in Okinawa Prefecture (south of Amamioshima). To investigate possible domestic dispersal of the pest from Amamioshima Island, a trajectory analysis was performed to reveal the timing and flight distance of possible dispersal. Surveillance data indicated that the first trappings on Tokunoshima and Yakushima islands occurred in November, which was after the number of trapped male adults on Amamioshima Island peaked in late October. Backward trajectories from Tokunoshima Island beginning 14 days prior to the first trapping passed over Amamioshima Island, which suggested possible dispersal between the islands. Several backward trajectories from the islands in Okinawa Prefecture also passed Amamioshima Island. Moreover, forward trajectories from Amamioshima Island beginning during peak occurrence, from mid‐October to early November, arrived over Tokunoshima, Iheya and Okinawa islands where the flies were caught. Such circumstantial evidence suggests that domestic dispersal of B. dorsalis complex occurred on Amamioshima Island. A situation similar to that on Tokunoshima Island also occurred on Yakushima Island. However, since the number of traps has been limited until the first capture, it was not clear when and from where the immigrants arrived on the island.     

Differentiation of golden-ringed dragonfly Anotogaster sieboldii (Selys, 1854) (Cordulegastridae: Odonata) in the insular East Asia revealed by the mitochondrial gene genealogy with taxonomic implications

Molecular phylogeographical analyses of Anotogaster sieboldii (Selys, 1854) were conducted to reveal the differentiation process of insular populations. The gene genealogy based on 845 bp of the mitochondrial genes (cytochrome oxidase subunit I and subunit II) indicated that A. sieboldii includes two deeply separated lineages. These two major lineages seem to have differentiated in Miocene before the formation of the insular East Asia. One lineage includes three inner clades that correspond to the populations of northern area (the Japanese main islands, Korean Peninsula, Yakushima), Amamioshima and Okinawajima. Populations of Central Ryukyu, including Amamioshima and Okinawajima, might have been divided from the northern populations in early Pleistocene. The other major lineage includes populations of the Yaeyama Group, Taiwan and East China. The former two populations were reconstructed as a reciprocal monophyletic group. Populations of Taiwan and Yaeyama Groups would have been separated from the continental ones in Pleistocene. These two highly divergent lineages should be recognized as distinct species. Furthermore, the mitochondrial lineages revealed six genetically distinct and geographically isolated assemblages: (1) northern populations, (2) Amamioshima, (3) Okinawajima, (4) Yaeyama Group, (5) Taiwan and (6) East China.     

Contrasting patterns of nuclear microsatellite genetic structure of Fraxinus mandshurica var. japonica between northern and southern populations in Japan

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.     

Prehistoric Sado Island populations of Sus scrofa distinguished from contemporary Japanese wild boar by ancient mitochondrial DNA

Ancient mitochondrial DNA (mtDNA) mainly from Jomon Period Sus scrofa bone specimens (6,100-1,700 years old) was examined to clarify the genetic relationships between prehistoric and contemporary S. scrofa on Hokkaido, Honshu, Sado, and Izu islands of the Japanese Archipelago. Phylogenetic analysis of the mtDNA control region (574 bp) and analysis of pairwise nucleotide differences between prehistoric and contemporary S. scrofa sequences showed the following relationships between these groups: (1) a group genetically similar to contemporary Japanese wild boars was found mainly on Honshu Island, Hokkaido Island, and the Izu Islands, and (2) a monophyletic group distinct from contemporary Japanese wild boars was found on Sado Island. These results suggest that prehistoric people introduced S. scrofa from Honshu Island to Hokkaido Island and the Izu Islands. The estimated divergence times between the prehistoric Sado group and the other prehistoric S. scrofa is approximately congruent with the geological isolation of Sado Island from Honshu Island. Our results suggest that this extinct S. scrofa population was present on Sado Island as recently as around 2,000 years ago.     

Growth and survival rates of large-type sporophytes of Ecklonia cava transplanted to a growth environment with small-type sporophytes

Stipe lengths of sporophytes of Ecklonia cava Kjellman have been reported to be longer along the southeast than southwest coast of the Izu Peninsula, central Japan. Two bays in this region that have natural populations of E. cava, but with different stipe lengths, were chosen for transplant experiments to examine if stipe length was an environmentally controlled trait. Transplant experiments were carried out in order to determine whether large-type sporophytes of E. cava with long stipes growing in Nabeta Bay (southeast Izu Peninsula, Japan) would turn into small-type sporophytes with short stipes when transplanted to Nakagi Bay (southwest Izu Peninsula). Ten juvenile sporophytes of E. cava (stipe length < 5 cm) were collected from Nabeta Bay (large-type habitat) and transplanted to Nakagi Bay (short-type habitat) in December 1995. As a transplant control, ten juvenile sporophytes of E. cava growing in Nakagi Bay were also transplanted to the same artificial reefs. Growth and survival rates of the sporophytes were monitored monthly for 3 y until December 1998. The transplanted sporophytes showed an increase in their stipe length and diameter from winter to spring, whereas almost no increase was observed from summer to autumn. However, the elongation was greater in Nabeta sporophytes than in Nakagi sporophytes. The primary blade length increased mainly from winter to early spring and decreased largely in autumn. Average primary blade lengths were similar in both Nabeta and Nakagi sporophytes from the end of the first year of transplanting. Although ca. 70% of both Nabeta and Nakagi sporophytes survived during the first 2 y after transplantation, no Nakagi sporophytes and only two Nabeta sporophytes survived to the end of the 3 y study period. Despite transplantation to Nakagi Bay, where short sitpes are naturally present, the sporophytes from Nabeta Bay persisted in having longer stipes, which suggests that stipe length is genetically, rather than environmentally, controlled.     

Intraspecific diversity of mitochondrial DNA in the land snail Euhadra peliomphala (Bradybaenidae)

Exceptionally high levels of intraspecific variation of mitochondrial DNA (mtDNA) sequences encoding 16S ribosomal RNA (16SrRNA) were detected in populations of the land snail Euhadra peliomphala from the eastern part of Japan. Geographical isolation has occurred within small areas and has created many genetically distinct local populations. These are morphologically segregated into two groups: the first consists of populations from the southern part of the Izu Peninsula, and the second of populations from other areas within the peninsula. They are separated by mountains in the middle of the peninsula. Sequence divergences between these two groups were 7.6–9.5%. The sequence divergences and geological ages of the Izu peninsula and its mountains suggest that the divergence rate of mitochondrial 16SrRNA sequences of this species is extremely rapid, approximately 10% per million years. This rapid evolutional")' rate of mtDNA and vicariance events due to tectonic events and sea level changes has also contributed to creating exceptional geographical variation in the mtDNA of this species.     

Invading a refugium: post glacial replacement of the ancestral lineage of a Nymphalid butterfly in the West Mediterranean

The power of a fixed scenario was compared to that of a dynamic scenario, in order to explain the distribution pattern of two well established subspecies (morphotypes) of the model butterfly species Maniola jurtina in the central Mediterranean. Samples were collected from a transect of 21 sites along the western side of the Italian Peninsula as well as in Sicily, North Africa and some Italian islets in the Tyrrhenian sea. Samples from the Balkans Peninsula have been added for comparison. Geometric morphometrics, suggested as a reliable marker to identify hybrid individuals, were applied to 150 male genitalia. Their shape was analysed by the means of the partial least square (PLS) discriminant analysis and then modelled through geographic information system (GIS) spatial analyses. The timing of invasion was reconstructed by comparing sea-level changes with the recent isobaths both on the mainland and on islands. The occurrence of the eastern morphotype on the Italian Peninsula and of the western morphotype in North Africa and Sicily was confirmed. However, we found intermediate populations at the tip of the Italian Peninsula and on the islands of Ischia and Capri. No intermediate populations were found in Sicily. The fixed scenario is unlikely, since a dispersal of the western morphotype from Sicily to the distant islands of Ischia and Capri might be hypothesized. A more parsimonious hypothesis minimises dispersal across the sea barriers. It assumes the ancestral presence over the entire study area of the western morphotype, which was later replaced on the Italian mainland but maintained on the islands. These rapid movements could drastically modify European biogeographic patterns.     

Late Pleistocene lineage divergence among populations of Neolitsea sericea (Lauraceae) across a deep sea‐barrier in the Ryukyu Islands

Aim Our goals were: (1) to assess the population genetic structure and demographic divergence history of a bird‐dispersed tree, Neolitsea sericea, endemic to East Asian land‐bridge islands; and (2) to interpret the results in the light of controversies over the dating and configurations of land bridges through the Japanese Ryukyu Island Arc. Location Japan–Ryukyu–Taiwan Island Arc and Chinese/Korean offshore islands. Methods We applied 10 nuclear microsatellites (nSSRs) and one chloroplast (cp) DNA sequence marker (psbA–trnH intergenic spacer) to 31 populations (397 and 326 individuals, respectively) from throughout the species’ range to infer current patterns of genetic diversity and structure, and pollen‐to‐seed migration ratios (r). A coalescent‐based isolation‐with‐migration (IM) model was applied to the combined nSSR/cpDNA data set to estimate lineage divergence times and population demographic parameters. Results The geographic structure of nSSRs and the distribution of most cpDNA haplotypes revealed two distinct lineages located in areas north and south of the ‘Tokara Gap’, a narrow (c. 37 km wide) but deep (> 1000 m) sea‐strait between the northern and central Ryukyus. Based on the IM analyses, we (1) dated the divergence of these northern and southern lineages to c. 0.07 Ma (90% highest posterior density interval: 0.02–0.38 Ma); (2) estimated a slightly smaller effective population size for the northern compared to the southern lineage; and (3) recovered only trivial signals of post‐divergence gene flow between them. Main conclusions The estimated divergence time for northern and southern lineages is consistent with geological evidence for the existence of land connections in the Tokara region during cold stages of the latest Pleistocene; it is thus incompatible with an ‘ancient sea‐barrier hypothesis’ for the Ryukyu Arc, where we would have expected much older divergences related to the initial formation of the Tokara and Kerama tectonic straits during the Pliocene. Multiple factors are likely to have had a role in the divergence of N. sericea, including not only land‐bridge submergence, but also island configuration, and/or constraints on adaptation along a latitudinal temperature gradient.     

Phylogeny and phylogeography of the sword-tailed newt,Cynops ensicauda (Amphibia: Caudata), as revealed by nucleotide sequences of mitochondrial DNA

We investigated the phylogenetic relationships and phylogeography among individuals of the endemic newt (Cynops ensicauda) of the Central Ryukyus, Japan based on the mitochondrial cytochrome b gene. The results of phylogenetic analyses showed the presence of remarkable differentiation between assemblages from the Amami and Okinawa Island Groups, supporting the validity of the subspecies C. e. popei described from the latter on morphological grounds. The group of individuals from Okinawa Island Group was further divided into two distinct subgroups unlike the results of previous morphological and allozyme studies. Geographic ranges of these subgroups overlapped in the northern part of Okinawajima Island. The phylogeographic pattern within the Okinawa Island Group suggests an initial division into two geographically isolated population lineages and subsequent secondary sympatry before formation of reproductive isolation. It is also likely that within the Okinawa Island Group emigration occurred from the central and northern parts of Okinawajima Island to its southern part, as well as to several small islets off its western coast. Within the Amami Island Group, recurring restricted gene flow with isolation by distance seems to have occurred around the southwestern region including three islets southwest of Amamioshima Island.     

Range-wide phylogeography of Juniperus thurifera L., a presumptive keystone species of western Mediterranean vegetation during cold stages of the Pleistocene

We investigate the range-wide population structure and phylogeography of thuriferous juniper (Juniperus thurifera L.), a species with a highly disjunct distribution in the western Mediterranean. We genotyped a total of 327 individuals from 20 populations using amplified fragment length polymorphisms (AFLP). Different analyses such as principal co-ordinate analysis (PCoA), nonmetric multidimensional scaling of F(ST) distances among populations, unweighted pair group method with arithmetic mean (UPGMA), and Bayesian clustering revealed that the Strait of Gibraltar acted as an efficient barrier against gene flow between the Moroccan and European populations for a very long time, and consequently support that the Moroccan populations should be recognised as a distinct subspecies (J. thurifera L. subsp. africana (Maire) Romo and Boratyńsky). The Algerian population was genetically more closely related to the European than to the Moroccan ones, probably due to dispersal events from Europe to Algeria. With respect to the mainland European populations, our data are not conclusive to reject any of the two following hypotheses: (1) the Iberian Peninsula was subdivided into different gene pools, and was the source for the colonisation of the Pyrenees and the Alps; and (2) the pattern we see today is partly the result of immigration into the Iberian Peninsula, e.g. from the Alps. Finally, the Corsican population was closely related genetically to two northern Iberian populations most probably due to relatively recent long-distance dispersal.     

Phylogeography of the eight-barbel loach <Emphasis Type="Italic">Lefua nikkonis</Emphasis> (Cypriniformes: Nemacheilidae): how important were straits in northern Japan as biogeographical barriers?

Many straits in the Japanese archipelago have been proposed as biogeographical boundaries, but there is disagreement regarding their importance as historic barriers against dispersal of terrestrial and freshwater taxa. Mitochondrial DNA haplotype and phylogenetic analyses of Lefua nikkonis, a primary freshwater fish inhabiting northern Japan and descendent from Siberia, revealed that the species is genetically structured within its geographic range, but that two major haplotypes are widely distributed across the Ishikari Lowland of Hokkaido Island as well as across the Tsugaru Strait between Hokkaido and Honshu Islands, two well-known biogeographical boundaries of northern Japan. The two major haplotypes were separated from each other by only one mutational step, and many other haplotypes, including those endemic to the region south of these barriers, have diverged from the major haplotypes, suggesting rapid range expansion and local differentiation. Divergence-time estimates, based on vicariance of the Honshu endemic congener L. echigonia via uplift of the Central Highlands, demonstrated that the southward dispersal of L. nikkonis from Hokkaido Island to Honshu Island occurred less than 0.08–0.19 Mya, suggesting that a land bridge emerged at the Tsugaru Strait during the Riss glaciation. Given that other freshwater taxa crossed the strait earlier (during the Middle Pleistocene), it is likely that land bridges in the strait have repeatedly emerged. The fact that L. nikkonis invaded only the northern part of Honshu, and that many other freshwater species also have the limit of their distribution ranges in this area as well, indicates that a faunal transition zone might persist even without the Tsugaru Strait. Thus, straits and lowlands in northern Japan are likely to have been less important as dispersal barriers to freshwater taxa than is currently thought.     

Vicariant versus dispersal processes in the settlement of Pseudamnicola (Caenogastropoda,Hydrobiidae) in the Mediterranean Balearic Islands

The genus Pseudamnicola comprises a group of tiny springsnails inhabiting several continental and insular regions of the Mediterranean basin. Given the limited dispersal capabilities of these animals, it is difficult to explain the wide distribution range of the genus and, more specifically, its presence in isolated habitats, such as on islands. Thus, to investigate the process(es) that may explain these distribution patterns, we morphologically re‐described and genetically analysed the six Pseudamnicola (Pseudamnicola) species occurring in the Iberian Peninsula and the nearby Balearic Islands. Genetic relationships were explored by sequencing two mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and one nuclear (28S rRNA) gene in 19 populations. Our morphological study confirmed the presence of previously described species, whereas our phylogenetic results revealed three lineages within the subgenus: one clade grouping the species from Minorca Island with an Iberian Peninsula species, a second clade grouping the three species from Majorca Island, and a third clade that consists of a single species, which occurs in both the Iberian Peninsula and Ibiza Island. Calculated speciation times show that the cladogenetic events involving the insular species seem to have occurred after the current conformation of the Balearic Islands (c. 20 Mya). Therefore, the speciation process may have been related to subsequent transmarine colonizations, probably during the Messinian Salinity Crisis, and the Pleistocene glaciations when landmass corridors connected the islands with the continent. © 2014 The Linnean Society of London